circuitdigestDetail6

Getting started with Python OpenCV: Installation and Basic Image Processing
is dated long back to more than 20 years.
etc.
it’s important to know what images are and how humans and machines perceive those images.
What are Images?
Images are a two-dimensional representation of the visible light spectrum. 
And the visible light spectrum is just a part of the electromagnetic spectrum lying there between infrared and ultraviolet spectrum.
: - when a light reflects off an object onto a film, a sensor or on retina.

, and it forms a much focused image and is a working model for a pin hole camera, but there is a problem in a pin hole camera, that same amount of light will be entering the aperture, which could not be suitable for the film or image formed also we can’t get a focused image, so as to focus the image we need to move film back and forth, but this is problematic in many situations.
is better in photography.
in photography, it allows us to have a blurred background while we focus on image.
How computer stores images
You may have heard of various image formats like .PNG, .JPEG and etc. 
all of this are digital representation of our analog world, computers do it by translating the image into digital code for storage and then interpret the file back into an image for display. 
But at the basics they use a common platform for storing the images, and same is true for the openCV.
).

Mixing different intensities of each color gives us the full spectrum, that’s why in painting or art these three colors are regarded as primary colors and all others as secondary, because most of the secondary colors can be formed by primary colors. 
Like for yellow, we have the following values: Red ᾠ255; Green ᾠ255; Blue ᾠ0.
In programming, array is a series of collection of objects. 
And here we deal with three type of arrays 1D, 2D and 3D where ‘Dᾠstands for dimensional.

and also there are two types of black & white images Greyscale and binary images.
are of pixels either of black or white.
Why it is difficult for a machine to identify images
Computer vision is a challenging task in itself, you can yourself imagine how hard it is to give a machine a sense of vision, recognition and identification. 

The following factors are there that makes computer vision so hard.
Camera sensor and lens limitations
View point variations
Changing lighting

Scaling
Occlusions
Object class variations
Ambiguous Images/Optical Illusions
Application and uses of OpenCV
Despite the difficulty, Computer Vision has many success stories
Robotic Navigation ᾠSelf Driving Cars
Face Detection & Recognition

Search Engine Image Search
License Plate Reading
Handwriting Recognition
Snapchat & Face Filters

Object Recognition
Ball & Player Tracking in Sports
And many more!
Installing OpenCV with Python and Anaconda
as Python is one of the easiest languages for beginners also It is extremely powerful for data science and machine learning applications and also it stores images in numpy arrays which allows us to do some very powerful operations quite easily.
Basic programming is useful with Exposure to High School Level Math, a webcam, Python 2.7 or 3.6 (Anaconda Package is preferred).
and choose according to your machine weather its windows, Linux or mac and you can choose for python 2.7 or python 3.7 version for either 64 Bit systems or 32 Bit systems, but now a days most of the system are 64 bit.
since it’s the future of the python and will take over python 2.7 form 2020, also most of the libraries are being developed in python 3.7 keeping the future aspect of python in mind. 

Also it also gives the expected results on basic mathematical operations such as (2/5=2.5), while the python 2.7 would evaluate it to 2. 
Also print is treated as a function in python 3.7 (print(“helloᾩ), so it gives hands-on to the programmers.
With the YML files we will install all the packages and libraries that would be needed, but however if you want to install any additional packages you can easily install through anaconda prompt, by running the command of that package.
Go to your windows search icon and find anaconda prompt terminal, you can find it inside your anaconda folder that you have just installed.

, and from here you have two choices either changing the directory of your terminal to the location where the your YML file is downloaded or either copy your YML file to the directory where your anaconda is installed in most cases it would be inside C:\ drive, after copying your YML file to the specified location RUN the following command on your prompt
conda env create –f  virtual_platform_windows.yml
the YML file and the command corresponds to the windows, however you can modify according to your system by replacing windows by linux or mac as respective.
first and then run the above command.
Opening and Saving images in OpenCV
#comments in python are given by # symbol
Import opencv in python by command
import cv2

specifying the path to the image
image =cv2.imread('input.jpg')
Now that image is loaded and stored in python as a variable we named as image
and the first parameter for imshow function is the title shown on the image window, and it has to be entered in (ᾠᾩ to represent the name as a string

cv2.imshow('hello world',image)
allows us to input information when image window is open, by leaving it blank it just waits for anykey to be pressed before continuing, by placing numbers (except 0), we can specify a delay for how long you keep the window open (time in milliseconds here).
cv2.waitKey()
closes all the open windows, failure to place this will cause your programme to hang.

cv2.destroyAllWindows()
is a library for python programming for adding support to large multidimensional arrays and matrices.
import cv2
#importing numpy

import numpy as np
image=cv2.imread('input.jpg')
cv2.imshow('hello_world', image)
#shape function is very much useful when we are looking at a dimensions of an array, it returns a tuple which gives a dimension of an image

print(image.shape)
cv2.waitKey()
cv2.destroyAllWindows()
- (183, 275, 3), The two dimensions of the image are 183 pixels in height and 275 pixels in width and 3 means that there are three other components (R, G, B) that makes this image (it shows that the colored images are stored in three dimensional arrays).

print('Height of image:',(image.shape[0],'pixels'))
print('Width of image:',(image.shape[1],'pixels'))
Height of image: (183, 'pixels')
Width of image: (275, 'pixels')

for specifying the filename and the image to be saved.
cv2.imwrite('output.jpg',image)
cv2.imwrite('output.png',image)
First argument is name of the file we want to save, {to read or to save the file we use (ᾠᾩ to indicate it as a string} and second argument is the file name.

OpenCV allows you to save the image in different formats.
Grey Scaling Image in OpenCV
is the process by which an image is converted from a full color to shades of grey (black and white)
In opencv, many functions greyscales the images before processing. 

This is done because it simplifies the image, acting almost as a noise reduction and increasing the processing time as there is less information in image (as greyscale images are stored in two dimensional arrays).
import cv2
# load our input image
image=cv2.imread('input.jpg')

cv2.imshow('original', image)
cv2.waitKey()
#we use cvtcolor, to convert to greyscale
gray_image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

cv2.imshow('grayscale', gray_image)
cv2.waitKey()
cv2.destroyALLWindows()
function aside to the image name

import cv2
grey_image=cv2.imread('input.jpg',0)
cv2.imshow('grayscale',grey_image)
cv2.waitKey()

cv2.destroyAllWindows()
import cv2
import numpy as np
image=cv2.imread('input.jpg')

print(image.shape)
cv2.imshow('original', image)
cv2.waitKey()
gray_image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

cv2.imshow('grayscale', gray_image)
print(gray_image.shape)
cv2.waitKey()
cv2.destroyALLWindows()

(183, 275, 3) ᾠfor colored image
(183, 275) ᾠfor grayscale image
Hence it clearly shows that the colored images are represented by three dimensional arrays, while the gray scale images by two dimensional arrays.
Color Spaces
, these are just simple ways to represent color.
Red, Green and Blue.
Hue, Saturation and Value.
is commonly used in inkjet printers.

OpenCV’s default color space is RGB. 
RGB is an additive color model that generates colors by combining blue, green and red colors of different intensities/ brightness. 
In OpenCV we use 8 bit color depths.
- Red (0-255)

- Blue (0-255)
- Green (0-255)
Fun Fact: - We use BGR order in computers due to how unsigned 32-bit integers are stored in memory, it still ends up being stored as RGB. 
The integer representing a color eg:- 0X00BBGGRR will be stored as 0XRRGGBB.

HSV color space
HSV (Hue, Saturation & value/ Brightness) is a color space that attempts to represent colors the humans perceive it. 
It stores color information in a cylindrical representation of RGB color points.
Hue ᾠcolor value (0-179)

Saturation ᾠVibrancy of color (0-255)
Value ᾠBrightness or intensity (0-255)
HSV color space format is useful in color segmentation. 
In RGB, filtering specific color isn’t easy, however HSV makes it much easier to set color ranges to filter specific color as we perceive them.

Hue represents the color in HSV, the hue value ranges from 0 ᾠ180 and not 360 so it is not completing the full circle and so it is mapped differently than the standard.
Color range filters 
Red ᾠ(165-15) 
Green ᾠ(45-75)

Blue ᾠ(90-120)
As we know the images being stored in RGB (Red, Green and Blue) color space and so OpenCV shows us the same, but the first thing to remember about opencv’s RGB format is that it’s actually BGR and we can know it by looking at the image shape.
import cv2
import numpy as np

image = cv2.imread('input.jpg')
#B,G,R value for the first 0,0 pixel
B,G,R=image[0,0]
print(B,G,R)

print(image.shape)
#now if we apply this on grayscale image
gray_img=cv2.cvtColor(image,cv2.COLOR_BGR2GRAY)
print(gray_img.shape)

#gray_image pixel value for 10,50 pixel
print(gray_img[10,50])
6 11 10
(183, 275, 3)

- (183, 275)
- 69
while in grayscale only two dimensions are present, since (R,G,B) is absent and for a particular pixel position we only get a single value while in colored image we got three values.
import cv2

image=cv2.imread('input.jpg')
hsv_image=cv2.cvtColor(image,cv2.COLOR_BGR2HSV)
cv2.imshow('HSV image',hsv_image)
cv2.imshow('Hue channel',hsv_image[:,:,0])

cv2.imshow('saturation channel',hsv_image[:,:,1])
cv2.imshow('value channel',hsv_image[:,:,2])
cv2.waitKey()
cv2.destroyAllWindows()

Hue channel image is quite dark because its value only varies from 0 to 180.
function tries to show you the RGB or BGR image, but HSV conversion overlaps it.
Also, the value channel will be similar to the grayscale of image due to its brightness.
Exploring individual components of RGB image
import cv2
image=cv2.imread('input.jpg')
#opencv's split function splits the imageinti each color index
B,G,R=cv2.split(image)

cv2.imshow("Red",R)
cv2.imshow("Green",G)
cv2.imshow("Blue",B)
#making the original image by merging the individual color components

merged=cv2.merge([B,G,R])
cv2.imshow("merged",merged)
#amplifying the blue color
merged=cv2.merge([B+100,G,R])

cv2.imshow("merged with blue amplify",merged)
#representing the shape of individual color components.
# the output wuld be only two dimension whih wouldbe height and width, since third element of RGB component is individually represented
print(B.shape)

print(R.shape)
print(G.shape)
cv2.waitKey(0)
cv2.destroyAllWindows()

#dimensions of image from shape function
Converting image into individual RGB component
In below code we have created a matrix of zeros with the dimensions of image HxW, zero return an array filled with zeros but with same dimensions.
would grab everything up to designated points i.e. 

upto second designated points which would be height and width of the image as third represents RGB component of image and we don't need it here.
import cv2
import numpy as np
image = cv2.imread('input.jpg')

B,G,R = cv2.split(image)
zeros=np.zeros(image.shape[:2],dtype="uint8")
cv2.imshow("RED",cv2.merge([zeros,zeros,R]))
cv2.imshow("Green",cv2.merge([zeros,G,zeros]))

cv2.imshow("Blue",cv2.merge([B,zeros,zeros]))
cv2.waitKey(0)
cv2.destroyAllWindows()
Histogram Representation of Image
The following code lets you analyze the image through the color histogram of its combined and individual color components.
import cv2
import numpy as np
#we need to import matplotlib to create histogram plots

import matplotlib.pyplot as plt
image=cv2.imread('input.jpg')
histogram=cv2.calcHist([image],[0],None,[256],[0,256])
#we plot a histogram, ravel() flatens our image array

plt.hist(image.ravel(),256,[0,256])
plt.show()
#viewing seperate color channels
color=('b','g','r')

#we know seperate the color and plot each in histogram
for i, col in enumerate (color):
    histogram2=cv2.calcHist([image],[i],None,[256],[0,256])
    plt.plot(histogram2,color=col)

    plt.xlim([0,256])
    plt.show()              
function with each of its individual parameters
cv2.calcHist(images, channels, mask, histsize, ranges)

: its the source image of type uint 8 or float 32. 
It should be given in square brackets, i.e. 
“[img]ᾬ which also indicate its second level array since an image for opencv is data in an array form.
it is also given in square brackets. 

It is the index of channel for which we calulate histogram, for example if input is grayscale image its value is [0], for color images you can pass [0], [1] or [2] to calculate histogram of blue, green and red channel respectively.
mask image. 
to find the histogram of full image, it is given as “noneᾮ but if you want to find the histogram of particular region of image, you have to create a mask image for that and give it as a mask.
This represents our BIN count. 

Needed to be given in square brackets for full scale we pass [256].
This is our range, normally is [0,256]
Drawing Images and Shapes using OpenCV
for drawing lines, rectangle, polygon, circle etc in OpenCV.

import cv2
import numpy as np
#creating a black square 
image=np.zeros((512,512,3),np.uint8)

#we can also create this in black and white, however there would not be any changes
image_bw=np.zeros((512,512),np.uint8)
cv2.imshow("black rectangle(color)",image)
cv2.imshow("black rectangle(B&W)",image_bw)

#create a line over black square
#cv2.line(image, starting coordinates, ending coordinates, color, thickness)
#drawing a diagonal line of thickness 5 pixels
image=np.zeros((512,512,3),np.uint8)

cv2.line(image,(0,0),(511,511),(255,127,0),5)
cv2.imshow("blue line",image)
#create a rectangle over a black square
#cv2.rectangle(image,starting coordinates, ending coordinates, color, thickness)

#drawing a rectangle of thickness 5 pixels
image=np.zeros((512,512,3),np.uint8)
cv2.rectangle(image,(30,50),(100,150),(255,127,0),5)
cv2.imshow("rectangle",image)

Circle
#creating a circle over a black square
#cv2.circle(image,center,radius,color,fill)
image=np.zeros((512,512,3),np.uint8)

cv2.circle(image,(100,100),(50),(255,127,0),-1)
cv2.imshow("circle",image)
Polygon
#creating a polygon

image=np.zeros((512,512,3),np.uint8)
#lets define four points
pts=np.array([[10,50], [400,60], [30,89], [90,68]], np.int32)
#lets now reshape our points in form required by polylines

pts=pts.reshape((-1,1,2))
cv2.polylines(image, [pts], True, (0,255,255), 3)
cv2.imshow("polygon",image)
Text

#putting text using opencv
#cv2.putText(image,'text to display',bootom left starting point, font,font size, color, thickness)
image=np.zeros((512,512,3),np.uint8)
cv2.putText(image,"hello world", (75,290), cv2.FONT_HERSHEY_COMPLEX,2,(100,170,0),3)

cv2.imshow("hello world",image)
cv2.waitKey(0)
cv2.destroyAllWindows()


article/embedded-firmware-development-tips-and-tools
Tips and Tools for Embedded Firmware Development
tedious.
generally involves below steps:

Development of product requirement
System Design and Algorithm Development
Coding
Testing

and some of the tools that could increase efficiency and productivity.
1. Development of Product Requirement
among other things and this costs firmware developers several man hours as they search through the document to identify things like which register belongs to which group and which bit field belongs to which register. 
Below are some tips which could be considered to ensure the development of a more useful project specification documents.

All registers in the control element could be assigned a distinctive name that makes them easy to identify across the document and they could all be hot-linked such that they lead to a list within the document which states the name, location, block and address of each register.
Also at this stage, there should be plans for error handling under each block. 
Essentially this looks like the firmware developer saying; “when I get here, I am to do this, this and this, ensuring this, this and that, does not occurᾮ This helps guide the work of the developer and helps evaluate the project even before design starts to identify potential errors and bugs, saving precious time and money.
There are other factors including document structure, the use of easy to read fonts (something the developers can work with even when fatigued), charts and pictures where possible which could all increase the efficiency of the firmware team after this stage.
2. System Design and Algorithm development
This stage involves the development of the pseudocodes, flowcharts, state machines and everything involved with the design of what the firmware. 
For this stage, quite a number of tools can be used to help organize thoughts, explore legacy/previously written software around the project and develop your own flowchart, state machine etc. 
Some of these tools are discussed below.

There are quite a number of PIMs out there but I will mention a few with some outstanding features.
Evernote helps you take notes that are available across any platform so you can check the note you made on your PC while in the bus home. 
The notes are well organized and are completely searchable so you will always find what you need.
Trunk note is a Wiki-like note taking application. 

It brings all the organizational power of wikis to note-taking. 
It is a mobile phone based application but can be easily synced with a PC via WIFI.
Other kinds of PIMs like Tiddlywiki etc. 
Each of them come with features that may make it more attractive to specific individuals and may take some sampling before you finally settle on one.

This might be quite a long road, especially if you were not a part of the team that built the previous software. 
There are quite a number of software that helps build trees, create documentation and flowcharts from already written code.
is a quite powerful tool that helps create documentation from source codes. 
It was majorly designed to work with C++ but also works with C, Python and some other languages. 

It has the ability to extract the code structure of any code, providing automatically generated dependency graphs and Inheritance diagrams to help visualize the code.
helps present structural information as diagrams of abstract graphs and networks. 
It can be used alongside Doxygen to better understand the graphics produced by it.
amongst others.

All the research and note-taking aggregates to the development of algorithms spinning off into pseudocodes and flowcharts for the project. 
Several tools exist for developing flowcharts and while most of them are not exclusive to firmware development, they provide useful and important features that simply gets the job done and also helps maintain the charts throughout the product development cycle. 
Below are some of the best tools out there for flowcharting.
QFSM is a graphical tool for designing and simulating finite state machines. 

Its ability to simulate the designs makes it way better than most of the other software in this group. 
It is particularly useful when you are designing state machines for FPGA and similar target hardware.
Lucid chart is arguably the best and most flexible flowcharting software out there. 
It is web-based and has team features which allow you to work between multiple devices and collaborate in real-time with teammates.

Visio is one of the best graphical tools currently. 
It has an array of objects from different fields that makes it easy to describe anything. 
However, it does not come with features that enhance collaboration among teams and can only be used on a windows machine on which it is installed.
One of the key things in the development of products in today's world is the use of tools that allow teams to collaborate effectively from wherever they are and that is one thing Google slides brings onboard. 

It can be used to develop all kind of charts from software flow charts to organizational charts and mind maps. 
It is cloud-based and works in almost all the popular browsers.
Several other tools exist for the creation of flowcharts and general algorithm development, as usual, each one with its own pro and cons.
3. Coding for Embedded Firmware
Everything that has been mentioned up till this point leads here. 
The world of SDKs and IDEs, the choice of tools at this stage depends on the target device and the features to be built into the device, for this reason, I will exclude popular SDKs and IDEs like MPLAB, etc from the discussion and just stick to tools that are more complementary in nature.
Displays (interactive or not) are the most popular mediums for providing feedback to users these days and QT’s SDK is one of the best out there and probably no stranger to anyone within the embedded circle. 
It provides "drag and drop" features that make it easy to develop complex, GUI based applications for embedded devices, irrespective of the target platform, or the programming language being used for the overall project development. 

It basically eliminates the stress of associated with using code to create user interfaces.
on which embedded software can be executed to determine systems performance before the hardware is ready.
One of the most important parts of writing any code is documentation and one of the most popular tools for that is Doxygen. 
Asides from its use to understand legacy software, Doxygen has the ability to automatically extract comments from a code and create documentation that includes it. 

Doxygen structures include files graphically and create references for every function, Variable, and macro used in your code. 
Flowcharts and data flow diagrams can also be embedded in the documentation by combining Doxygen with graphviz.
stands out among all the version control tools out there for several reasons. 
It is open source, fast, efficient and mostly local. 

Asides Git, tools like subversion are also worth mentioning.
Testing Embedded Firmware
Testing is an important part of the development process for anything. 
Firms lose thousands of dollars when devices are recalled due to firmware errors so it's one part of the development that should be taken very seriously. 

It is often done, hand in hand, with coding and the first set of tools for code testing, are probably the debuggers within the IDE or SDK being used for the project. 
Testing comes in different forms and is performed at different stages, as such, it involves diverse kind of tools. 
Testing tools form firmware development cuts across design validation to static analysis and runtime test tools. 
Below are few tools I find really useful.

Crystal revs is a tool for studying code. 
It can be used to generate flowchart from C/ C++ code which makes it a great tool to review your own code and see if the preliminary design is what was implemented. 
With crystal rev, you will be able to quickly see the difference between the design and implementation. 
Its ability to generate flow charts, data and call flow from codes also makes it a tool, useful for analyzing legacy code.

PC-lint is one of the oldest firmware testing tools around. 
It is capable of analyzing software to identify bugs, security vulnerabilities, and ensure code was written in line with industry standards. 
Similar tools include polyspace, and LRDA, Eggplant, and Tessy among others.
This comes in handy when building network devices. 

It is essentially a packet sniffer and could help view the data your device is transmitting. 
This could help in securing the device.
is a tool I recently got introduced too by a friend. 
It comes really handy when working on device drivers and other com port-related developments. 

The virtual serial com port gives you the ability to test com ports behavior without the target device. 
You could create an unlimited number of ports which is capable of emulating all the settings of real com ports. 
The software also comes with features like Serial port splitting, Com ports merger, use bundle com port connections amongst other cool features.
That’s it for this article, thanks for taking time out to read. 

While it’s impossible to probably list all the tools out there, I hope you find some of these tools useful.

tutorial/lead-acid-battery-working-construction-and-charging-discharging
Lead Acid Battery: Working, Construction and Charging/Discharging

is commonly used for high power supply. 
Usually Lead Acid batteries are bigger in size with hard and heavy construction, they can store high amount of energy and generally used in automobiles and inverters.
comes with Lithion-ion batteries, but still there are many electric two wheeler which use Lead Acid battries to power the vehicle.
We will also learn about charging/discharging ratings, requirements and safety of Lead Acid Batteries.
Construction of Lead Acid Battery
(sometimes wrongly called as lead peroxide), is called as Lead Acid Battery.
A Lead Acid Battery consists of the following things, we can see it in the below image:
is water and sulfuric acid.

The hard plastic case is one cell. 
A single cell store typically 2.1V. 
Due to this reason, A 12V lead acid battery consists of 6 cells and provide 6 x 2.1V/Cell = 12.6V typically.
We will describe this in later section.
Working of Lead Acid Battery
- and Cathode with 2H+ interchange electrons and which is further react with the H2O or with the water (Diluted sulfuric acid, Sulfuric Acid + Water).
Lead Acid Battery Charging
As we know, to charge a battery, we need to provide a voltage greater than the terminal voltage. 

So to charge a 12.6V battery, 13V can be applied.
). 
The energy gets stored by increasing the gravity of sulfuric acid and increasing the cell potential voltage.
As explained above, following chemical reactions takes place at Anode and Cathode during the charging process.

At cathode
PbSO4 + 2e- => Pb + SO42-
At anode
PbSO4 + 2H2O => PbO2 + SO42- + 4H- + 2e-

Combining above two equation, the overall chemical reaction will be
2PbSO4 + 2H2O => PbO2 + Pb + 2H2SO4 
which is an effective process in terms of charging time. 
In full charge cycle the charge voltage remains constant and the current gradually decreased with the increase of battery charge level.
Lead Acid Battery Discharging
O.
reacting with the Pb.
As explained above, following chemical reactions takes place at Anode and Cathode during the discharging process. 

These reaction are exactly opposite of charging reactions:
At cathode
Pb + SO42- => PbSO4 + 2e-
At anode:

PbO2 + SO42- + 4H- + 2e- => PbSO4 + 2H2O
Combining above two equation, the overall chemical reaction will be
PbO2 + Pb + 2H2SO4 => 2PbSO4 + 2H2O
Due to the electron exchange across anode and cathode, electron balance across the plates is affected. 

The electrons then flow through the load and the battery gets discharged.
During this discharge, the diluted sulfuric acid gravity decrease. 
Also, at the same time, the potential difference of the cell decrease.
Risk Factor and Electrical Ratings
The Lead Acid battery is harmful if not maintained safely. 
As the battery generates Hydrogen gas during the chemical process, it is highly dangerous if not used in the ventilated area. 
Also, inaccurate charging severely damages the battery.
Every lead-acid battery is provided with datasheet for standard charge current and discharges current. 

Typically a 12V lead-acid battery which is applicable for the automotive application could be ranged from 100Ah to 350Ah. 
This rating is defined as the discharge rating with an 8 hour timing period.
We can draw more current but it is not advisable to do so. 
By drawing more current than the maximum discharge current in respect of 8 hours will damage the battery efficiency and the battery internal resistance could also be changed, which further increases the battery temperature.

is dangerous for the lead-acid battery charging. 
The readymade charger comes with a charging voltage and charging current meter with a control option. 
We should provide greater voltage than the battery voltage to charge the battery. 
Maximum charge current should be the same as the maximum supply current at 8 hours discharging rates. 

If we take the same 12V 160Ah example, then the maximum supply current is 20A, so the maximum safe charging current is the 20A.
as this will result in heat and increased gas generation.
Lead-acid battery maintenance rules
Watering is the most neglected maintenance feature of flooded lead-acid batteries. 

As overcharging decreases water, we need to check it frequently. 
Less water creates oxidation in plates and decreases the lifespan of the battery. 
Add distilled or ionized water when needed.
Check for the vents, they need to be perfected with rubber caps, often the rubber caps sticks with the holes too tightly.

Recharge lead-acid batteries after each use. 
A long period without recharging provides sulfating in the plates.
Do not freeze the battery or charge it more than 49-degree centigrade. 
In cold ambient batteries need to be fully charged as fully charge batteries safer than the empty batteries in respect of freezing.

Do not deep discharge the battery less than 1.7V per cell.
To store a lead acid battery, it needs to be completely charged then the electrolyte needs to be drained. 
Then the battery will become dry and can be stored for a long time period.


tutorial/different-types-of-inverters
Introduction to Different Types of Inverters
The inverter is used to convert DC to variable AC. 
This variation can be in the magnitude of voltage, number of phases, frequency or phase difference.
Classification of Inverter 
Inverter can be classified into many types based on output, source, type of load etc. 
Below is the complete classification of the inverter circuits:
Square Wave Inverter

Sine Wave Inverter
Modified Sine Wave Inverter
Current Source Inverter
Voltage Source Inverter

Single Phase Inverter

Half Bridge Inverter
Full Bridge Inverter

Three Phase Inverter

180-degree mode
120-degree mode

Simple Pulse Width Modulation (SPWM)
Multiple Pulse Width Modulation (MPWM)
Sinusoidal Pulse Width Modulation (SPWM)
Modified sinusoidal Pulse Width Modulation (MSPWM)

Regular Two-Level Inverter
Multi-Level Inverter
design here.
(I) According to the Output Characteristic 
Square Wave Inverter
Sine Wave Inverter
Modified Sine Wave Inverter
The output waveform of the voltage for this inverter is a square wave. 

This type of inverter is least used among all other types of inverter because all appliances are designed for sine wave supply. 
If we supply square wave to sine wave based appliance, it may get damaged or losses are very high. 
The cost of this inverter is very low but the application is very rare. 
It can be used in simple tools with a universal motor.

The output waveform of the voltage is a sine wave and it gives us a very similar output to the utility supply. 
This is the major advantage of this inverter because all the appliances we are using, are designed for the sine wave. 
So, this is the perfect output and gives guarantee that equipment will work properly. 
This type of inverters is more expensive but widely used in residential and commercial applications.

The construction of this type of inverter is complex than simple square wave inverter but easier compared to the pure sine wave inverter. 
The output of this inverter is neither pure sine wave nor the square wave. 
The output of such inverter is the some of two square waves. 
The output waveform is not exactly sine wave but it resembles the shape of a sine wave.
(II) According to the Source of the Inverter
Voltage Source Inverter
Current Source Inverter
In CSI, the input is a current source. 

This type of inverters is used in the medium voltage industrial application, where high-quality current waveforms are compulsory. 
But CSIs are not popular.
In VSI, the input is a voltage source. 
This type of inverter is used in all applications because it is more efficient and have higher reliability and faster dynamic response. 

VSI is capable of running motors without de-rating.
(III) According to the Type of Load
Single-phase Inverter
Three-phase Inverter

Generally, residential and commercial load uses single phase power. 
The single-phase inverter is used for this type of application. 
The single-phase inverter is further divided into two parts;
Single Phase Half-bridge Inverter

Single Phase Full-bridge Inverter
and connection is as shown in below figure.
In this case, total DC voltage is Vs and divided into two equal parts Vs/2. 
Time for one cycle is T sec.

For half cycle of 0 <t <T/2, thyristor T1 conducts. 
The load voltage is Vs/2 due to the upper voltage source Vs/2.
For the second half cycle of T/2 <t <T, thyristor T1 is commutated and T2 conducts. 
During this period, the load voltage is -Vs/2 due to the lower source Vs/2.

Vo = Vs/2
By this operation, we can get alternating voltage waveform with 1/T Hz frequency and Vs/2 peak amplitude. 
The output waveform is a square wave. 
It will be passed through the filter and remove unwanted harmonics which give us pure sine waveform. 

The frequency of the waveform can be controled by the ON time (Ton) and OFF time (Toff) of the thyristor.
In this type of inverter, four thyristors and four diodes are used. 
The circuit diagram of single-phase full bridge is as shown in below figure.
At a time two thyristors T1 and T2 conduct for first half cycle 0 < t < T/2. 

During this period, the load voltage is Vs which is similar to the DC supply voltage.
For second half cycle T/2 < t < T, two thyristors T3 and T4 conducts. 
The load voltage during this period is -Vs.
Here we can get AC output voltage same as DC supply voltage and the source utilization factor is 100%. 

The output voltage waveform is square waveform and the filters are used to convert it into a sine wave.
If all thyristors conduct at the same time or in a pair of (T1 and T3) or (T2 and T4) then the source will be short-circuited. 
The diodes are connected in the circuit as feedback diode because it is used for the energy feedback to the DC source.
If we compare full bridge inverter with half bridge inverter, for the given DC supply voltage load, output voltage is two times and output is power is four times in full bridge inverter.

In case of industrial load, three phase ac supply is used and for this, we have to use a three-phase inverter. 
In this type of inverter, six thyristors and six diodes are used and they are connected as shown in below figure.
It can operate in two modes according to the degree of gate pulses.
180-degree mode

120-degree mode
In this mode of operation, conduction time for thyristor is 180 degree. 
At any time of period, three thyristors (one thyristor from each phase) are in conduction mode. 
The shape of phase voltage is three stepped waveforms and shape of line voltage is a quasi-square wave as shown in the figure.

Vab = Va0 – Vb0
Vbc = Vb0 – Vc0
Vca = Vc0 ᾠVa0


Phase A

T1


T4

T1


T4
Phase B

T6


T3

T6


T3
T6
Phase C
T5


T2

T5


T2

T5
Degree
60
120
180
240
300
360
60


120
180
240
300
360
Thyristor conducts
1 5 6
6 1 2
1 2 3
2 3 4
3 4 5
4 5 6
1 5 6


6 1 2
1 2 3
2 3 4
3 4 5
4 5 6

In this operation, the time gap between the commutation of outgoing thyristor and conduction of incoming thyristor is zero. 
So the simultaneous conduction of incoming and outgoing thyristor is possible. 

It results in a short circuit of the source. 
To avoid this difficulty, 120-degree mode of operation is used.
In this operation, at a time only two thyristors conduct. 
One of the phases of the thyristor is neither connected to the positive terminal nor connected to the negative terminal. 

The conduction time for each thyristor is 120 degree. 
The shape of line voltage is three stepped waveform and shape of the phase voltage is a quasi-square waveform.

Phase A


T1


T4



T1


T4


Phase B
T6


T3



T6


T3
T6
Phase C



T2


T5



T2


T5

degree
60
120
180
240
300
360
60
120
180
240
300
360
Thyristor conducts
1 6
2 1
3 2
3 4
4 5
6 5
1 6
2 1
3 2
3 4
4 5
5 6

The waveform of line voltage, phase voltage and gate pulse of the thyristor is as shown in the above figure.

in the switch and the switching loss means OFF state loss in switch. 
Generally, the conduction loss is greater than the switching loss in most of the operation.
If we consider 180-degree mode for one 60-degree operation, three switches are open and three switches are closed. 
Means total loss is equal to three times of conduction loss plus three times of switching loss.

Total loss in 180-degree = 3 (conductance loss) + 3 (switching loss)
If we consider 120-degree mode for one 60-degree operation, two switches are open and rest of the four switches are closed. 
Means total loss is equal to two times of conductance loss plus four times of switching loss.
Total loss in 120-degree = 2 (conductance loss) + 4 (switching loss)
(IV) Classification According to Control Technique
Single Pulse Width modulation (single PWM)
Multiple Pulse Width Modulation (MPWM)
Sinusoidal Pulse Width Modulation (SPWM)

Modified Sinusoidal Pulse Width Modulation (MSPWM)
The output of the inverter is square wave signal and this signal is not used for the load. 
Pulse width modulation (PWM) technique is used to control AC output voltage. 
This control is obtained by the controlling of ON and OFF period of switches. 

In PWM technique two signals are used; one is reference signal and second is triangular carrier signal. 
The gate pulse for switches is generated by comparing these two signals. 
There are different types of PWM techniques.
For every half cycle, the only pulse is available in this control technique. 

The reference signal is square wave signal and the carrier signal is triangular wave signal. 
The gate pulse for the switches is generated by comparing the reference signal and carrier signal. 
The frequency of output voltage is controlled by the frequency of the reference signal. 
The amplitude of the reference signal is Ar and the amplitude of the carrier signal is Ac, then the modulation index can be defined as Ar/Ac. 

The main drawback of this technique is high harmonic content.
The drawback of single pulse width modulation technique is solved by multiple PWM. 
In this technique, instead of one pulse, several pulses are used in each half cycle of the output voltage. 
The gate is generated by comparing the reference signal and carrier signal. 

The output frequency is controlled by controlling the frequency of the carrier signal. 
The modulation index is used to control the output voltage.
The number of pulses per half cycle = fc/ (2*f0)
Where fc = frequency of carrier signal

f0 = frequency of output signal
This control technique is widely used in industrial applications. 
In above both methods, the reference signal is a square wave signal. 
But in this method, the reference signal is a sine wave signal. 

The gate pulse for the switches is generated by comparing the sine wave reference signal with the triangular carrier wave. 
The width of each pulse varies with variation of amplitude of the sine wave. 
The frequency of output waveform is the same as the frequency of the reference signal. 
The output voltage is a sine wave and the RMS voltage can be controlled by modulation index. 

Waveforms are as shown in below figure.
Due to the characteristic of sine wave, the pulse width of the wave cannot be changed with variation in the modulation index in SPWM technique. 
That is the reason, MSPWN technique is introduced. 
In this technique, the carrier signal is applied during the first and last 60-degree interval of each half cycle. 

In this way, its harmonic characteristic is improved. 
The main advantage of this technique is increased fundamental component, reduced number of switching power devices and decreased switching loss. 
The waveform is as shown in below figure.
(V) According to the Number of Levels at the Output
Regular Two-Level Inverter
Multi-level Inverter
These inverters have only voltage levels at the output which are positive peak voltage and negative peak voltage. 
Sometimes, having a zero-voltage level is also known as a two-level inverter.

These inverters can have multiple voltage levels at the output. 
The multi-level inverter is divided into four parts.
- Flying capacitor Inverter
- Diode-clamped Inverter

- Hybrid Inverter
- Cascade H-type Inverter
Every inverter has its own design for operation, here we have explained these inverter briefly to get an basic ideas about them.


tutorial/classes-of-power-amplifier-explained
Classes of Power Amplifiers
along with their advantages and disadvantages.
Classifications of Amplifiers using Letters
technique to drive the output load. 
Sometimes, improved version of traditional classes are assigned a letter to classify them as a different class of amplifier, like class G amplifier is a modified Amplifier class of Class B or Class AB amplifier.
So, if an amplifier provides 360-degree conduction angle, then the amplifier used complete input signal and the active element conducted through the 100% time period of a complete sinusoidal cycle.
Class A Amplifier 
In the below image an ideal class A amplifier is shown.
Other than these advantages, Class A amplifier is easy to construct with a single-device component and minimum parts count.
Also, due to high linearity, Class A amplifier provides distortion and noises. 
The power supply and the bias construction need careful component selection to avoid unwanted noise and to minimize the distortion.
Class B Amplifier 
, ie 180 degrees of the cycle. 
Two devices provide combined current drive for the load.
As two devices provides each half of the sinusoidal waves which are combined and joined across the output, there is a mismatch (cross over) in the region, where two halves are combined. 

This is because when one device complete the half cycle, the other one needs to provide the same power almost at the same time when other one finish the job. 
It is difficult to fix this error in class A amplifier as during the active device the other device remains completely inactive. 
The error provides a distortion in the output signal. 
Due to this limitation, it is a major fail for precision audio amplifier application.
Class AB Amplifier
Class AB amplifier uses intermediate conduction angle of both Classes A and B, thus we can see the property of both Class A and Class B amplifier in this AB class of amplifier topology. 
Same as class B, it has the same configuration with two active devices which conducts during half of the cycles individually but each device biased differently so they do not get completely OFF during the unusable moment (crossover moment). 
Each device does not leave the conduction immediately after completing the half of the sinusoidal waveform, instead they conduct a small amount of input on another half cycle. 

Using this biasing technique, the crossover mismatch during the dead zone is dramatically reduced.
But in this configuration, efficiency is reduced as the linearity of the devices is compromised. 
The efficiency remains more than the efficiency of typical Class A amplifier but it is less than the Class B amplifier system. 
Also, the diodes need to be carefully chosen with the exact same rating and need to be placed as close as possible to the output device. 

In some circuit construction, designers tend to add small value resistor to provide stable quiescent current across the device to minimize the distortion across the output.
Class C Amplifier
Maximum 80% efficiency can be achieved in radio frequency related operations
During this operation, the signal gets its proper shape and the center frequency became less distorted.

In typical uses, Class C amplifier gives 60-70% efficiency.
Class D Amplifier
Class D amplifier is a switching amplifier which uses Pulse Width Modulation or PWM. 
The conduction angle is not a factor in such case as the direct input signal is changed with a variable pulse width.

In this Class D amplifier system, the linear gain is not accepted as they work just like a typical switch which have only two operations, ON or OFF.
across the output.
in the A, B, AB, and C and D segment. 
It has smaller heat dissipation, so small heatsink is needed. 

The circuit requires various switching components like MOSFETs which has low on resistance.
It is a widely used topology in digital audio players or controlling the motors as well. 
But we should keep in mind that It is not a Digital converter. 
Although, for higher frequency, Class D amplifier is not a perfect choice as it has bandwidth limitations in few cases depending on the low pass filter and converter module capabilities.
Other Amplifier Classes
Other than the Traditional amplifiers, there are few more classes, which are class E, Class F, Class G, and H.
is a highly efficient power amplifier which uses switching topologies and works in radio frequencies. 
A single pole switching element and the tuned reactive network is the main component to use with the class E amplifier.

is high impedance amplifier in respect of the harmonics. 
It can be driven using square wave or sine wave. 
For the sinusoidal wave input, this amplifier can be tuned using an inductor and can be used to increase the gain.
is the further improved version of Class G.

Additional classes are special purpose amplifier. 
In some cases, the letters are provided by the manufacturer for signifying their proprietary design. 
One best example is Class T amplifier which is a trademark for a special type of switching Class D amplifier, used for Tripath’s amplifier technologies which is a patented design.


article/battery-management-system-bms-for-electric-vehicles
Battery Management System (BMS) for Electric Vehicles
January another battery failure occurred in a 787 flight operated by All Nippon Airways which caused an emergency landing at the Japanese airport. 
These two frequent catastrophic battery failures made the Boeing 787 Dreamliners flight to be grounded indefinitely which tarnished the manufacturer’s reputation causing tremendous financial losses.

After a series of joint investigation by the US and Japanese, the Lithium battery Pack of B-787 went through a CT scan and revealed that one of the eight Li-ion cell was damaged causing a short circuit which triggered a thermal runaway with fire. 
This incident could have been easily avoided if the Battery management system of the Li-ion battery pack was designed to detect/prevent short circuits. 
After some design changes and safety regulations the B-787 started flying again, but still the incident remains as an evidence to prove how dangerous lithium batteries could get if not handled properly.
Why do we need a Battery Management System (BMS)?
Also to get the maximum efficiency from a battery pack, we should completely charge and discharge all the cells at the same time at the same voltage which again calls in for a BMS. 
Apart from this the BMS is held responsible for many other functions which will be discussed below.
Battery Management system (BMS) Design Considerations
There are lot of factors that are to be considered while designing a BMS. 

The complete considerations depend on the exact end application in which the BMS will be used. 
Apart from EV’s BMS are also used wherever a lithium battery pack is involved such as a solar panel array, windmills, power walls etc. 
Irrespective of the application a BMS design should consider all or many of the following factors.
The primary function of a BMS is to maintain the lithium cells within the safe operating region. 

For example a typical Lithium 18650 cell will have an under voltage rating of around 3V. 
It is the responsibility of the BMS to make sure that none of the cells in the pack get discharged below 3V.
stage is used during which a constant voltage is supplied to the battery at a very low current. 
The BMS should make sure both the voltage and current during charging does not exceed permeable limits so as to not over charge or fast charge the batteries. 

The maximum permissible charging voltage and charging current can be found in the datasheet of the battery.
; we will discuss more on this later in the article. 
Measuring the values and calculating the SOC is also the responsibility of a BMS.
based on its usage history. 

This way we can know how much the mileage (distance covered after full charge) of the EV reduces as the battery ages and also we can know when the battery pack should be replaced. 
The SOH should also be calculated and kept in track by the BMS.
, say if one cell is at 3.5V while the other three is at 4V. 
During charging these three cells will attain 4.2V while the other one would have just reached 3.7V similarly this cell will be the first to discharge to 3V before the other three. 

This way, because of this single cell all the other cells in the pack cannot be used to its maximum potential thus compromising the efficiency.
In passive balancing the idea is that the cells with excess voltage will be forced discharge through a load like resistor to reach the voltage value of the other cells. 
While in active balancing the stronger cells will be used to charge the weaker cells to equalize their potentials. 
We will learn more about cell balancing later in a different article.

Adding to this the consumption of high current would further increase the temperature. 
This calls for a Thermal system (mostly oil) in a battery pack. 
This thermal system should only be able to decrease the temperature but should also be able to increase the temperature in cold climates if needed. 
The BMS is responsible for measuring the individual cell temperature and control the thermal system accordingly to maintain the overall temperature of the battery pack.

which it is supposed to protect and maintain. 
This might sound simple but it does increase the difficulty of the design of the BMS.
: A BMS should be active and running even if the car is running or charging or in ideal mode. 
This makes the BMS circuit to be powered continuously and hence it is mandatory that the BMS consumes a very less power so as not to drain the battery much. 

When a EV is left uncharged for weeks or months the BMS and other circuitry tend to drain the battery by themselves and eventually requires to be cranked or charged before next use. 
This problem still remains common with even popular cars like Tesla.
All the information collected by the BMS has to be sent to the ECU to be displayed on the instrument cluster or on the dashboard. 
So the BMS and the ECU should be continuously communicating most through the standard protocol like CAN communication or LIN bus. 

The BMS design should be capable of providing a galvanic isolation between the battery pack and the ECU.
, and interrupt these data when required. 
This also aids in providing after sales service or analyzing a problem with the EV for the engineers.
When a cell is being charged or discharged the voltage across it increases or decreases gradually. 

Unfortunately the discharge curve (Voltage vs time) of a lithium battery has flat regions hence the change in voltage is very less. 
This change has to be measured accurately to calculate the value of SOC or to use it for cell balancing. 
A well designed BMS could have accuracy as high as ±0.2mV but it should minimum have an accuracy of 1mV-2mV. 
Normally a 16-bit ADC is used in the process.

The BMS of an EV has to do a lot of number crunching to calculate the value of SOC, SOH etc. 
There are many algorithms to do this, and some even uses machine learning to get the task done. 
This makes the BMS a processing hungry device. 
Apart from this it also has to measure the cell voltage across hundreds of cells and notice the subtle changes almost immediately.
Building Blocks of a BMS
BMS Data Acquisition
We know that Battery packs are formed by connecting many cells in series or parallel configuration, like the Tesla has 8,256 cells in which 96 cells are connected in series and 86 are connected in parallel to form a pack. 
If a set of cells are connected in series then we have to measure voltage across each cell but current for the entire set will be same since current will be same in a series circuit. 

Similarly when a set of cells are connected in parallel we have to measure only the entire voltage since the voltage across each cell will be same when connected in parallel. 
The below image shows a set of cells connected in series, you can notice the voltage and temperature being measured for individual cells and pack current is measured asa whole.
Since a typical EV has a large number of cells connected together, it is a bit challenging to measure the individual cell voltage of a battery pack. 
But only if we know the individual cell voltage we can perform cell balancing and provide cell protection. 

To read the voltage value of a cell an ADC is used. 
But the complexity involved is high since the batteries are connected in series. 
Meaning the terminals across which the voltage is measured has to be changed every time. 
There are many ways to do this involving relays, muxes etc. 

Apart from this there is also some battery management IC like MAX14920 which can be used to measure individual cell voltages of multiple cells (12-16) connected in series.
Apart from cell temperature, sometimes the BMS also have to measure the bus temperature and motor temperature since everything works on a high current. 
The most common element used to measure the temperature is called a NTC, which stands for Negative temperature Co-efficient (NTC). 
It is similar to a resistor but it changes (decreases) its resistance based on the temperature around it. 

By measuring the voltage across this device and by using a simple ohms law we can calculate the resistance and thus the temperature.
Multiplexed Analog Front End (AFE) for Cell Voltage and Temperature Measurement
Measuring cell voltage can get complex since it requires high accuracy and might also inject switching noises from mux apart from this every cell is connected to a resistor through a switch for cell balancing. 
To overcome these problems an AFE ᾠAnalog Front end IC is used. 

An AFE has built-in Mux, buffer and ADC module with high accuracy. 
It could easily measure the voltage and temperature with common mode and transfer the information to the main microcontroller.
EV Battery Pack can source a large value of current upto 250A or even high, apart from this we also have to measure the current of every module in the pack to make sure the load is distributed evenly. 
While designing the current sensing element we also have to provide isolation between the measuring and sensing device. 

The most commonly used method to sense current are the Shunt method and the Hall-sensor based method. 
Both methods have their pros and cons. 
Earlier shunt methods were considered less accurate, but with recent availability of high-precision shunts designs with isolated amplifiers and modulators they are more preferred than the hall-sensor based method.
Battery state Estimation
SOC can be calculated using the cell voltage, current, charging profile and discharging profile. 
SOH can be calculated by using the number of charge cycle and performance of the battery.
We will discuss more on that later. 
Apart from that there are many other advanced and more sophisticated algorithms that are listed below.

Coulomb Counting method
Ampere-hour (Ah) method
Open-Circuit Voltage (OCV) method
Impedance / IR Measurement Method

Neural Network Fuzzy Logic
Support Vector Machine
State-Space Model Estimation using Kalman Filter
Coulomb Counting Technique
The formula for the same is given below.
SOC = Total Charge Input / Maximum Capacity
requires some mathematical approach. 
The total charge input is nothing but the product of the current and time, but the value of current varies based on time and hence we have to use current integration method to determine the Total charge Input. 

Discrete values of current are taken at regular internal and the integral of these values will give us the value of Total Charge Input.
For understanding purpose if we consider that the value of current is constant say 2A for 4 hours then the value of Total charge input will be 8Ah and if the maximum capacity of the battery is 25Ah then the SOC value is simply ((2*4)/25) 32%. 
But this method is not very reliable because the maximum capacity of the battery will get reduced as the battery ages. 
Hence many other algorithms were developed.
Battery Modeling
To use any of the above-discussed algorithms or to verify if your BMS is working as expected we need to develop a mathematical model for our battery pack.
A typical battery pack takes about 6 hours to get charge and another 6 hours to get discharged. 
The voltage and current profile of the cells will be different during charging and discharging based on the load, age, temperature and many such conditions. 

It is not practically possible to charge and discharge a battery in all required condition for the entire life cycle of the Battery pack to check if the BMS is working as expected. 
This is why Battery model is developed. 
This model can act as a virtual battery (Hardware in loop) during the developmental stage of the BMS.
The accuracy of the SOC and SOH also depends on the accuracy of the battery model; hence it should always provide high fidelity and robustness. 

A typical usage of battery model is shown below using the below image
In an ideal Battery model, the input voltage should be equal to the output voltage and the error value should be zero. 
But in practical this scenario is hard to achieve since there are many parameters like temperature, age etc which can affect the system. 
There are many battery models available they can be broadly classified as Lumped-Parameter Model, Equivalent Circuit Model and Electro-chemical model out all three the Electro-chemical model is the most hard and most accurate model.
BMS ᾠThermal Management
A battery pack would drain faster if operated in higher or lower temperatures. 
To prevent this cooling systems are used in the battery. 
The Tesla for example uses liquid cooling where a tube is passed through the battery pack to get in contact with all the cells. 

A coolant like water or Glycol is then passed through the tubes. 
The temperature of the coolant is controlled by the BMS based on the cell temperatures. 
Apart from this the batteries also use air or chemicals to maintain the required temperature.
’s and Tool kits which could do the hardware pulling for you and you can use it without diving deep into all this. 

With every new EV in the market the BMS evolves to get much smarter and easy to use.

tutorial/pull-up-and-pull-down-resistor
Pull Up and Pull Down Resistor
What is Resistor?
Resistance is measured in Ohm with a sign of Ω.
What are Pull-up and Pull-Down Resistor and Why we need them?
ᾠbut it cannot be left floating.

So, in each case, the state gets changed as shown below.
Now, if we replace the High and Low value with the actual voltage value then the High will be the logic level HIGH (lets say 5V) and Low will be the ground or 0v.
does exactly opposite, it makes the default state of the digital pin as Low (0V).
instead we could connect the digital logic pins directly to the Logic level voltage or with the ground like the below image?

A pull-up resistor allow controlled current flow from supply voltage source to the digital input pins, where the pull-down resistors could effectively control current flow from digital pins to the ground. 
At the same time both resistors, pull-down and pull-up resistors hold the digital state either Low or High.
Where and How to use Pull-up and Pull-down resistors
By referencing the above microcontroller image, where the digital logic pins are shorted with the ground and VCC, we could change the connection using pull-up and pull-down resistors.

Suppose, we need a default logic state and want to change the state by some interaction or external peripherals, we use a pull-up or pull-down resistors.
Pull-up Resistors
like the image below-
It is connected with the logic voltage from the supply source of 5V. 

So, when the switch is not being pressed, the logical input pin has always a default voltage of 5V or the pin is always High until the switch is pressed and the pin is shorted to ground making it logic Low.
However, as we stated that the pin cannot be directly shorted to the ground or Vcc as this will eventually make the circuit damaged due to short circuit condition, but in this case, it is again getting shorted to the ground using the closed switch. 
But, look carefully, It is not actually getting shorted. 
Because, as per the ohms law, due to the pull-up resistance, a small amount of current will flow from the source to the resistors and the switch and then reach the ground.
Pull Down Resistor
Consider the below connection where pull-down resistor is shown with the connection-
Thus making the digital logic level pin P0.3 as default 0 until the switch is pressed and the logic level pin became high. 
In such case, the small amount of current flows from the 5V source to the ground using the closed switch and Pull-down resistor, hence preventing the logic level pin to getting shorted with the 5V source.

and various embedded sectors as well as for the CMOS and TTL inputs.
Calculating the Actual Values for Pull-up and Pull-down Resistors
we can see pull-up or pull-down resistors ranging from 2k to 4.7k. 
But what will be the actual value?

For various logic levels, various microcontrollers use a different range for the logic high and logic low.
If we consider a Transistor-Transistor Logic (TTL) Level input, below graph will show the minimum logic voltage for the Logic high determination and maximum logic voltage for detecting the logic as 0 or Low.
But at the 0.8V to the 2V, it is a blank region, at that voltage it cannot be guaranteed that the logic will be accepted as High or Low. 
So, for safe side, In TTL architecture, we accept 0V to 0.8V as Low and 2V to the 5V as High, which is guaranteed that Low and High will be recognized by the logic chips at that marginal voltage.

As per the ohms law, the formula is
V = I x R
R = V/I
, the V will be the source voltage ᾠminimum voltage accepted as High.

And the current will be the maximum current sunk by the logic pins.
So,
Rpull-up = (Vsupply ᾠVH(min)) / Isink
is the maximum current sinked by the digital pin.

But the formula has a slight change.
Rpull-up = (VL(max) ᾠ0) / Isource
is the maximum current sourced by the digital pin.
Practical Example
using the formula like this way-
will be,
More about Pull-Up and Pull-Down Resistors
Besides adding Pull-up or Pull-down resistor, modern days microcontroller supports internal pull up resistors for digital I/O pins which are present inside the microcontroller unit. 

Although in maximum cases it is a weak pull-up, means the current is very low.
Often, we need pull up for more than 2 or 3 digital input-output pins, in such case a resistor network is used. 
It is easy to integrate and provide lower pin counts.
Pin 1 is connected with the resistor pins, this pin needs to be connected at VCC for Pull-Up or to the Ground for Pull-down purposes. 

By using this SIP resistor, individual resistors are eliminated thus reducing the component counts and space in the board. 
It is available in various values, ranging from few ohms to kilo-ohms.

article/all-you-want-to-know-about-electric-vehicle-batteries

All you want to know about Electric Vehicle Batteries
and what are the vital parameters associated with batteries that has to be taken care of.
What is inside an Electric Vehicle Battery Pack?
being ripped apart to cell level from its Pack.

To attain such high voltage and Ah Rating Lithium cells are combined in series and parallel combination to form modules and these modules along with some protection circuits (BMS) and cooling system are arranged in a mechanical casing collectively called as a Battery Pack as shown above.
Types of Batteries
While most cars uses Lithium Batteries, we are not only limited to it. 
There are many types of battery chemistry available. 

Broadly batteries can be classified into three types.
These are non-rechargeable batteries. 
That is it can convert chemical energy to electrical energy and not vise-versa. 
An example would be the Alkaline batteries (AA,AAA) use for toys and remote controls.

These are the batteries in which we are interested in for electrical vehicles. 
It can convert chemical energy to electrical energy to power the EV and also it can convert Electrical energy to Chemical energy again during the charging process. 
These batteries are commonly used in mobile phones, EV’s and most of the other portable electronics.
These are special type of batteries used in very unique application. 

As the name states the batteries are kept as reserve (standby) for most of its life time and hence have a very low self-discharge rate. 
Example would be Life vest batteries.
Basic Chemistry of a Battery
As told earlier there are many different chemistries available for batteries. 

Every chemistry has its own pros and cons. 
But irrespective of the type of chemistry there are few things that are common for all batteries let us take a look at them without getting much into its chemistry.
The Cathode is the positive layer of the battery and the anode is the negative layer of the battery. 
When a load is connected to the battery terminals, current (electrons) flow from Anode to Cathode. 

Similarly when a charger is connected to the battery terminals the flow of electrons is reversed, that is from Cathode to Anode as shown in the figure above.
should take place. 
Sometimes also called as Redox Reaction. 
This reaction takes place between the Anode and Cathode of the battery through the electrolyte (separator). 

The Anode side of the battery will be willing to gain electrons and hence an Oxidation reaction will occur and the Cathode side of the battery will be willing to loose electrons and hence Reduction Reaction will occur. 
Because of this reaction ions are transferred from the Cathode to the Anode side of the battery through separator. 
As a result there will more ions accumulated in the Anode. 
To neutralize this Anode has to push the electrons from its side to the Cathode.

But the Separator only allows flow of ions through it and blocks any electron movement from the Anode to Cathode. 
So the only way battery can transfer the electrons is through its outer terminals, this is why when we connect a load to the terminals of battery we get a current (electrons) flowing thought it.
Lithium Battery Chemistry Fundamentals
We will get into more of these parameters later in this article. 

But one common thing you can notice here is that Lithium is present in all batteries. 
This is mainly because of the electron configuration of the Lithium. 
A neutral Lithium metal atom is shown below.
It has an atomic number of three meaning three electrons will be around its nuclease and the outmost shell has only one valence electron. 

During reaction this valance electron is pulled out thus given us one electron and a lithium ion with two electrons forming a lithium ion. 
As discussed earlier, the electron will flow as current through the outer terminals of the battery and the lithium ion will flow though the electrolyte (separator) during the redox reaction.
Basics of Electrical Vehicle Batteries
Now we know how a battery works and how it is used in an Electric Vehicle, but to proceed from here we need to understand some basic terminologies that are commonly used when designing a battery pack. 

Let us discuss them‐󋈍
of a battery. 
This does not mean the battery will provide 3.7V across its terminals all the time. 
The value of voltage will vary based on the capacity of the battery. 

We will discuss more on this later.
For example a 2Ah battery can give 2A for one hour, the same battery will give 1A for 2 hours and if we take 4A from it, the battery will last only 30 minutes.
Run time = Ah Rating / Current rating
The above formulae does not hold true for all cases but should give you a rough idea of how long your battery will last. 

You cannot expect to draw 30A form a 2Ah battery and expect it to last 3.6 minutes. 
There are limits for maximum current that you can draw, and there will also be some losses in the process which will always reduce of runtime. 
Also no EV will consume a constant current, so determining how long your EV will run on this battery is not an easy task.
“When should I stop using battery?ᾼ/em>
The cut-off voltage is the minimum voltage of a battery below which it should not be used. 
Say for a lithium cell with 3.7V its cut-off voltage will be somewhere around 3.0V. 
This means that under no circumstances this battery should be connected to load when its voltage goes below 3.0V. 
The value of cut-off voltage of a battery can be found in its datasheet.

This will damage the battery affecting its capacity and lifespan. 
Over discharging a battery will disturb the chemistry of a battery which might lead to smoking or fuming of batteries.
“When should I charge a battery?ᾼ/em>
While cut-off voltage is the minimum voltage of a battery, Max. 

Charge voltage is the maximum voltage that a battery can reach. 
When we charge a battery its voltage gets increased, the value of voltage at which we should stop charging is called as the max. 
Charge voltage for a lithium cell with 3.7V nominal voltage the maximum charge voltage will be 4.2V. 
This value can also be found in the datasheet.

Overcharging will also damage the battery permanently and might also lead to fire hazards.
The OCV of a lithium battery should always be between 3.0V to 4.2V for a healthy battery. 
The Cut-off voltage and max. 
Discharge voltage is measured during the open circuit condition.

The value of OCV and Terminal voltage will not be equal, because when a load is connected and current is drawn form a battery its voltage tends to decrease based on the amount of current drawn.
“How much current can I get from a battery?ᾼ/em>
This is another important rating when it comes to batteries. 
This rating is closely associated with the Ah rating of a battery. 

The C-rating of a battery helps us to know what is the maximum current that can be drawn from a battery. 
For example if a battery is said to be 2Ah @ 8C. 
Then it means that a maximum of (8*2) 16A can be drawn from the battery and it would last for 7.5 minutes. 
We did the calculations for this earlier. 

A battery will be at the maximum of its efficiency during lower C ratings. 
An application in which the battery size is small but current draw is very high (example drones) requires high C rating batteries.
C-rate = Current / Ah Rating
Every component has its own resistance, the capacitance has it in the name of capacitive reactance and the inductor has it in the name of inductive reactance. 

Similarly the battery also has some resistance in between the anode and cathode terminals internally. 
This resistance is called as the internal resistance, sometimes also called as Internal Impedance.
Like all resistors these also contribute to losses by dissipating heat, so for an ideal system the internal resistance should be zero. 
In practical it is not possible to design a battery with zero IR (Internal resistance) so it should be made as low as possible. 

The value of IR is not fixed parameters it varies based on the capacity and age of the battery.
is also the same but it also considers the time into account. 
It tells us how quick the energy can be obtained from the battery.
is also the same but it also considers the time into account. 

It tells us how quick the energy can be obtained from the battery.
The Battery pack of EVs are rated in kWh (Kilo-Watt hour). 
This gives an idea of how long (mileage) the EV will run. 
It is similar to Ah rating but here we consider both voltage and current into account. 

For example the Tesla has 60-100 kWh battery meaning it can supply 60W power for 3 hours.
A battery losses some of its capacity even when it is ideal. 
This cannot be avoided due to its chemical properties but can be designed to minimize this. 
The rate at which the battery loses its charge even when not connected to a load is called as self discharge.

There are still a lot of small terminologies that we might have missed but this sum up almost all the important terms that you should know when working with batteries.
Battery Management System (BMS)
Battery management system or BMS is considered to be the brain of a battery pack. 
It is a circuit combined with an algorithm that monitors the voltage, current and temperature of the cells in a battery pack and ensures performance and safety of the individual cells in a battery pack. 

It is also responsible for balance charging, SOC and SOH measurement of the cells and much other important functionality. 
Let us look into what they do.
“How to find the amount of charge left in battery?ᾼ/em>
Imagine how hard it is to your phone when it has no information about battery percentage.

We will discuss how this is done in a separate article.
SOC = Total charge Input / Maximum Capacity
The further it ages the lower will be health of the battery.
for example in a pack of four 18650 cells connected in series the voltage across all the cells should be same else cell with lower voltage will be over discharged and the cell with higher voltage will be over charged. 

To prevent this BMS performs something called Cell balancing, it detects the cells with higher voltages and discharges them till the potential matches with its neighbors.
The Tesla model S has a liquid cooling system (Glycol) inside the Battery Pack which is controlled by the BMS. 
The coolant not only cools the battery but also heats it up to nominal temperature if required during the winters.
With this we have reached the end of the article but defiantly not the end with what can be learned about EV batteries. 

So if you wanna be an expert this is where you just get started. 
There is so much more to learn like battery Modeling, BMS design Battery Testing protocols etc. 
but let’s have all these for a different article. 
I believe this information was useful and has sparked the interest in you to know more about EV batteries and how it works. 

Let me know your thoughts in the comment section and let’s meet in another interesting article on Electric vehicle.

tutorial/vehicle-number-plate-detection-using-matlab-and-image-processing
Car Number Plate Detection Using MATLAB and Image Processing

Have you ever wonder that how an ANPR (Automatic Number Plate Recognition) system works? Let me tell you the concept behind it, the camera of the ANPR system captures image of vehicle license plate and then the image is processed through multiple number of algorithms to provide an alpha numeric conversion of the image into a text format. 
ANPR system is used at many places like Petrol Pumps, Shopping Malls, Airports, highways, toll booths, Hotels, Hospitals, Parking lots, Defense & Military check points etc.
into the text format. 
If you are new with MATLAB or image processing, then check our previous MATLAB projects:

Getting started with MATLAB: A Quick Introduction
Getting Started with Image Processing using MATLAB
First, let me brief you about the concept we are using for detecting number plates. 
There are three programs or ᾮmᾠfiles for this project.

Template Creation (template_creation.m)ᾠThis is used to call the saved images of alphanumerics and then save them as a new template in MATLAB memory.
Letter Detection(Letter_detection.m) ᾠReads the characters from the input image and find the highest matched corresponding alphanumeric.
Plate Detection(Plate_detection.m) ᾠProcess the image and then call the above two m-files to detect the number.
Template Creation
Now, open the Editor window in the MATLAB, as shown in the below image,
I suggest you to check the linked tutorial.
given at the end of this project.
%Alphabets

A=imread('alpha/A.bmp');B=imread('alpha/B.bmp');C=imread('alpha/C.bmp');
D=imread('alpha/D.bmp');E=imread('alpha/E.bmp');F=imread('alpha/F.bmp');
G=imread('alpha/G.bmp');H=imread('alpha/H.bmp');I=imread('alpha/I.bmp');
J=imread('alpha/J.bmp');K=imread('alpha/K.bmp');L=imread('alpha/L.bmp');

M=imread('alpha/M.bmp');N=imread('alpha/N.bmp');O=imread('alpha/O.bmp');
P=imread('alpha/P.bmp');Q=imread('alpha/Q.bmp');R=imread('alpha/R.bmp');
S=imread('alpha/S.bmp');T=imread('alpha/T.bmp');U=imread('alpha/U.bmp');
V=imread('alpha/V.bmp');W=imread('alpha/W.bmp');X=imread('alpha/X.bmp');

Y=imread('alpha/Y.bmp');Z=imread('alpha/Z.bmp');
%Natural Numbers
one=imread('alpha/1.bmp');two=imread('alpha/2.bmp');
three=imread('alpha/3.bmp');four=imread('alpha/4.bmp');

five=imread('alpha/5.bmp'); six=imread('alpha/6.bmp');
seven=imread('alpha/7.bmp');eight=imread('alpha/8.bmp');
nine=imread('alpha/9.bmp'); zero=imread('alpha/0.bmp');
%Creating Array for Alphabets

letter=[A B C D E F G H I J K L M N O P Q R S T U V W X Y Z];
%Creating Array for Numbers
number=[one two three four five six seven eight nine zero];
NewTemplates=[letter number];

save ('NewTemplates','NewTemplates')
clear all
This function is used to call the images from the folder or from any location of the PC into the MATLAB. 
Let’s take an example from the above code:

A=imread('alpha/A.bmp');
is the file name.
%Creating Array for Alphabets
letter=[A B C D E F G H I J K L M N O P Q R S T U V W X Y Z];


%Creating Array for Numbers
number=[one two three four five six seven eight nine zero];
NewTemplates=[letter number];

save ('NewTemplates','NewTemplates')
clear all
, in a new editor window.
Letter Detection
, this attached zip files also contains other files related to this Number plate detection project.
function letter=readLetter(snap)
load NewTemplates
snap=imresize(snap,[42 24]);

rec=[ ];
for n=1:length(NewTemplates)
    cor=corr2(NewTemplates{1,n},snap);
    rec=[rec cor];

end
ind=find(rec==max(rec));
display(find(rec==max(rec)));
% Alphabets listings.

if ind==1 || ind==2
    letter='A';
elseif ind==3 || ind==4
    letter='B';

elseif ind==5
    letter='C'
elseif ind==6 || ind==7
    letter='D';

elseif ind==8
    letter='E';
elseif ind==9
    letter='F';

elseif ind==10
    letter='G';
elseif ind==11
    letter='H';

elseif ind==12
    letter='I';
elseif ind==13
    letter='J';

elseif ind==14
    letter='K';
elseif ind==15
    letter='L';

elseif ind==16
    letter='M';
elseif ind==17
    letter='N';

elseif ind==18 || ind==19
    letter='O';
elseif ind==20 || ind==21
    letter='P';

elseif ind==22 || ind==23
    letter='Q';
elseif ind==24 || ind==25
    letter='R';

elseif ind==26
    letter='S';
elseif ind==27
    letter='T';

elseif ind==28
    letter='U';
elseif ind==29
    letter='V';

elseif ind==30
    letter='W';
elseif ind==31
    letter='X';

elseif ind==32
    letter='Y';
elseif ind==33
    letter='Z';

 %*-*-*-*-*
% Numerals listings.
elseif ind==34
    letter='1';

elseif ind==35
    letter='2';
elseif ind==36
    letter='3';

elseif ind==37 || ind==38
    letter='4';
elseif ind==39
    letter='5';

elseif ind==40 || ind==41 || ind==42
    letter='6';
elseif ind==43
    letter='7';

elseif ind==44 || ind==45
    letter='8';
elseif ind==46 || ind==47 || ind==48
    letter='9';

else
    letter='0';
end
end

loop is used to correlates the input image with every image in the template to get the best match.
ᾠis created to record the value of correlation for each alphanumeric template with the characters template from the input image, as shown in the below code, 
cor=corr2(NewTemplates{1,n},snap);
statement.

Now, after completing with this open a new editor window to start code for the main program.
Number Plate Detection
close all;
clear all;

im = imread(' Number Plate Images/ image1.png');
imgray = rgb2gray(im);
imbin = imbinarize(imgray);
im = edge(imgray, 'prewitt');

%Below steps are to find location of number plate
Iprops=regionprops(im,'BoundingBox','Area', 'Image');
area = Iprops.Area;
count = numel(Iprops);

maxa= area;
boundingBox = Iprops.BoundingBox;
for i=1:count
   if maxa<Iprops(i).Area

       maxa=Iprops(i).Area;
       boundingBox=Iprops(i).BoundingBox;
   end
end   

im = imcrop(imbin, boundingBox);
im = bwareaopen(~im, 500);
 [h, w] = size(im);


imshow(im);
Iprops=regionprops(im,'BoundingBox','Area', 'Image');
count = numel(Iprops);
noPlate=[];

for i=1:count
   ow = length(Iprops(i).Image(1,:));
   oh = length(Iprops(i).Image(:,1));
   if ow<(h/2) & oh>(h/3)

       letter=Letter_detection(Iprops(i).Image);
       noPlate=[noPlate letter]
   end
end

Basic commands used in above code are mentioned below:
ᾠThis command is used to open the image into the MATLAB from the target folder.
–This command is used to convert the RGB image into grayscale format.
ᾠThis command is used to Binarize 2-D grayscale image or simply we can say it converts the image into black and white format.

ᾠThis command is used to detect the edges in the image, by using various methods like Roberts, Sobel, Prewitt and many others.
ᾠThis command is used to measure properties of image region.
ᾠThis command is used to calculate the number of array elements.
ᾠThis command is used to crop the image in the entered size.

ᾠThis command is used to remove small objects from binary image.
,
Iprops=regionprops(im,'BoundingBox','Area', 'Image');
area = Iprops.Area;

count = numel(Iprops);
maxa= area;
boundingBox = Iprops.BoundingBox;
for i=1:count

   if maxa<Iprops(i).Area
       maxa=Iprops(i).Area;
       boundingBox=Iprops(i).BoundingBox;
   end

end   
respectively.
(in the command window).
Iprops=regionprops(im,'BoundingBox','Area', 'Image');

count = numel(Iprops);
noPlate=[];
for i=1:count
   ow = length(Iprops(i).Image(1,:));

   oh = length(Iprops(i).Image(:,1));
   if ow<(h/2) & oh>(h/3)
       letter=Letter_detection(Iprops(i).Image);
       noPlate=[noPlate letter]

   end
end
Working of Vehicle License Plate Number Detection System using MATLAB 
as you can see in the below

code file is called when we process the image as shown in image below,
Now, click on the ‘RUNᾠbutton to run the .m file
MATLAB may take few seconds to respond, wait until it shows busy message in the lower left corner as shown below,
As the program start you will get the number plate image popup and the number in the command window. 

The output for my image will look like the image given below;

interview/log9-kartik-hajela-tells-how-ev-of-future-will-run-on-water-using-their-metal-air-batteries
Log9's Kartik Hajela tells us how the EV’s of future will run on Water using their Metal-Air batteries

and make them run for about 300km with just 1 liter of water. 
The battery is expected to be ready for commercial prototyping by as soon as 2020. 
How is it even made possible, you ask? Well.. 
we had the same question in mind until we approached Mr. 

Kartik with the following questions
What inspired you to start Log 9 Materials? How did it initially get off the ground?
Graphene is a material that has been available since 10 - 12 years but, it has not seen much of commercialization yet. 
Mr. 

Akshay Singhal and I, both are IIT Roorkee alumnus, Akshay is Materials engineer and I am a chemical engineer. 
While in college we came across a lot of other materials that were coming up and were saturated in terms of scope of improvement, so we realized the need for a new material with superior qualities than the others. 
This is when Graphene stuck us.
This resulted to our research on graphene, and to come up with our startup Log9 materials, which focuses on graphene and developed products out of it. 

This way we came up with our first graphene based filtration product, ‘Ppuffᾬ which got us incubated at the IIT Roorkee campus by TIDES. 
We raised our first funding last year with which we finally moved to Bangalore and set up our office there.
Graphene is the wonder material for Log9, what is it so special? Is a Graphene RevolutionUnderway?
Graphene has been proved, since its inception to be much more superior than other materials. 

But, then the cost is also equivalently high. 
Well, the properties that Graphene posses can be leveraged, but, there was a need to develop processes to manufacture this sort of graphene to make it commercially viable for the market. 
That is all Log9 is based upon, it develops processes to manufacture a certain type of graphene material for a particular application in an economical way so that it can actually see the light of market.
As the other materials have already reached their peak of efficiency and innovation, and there is a lot of revolution happening in the hardware and software. 

There is a need of new materials to support these advancements happening all across other spectrums. 
There is already lot of research happening in graphene and Log9 is commercializing it through different products. 
This way it will be true to say that Graphene revolution is underway.
Is there any interesting reason behind naming the company as “Log9 Materials᾿
Basically it is 10 to the power minus 9 that is 1 Nanometer. 
Now, because graphene is a subset of nanotechnology, and the nanotechnology is actually graphene because the thickness of the material is in NM. 
1 NM is equivalent to 10 to the power minus 9 so this, is how the company is named Log 9.
What are the Technology Developments that are currently being carried out at Log9 Materials?
Log 9 majorly works in two broad domains, filtration and energy.
In the filtration sector the first product was PPuF, which in itself was a Graphene based selective filter for the smoking application.
Log9 has their product in the Oil Sorbent domain wherein the material that they have developed will have higher absorption capacities going upto 4 times the conventional material at the same cost.
In the energy segment we are working on utilizing the material’s capabilities to create sustainable energy and reduce burden on natural resources. 

In the energy segment, log9 is working on Metal air battery, which is different from the normal lithium ion battery, as it runs on aluminum, water and air and is an energy generating technology. 
It is the major project which Log 9 is working upon.
The Metal-Air Battery claims to run Electric Vehicles by just using Water and Aluminium with a range of 300km. 
Can you tell us more about it?
The metal-air battery, concept is about to revolutionize the energy sector. 
It is powered by water, air and metal. 
This battery is a primary energy generation technology quite similar to a fuel cell. 
We are using Graphene to make the batteries commercially viable and economical.

Conventional lithium ion batteries store energy rather than generating the same. 
Thus if we take the example of an EV, the car has a range of 100-150 kms post which it has to be charged which in itself takes up to 5 hours on an average. 
Whereas this battery technology has 10x more energy density which will provide a range of more than 1000 km, post which the metal can be replaced within minutes. 
The energy generated is complete clean, zero emission and this is a truly environment friendly battery technology built with sustainable raw materials. 

The metal itself is recyclable once it has been used in the battery to generate energy.
So does that mean, running our cars on water is really going to be feasible in future?
running on water and aluminium. 
As Aluminium is a large energy density material, it has properties which alliance with this technology. 

Therefore, Aluminium and water can be the future for electric vehicle.
What does Graphene has to do with Metal-air batteries?
Basically, this metal-air technology battery has been there since quite some time, but hasn’t seen light of commercialization because of one thing, cost of the product. 
Log 9 is trying to work on that prospect by lowering the cost with the use of alternate material. 

we are replacing graphene with the usual raw materials used in this concept. 
Graphene is cost effective and it has almost similar properties, in fact, superior than other materials. 
Log9 is leveraging its material competency and lowering the cost of the battery to make it commercially viable
Since the battery runs on water? How and when should one charge it?
The battery is an energy generating technology which will need water to be replaced ( normal RO water) after around 300 kms and will need aluminium to change after around 1000 kms. 
So it does not need to be charged.
Will the form factor and weight of such Metal air battery be less than the lithium batteries?
The aim is to, if not less, then at par in size and weight with current lithium ion batteries so that it can fix inside the current design of cars as well.
Are these batteries stable by nature? Or do they require a dedicated management system like the existing Lithium batteries?
Just like any other battery vehicles the battery will require a Battery Management System to monitor the battery mostly.
It is totally eco-friendly and clean in nature without generating any toxic gases etc.
At what stage of development are these batteries currently in? Can you share us few pictures of the prototype?
We are currently optimizing the battery. 
POC has been done. 
We are optimizing the battery and are going through that product development cycle to make it feasible for the market.
The aim is to do commercial prototyping by 2020 and to make it cheaper than current battery technologies available for EVs.


article/top-10-common-issues-while-using-raspberry-pi
Top 10 Common Issues while using Raspberry Pi and Their Solutions
.

All set? Let’s dive in!
1. Boot Issues
(activity LED) is either “OFFᾠor permanently “onᾮ
The green light on the Raspberry Pi represents software activity, so when it is blinking at intervals, it means the Pi is working. 

Thus, when it’s off or not blinking, the first place you should check is where the PI’s software is housed; the SD card slot. 
Ensure that the SD card is correctly inserted. 
If things do not change, check the SD card to be sure it was properly flashed with the OS and that the files on it are not corrupted.
If you have data you will like to keep on the SD card, insert it into a PC and copy it out before formatting.
2. NOOBS OS Stuck on splash screen
When this error occurs, the Raspberry Pi's boot process gets stuck on the splash screen.
If this doesn’t work, try another SD card or the same SD card on another raspberry pi. 
If the problem persists after doing all this, it might save you more time to install Raspbian stretch or any other distro.
3. Unable to Access the Pi over SSH
, with the PI connected to a monitor, go to preferences, and then select Raspberry pi configuration.
in front of SSH.
and Insert the SD card back into the Raspberry Pi. 

You should now be able to access the PI over SSH.
4. Board goes off intermittently
and sometimes when the board is on, the power LED will be off.
The Raspberry Pi 3 for instance, requires a 5V, 2.5A power supply to function properly so anything short of that is likely to affect its performance. 

Although I have worked with 5V 1.5A on the PI but performance depends on the task to which the Pi is set. 
Essentially when this happens, check to ensure you are giving the Pi enough juice to stay awesome.
5. USB not Working
As the tag implies, this error describes scenarios where USB devices connected to the raspberry pi, are either not recognized by the Pi or do not work properly.

A bunch of things could be wrong here.
and it’s thus unable to power the USB device. 
So ensure your Pi is properly powered.
Test it with your PC or any other computer to be sure it is working correctly.

While this shouldn’t probably be a problem, for USB devices like your Keyboard and Mouse, the Pi might need to do some initialization especially if you are connecting it to the Pi for the first time. 
Weird solution but works at times.
lsusb –t
This should give you a list of USB devices connected to your pi as shown in the image below.

The list is quite well ordered and it should help you determine if your device is compatible or not.
It is important before starting any new project on the raspberry pi to run an update or upgrade. 
The reason for this is to ensure you have compatible and latest software running on your pi. 
This at times could be a reason for hardware not responding to specific commands as it should.
5. Keyboard Character Display Errors
on the keyboard especially the # key. 
This error, most times occurs as a result of the default UK keyboard configuration of the raspbian and NOOBS software.
This can be done by going to the raspberry pi’s config menu, under the Internationalization menu, select the keyboard setup menu and scroll down to select the keyboard layout that matches the country of origin/language of your keyboard.

If you are working with a display, go to preferences and select the mouse and keyboard settings.
Select a keyboard layout and on the new window select your keyboard layout.
6. Raspberry Pi Not Working with HDMI Based Display
So you could connect with your Pi via ssh but you can’t just seem to get it to work with a display over HDMI? There are two things to do;

Do a check on your HDMI cable
Connect the display to the Pi and select the correct mode (HDMI or VGA) on the monitor before powering your Raspberry Pi. 
It is important that your screen is turned on before powering the Pi.
7. Raspberry Pi Camera not working
I have discovered most people expect the Raspberry Pi camera to work straight out of the box and I’ve so often had to recommend this simple solution that it probably deserves a place on this list.
This should, however, be done after the PI has been updated and upgraded.
To do this, start by running the update and upgrade commands;
Sudo apt-get update

Sudo apt-get upgrade
Followed by;
Sudo raspi-config
This will be open the raspberry pi configuration window shown below.

Scroll down, select the camera and select Enable.
radio button in front of the camera.
You should now be able to get your feeds and pictures. 
If you are still unable to access the camera, try with a different connector strip and camera if that does not work.
8. Raspberry Pi Camera Blank or Black Capture
This describes a scenario where the Raspberry Pi would seem to have taken a picture but the image will appear blacked out.
to grab the latest software and fixes. 
Reboot after upgrading to effect changes.
9. Ethernet On WiFi Off
which has to be disabled if you want to use the Wi-Fi and Ethernet connections at the same time.
To do this, run;
sudo update-rc networking disable

Or 
sudo apt-get purge ifplugd
You should now be able to use both network options at the same time but do not forget the security loophole this could create as the Pi will behave like a router in this mode.
10. 

Trying to Change Password Hangs the Pi
This refers to a scenario where an attempt to change the password of the raspberry pi either hangs the pi or is rejected (i.e. 
new password not registered).
or there is some fluctuation in the output of the power supply. 

Fixing this is as easy as changing the power supply to your Raspberry Pi or plugging it to a different port on your PC.
section to get started with cool applications using Raspberry Pi.
Once faced an error that took days to resolve? Feel free to share them via the comment section.
Till next time.


article/selecting-the-right-iot-platform-for-your-solution
Selecting the Right Platform for your IoT Solution
ᾠin the Internet would be over 20.4 billion. 

But with the rate at which IoT solutions are currently being deployed around the world by businesses who are discovering how it could help optimize their processes, and by entrepreneurs who are disrupting existing markets and carving out new ones with diverse innovative solutions, It is probably safe to say that there would be a far greater number by 2020.
They provide a series of integrated services and infrastructure (data storage, connectivity etc.) generally required to connect "things" to the internet. 
They handle most of the project's heavy lifting, reducing the amount of work and investments required for deployment of solutions and have by far been one of the main reasons behind some of the most successful IoT solutions around.
and the factors to consider when making a choice between them.
Types of IoT platforms
(shown below).
Which (probably oversimplified) can be said to consist mainly of 4 modules;
The “thingsᾠ(physical/tangible hardware e.g smart switches)

Connectivity e.g WiFi, LoRa
Device cloud e.g AWS, ThingsWrox
Apps/Devices/APIs
module represents end devices which are usually also referred to as things. 

Based on this, we could categorize IoT platforms into four major types;
Hardware platforms
Connectivity Platforms
Device cloud platforms

End to End platforms
1. Hardware Platforms
which have special features that make them suitable for several IoT use cases. 
Examples include boards from Particle amongst others.
2. Connectivity Platforms
These are platforms focused mainly on how devices are connected to the internet using diverse low power, low-cost telecommunication mediums from NB-IoT to LoRa. 
Good examples include Sigfox, AirVantage, Hologram, and particle.
3. Device Cloud Platforms
4. End to End Platforms
(from particular industries to unique kind of clients) in which they operate. 
For example, platforms like the GE Predix and Honeywell IoT suite are tailored to serve users in the industry IoT market while platforms like BluePillar provides an energy-as-a-service platform which could be useful for energy-related projects. 
Seemingly general purpose platforms like AWS, and thingsWorx also exist and may be best for certain projects.
Factors to consider when selecting a Platform
% of data generated by IoT devices are currently not being used with the failure to use the right platform for deployment, being one of the chief causes. 
For IoT platforms, there is no "one size fits all" for any project. 
Careful considerations have to be made to ensure the platform being used is the best for the project.

Below are some of the factors you should look out for when selecting a platform;
Type of Service and Model
Compatibility (Architecture and Technology Stack)
Domain Expertise

Reliability
Connectivity
Scalability
Security

Device management and monitoring features
Integrations and Data handling
Support
Cost
1. Type of Service / Model
It is important to truly understand the offerings of platforms and determine how it fits into the goals of your project.
2. Compatibility
3. Domain Expertise
Domain expertise could be in terms of expertise around a particular IoT vertical or expertise in the service being provided. 
As mentioned above, certain IoT platforms are developed with a certain section of the IoT market in mind, if developing around that vertical, it may then be smart to choose platforms within that space. 
A good example will be choosing the GE predix or IBM Watson over Particle for the implementation of an Industrial IoT based solution. 
For expertise in the service being provided, it is important to ensure the platform provider has spent a good number of years within that space.
4. Connectivity
Compatibility of the answers to this question with your solution’s use case and your hardware especially is quite important. 
The communication mode must be one that works within your device's power budget and location constraints, while the data plan must be one that is cost effective based on the rate at which your devices upload and download data.
5. Reliability
How reliable is the platform? What are the chances of it failing? What happens when it fails? Can data be recovered? This and more are the questions to be asked around the reliability of the platform to be used. 
Get as many details as needed about the offerings of the platform around production level reliability before making a decision.
6. Scalability
to achieve the scale you envisage for your project.
7. Security
Security is no doubt a very important factor to consider when selecting a platform. 
You should know the measures the platform providers take to ensure the security of the platform, from regular updates to authentication and data encryption. 
The connected nature of IoT solutions makes them possible targets for diverse kind of attacks that could compromise your data and the overall essence of your project. 

This factor should be one of the first to consider.
8. Device management and monitoring features
IoT implementations usually involve the deployment of devices in places with limited access. 
This makes having a medium of monitoring and managing device health and status via an IoT platform an important feature. 

Some platforms are so robust for device management that they include features to push OTA firmware updates to devices. 
Ensure the platform is able to support all the monitoring and management features your device could require.
9. Integrations and Data handling
Device cloud platforms are essential for the collection of data, but most of those platforms have gone beyond that, implementing several features that enable data analysis and generation of actionable insights. 

For some platforms, this comes as an added cost while it is free for others. 
Asides data analysis, most of the data generated by IoT is used to serve diverse processes. 
Ensure the platform is capable of generating the kind of insights your project requires and the processes that will benefit directly from your IoT solution, can be integrated easily before making a decision.
10. 

Support 
You need to be sure of the kind of support you will be getting before going with any particular platform.
11. 
Cost
, place it side by side with the number of devices your solution will involve, the amount and frequency of data that will be generated and decide if that particular platform is best for you.
, having a sit down (or phone conversation) with sales representatives of the platforms you are considering is quite key. 
This will give you insights into their capabilities and future plans.


article/an-engineers-introduction-to-electric-vehicles
An Engineer's Introduction to Electric Vehicles (EVs)
, where there is already one Tesla car traveling beyond Mars as I write this article.
So in this article let’s break down an Electric Vehicle to its bones and flesh to learn about them.

Before we dive in I would like to mention that the term Electric Vehicle is a vast ground. 
Any locomotive that does not have a fuel tank is referred to as an Electric Vehicle. 
But in this article by Electric vehicle or EV in short, I am referring only to Electric cars, bus and trucks. 
Unless otherwise specified special EVs like segway, Airborne or waterborne EV’s are not within the scope of this article.
What makes an Electric Car?
An Electric Car is an automobile by itself and consists of many components and a large cluster of wires connecting them all. 
But there are few basic bare minimum materials for an Electric Car which is shown in the block diagram below.
Vital Parts of an Electric Car
The DC voltage from battery cannot be used to drive a motor so we need the controller which drives the motor, and the Transmission system transfers the rotational energy from motor on to the wheels through some gear arrangements. 
Let’s look into each Part in details to understand more on EV’s.
EV Batteries
but both of them are still in development stage and no commercial cars on the road use them. 

So let us focus only on Battery Operated EV in this article.
The complete battery anarchy consists of the Cell, Battery Module and Battery Pack.
Cell
These batteries are available in many different shapes like cylindrical, Coin, Prismatic and Flat type few of which are shown below.
Battery Module
So to get the higher voltage from 3.7v lithium cells, battery packs are used which are formed bycombining more than one battery together. 
When two batteries are connected in series their voltage ratings is added and when two batteries are connected in parallel their Ah rating is added. 
For example assume we have 3.7V 2000mAh Lithium batteries. 

If you connect two of these in series the resulting system is called a module and this module will have 7.4V 2000mAh. 
Likewise if we connect two of these in parallel the resulting module will be 3.7V 4000mAh.
Battery Pack
We will get deep into it later.

This image is of the Nissan Leaf cut half way for you to give an idea.
There is still tons of information to be covered on the batteries but for the sake of this tutorial let us wind it up with this.
Battery Management System (BMS)
, as we saw earlier there are many batteries in an EV and each battery has to be monitored to ensure safety. 

For Lead Acid batteries BMS is not mandatory although some people use it but for Lithium cells due to its unstable nature BMS becomes essential.
.
It is the duty of the BMS to measure both these parameters. 
How does this measuring take place is totally a different story and we will cover in a separate article.

BMS circuits are often complex, a simple 4 Cell Lithium BMS is shown in the picture below. 
Imagine the BMS of a car that has to monitor around 7000 cell.
Electric Vehicle Motors
, Brushed DC motors and AC Induction Motor. 

A more detailed article on EV motors will be covered later.
, these motors have a constant torque and fast response making it suitable for automotive applications. 
Apart from EV’s these motors are also used in wipers, power windows etc. 
The BLDC motor for EV can again be classified into the following two types
BLDC Hub Motors
In BLDC Hub type motor, the rotor of the magnet is the wheel itself, meaning there is no need of coupling arrangement since the rim of the wheel forms the motor. 
These motors are also called as the BLDC out runner motor. 
Advantage of this type of motor is that there is less mechanical loss and since there is no transmission unit cost and weight is reduced. 

Downside is that we cannot have gear ratio of high power motors due to size limitations. 
A BLDC hub motor of scooteris shown below. 
Almost all electric cycles and scooters you find on road uses such type of motors.
Another type of BLDC motors are the In-runner types. 

They are used in applications where a transmission unit is required. 
They are normally coupled along with a differential for 3-wheeled or 4-wheeled EVs. 
These motors look like normal motors with a shaft and the shaft rotates when the motor is powered. 
An In-runner type Motor of an E-rickshaw coupled with differential is shown below.

The Brushed DC motor also known as DC series motor was the preferable choice for all old Electric cars. 
These motors provide a lot of torque which could easily give a sporty feel to the EV. 
The pull/pick-up of the EV would be almost at par with an average conventional car that these motors were used by drag racers during then. 
But now after 2008, these motors are not much in use any longer the reason is DC motors cannot provide a constant torque under a varying load. 

Meaning cursing or climbing a hill with the car will be difficult. 
Also DC motors cannot start without a load that is it cannot self start due to its high initial current which might damage the motor itself. 
Today these motors are used in Golf carts commonly a picture of the same is shown below
front wheel, taken from Wikipedia.
Controller
every EV has its own controller that converts the DC voltage from the Battery to a suitable level for the Motors to run. 
It also controls the speed of the motor.
If motors are considered to the muscle of a car, controller is its brain. 

A controller is often a generic term and it might include other circuits like a DC-DC converter, Speed controller, Inverter etc. 
The DC-DC converter is used to power all the peripherals of the car like the infotainment system, Headlights and other low level electronic devices.
Apart from this the controller also takes care of regenerative braking. 
It is the process of converting kinetic energy into electric energy. 

That is when the EV runs down a slope the motor are rotating freely due to the kinetic energy, at this situation the motors can be made to act as a generator so that the power thus obtained can be used to charge the batteries. 
Most modern day EV’s have this but its performance and functionality is still debatable.
EV Chargers
Another important component in an EV which requires advancement is the Chargers. 

An average E-Car takes a minimum of 5 hours to get charge that combined with its very low mileage becomes a disaster. 
An average American drives more than 50km per day, in this scenario an EV which gives a rage of 90km for full charge has to get charged almost every day. 
This makes the charges a most used component.
It gets plugged into the AC mains and converts the AC to DC to charge the batteries. 

But there are more to add to it. 
Charging is a process in which the batteries and charger should coexist you cannot push current inside a battery if the battery is not ready to accept it. 
There are many types of chargers; the most common types are discussed below.
These are the most basic chargers and it is probably the one that you get along with your car. 

They take a long time to charge the batteries since they operate in 120V AC, They convert this 120V AC to DC and use it to charge the batteries. 
The current rating of the charger will also be low somewhere near 8-10 A, this means you will be sending less current and thus taking a long time to charge your batteries overnight. 
On the positive side, this method improves the life cycle of the battery since our charging current is less.
These are a bit faster that Level 1 charger, it depends on the manufacturer to provide you with Level 1 or Level 2 charger. 

Level 2 chargers operate on higher voltages like 240V or above and also have high current rating near 40A to 50A. 
This makes the car to get charged faster.
They can charge your car to 60% of its total capacity within 30 minutes. 
The downside is that since it is pushing a lot of current inside your battery like 100A for a Tesla (insane! Yes) the batteries inside would feel like taking a crash course all year. 

So eventually the life of the battery is reduced. 
Also most superchargers do not charge the batteries till 100% since more time will be required to charge the battery from 80% to 100%. 
A super charger station of Tesla is shown below.
I believe by now you have an overview of what an EV actually is and how it works. 

From here let us address few common questions that arise with EV in everyone’s mind.
Since electricity also comes from coal Power plant. 
Are electric Vehicles really Green? 
This question has been debatable while EV run in batteries the electricity to charge these batteries comes from power plant and about 61% of worlds electricity is produced from non-renewable resources like coal and gas according to a survey shown below.

Apart from this the batteries of the EV is made of harmful chemicals and when get disposed they again pollute the environment. 
Considering all this the EV might not be as eco-friendly as we thought it would be. 
Or is it?
Many experts agree on the conclusion that EVs are defiantly greener than conventional ICE vehicles. 

It is because of the following reasons.
Like EV’s are getting popular so are the renewable energy sector. 
We are slowly moving towards Wind and Solar for electricity generation and thus making the electricity generation process greener.
Many people do not consider this. 

The gasoline that you get in your gas station has been pumped, processed and transported from an oil-well elsewhere. 
All these process involve pollution at some level. 
On the other hand for EVs the electricity is transmitted from Power plant to your house through wires and this set-up is already established.
Another that is only possible with EVs is Electricity re-generation. 

This does not add much but still it has a small impact on making the EVs greener.
So to conclude EVs are sure to be a lot greener than ICE if we shift towards renewable energy for electricity production and practice safe disposal of batteries.
What is the difference between a Hybrid Vehicle and an Electric Vehicle? 
Some people tend to use the term Hybrid Vehicle and Electric Vehicle interchangeably which is not the case. 

Both have entirely different meaning. 
To put it in lay mans terms if the vehicle runs both on Electricity and gas then it is a hybrid vehicle, if it runs only on Electricity and cannot run on gas then it is called as Electric Vehicle. 
You can make sure if a car is EV by checking if it has a fuel tank, if there is not fuel tank then the car is surely an EV.
Both EVs and Hybrids have they own significance, A hybrid car can rule out the disadvantages of EV like fuel time, short travel range etc but since it has the hardware for both ICE and EV these cars are normally costly. 

Hybrids cars are normally aimed to increase the efficiency of a Car by leveraging a Motor to run the car at low speeds.

tutorial/getting-started-with-image-processing-using-matlab
Getting Started with Image Processing using MATLAB

is the most suitable to start with.
, here we will explain some basic operations like RGB to Gray, rotate the image, binary conversion etc. 
You can further make automated programs for noise removal, image clarity, filtering by using the functions explained in this tutorial.
Before proceeding further, if you are new to MATLAB you can check our previous MATLAB tutorials for better understating:

Getting started with MATLAB: A Quick Introduction
Interfacing Arduino with MATLAB - Blinking LED
DC Motor Control Using MATLAB and Arduino
Stepper Motor Control using MATLAB and Arduino

How to Plot Real Time Temperature Graph using MATLAB
In MATLAB, as always, there are two ways to perform any image processing algorithm, one is by directly entering the command in the editor/command window and other is by creating a GUI for the same. 
Here, we will show you both the methods to perform basic operations of image processing in MATLAB.
1. Image Processing by using MATLAB Editor Window
follow the link. 
Copy and paste the below code in the editor window,
a = imread('F:\circuit digest\image processing using matlab\camerman.jpg');
subplot(2,3,1);

imshow(a);
b = rgb2gray(a);
subplot(2,3,2);
imshow(b);

c = im2bw(a);
subplot(2,3,3);
imshow(c);
d = imadjust(b);

subplot(2,3,4);
imshow(d);
e = a;
e=rgb2gray(e);

subplot(2,3,5);
imhist(e);
imfinfo('F:\circuit digest\image processing using matlab\beard-man.jpg')
[height, width, colour_planes] = size(a)

%colormap('spring')
Below are few commands to perform some basic processing on uploaded image:
In variable ‘bᾬ we are converting the RGB image into grayscale intensity image by using the command rgb2gray(‘filenameᾩ and displaying it in plot on position ᾲᾮ
In variable ‘cᾬ we are converting the image into binary image or you can say in format of ᾰᾠ(black) and ᾱᾠ(white) by using the command im2bw(‘filenameᾩ and displaying it in plot on position ᾳᾮ

In variable ‘dᾬ we are adjusting or mapping the grayscale image intensity values by using the command imadjust(‘filenameᾩ and displaying it in plot on position ᾴᾮ
In variable ‘eᾬ we are plotting the histogram of the grayscale image by using the command imhist(‘filenameᾩ and displaying it in plot on position ᾵ᾮ For plotting the histogram you always have to convert the image into grayscale and then you will be able to see the histogram of that graphic file.
Imfinfo(‘filename with locationᾩ command is used to display information about the graphical file.
[height, width, colour_planes] = size(‘filenameᾩ command is used to display the size and color planes of a particular graphic file.

colormap('spring') is used to change the type of colormap of graphic file. 
Here, in my code I set this command as comment but you can use it by removing the percentage sign. 
There are many types of color in MATLAB like Jet, HSV, Hot, Cool, Summer, Autumn, Winter, Gray, Bone, Copper, Pink, Lines and spring.
by following the link.
2. Image Processing with MATLAB GUI
Creating MATLAB Graphical User Interface for Image Processing
guide
as shown in below image,

Now we have to choose number of pushbuttons (every pushbutton will perform different task) and one axis to display image.
To resize or to change the shape of the Pushbutton or Axes, just click on it and you will be able to drag the corners of the button. 
By double-clicking on any of these you will be able to change the color, string, tag and other options of that particular button. 
After customization it will look like this

of MATLAB. 
Edit the generated code to set the task for different pushbuttons. 
Below we have edited the MATLAB code.
MATLAB GUI Code for Image Processing
, is given at the end of this project. 
Further we are including the GUI file (.fig) and code file(.m)here for download, using which you cancustomize the buttons or Axes size as per your requirement. 
We have edited the generated code as explained below.
store the variable in the GUI so the variable will be accessible to one part of the GUI to the other part of the GUI.

a=uigetfile('.jpg')
a=imread(a);
axes(handles.axes1);
imshow(a);

setappdata(0,'a',a)
() in the GUI.



1.
uigetfile()
Upload Image
Click to import image from Disk
2.
rgb2gray()
RGB to Gray
Click to convert RGB image into grayscale
3.
im2bw()
Convert to Binary Image
Click to convert the image into binary
4.
-
RESET
Click to reset the image as original

5.
imhist()
Histogram
Click to see the histogram of the image
6.
imcomplement()
Complement Image
Click to check the complement image
7.
edge(filename,method)
Edge Detection
Click to detect the edges in the image
8.
imrotate(filename,angle)
Rotate Clockwise
Click to rotate the image into the clockwise direction

9.
imrotate(filename,angle)
Rotate Anti-Clockwise
Click to rotate the image into the anti-clockwise direction

a=getappdata(0,'a');
agray=rgb2gray(a);

axes(handles.axes1);
imshow(agray);
a=getappdata(0,'a');
abw=im2bw(a);

axes(handles.axes1);
imshow(abw);
a=getappdata(0,'a');
axes(handles.axes1);

imshow(a);
and then you will be able to see the histogram of that graphic file.
a=getappdata(0,'a');
ahist=a;

ahist=rgb2gray(ahist);
axes(handles.axes1);
imhist(ahist);
a=getappdata(0,'a');

acomp=a;
acomp=imcomplement(acomp);
axes(handles.axes1);
imshow(acomp);

and then you can able to detect the edges.
a=getappdata(0,'a');
aedge=a;
aedge=rgb2gray(aedge);

aedge=edge(aedge,'Canny')'
axes(handles.axes1);
imshow(aedge);
a=getappdata(0,'a');

aclock=a;
aclock=imrotate(aclock,270);
axes(handles.axes1);
imshow(aclock);

a=getappdata(0,'a');
aclock=a;
aclock=imrotate(aclock,90);
axes(handles.axes1);

imshow(aclock);
Run MATLAB GUI code for Image Processing
Now, click on the ‘RUNᾠbutton to run the edited code in .m file
MATLAB may take few seconds to respond, do not click on any GUI buttons until MATLAB is showing busy message in the lower left corner as shown below,

When everything is ready, import the image from the PC by clicking on the ‘Upload Imageᾠbutton. 
Now, you will be able to convert or rotate the image by clicking any button accordingly. 
Below table will show you the task we are performing on the click of any particular button:
The result on click of each button will give shown below,

You can even do advanced level of image processing with the Image Processing Toolbox which you can purchase from MATHWORKS official site, some of advance level operation are listed below:
Geometric operations
Block operations
Linear filtering and filter design

Transforms
Image analysis and enhancement
Binary image operations


interview/atomberg-founder-manoj-meena-tells-about-their-energy-efficient-fans
Manoj Meena Founder of Atomberg tells us how his sensors-less BLDC motor Fans are the most energy efficient fans of India.
, in which the company has cleverly engineered a Controller to drive the BLDC fans without sensors by just measuring their back EMF and Coil Inductance. 
Interested in their amazing work, we had few question to know more about the company and its products for which Manoj was generous enough to give the following answers.

I had passion for robotics and electronics since my college days, and was extremely involved into robotics activities and competitions—all this as a part of my curiosity-driven learning. 
Then, I founded Atomberg in 2012, for first three years I was bootstrapping in a project mode, developing data acquisition, motor control and process control systems. 
As the years passed, I realized that we were working in a not scalable project mode, so started thinking to build something scalable from our motor and electronics design expertise. 
In 2015, I came out with thought of making energy efficient and smart ceiling fan. 

With Sibabrata Das joined as co-founder and a small team of 5 member, we made our first prototype of BLDC motor for ceiling fan in April 2015, this was our turning point to foray into motor-based home appliances market in India.
which is inside IIT Bombay. 
In the initial 3 years incubation at SINE, IITB was really helpful for us to get a kick start of RnD activities. 
It was a good startup ecosystem and some exposure to the investor network. 

Also got good guidance from relevant faculties and had access to the various labs for initial development and prototype testing.
Atomberg fan runs on our revolutionary BLDC motors technology optimized for ceiling fan application. 
It consumes only 28W (65% saving) where ordinary fan consumes around 75-80W, this makes it to run almost 3 times longer on an invertor. 
Since motor runs on DC power inside, output of fan is constant even with input AC power variations. 

BLDC motors do not create any humming noise and run very cool. 
With 3 years warranty, our customers are saving up to INR 1200-1500 annually. 
So, they are not only recovering the complete cost of fan within warranty period but also saving afterwards. 
Saving of greater than INR 10,000 could be easily realized per fan in the lifespan of fan. 

Adding more to it, all our fans come with a smart remote with features like TIMER and SLEEP. 
A smart LED interface at bottom of fan gives a WOW factor to our user.
The Remote works with Simple IR Based technology. 
Remote is normal IR based and all fans could be controlled from a single remote. 

Our Remotes are compatible with all our Fans.
Our fan comes under brand name ‘Gorillaᾠstarting from INR 3000 ᾠ4200. 
You can get your ‘Gorillaᾠonline from Amazon, Flipkart, Paytm, Pepperfry, Atomberg website. 
We have few retail outlets in Mumbai, Pune, Ahmedabad and Chennai.

BLDC stands for Brushless Direct Current, as name says BLDC motor has no mechanical brush for commutation of the windings. 
Commutation is deployed by help of smart electronics which is responsible for sensing the magnet rotor position with respect to stator and controls the motor driving switches. 
Winding magnetic field react with field of permanent magnets on the rotor to develop the required torque. 
Like, induction motors there is no current flow in rotor, it has permanent magnetic field. 

As a result, rotor losses are negligible.
also measured.
) method is implemented using sensor less rotor position sensing techniques and commute the stator winding accordingly. 
FOC is small part of the AtomSENSE algorithm, a lot noise filtering and processing is required to capture the data accurately in real time. 

Motor control flow has various exception handling routine implemented to take care of exceptions like external loading from wind, fan halt, blade bending, motor wobbling, ambient heating (affects motor coil resistance), flux saturation etc. 
Protection handlers are other layer in also which ensures that the motor runs safely, protection from voltage surges, current surges in coil, peak power locking and heating etc is implemented. 
Supporting electronics hardware is also implemented wherever required. 
Motor phases are excited with smooth sinusoidal current profile generated by motor driver, this reduces harmonics which cause noise and power loss.

Today we use Ferrite magnets for ceiling Fans and neodymium for wall mounted fans. 
The reason is that Ferrite magnets are cost effective and easily available in India, this is a good choice in ceiling fans because there you will need more number of magnets of bigger size since the hub is bigger. 
Whereas the neodymium magnets form china are smaller yet powerful and hence can be used in places where the product has to be compact like the wall mounted fan with a smaller hub.
Apart from ceiling fans and wall mounted Fans Atmoberg has already started to work with Air Coolers. 

The other products that we are currently focusing on are Fan Motor based appliances like Air Coolers, AC, Pumps, Mixtures, Washing Machine etc could be targeted.
Then, at Navi Mumbai setting up initial production and developing supply chain took us another 6 months time. 
After that we have been continuously upgrading our product design to optimize cost, enhance performance and improve quality. 
At backend, we keep doing automation and assembly line upgrades to meet the sales demand.

One is getting the prototype ready because it take 6 months time, and then at the same time you have to make infrastructure ready for production for which you have to set up machinery and establish supply chain. 
There are two different activities here and it took around 6 months for each. 
We were lucky enough to get the prototype running in 6 month because of our earlier expertise in motors.
Pilot lot of first few hundred units was assembly in a much unorganized fashion by our RnD team only. 

This gave us good understanding of assembly flow and required machinery/ setups. 
Soon we build a full-fledged assembly line with trained operators. 
Most difficult part was to setup a robust and reliably supply chain and vendor base. 
Working capital management and managing cash flow in such industry was very new to us but we learned it in a hard way with time.

During the initial pilot, team was very small. 
There were only 7-8 R&D people and we had around 400 fans to be manufactured for which the customers were waiting. 
So our R&D team itself manufactured it, which gave us good understanding of the manufacturing process. 
This happened for the initial 6 months, but then the manufacturing set-up was established. 

Today we have lots of operators and machineries for dedicated tasks.
party vendors. 
Then we approached ceiling fan vendors who manufacture these fans in masses, and we handed our tool to them. 
For the Fan blade which is just a sheet metal, we developed a simple punching tool.

This is what happened initially but then now; to scale capacity and obtain good quality we had set-up our own dedicated vendors today.
For electronics components we had various EMS (Electronic Manufacturing Services) parties, we used the one that was available to us in Mumbai. 
Basically once the design of PCB and components is finalized, you hand them over to these parties for manufacturing and assembling. 
After that the boards were then tested and analyzed by our engineers before it gets into the product. 

We follow the same procedure even for bulk production since it makes a lot more sense.
We do lot of process RnD and automation activities to enhance capacity and quality. 
So, it is 50-50. 
Half my time is spent with R&D while the rest with Production.

Today we are the leading manufacturer of BLDC motors in India, we get very quick support from companies like TI, STM, Infineon and On-Semi etc. 
We are able to get quick samples, evaluation boards and supporting infra from their team for our RnD activities. 
For manufacturing, we deal with their authorized sales partners.

It requires a good experience of manufacturing processes and sufficient capital to deploy the plant. 
Initially it makes sense to outsource some of the components and understand the processes. 
Gradually process should be brought in-house one by one when you reach sufficient volume when it makes financial sense. 
In-house manufacturing also gives a better control over the product quality.

In the long term, we want to become the Tesla of Household Consumer Appliances by combining the virtues of energy efficiency and smartness in all our products. 
Currently, we are the number 1 player in BLDC ceiling fans in India. 
We have also launched pedestal and wall mounted BLDC fans recently. 
Looking at current growth and revenue, we are on track to have INR 500Cr revenue from fans by 2022-23. 

Since our core expertise is in motors, we are also exploring other appliances like coolers, air purifiers, air conditioners etc where we can use our super energy efficient BLDC motors.
For such abigimpact on energy efficiency and electricity saving I have got the following awards and recognition:
2017 by Govt of India.
organisedby 'WWF' (World Wildlife Fund)

in Energy Efficiency categoryorganisedby 'United Nations Industrial Development Organisation' held in San Fransisco, USA
in the startup ecosystem
category
category


tutorial/getting-started-with-simulink-in-matlab
Getting Started with Simulink in MATLAB: Designing a Model
What is Simulink?
software which is used for modelling, simulating and analyzing the dynamic systems. 
Simulink provides a Graphical User Interface (GUI) as block diagrams to build your model like you are building on using pencil and paper.
To understand Simulink you can consider a simple example,
Here, in the above example we are generating a sine wave from sine wave block and amplifying it by a gain factor which you directly check on Simulink by double clicking the scope block.
How to Launch Simulink in MATLAB?
To open the Simulink in MATLAB, you can just click on the Simulink button from the MATLAB menu bar, as shown in below image
Else, you can just use the command window to open Simulink. 
Just write ‘simulinkᾠin the command line and hit enter.

simulink
Below is the first window which appears after opening Simulink:
As you can see in the image there are different options to do different tasks, like you can create your template, blank model, blank library and many others.
looks like the image below.
Simulink Library Browser
Simulink Library Browser contain sinks, sources, connectors, linear and non-linear components. 
Simulink is far better than the other previous simulation packages that needs to formulate the equations into a program, while in Simulink you can choose the function and blocks and you just have to enter the values of the variable of the equations.
button from the Simulink menu, as shown below image

The other way to open the Simulink library browser is to type the below command in the command window. 
The command is case-sensitive so be careful while typing:
slLibraryBrowser
This is how the Simulink library browser looks, in which you can search for sinks, sources, connectors, linear and non-linear components.
Running Demo Model with MATLAB Simulink
Simulink already contains number of simple and advanced models of different types of systems like audio, communication, computer vision, DSP, real-time and many others, as you can see in the below image,
will appear, as shown in below image
, as shown in below image

You can also able to use or edit the demo model if you want to.
Starting the Debugger
Simulink Debugger is a tool of Simulink to locate or diagnose bugs in a model. 
Debugger helps you to check or run the simulation step by step and also displays the input, output and block states.

you just have to click on debug model in the simulation section of the Simulink menu bar, as shown in below image
just by typing the below command,
sldebug (‘model nameᾩ
Creating a Simulink Model for Signal Amplifier
in the command window.
from the Simulink, as shown in the below image
which takes an input and amplifies it by a gain factor.
in the command window. 

And, choose the required blocks and drag them into the Simulink window from library browser window, as shown in below image
After placing all the blocks into the Simulink window, you have to connect them according to the image shown below,
to ᾲᾬ as shown in below image
, you can set the value of amplitude of sine wave and gain factor by double clicking on the respective block.

given in the Simulink menu.
Wait till Simulink compile your model, which you can see in the bottom right corner of the window.
and you will be able to see both input and amplified waveform, as shown in image below,
As a result, if you observe the output waveform, it is amplified by a factor of 3.

Now, you can save your model and can also get a print out, the extension for Simulink design is ᾮslxᾠso keep an eye on extension while saving, generally it automatically takes the ᾮslxᾠextension.
Modelling a Dynamic Control System
You will be redirected to the help browser of the MATLAB, as shown in below image
:


article/10-most-common-mistakes-while-using-arduino
10 Most Common Mistakes while using Arduino
along with possible solutions to them.
1. Arduino Board not Recognized
This refers to a situation where an Arduino board, connected to a computer is not recognized by the computer. 
When this happens, the board is usually not listed under the port lists of the Arduino IDE and is sometimes labeled USB2.0 under the device manager.
Installing it is as simple as clicking the install button on the setup interface shown below.

With this done, you should now be able to locate the port to which the board is connected on the Arduino IDE.
2. Board not in Sync
ᾮ
ᾠon the Arduino. 

When this happens, there is a whole bunch of things that could be wrong. 
Here are some steps that could be taken to clear this error.
1. Ensure there is nothing connected to digital pins 0 and 1 on the Arduino (including shields).
2. Ensure the correct com port and board were selected under the tools menu.

3. Press the reset button on the Arduino couple of times and re-upload the code.
4. Disconnect and reconnect the Arduino to the PC.
5. Restart the Arduino IDE.
If none of the above works, it might be time for you to change the Arduino Board.
3. The code doesn't start on Power Reset
and in most cases, just reverts back to the blink sketch associated with the bootloader.
Just like the other problems treated there are a number of things that could cause this.
When the Arduino is switched on, the bootloader, in the first few seconds, listens for the computer to send it a new sketch for upload to the board. 

If no new sketch is received, after a short while, the bootloader will time out and run the last sketch uploaded to the board. 
If your code is sending serial data during the first few minutes, the bootloader will not time out and the last sketch uploaded to the board will not start.
If sending serial data as soon as the board comes on is an important part of your project, you may need to find a way to give it some delay to stop serial data from arriving immediately the Arduino comes on. 
If making adjustments will affect the task the project is to perform, then you may have to upload your sketch to the board using an external programmer, as the bootloader can be bypassed by them.

If the board doesn’t hang but returns to the Arduino blink sketch (Led on pin 13 blinks every now and then), a straightforward fix will be to flash the board with the Arduino bootloader, as the one on the board may have been corrupted.
4. Invalid Device Signature Error 
This error is displayed when an attempt is made to upload code, to a board, different from the one selected under the tools>board list on the Arduino IDE. 
This error usually occurs as a result of the device signature on the target board is different from that of the board selected on the IDE.

The solution to this error is as simple as ensuring the correct board is selected on the Arduino IDE. 
If this does not work, there might be a need to flash the microcontroller with the latest version of the Arduino bootloader.
5. Launch4j Error
The Arduino IDE sometimes takes a while before loading and when it loads, if you click on anything, it will display the Launch4J error as shown above. 

Launch4j is a tool used for wrapping Java applications (jars) in Windows native executable, allowing them to be used as a regular Windows program.
supplied with the Arduino IDE.
with a recent version.
6. Serial Port Already in Use 
(this is no longer an issue if using recent IDE versions) or when you try to launch the serial monitor when the Arduino is talking to another software or device via the serial port. 
Essentially, it occurs when you try to use the Arduino serial port for two different things at the same time.
If you are not sure of the particular software, unplug the Arduino. 
It should be ready to go by the time you plug it back.
7: Sketch Uploads Successfully but Nothing Happens
This error is similar to some of the other errors already treated above. 
For this error, the Arduino IDE will suggest the code has been uploaded successfully, but the board does nothing.
Ensure the board selected in the IDE is the same as the target board.

This could be as a result of the sketch size being larger than the board’s capacity. 
Check the sketch size and use some of the methods mentioned above to reduce the size.
Lastly, this error could occur when a noisy power supply is being used. 
Ensure the power supply is stable enough.
8. Unsatisfied Link Error
lying around on your PC, most likely from a previous install.
environment variables.
9. Sketch Too Large
of that particular Arduino board. 
The size of the flash memory of the Arduino Uno, for instance, is 32Kb with 2KB already being used by the Arduino bootloader. 
If you should upload a code with a size higher than 32Kb, the Arduino will display this warning.
Some of the tips for achieving this include;

Where possible, use integer data types in place of a float.
Where possible use the “constᾠqualifier when declaring variables.
Include necessary libraries only. 
Where possible, use the lightweight versions of the most important libraries.

Improve on the code generally. 
Develop algorithms that could help make your code shorter and generally lightweight.
, which has a larger flash memory compared to the Uno.
10. 

java.lang.StackOverflowError
When processing the sketch, the Arduino uses some regular expressions for processing and sometimes gets confused when it encounters certain strings related errors like missing quotes.
This error is solved by taking a second look at the code, especially the parts where string sequences are used. 
Ensure the quotes are complete, backslashes are rightly used etc.

o. 
Are you battling a particular error, feel free to drop a comment, hopefully, we can work through it together.
Next time.


interview/sensegiz-vp-rahul-kednurkar-explains-how-their-product-coin-leverages-iot-to-provide-end-to-end-solution
SenseGiz’s VP Rahul Kednurkar explains how their product COIN leverages IoT to provide end-to-end Solution
Rahul Kednurkar is the VP-Business Development of SenseGiz, with a Bachelor’s Degree on Industrial Production, and takes the responsibility for charting the go-to-market factors and planning market/business strategies for SenseGiz.
grabbed our attention, this candy sized device powered by a CR2477 lithium cell has a Temperature, Humidity and Vibration sensor inside it and is also connected to the could through IoT. 

Like an army of ants these tiny devices can be scattered over a large workspace to connect with each other forming a mesh network, to monitor and analyze people or assets. 
Adding to this, these devices can go upto 2 years without having to replace its battery. 
Thrilled by its abilities, we approached Rahul with few questions for which he was kind enough to give the following answers.
Once in 2011, Abhishek (Founder) had to take a train at London. 

He boarded the train, placed the luggage in the compartment and got off it to beat the boredom. 
By the time he re-boarded the train, the cops had come in on a routine check, noticed the unattended baggage and took it away and put it in lost and found center. 
That was when Abhishek contemplated a venture in lost and found space.
With just about 5 years since inception, we have developed a series of products. 

In fact we are very proud of repeatedly selling our previous generation of IoT products successfully in the US, Japan and several other countries over the last 3 years. 
We are also proud of the fact that all our products are designed, developed and manufactured in India for the world. 
We have an in-house team of engineers to design and develop these products. 
So far we have one patent granted for our product in India and also in the US, and we have filed 4 more patents for our new technology.

We did a primary and secondary research and spoke to various customers and stake holders and found out that:
Around USD 680 bn were lost per year due to improper storage of food, goods and various assets
About 300 hours per year per employee were lost per year just to track assets in manufacturing units and warehouses, and
Approx USD 14 bn were lost per year due to illegal intrusion.

With these in mind, our team started working on this problem for around 8 to 10 months and in 2018 we came up with a solution using which:
Storage losses were reduced by 50%
Reduction in asset tracking time was reduced by 70%
Efficiency of the employees was increased by 50%, and

And with a payback period of 10 to 14 months.
Through our product solution COIN, we have created a proprietary low powered point to point mesh network of tiny low-cost sensor nodes. 
The mesh network is based on top of Bluetooth 5.0 and has an effective communication speed of 1 Mbps, suitable for high speed and high data applications with self-learning and self-healing capabilities.
Using our solution, hundreds or thousands of assets and people can be tracked in real time in a given workplace such as a shop floor, manufacturing unit or warehouse etc. 

Also, geofencing can be set to make sure that the assets do not enter or leave the assigned areas. 
The complete activities can be seen and can be controlled in real time on our dashboard.
Each Coin sensor has a temperature, humidity, motion and vibration sensor on-board. 
All these together enable each Coin to perform multiple tasks based on the customer's choosing. 

One can also use this to monitor condition of any assets such as vibration. 
The Coin nodes are fully customizableby the user/admin from the cloud. 
One can either set thresholds or get alerts by multiple means if those have crossed, or set up user defined data streaming intervals (suited for enterprise applications).
There are no limitations as such, however one gateway can connect upto 100 COINs. 

One can have multiple gateways and any number of COINs connected to one another. 
Each COIN has an effective range of 150 feet per node. 
COIN to Gateway communication happens over bluetooth and the effective range between them is 150 feet. 
Our long range wireless gatewayhas WiFi and Bluetooth embedded to make communication with server and other COIN devices. 

We also provide Ethernet gateway in case customer prefers to use them. 
Ethernet gateways are more convenient for remote location where WiFi connections are unavailable.
The battery lasts upto 1-2 years. 
It again depends on the how COINs are configured. 

One can set threshold intervals, a higher and a lower one where the alert is generated only when the threshold is crossed or stream data at regular interval of time.
We have other versions of COINs which is powered by external power supply and D type batteries. 
With the D types batteries, COIN can now last upto 3-4 years.
On the hardware side COIN has Powerful ARM Cortex-M3 with 128kB of in system programmable flash and 8kB of SRAM, 2.4-GHz RF Transceiver Compatible with Bluetooth Low Energy (BLE) 4.2 Specification and IEEE 802.15.4 PHY and MAC, AES-128 Security Module, UART, ECOPACK, RoHS and “Greenᾠcompliant, 2× SSI (SPI, MICROWIRE, TI).

On the cloud side, AWS hostingwithUbuntu 14.04Os, Programming language-PHP (Slim PHP framework-2), LAMPPenvironment to run PHP project, PostgreSQLdatabase-Which will come with LAMPP,phpMqttas a client.eMQTT-It is a MQTT broker to handle commands between Gateway and clients, Web panelfrontend coded usingHTML5, CSS3, Jquery.
We would like to share few case studies here:
A Government organization that supplies electricity to the city wanted to do the predictive maintenance of transformers and to obtain alerts before any failure.
COINs were placed on the transformers and fins to monitor the temperature and vibrations. 

Here we do predictive maintenance before the failure occurs. 
Different thresholds were set so that the management gets an alert when the temperature andvibration crosses set threshold values and take immediate action. 
COINs can also work when dipped completely inside the oil.
An enterprise with 1.5 lakh sq. 

ft. 
workspace wanted an alert and pin point location whenever a forklift vehicle bumps into the racks while material handling.The enterprise also needed to monitor the pin point location of its 1000+ employees which would help them at the time of emergency situations. 
Also, food stored in the warehouse was getting damaged due to abrupt temperature variations and the inability of the enterprise to record it correctly.
A Large number of coins were installed at certain locations on the racks. 

Whenever an incident occurs, coin detects vibrations and sends real time data to the user. 
Additionally, SAFRs worn by employees helped the enterprise monitor their pin point location. 
Temperature sensor in our coins send real time data from various warehouse locations and helps the enterprise to keep a record and find actual reason for these temperature variations.
A government organization wanted real time data on trespassing and intrusion activity in an area where no person was allowed. 

The entire perimeter was to be covered against such activities and hence the solution was required to be very cost effective and efficient. 
The organization also demanded no false alarms due to rains, winds etc. 
The perimeter was covered with our Coins. 
Sensors in the coin would detect intrusion activity and send real time notification to its users, which helped them take appropriate action. 

Hence a perfect fit in such cases.
Due to its small size, the coin is not visible to the intruders. 
Real time data analysis can distinguish between humans (walking, running, crawling or tunneling) and other objects like vehicles, animals, etc.
It feels great to win prestigious awards like Indian National Entrepreneurship Award from Govt of India and CISCO Launchpad award. 

It surely gives a lot of encouragement to the entire team to work harder and get more products andsolutions rolling. 
The technical team is greatly benefited in terms of motivation and support. 
It also puts us on the global map of visibility and helps us gain the customer’s trust.
Apart from NEAS and Cisco award, we are chosen as one of the iconic IoT start-ups under the NASSCOM ᾠGovt of India IoT Centre of Excellence and received most promising IoT startup award by IESA. 

Recently we have also won the defEnnovation Award in the MSME Category at ELCINA Strategic Electronics Summit 2018. 
Recently we were the winners of IoT India Congress-2018 Top Start up Awards.
Security is handled in 3 parts- 128 bit AES encryption for device to device communication, secure MQTT connection with 2 factor authentication for device to cloud and vice versa and industry standard security for the data stored on the cloud. 
We are compliant with the security norms of various countries and working with well known customers have helped us maintain the highest standards.

Currently, our company is a team of 18, spread across engineering, sales, marketing and admin roles with all products designed in-house. 
We have the R&D centre in Belgaum, where our technical team is placed; Bangalore from where our business development team operates. 
We have an office in San Francisco.
Yes, we have our R&D centre in Belgaum. 

All our products are designed, developed and manufactured in India. 
We are strong believer in the Make in India initiative. 
Pros of having a manufacturing unit in India are lesser turnaround time as compared to foreign manufacturing units. 
Skilled engineers are available for product development in India, which is crucial. 

We are not giving our IP outside India.
Cons being, the manufacturing lead time is lesser in some countries as compared to India. 
The production cost is less in South East Asian Countries.
is the next big thing. 

It will increase flexibility in manufacturing, along with mass customization, better quality, and improved productivity. 
It thus enables companies to cope with the challenges of producing increasingly individualized products with a short lead-time to market and higher quality. 
Intelligent manufacturing plays an important role in Industry 4.0. 
Typical resources are converted into intelligent objects so that they are able to sense, act, and behave within a smart environment.

We feel India is ready for Industry 4.0. 
We can see people adopting latest technologies right from tracking, real time asset monitoring, robotics, intelligent manufacturing etc. 
India has now been ranked sixth among the world’s 10 largest manufacturing countries. 
India is no exception to this global trend and is steadily increasing its share of Global Manufacturing. 

All leading countries are embarking on major initiatives to promote manufacturing by adopting the advancements in Internet and Information Technology arenas.
We used all of our experience of making Bluetooth low energy products to overcome this challenge. 
The next challenge was to take this to mass production. 
As we already have experience of doing this for our earlier products, we were confident that we will be able to overcome this challenge and we did so.

They need to educate themselves with the right tools. 
There is a big gap between what the market needs and what is being taught in the institutions. 
For instance, while IoT is proving to be the next growth driver for the industry, the curriculum does not reflect it. 
There are so many startups that are into IoT, budding engineers must try to get internship in these startups to get hands-on on what skilland knowledge etc is actually required.

Be different! They must posses problem solving skills and must look at an issue from the solution point of view rather than considering it as a problem. 
Some people like challenges; it excites and motivates them. 
I would advise them to consider the burning issues at the moment and solve them. 
That way a task is accomplished and a sense of achievement is gained; which in turn pushes them to do more. 

They need to be motivated enough to innovate.

article/an-overview-of-circuit-switching-and-packet-switching
An Overview of Circuit Switching and Packet Switching
What is switching?
is the most important mechanism which exchanges the information between different networks or different computer(s). 
Switching is the way which directs data or any digital information towards your network till the end point.
Suppose you are searching any type of circuit related information on the internet or looking for a hobby project in electronics, or if you open circuitdigest.com to find a specific article about electronics, there are lots of data movement happens behind your computer network. 

These movements are directed by the network switches which are using various switching techniques in various network junctions.
Circuit and Packet Switching are the most popular among these three.
Circuit Switching
is a switching method where an end-to-end path is created between two stations within a network before starting the data transfer.

To create these dedicated connections, a set of switches are connected by physical links.
In the below image, three computers on the left side are connected with three desktops PCs on the right side with physical links, depending on the four circuit switchers. 
If the circuit switching is not used, they need to be connected with point-to-point connections, where many number of dedicated lines are required, which will not only increase the connection cost but also increase the complexity of the system.
The routing decision, in the case of circuit switching, is made when the routing path is being established in the network. 

After the dedicated routing path is established the data continuously submitted to the receiver destination. 
The connection is maintained until the end of the conversation.
Three Phases in Circuit switching Communication
The start to the end communication in Circuit Switchingis done using this formation-

, in the circuit switching network, a dedicated routing or connection path is established between the sender and the receiver. 
At this period End to End addressing, like source address, destination address is must create a connection between two physical devices. 
The circuit switching happens in the physical layers.
only happens after the setup phase is completed and only when a physical, dedicated path is established. 

No addressing method is involved in this phase. 
The switches use time slot (TDM) or the occupied band (FDM) to route the data from the sender to the receiver. 
One thing needs to keep in mind that the data sending is continuous and there may be periods of silence in data transmitting. 
All internal connections are made in duplex form.

in circuit switching method.
A Circuit switch creates a temporary connection between an input link with an output link. 
There are various types of switches available with multiple inputs and output lines.
Generally, Circuit Switching is used in Telephone Lines.
Advantages of Circuit Switching
Circuit Switching Method provides large advantages in specific cases. 
The Advantages are as follows-
The data rate is fixed and dedicated because the connection is established using dedicated physical connection or circuits.

As there are dedicated transmission routing paths involved, it is a good choice for continuous transmission over a long duration.
The data transmission delay is negligible. 
No waiting time is involved in switches. 
So, the data gets transmitted without any prior delay in the transmission. 

This is definitely a positive advantage of Circuit Switching method.
Disadvantages of Circuit Switching
Other than the Advantages, Circuit switching also have some disadvantages.
Whether the communication channel is free or busy, the dedicated channel could not be used for other data transmission.

It requires more bandwidth, and continuous transmission offers wastage of bandwidth when there is a silence period.
It is highly inefficient when utilizing the system resource. 
We cannot use the resource for other connection as it is allocated for the entire conversation.
It takes huge time during the establishment of physical links between senders and receivers.
Packet Switching
After receiving those broken data or packets, all are reassembled at the destination and thus making a complete file. 
Due to this method, the data gets transferred fast and in an efficient manner. 
In this method, no pre-setup or resource reservation is required like circuit switching method.

This method use Store and Forward techniques. 
So each hop will store the packet first and then forward the packets to the next host destination. 
Each packet contains control information, source address and destination address. 
Due to this packets can use any route or paths in an existing network.
VC Based Packet Switching
As we can see switches are connected with each other and share the communications path with each other. 
Now in the virtual circuit, a predefined route needs to be established. 
If we want to transfer data from PC1 to the PC 4 the path will be directed from the SW1 to SW2 to SW3 and then finally at PC4. 

This route is predefined and All SW1, SW2, SW3 are provided with a unique ID to identify the data paths, so the data is bound by the paths and could not choose another route.
Datagram Based Packet Switching
The Packets have all the necessary information like Source address, destination address and Port identity etc. 
So in connectionless datagram-based packet switching mode, each packet is treated independently. 

They can choose different routes and the routing decisions are made dynamically when data are transmitting inside the network. 
So, at the destination, the packets can be received out of order or in any sequence, there is no predefined route and the guaranteed packet delivery is not possible. 
To secure guaranteed packet receiving, additional end system protocols need to be configured.
Again in the above image, 4 computers are connected and we transferring data from PC1 to PC4. 

The data contains two packets labeled as 1 and 2. 
As we can see, in Datagram mode, packet 1 chose to follow the SW1- SW4-SW3 path whereas Packet 2 chose the route path of SW1- SW5- SW3 and finally reached PC4. 
The packets can choose different path depending on the delay time and congestion on other paths in Datagram packet switching network.
Advantages of Packet Switching 
Packet switching network is designed to overcome the drawbacks of Circuit Switching method.
Efficient in terms of Bandwidth.
Transmission delay is minimum
Missing packets can be detected by the destination.

Cost-effective implementation.
Reliable when busy path or links breakdown is detected in the network. 
Packets can be transmitted by other links or can use a different path.
Disadvantages of Packet Switching
Packet switching also encounters few drawbacks.
Packet switching does not follow any particular order to transmit the packet one by one.
Packet missing occurs in large data transmission.
Each packet needs to be encoded with sequence numbers, Receiver and Senders address, and other information.

Routing is complex in the nodes as packets can follow multiple paths.
When rerouting occurs for some reason, the delay in receiving the packets is increased.
Differences between Circuit Switching and Packet Switching
We already got an idea about what are the differences between circuit switching and packet switching. 

Let’s see the differences in a table format for better understanding-


Steps Involvement
In circuit switching, 3 phase setup is required for total conversation.

Connection Establishment, Data Transfer, Connection Teardown
In the case of Packet Switching, we can make data transfer directly.
Destination Address
Entire Path Address is provided by the source.
Each Data packets knows only the final destination address, the routing path depends on routers decision.
Data Processing
Data Processing takes place at the Source system.
Data Processing takes place at nodes and source systems.
Uniform Delay Between data Units
Uniform Delay happens.
The delay between data units is not uniform.

Reliability
Circuit Switching is more reliable compared with Packet Switching
Packet Switching is less reliable compared with Circuit Switching.
Resource Wasteage
Resource Wastage is high in Circuit Switching.
Resource wastage is Less in Packet Switching.
Store and Forward Technique
It does not use store and forward technique
It uses store and forward technique
Congestion
Congestion occurs at only connection Establishment time.
Contestation can occur on data transfer phase.

Transmission Data
The source makes the transmission of the data.
Transmission of data is done by the source, routers.


article/top-hardware-platforms-for-internet-of-things-iot

Top Hardware Platforms for Internet of Things (IoT)
While some of the businesses are leveraging on IoT for direct business solutions, other firms are tapping into the business opportunities that exists in the provision of IoT platforms to serve as backbones for rapid development and deployment of IoT solutions. 
These platforms have become a key part of the development of IoT solutions and today, we will take a look at some of them.
IoT Hardware Development Platforms
1. Particle.io
ensuring there is a lot of support for product development.
Personally, one of the major reasons I like particle boards is the end to end nature of the services they provide. 
This ensures you to get support on every step of the way, without worrying about compatibility.
2. Espressif ESP8266 Boards
The Modules are usually low-cost, low-power, and easy to use. 
These among other factors, endear them to the heart of hardware designers. 
The ESP chips come with a lot of flexibility and can be used either as WiFi modules, connected to other microcontrollers or used in standalone modes without additional microcontrollers.

They Possess small form factors and make it easy to implement IoT enabling functions like OTA firmware updates. 
The availability of Development boards like NodeMCU and several other ESP based third party boards enables developers to get a feel of the board before using them in Designs. 
Just like the particle boards, ESP8266 boards, come with FCC and CE certification to reduce the general cost of certifying the device after manufacturing. 
The ESP provides one of the most robust, dedicated WiFi interface in the industry, featuring several protocols that support the IoT like the ESP Touch protocol that enables the device to safely and seamlessly access the internet via WiFi networks.
3. Intel IoT Development Boards
which is a platform designed specifically to suit the rugged demands of industrial IoT applications.
4. Adafruit Range of Development boards
It’s a solution perfect for prototype development. 

Particle on the other hand, has a more commercial, product grade undertone.
5. Arduino IoT Product Line
It’s impossible for the Arduino to be an unfamiliar name to anyone within the IoT space. 
Long before the IoT became mainstream, several of the Arduino boards were already being used to develop prototypes for connected devices. 

With the ease of programming and the plug and play nature of Arduino based system, it quickly became loved by many in the hardware space. 
The early Arduino boards, were mostly general purpose microcontrollers which were connected to the internet using GSM and WiFi modules, but as the IoT began to Open up, boards with special features that support the IoT were developed. 
Boards like the Arduino 101(developed with Intel), the MKR1000, Arduino WiFi Rev 2 and the MKR Vidor 4000 which is the first Arduino board based on an FPGA Chip.
Each of these boards was made with the IoT in mind, and they all have different features that make them more suitable for specific IoT solution. 

The Arduino WiFi Rev 2 for instance comes with an IMU which makes it suitable for drone based applications.
dedicated to be used by certain Arduino boards including; the MKR1000, Arduino Yun/Yun Shield and the Arduino 101/WiFi Shield 101. 
The Arduino device cloud (cloud.arduino.cc) offers a simple tool for makers to connect their device to the internet and takes a very short setup process to get things working.
6. The Raspberry Pi
While the Raspberry Pi is naturally a general purpose device, it will be injustice to ignore the contribution of the raspberry to the development of some of IoT products and projects currently in vogue. 
They are generally too robust and sophisticated to be used in the development of simple connected sensors or actuators, but they find application serving as data aggregators, hubs and device gateways in IoT projects. 
The latest of the raspberry pi boards; the Raspberry pi 3 model B+ features a 1.4GHz Broadcom BCM2837B0, Cortex-A53 (ARMv8) 64-bit SoC, 2.4GHz and 5GHz IEEE 802.11.b/g/n/ac wireless LAN, Bluetooth 4.2, BLE, and a Gigabit Ethernet port over USB 2.0 (maximum throughput 300 Mbps). 
Asides several other features including 4 USB ports, Audio output, to mention a few, the board comes with a 1GB LPDDR2 SDRAM which makes it quite fast for IoT based tasks.

To appeal to the Industrial IoT crowd and generally people who would love to use the Raspberry pi in their products, the raspberry pi compute module was launched. 
The Raspberry pi compute module three (CM 3) is currently the latest and it contains the guts of a Raspberry Pi 3 (the BCM2837 processor and 1GB RAM) as well as a 4GB eMMC Flash device (which is the equivalent of the SD card in the Pi) running at a 1.2GHz processor speed all integrated on a small 67.6mm x 31mm board which fits into a standard DDR2 SODIMM connector (the same type of connector as used for laptop memory).
This feature makes the raspberry suitable for use as gateways and in projects high processing speed requirements.
which means there is a lot of support for development irrespective of the platform you choose. 

As mentioned in the beginning, this is not an exhaustive as several other platforms like the Beaglebone, Banana Pi and the SparkFun list of IoT boards exist.

article/microcontroller-vs-plc-detailed-comparison-and-difference-between-plc-and-microcontroller
Microcontroller vs PLC: A Detailed Comparison
Programmable Logic Controller
(PLC) is simply a special purpose computing device designed for use in industrial control systems and other systems where the reliability of the system is high.
as they have high ability to produce outputs to specific inputs within a very short timeframe which is a key requirement for industrial settings as a second delay could disrupt the entire operation.
Microcontrollers
as they usually just have GPIOs to which these components can be connected.
which include;
Architecture
Interfaces

Performance and Reliability
Required Skill Level
Programming
Applications
1. Architecture
The processor module consists of the central processing unit (CPU) and memory. 
In addition to a microprocessor, the CPU also contains at least an interface through which it can be programmed (USB, Ethernet or RS232) along with communication networks. 
The power supply is usually a separate module, and the I/O modules are separate from the processor. 

The types of I/O modules include discrete (on/off), Analog (continuous variable), and special modules like motion control or high-speed counters. 
The field devices are connected to the I/O modules.
Depending on the amount of I/Os modules possessed by the PLC, they may be in the same enclosure as the PLC or in a separate enclosure. 
Certain small PLCs called nano/micro PLCs usually have all their parts including power, processor etc. 

in the same enclosure.
The architecture of PLCs described above is somewhat similar to the microcontrollers in terms of constituents, but the microcontroller implements everything on a single chip, from the CPU to the I/O ports and interfaces required for communication with the outside world. 
Architecture of the microcontroller is shown below.
Just like the microcontroller has diverse architecture from the AVR architecture to the 8051 architecture, PLCs likewise have variations in their design which supports the configuration and desire of a particular manufacturer but they generally all adhere to the industry standard (IEC 61131-3) for PLCs. 

This standard fosters interoperability between modules and parts.
2. Interfaces
PLCs are standard designed to interface with industrial grade sensors, actuators, and communication modules and are thus given current and voltage ratings which are often incompatible with microcontrollers without extra hardware.
nowadays, is creating a surge in the number of connected PLC devices capable of transmitting data over wireless communication interfaces.

As mentioned earlier, they come in different sizes, from small devices (with few IO pins/modules) which are referred to as building blocks to large, giant rack mounted PLCs with hundreds of IOs.
as well have sensors, actuators, and modules designed to meet their specific needs which might be difficult to interface with a PLC. 
They are however usually designed to handle processing of only a few 100 IOs. 
While several techniques can be explored to increase the IOs of the microcontroller, this are still possible with PLCs and is thus not unique to the microcontrollers, asides from the fact that it increases the entire project budget.
3. Performance, Sturdiness and Reliability
As mentioned initially, the PLC was designed for use in industrial setups and was thus fortified to be able to withstand several adverse conditions associated with that environment like, extreme temperature ranges, electrical noise, rough handling and high amount of vibration. 
PLCs are also a good example of real time operation system due to their ability to produce outputs within the shortest time possible after evaluating an input. 
This is very important in industrial system as timing is a huge part of the manufacturing plant/process.

however are less sturdy. 
By design they were not designed to serve as standalone devices like PLCs. 
They were designed to be embedded in a system. 
This provides an explanation for their less sturdy look compared to PLCs. 

For these reasons, microcontrollers may fail when deployed in certain scenarios as the chips are fragile and can easily be damaged.
4. Skill Requirement for Use
for programming, and generally operating it. 
The PLC was designed to be use by both the highly skilled automation experts and factory technicians who have little or no formal training. 

It is relatively easy to troubleshoot and diagnose faults. 
Modern PLC devices usually come with a display screen that makes things easier to monitor without sophisticated tools.
Designers need to have a good knowledge of electrical engineering principles and programming to be able to design complementary circuits for the microcontroller. 
Microcontrollers also require special tools (e.g Oscilloscope) for fault diagnosis and firmware trouble shooting. 

Although several simplified platforms like the Arduino currently exists, it is still a lot more complex than the plug and play PLCs both from connection stand point, programming standpoint, and ease of use.
5. Programming
that mimics the connections/schematics of relay logic diagrams. 
This reduced the training requirements for existing technicians. 

The primary, most popular programming language used for PLCs are the Ladder Logic and instruction list programming language. 
Ladder logic uses symbols, instead of words, to emulate the real world relay logic control, which is a relic from thePLC's history. 
These symbols are interconnected by lines to indicate the flow of current through relay, like contacts and coils. 
The number of symbols has increased tremendously over the years enabling engineers to easily implement high level of functionalities.

based code is shown above. 
It usually looks like a ladder which is the reason behind its name. 
This simplified look makes PLCs very easy to program such that if you can analyse a schematic, you can program PLCs.
Due to the recent popularity of modern high level programming languages, PLCs are now being programmed using these languages like C, C++ and basic but all PLCs generally still adhere to the industry IEC 61131/3 control systems standard and support the programming languages stipulated by the standard which include; Ladder Diagram, Structured Text, Function Block Diagram, Instruction List and Sequential Flow Chart.

Modern day PLC are usually programmed via application software based on any of the languages mentioned above, running on a PC connected to the PLC using any of, USB, Ethernet, RS232, RS-485, RS-422, interfaces.
It usually requires a high level of experience with the programming language being used and a general understanding of the principles of firmware development. 
Programmers usually need to understand concepts like data structures and a deep understanding of the microcontroller architecture is required to develop a very good firmware for the project.
and it’s similar to a microcontroller going through a loop.

is shown below.
6. Applications
are the primary control elements used in industrial control systems. 
They find application in the control of industrial machines, conveyors, robots and other production line machineries. 

They are also used in SCADA based systems and in systems that require a high level of reliability and ability to withstand extreme conditions. 
They are used in industries including;
1. Continuous bottle filling system
2.Batch mixing system

3.stage air conditioning system
4.Traffic control
on the other hand find application in everyday electronic devices. 
They are the major building blocks of several consumer electronics and smart devices.
Replacing PLCs in Industrial Applications with Microcontrollers
, the main argument being the cost of PLCs compared to that of microcontrollers. 
It is important that a lot needs to be done to the regular microcontrollers before it can be used in industrial applications.
While the answer can be found from the points already mentioned within this article, it is sufficient to highlight two key points.

1. Microcontrollers are not designed with the ruggedness and ability to withstand extreme conditions like PLCs. 
This makes them not ready for industrial applications.
2. Industrial sensors and actuators are usually designed according to the IEC standard which is usually at a range of current/voltage and interfaces which may not be directly compatible with microcontrollers and will require some sort of supporting hardware which increases cost.
Other points exist but to stay within the scope of this article, we should stop here.

now make Arduino based PLCs shown below.

article/bluetooth-or-wifi-which-is-best-for-your-new-wireless-product
Bluetooth or WiFi ᾠWhich is Best for Your New Wireless Product?
The Need for Speed
If high-speed data transmission is themost critical requirementfor your product then most likely WiFi Direct will be the best choice. 
Everyone has heard of WiFi, but few know of WiFi Direct. 
Although that is changing. 

Standard WiFi requires an access point. 
So if you want to transfer data from one device to another it must pass through the access point. 
WiFi Direct has the speed advantages of WiFi without the need for an access point. 
Data can be transmitted directly from one device to another just like with Bluetooth.



Wireless Standard
Speed

Bluetooth Low-Energy
1 Mbps
Bluetooth Classic
2-3 Mbps

Wifi-Direct
100-250 Mbps

WiFi Direct has a maximum data transfer speed about 10x the speed obtainable with Bluetooth Classic. 

So, for example, if your product needs to stream video, especially high-definition video, you’ll need the fastest wireless connection possible. 
There is no way Bluetooth will be fast enough, so you’ll almost surely need to offer WiFi Direct connectivity.
At the other end of the speed spectrum is Bluetooth Low-Energy (also called Bluetooth Smart) which is about 2-3x slower than Bluetooth Classic, or 20-30x slower than WiFi Direct. 
It is typically used for transmitting small amounts of intermittent data, such as sensor readings (temperature, acceleration, etc.) or perhaps GPS coordinates.

When you need to constantly transmit data, such as when streaming audio, you’ll usually need to use Bluetooth Classic. 
Bluetooth Classic is optimized for streaming applications, versus BLE which is optimized for short, infrequent bursts of data.
can provide you with a custom Bluetooth LE stack that allows audio streaming.
Transmission Range
WiFi Direct has a maximum range of about 200 feet, compared to only about 50 feet typically for Bluetooth (Classic and Low-Energy). 
The increased range of WiFi Direct is possible because of the higher transmission power used by WiFi Direct.
The tradeoff is battery life and this increased transmission power will drain a small battery much faster than either Bluetooth standard.



Bluetooth Low-Energy
50 ft typically, but up 1,500 ft with range extender
Bluetooth Classic
50 ft typically, but up to 3,000 ft with range extender
Wifi-Direct
200ft


But wait a minute…things aren’t always so simple. 
There are some exceptions. 
First of all, there are actually different classes of Bluetooth transmitters. 

Most Bluetooth products use a class 2 transmitter with a range around 50 feet as previously stated. 
But it’s possible to use a class 1 transmitter with a range closer to about 300 feet. 
But, just like with WiFi Direct, the higher transmission power comes at the cost of reduced battery life.
) with a range up to 3,000 feet!

There is yetanother exception. 
In some applications, it’s actually possible for Bluetooth (even the Low-Energy version) to transmit over a larger range than WiFi Direct while still using very little power. 
This is possible due to an awesome feature called mesh networking.
Normally to send data from device A to device C you must form a direct link between A and C. 

But with mesh networking you can instead send data from device A to device C via device B. 
So if device B happens to be halfway between A and C, then A and C can be twice as far apart as normally allowed. 
This is because device B acts as a relay, or in many ways a signal booster. 
This idea can be expanded making possible a large network of interconnected, low power devices spread out over a large distance. 

In fact, up to 65,000 devices may be interconnected using mesh.
A leading maker of Bluetooth microchips called CSR started including mesh networking with their Bluetooth Low-Energy chips in 2014. 
So far they are the only chip maker to offer mesh with BLE. 
However, I doubt that will be the case much longer.

There is the option of having a custom Bluetooth stack developed to allow mesh networking with other chips, or with Bluetooth Classic. 
I know that Bluetooth stack provider Searan has the ability to add mesh networking to their Bluetooth stacks.
Power / Battery Life / Battery size
Higher speed and longer direct transmission range correlate with higher power usage and thus shorter battery life. 

So if battery life or battery size are important for your product then power usage becomes critical.
Bluetooth Low-Energy (BLE) is the clear winner in regards to low power usage. 
It was primarily developed for Internet of Things applications which many times need to run from a small, single watch battery. 
A BLE device can run for a year or two on a single watch battery. 

This is possible primarily because these types of products are designed to only transmit occasionally. 
For example, a BLE device may only transmit data for 1 second once per minute. 
This means the device is idle for 59/60 = 98.3% of the time.
Compatibility
If compatibility with older smartphones is critical for your product, then Bluetooth Classic may be the best choice. 
All smartphones support Bluetooth Classic, but only moderately newer phones support BLE and WiFi Direct.



Bluetooth Low-Energy
All versions
All versions
Bluetooth Classic
Version 4.3 or later
Version 4S or later
Wifi-Direct
Version 4.0 or later
Version 5S or later

Best of Two Worlds: Bluetooth Dual-Mode
For some applications at times Bluetooth Classic is best choice, and at other times Bluetooth Low-Energy is the better option. 
For example, perhaps you prefer Bluetooth Low-Energy to conserve battery life, but you also want to allow compatibility with older smart phones.
The best solution may be Bluetooth Dual-Mode. 

When communicating with newer phones you could use the battery saving BLE mode, but when you need to link to older phones then you could select Classic mode. 
Most of the Bluetooth chip makers and module providers offer dual-mode Bluetooth solutions.
Security
All three wireless standards offer a high level of security. 

However, WiFi uses 256 bit encryption versus Bluetooth (Classic and LE) use only 128 bit encryption. 
In most cases Bluetooth’s level of security is sufficient, but if security is critical for your product then WiFi Direct may be the better option.
Summary
As is always the case with engineering, there are trade-offs between the various solutions. 

No solution is best in all applications. 
You need to decide which criteria is most important for your product. 
This may be simple or complex. 
If speed is all you care about then your choice is easy. 

Or if battery life is your primary concern then your choice is pretty simple. 
But if you care about both speed and power usage equally then your choice becomes more complex.
Deciding which specifications are the most critical for your product is always a challenging aspect of product development. 
Welcome to the world of product development where nothing is truly simple. 

If it was easy, every company would be as successful as Apple.
About the Author
tutorial/what-is-stepper-motor-and-how-it-works

What is Stepper Motor and How it Works
, Robotics, Assembly robots, Laser cutters and much more. 
In this article let us learn what makes these motors special and the theory behind it. 
We will learn how to use one for you application.
Introduction to Stepper Motors
, but for now just understand that in a stepper motor the rotor consists of metal poles and each pole will be attracted by a set of coil in the stator. 
The below diagram shows a stepper motor with 8 stator poles and 6 rotor poles.
Similarly by energising the coils in a sequence we can rotate the motor in small steps to make a complete rotation.
Types of stepper motors
There are mainly three types of stepper motors based on construction, which are:
Variable reluctance stepper motor: They have iron core rotor which is attracted towards the stator poles and provide movement by minimum reluctance between stator and rotor.
Permanent magnet stepper motor: They have permanent magnet rotor and they are repelled or attracted towards the stator according to pulses applied.

Hybrid synchronous stepper motor: They are combination of Variable reluctance and permanent magnet stepper motor.
based on the type of stator winding.
Bipolar Stepper Motor: The stator coils on this type of motor will not have a common wire. 
The driving of this type of stepper motor is different and complex and also the driving circuit cannot be easily designed without a microcontroller.

Unipolar Stepper Motor: In this type of stepper motor we can take the center tapping of both the phase windings for a common ground or for a common power as shown below. 
This makes it easy to drive the motors, there are many types in Unipolar stepper motor as well

Modes of operation in Stepper Motor
Since the stator of the stepper mode is built of different pairs of coils, each coil pair can be excited in many different methods, this enabling the modes to be driven in many different modes. 
The following are the broad classifications
Full Step Mode
In this mode only one terminal (phase) of the motor will be energised at any given time. 

This has less number of steps and hence can achieve a full 360° rotation. 
Since the number of steps is less the current consumed by this method is also very low. 
The following table shows the wave stepping sequence for a 4 phase stepper motor


Step
Phase 1
Phase 2
Phase 3
Phase 4
1
1
0
0
0
2
0
1
0
0
3
0
0
1
0

4
0
0
0
1

As the name states in this method two phases will be one. 
It has the same number of steps as Wave stepping, but since two coils are energised at a time it can provide better torque and speed compared to the previous method. 

Although one down side is that this method also consumes more power.

Step
Phase 1
Phase 2
Phase 3
Phase 4
1
1
1
0
0

2
0
1
1
0
3
0
0
1
1
4
1
0
0
1

Half Step Mode
The Half Step mode is the combination of one phase-on and two-phase on modes. 
This combination will help us to get over the above mentioned disadvantage of the both the modes.
in this method to get a complete rotation. 

The switching sequence for a 4-phase stepper motor shown below


1
1
0
0
0

2
1
1
0
0
3
0
1
0
0
4
0
1
1
0
5
0
0
1
1

6
0
0
0
1
7
1
0
0
1
8
1
0
0
0

Micro Step Mode
Micro stepping mode is the complex of all, but it offers very good precision along with good torque and smooth operation. 
In this method the coil will be excited with two sine waves which are 90° apart. 
This way we can control both the direction and amplitude of the current flowing through the coil which helps us to increase the number of steps the motor has to make for one complete rotation. 

Micro stepping can take as high as 256 steps to make one complete rotation, this makes the motor to rotate faster and smoother.
How to use a Stepper Motor
Enough of boring theory, let’s assume someone gives you a stepper motor say the famous 28-BYJ48 and you are really curious to make it work. 
By this time you would have understood that it is not possible to make these motors rotate by just powering them through a supply, so how would you do it?

Meaning, they will move only one step at a time. 
These motors have a sequence of coils present in them and these coils have to be energized in a particular fashion to make the motor rotate. 
When each coil is being energized the motor takes a step and a sequence of energization will make the motor take continuous steps, thus making it to rotate. 
Let us take a look at the coils present inside the motor to know exactly know from where these wires come from.

control can also be used. 
The sequence table for 4-step control is shown below.



Step 1
A and B
Step 2
B and C
Step 3
C and D
Step 4
D and A


? Seriously!!! I don’t know. 
There is no technical reason for this motor for being named so; maybe we should not dive much deeper into it. 
Let us look at some of the important technical data obtained from the datasheet of this motor in the picture below.

That is a head full of information, but we need to look at few important ones to know what type of stepper we are using so that we can program it efficiently. 
First we know that it is a 5V Stepper motor since we energize the Red wire with 5V. 
Then, we also know that it is a four phase stepper motor since it had four coils in it. 
Now, the gear ratio is given to be 1:64. 

This means the shaft that you see outside will make one complete rotation only if the motor inside rotates for 64 times. 
This is because of the gears that are connected between the motor and output shaft, these gears help in increasing the torque.
This means that the motor when operates in 8-step sequence will move 5.625 degree for each step and it will take 64 steps (5.625*64=360) to complete one full rotation.
Calculating the Steps per Revolution for Stepper Motor
It is important to know how to calculate the steps per Revolution for your stepper motor because only then you can program/drive it effectively.
Lets assume we will be operating the motor in 4-step sequence so the stride angle will be 11.25° since it is 5.625°(given in datasheet) for 8 step sequence, it will be 11.25° (5.625*2=11.25).
Steps per revolution = 360/step angle
Here, 360/11.25 = 32 steps per revolution.
Why do we need Driver modules for Stepper Motors?
There are a many types of driver module and the rating of one will change based on the type of motor used. 
The primary principle for all driver modules will be to source/sink enough current for the motor to operate. 
Apart from that there are also driver modules which have the logic pre-programmed into it, but we will not discuss about it here.

using some microcontroller and driver IC, then we have covered many articles on its operation with different microcontrollers:
Interfacing Stepper Motor with Arduino Uno
Interfacing Stepper Motor with STM32F103C8
Interfacing Stepper Motor with PIC Microcontroller

Interfacing Stepper Motor with MSP430G2
Stepper Motor Interfacing with 8051 Microcontroller
Stepper Motor Control with Raspberry Pi
Now I believe you have enough information to control any stepper motor that you require for your project. 

Let’s take a look at the advantage and disadvantage of Stepper motors.
Advantages of Stepper motors
One major advantage of stepper motor is that it has excellent position control and hence can be used for precise control application. 
Also it has very good holding torque which makes it an ideal choice for robotic applications. 

Stepper motors are also considered to have high life time than normal DC or servo motor.
Disadvantages of Stepper Motors
Like all motors Stepper Motors also come with its own disadvantages, since it rotates by taking small steps it cannot achieve high speeds. 
Also it consumes power for holding torque even when it is ideal thus increasing the power consumption.


tutorial/an-introduction-of-supercapacitors
An Introduction to Supercapacitors
.Asupercapacitoris nothing but a high-capacitycapacitorwith capacitance values much higher than normal capacitors but lower voltage limits.They can store 10 to 100 times moreenergy per unit volume or massthan electrolytic capacitors, can receive and deliver charge much faster than batteries, and tolerate more charging-dischargingcycles thanrechargeable batteries.

Supercapacitors or Ultracapacitors are a new energy storage technology which is developed heavily in modern times. 
Supercapacitors are providing significant industrial and economic benefits
The capacitance of a capacitor is measured in Farad (F), like .1uF (microfarad), 1mF (millifarad). 
However, while the lower value capacitors are quite common in electronics, very high-value capacitors are also available, which store energy in much more high density and available in very high capacitance value, ranged in Farad likely.

In the above image, a locally available 2.7V, 1Farad super capacitor image is shown. 
The voltage rating is much lower but the capacitance of the above capacitor is quite high.
Benefits of Super-Capacitor or Ultra-Capacitor
is rising day byday. 

The main reason for the rapid development and demand is due to many other benefits of Supercapacitors, few of them are stated below:
It provides a very good life of approx 1million charge cycles.
The operating temperature is -50 degrees to 70 degrees almost, which makes it suitable for use in consumer applications.
A high power density up to 50times, which is achieved by batteries.

Harmful materials, toxic metals are not the part of the Super Capacitors or Ultracapacitors manufacturing process which makes it certified as the disposable component.
It is more efficient than batteries.
Requires no maintenance compared with batteries.
Supercapacitorsstore energies in its electric field, but in case of batteries, they use chemical compounds to store energies. 

Also, because of its ability to quick charge and discharge, the Supercapacitors are slowly entering in the battery market. 
Low internal resistance with very high efficiency, no maintenance cost, higher lifetimes are the main reason for its high demand in the modern power source related market.
Energies in capacitor
Q stands for Charge in Coulombs, C for capacitance in Farads and V for voltage in volts. 

So, if we increase the capacitance the stored energy Q will also increase.
The unit of capacitance is Farad (F) which is named after M. 
Faraday. 
Farad is the capacitance unit in respect of coulomb/volt. 

If we say a capacitor with 1 Farad, then it will create a 1-volt potential difference between its plates depending on the 1-coulomb charge.
F)
Joules. 
E is the stored energy in joules, C is the capacitance in Farad and V is the potential difference between the plates.
Construction of a Supercapacitor
here.
acts as an electrostatic device storing its electrical energy as the electric field between the conductive electrodes.
They generally made of graphite carbon in the form of carbon nanotubes or gels or a special type of conductive activated carbons.

To block the large electron flow between electrodes and passing the positive ion, a porous paper membrane is used. 
The paper membrane also separates the electrodes. 
As we can see in the above image, the porous paper membrane is situated in the middle which is green in color. 
The electrodes and paper separator are impregnated with the liquid electrolyte. 

The aluminum foil is used as a current collector which establishes the electrical connection.
The separation plate and the area of the plates are responsible for the capacitance value of the capacitor. 
The relation can be denoted as
Where,  is the permittivity of the material present between plates

A is the area of the plate
D is the separation between plates
So, in case of supercapacitor, the contact surface is needed to be increased, but there is a limitation. 
We cannot increase the physical shape or size of the capacitor. 

To overcome this limitation special type of electrolytes are used to increase the conductivity between plates thus increasing the capacitance.
There is a reason behind it. 
Very small separation and large surface area using special electrolyte, the surface layer of electrolytic ions form a double layer. 
It creates two capacitor construction, one at each carbon electrodes and named a double layer capacitor.

These constructions have a drawback. 
The voltage across the capacitor became very low because of the decomposition voltage of the electrolyte. 
The voltage is highly dependent on the electrolyte material, the material can limit the electrical energy storing capacity of the capacitor. 
So, due to the low terminal voltage, an supercapacitor can be connected in series to store electrical charge at a useful voltage level. 

Due to this, the supecapacitor in series produce higher voltage than usual and in parallel, the capacitance became larger. 
It can be clearly understood by the below Supercapacitor Array Construction technique.
Supercapacitor Array construction
To store charge at a useful required voltage, supercapacitors need to be connected in series. 

And for increasing the capacitance they should be connected in parallel.
Let's see the array construction of the Supercapacitor.
If we create the array, the voltage in series will be
Total voltage = Cell Voltage (Cv) x Number of rows

And the capacitance in parallel will be
Total capacitance =Cell Capacitance (Cc) x (Number of Column / Number of Row) 
Example
We need to create a backup storage device, and for that a 2.5F super or supercapacitor is required with the 6V rating.

Total voltage = Cell Voltage x Row number
Then, Row number = 6/3
Row number = 2
Means two capacitor in series will have a 6V potential difference.

Now, the capacitance,
Total capacitance = Cell capacitance x (Column Number / Row Number)
Then, Coloumn number = (2.5 x 2) / 1 
So, we need 2 rows and 5 column.

Let's construct the array,
The total energy stored in the array is
Supercapacitors are good in storing energy and where fast charging or discharging is needed. 
It is widely used as backup devices, where back up power supply or quick discharging is needed. 

They are further used in Printers, cars and various potable electronics devices.

article/ultimate-guide-how-to-develop-a-new-electronic-hardware-product
Ultimate Guide ᾠHow to Develop a New Electronic Hardware Product

So you want to develop a new electronic hardware product? Let me start with the good news ᾠit’s possible. 
You can develop a hardware product regardless of your technical level and you don’t necessarily need to be an engineer to succeed (although it certainly helps).
this guide will help you understand the new product development process.
for individuals and small teams to develop new hardware products.

However, if you are looking for an easy, quick way to make money then I suggest you stop reading right now because bringing a new hardware product to market is far from easy or quick.
In this guide I’ll first discuss the product development strategies for both technical creators and non-technical entrepreneurs wishing to create a new electronic hardware product. 
Then, we’ll move on to developing the electronics followed by the development of the plastic enclosure.


Part 1 - Product Development Strategies
There are essentially five options for entrepreneurs and startups to develop a new hardware product. 
However, many times the best overall strategy is a combination of these five development strategies.
1) Develop the Product Yourself
This is rarely a viable strategy completely by itself. 
Very few people have all of the skills needed to develop a market-ready electronic product completely on their own.
Even if you happen to be an engineer, are you an expert in electronics design, programming, 3D modeling, injection molding, and manufacturing? Probably not. 
Also most of these specialties are made up of numerous sub-specialties.

That being said, if you have the necessary skills, the farther you take the development of your product yourself the more money you will save and the better off you will be in the long run.
For example, I brought my own hardware product to market about 6 years ago. 
The product was more complex mechanically than it was electrically. 
I’m an electronics engineer by training and not a mechanical engineer, so I initially hired a couple freelance mechanical engineers.

However, I quickly became frustrated with how slow things progressed. 
After all, I was thinking about my product almost every waking hour! I was obsessed with getting my product developed and on the market as fast as possible. 
But the engineers I hired were juggling it with lots of other projects and not giving my project the attention I felt it deserved.
So I decided to learn everything needed to do the mechanical design myself. 

No one was more motivated than myself to get my product developed and on the market. 
Ultimately, I was able to complete the mechanical design much faster (and for much less money).
The moral of the story is to do as much of the development as your skills allow, but also don’t take that too far. 
If your sub-expert skills cause you to develop a less than optimal product then that is a big mistake. 

Also, any new skills you must learn will take time and that may ultimately lengthen the time to market. 
Always bring in experts to fill in any gaps in your expertise.
and All About Circuits. 
Be sure to check out the YouTube channel called AddOhms which has some absolutely excellent introductory videos for learning electronics.
2) Bring on Technical Co-Founder(s)
If you are a non-technical founder then you would definitely be wise to bring on a technical co-founder. 
One of the founders on your startup team needs to at the very least understand enough about product development to manage the process.
If you plan to eventually seek outside funding from professional investors then you definitely need a team of founders. 

Professional startup investors know that a team of founders is much more likely to succeed than a solo founder.
The ideal co-founder team for most hardware startups is a hardware engineer, a programmer, and a marketer.
may sound like the perfect solution to your problems, but there are some serious downsides as well. 
First of all, finding co-founders is difficult and will likely take a tremendous amount of time. 

That is valuable time that isn’t being spent developing your product.
Finding co-founders is not something you should rush and you need to take time to find the right match. 
Not only do they need to compliment your skills, but you also really need to like them personally. 
You are essentially going to be married to them for at least a few years so be sure you get along well.

The major downside of bringing on co-founders is they reduce your equity in the company. 
All founders of a company should really have equal equity in the company. 
So if you are going solo right now, be prepared to give any co-founder half of your company.
3) Outsource to Freelance Engineers
One of the best ways to fill in any gaps in your teams technical ability is by outsourcing to freelance engineers.
Just keep in mind that most products will require multiple engineers of different specialties so you will need to manage the various engineers yourself. 
Ultimately, someone on the founding team will need to serve as the project manager.
Make sure you find an electrical engineer that has experience designing the type of electronics required by your product. 

Electrical engineering is a huge field of study and many engineers lack any experience with circuit design.
For the 3D designer make sure you find someone that has experience with injection molding technology, otherwise you’re likely to end up with a product that can be prototyped but not mass manufactured.
4) Outsource to a Development Firm
The best known product design firms such as Frog, IDEO, Fuse Project, etc. 

can generate fantastic product designs, but they’re insanely expensive. 

Startups should avoid expensive design firms at all costs. 
Top design firms can charge $500k+ to fully develop your new product. 

Even if you can afford to hire an expensive product development firm, don’t do it. 
Not only are you likely to never recuperate that money, you also don’t want to make the mistake of founding a hardware startup that isn’t heavily involved in the actual product development.
5) Partner with a Manufacturer
One avenue to pursue is partnering with an overseas manufacturer that already makes products that are similar to your product. 


Large manufacturers will have their own engineering and development departments to work on their own products. 
If you can find a manufacturer already making something similar to your own product, they may be able to do everything for you ᾠdevelopment, engineering, prototyping, mold production and manufacturing.
This strategy can lower your upfront development costs. 

Manufacturers will, however, amortize these costs, which means adding an additional cost per product for the first production runs. 
This essentially works like an interest free loan, allowing you to slowly pay back your development costs to the manufacturer.
Sounds great and easy, so what’s the catch? The main risk to consider with this strategy is you are putting everything related to your product into a single company.
They will surely want an exclusive manufacturing agreement, at least until their costs have been recovered. 

This means you can’t migrate to a cheaper manufacturing option when your production volume increases.
Also be warned that many manufacturers may want part, or all, of the intellectual rights to your product.
Part 2 ᾠDevelop the Electronics
Development of the electronics for your product can be broken down into seven steps: preliminary production design, schematic diagram, PCB layout, final BOM, prototype, test and program, and finally certification.
Step 1 ᾠCreate a Preliminary Production Design
This is not to be confused with a Proof-of-Concept (POC) prototype.
A POC prototype is usually built using a development kit like an Arduino. 
They can sometimes be useful to prove that your product concept solves the desired problem. 

But a POC prototype is far from being a production design. 
Rarely can you go to market with an Arduino embedded in your product.
focuses on your product’s production components, cost, profit margin, performance, features, development feasibility and manufacturability.
You can use a preliminary production design to produce estimates for every cost your product will need. 

It is important to accurately know the costs to develop, prototype, program, certify, scale, and manufacture the product.
A preliminary production design will answer the following pertinent questions. 
Is my product feasible to develop? Can I afford to develop this product? How long will it take me to develop my product? Can I mass manufacture the product? Can I sell it at a profit?
Many entrepreneurs make the mistake of skipping the preliminary production design step, and instead jump right into designing the schematic circuit diagram. 

By doing so, you may eventually discover you’ve spent all this effort and hard-earned money on a product that can’t be affordably developed, manufactured, or most importantly, sold at a profit.
When creating the preliminary production design you should start by defining the system-level block diagram. 
This diagram specifies each electronic function and how all of the functional components interconnect.
or a microprocessor with various components (displays, sensors, memory, etc.) interfacing with the microcontroller via various serial ports.

By creating a system block diagram you can easily identify the type and number of serial ports required. 
This is an essential first step for selecting the correct microcontroller for your product.
Next, you must select the various production components: microchips, sensors, displays, and connectors based upon the desired functions and target retail price of your product. 
This will allow you to then create a preliminary Bill of Materials (BOM).

are the most popular suppliers of electronic components. 
You can purchase most electronic components in ones (for prototyping and initial testing) or up to thousands (for low-volume manufacturing).
Once you reach higher production volumes you will save money by purchasing some components directly from the manufacturer.
(or Cost of Goods Sold ᾠCOGS) for your product. 

It’s critical to know as soon as possible how much it will cost to manufacture your product.
You need to know your product’s manufacturing unit cost in order to determine the best sales price, the cost of inventory, and most importantly how much profit you can make.
The production components that you’ve selected will of course have a big impact on the manufacturing cost.
But to get an accurate manufacturing cost estimate you also must include the cost of the PCB assembly, final product assembly, product testing, retail packaging, scrap rate, returns, logistics, duties, and warehousing.
Step 2 ᾠDesign the Schematic Circuit Diagram
Now it’s time to design the schematic circuit diagram based upon the system block diagram you created in step 1.
The schematic diagram shows how every component, from microchips to resistors, connects together. 
Whereas a system block diagram is mostly focused on the higher level product functionality, a schematic diagram is all about the little details.

Something as simple as a mis-numbered pin on a component in a schematic can cause a complete lack of functionality.
In most cases you’ll need a separate sub-circuit for each block of your system block diagram. 
These various sub-circuits will then be connected together to form the full schematic circuit diagram.
which is affordable, powerful, and easy to use.
Step 3 ᾠDesign the Printed Circuit Board (PCB)
Once the schematic is done you will now design the Printed Circuit Board (PCB). 
The PCB is the physical board that holds and connects all of the electronic components.
Development of the system block diagram and schematic circuit have been mostly conceptual in nature. 

A PCB design though is very real world.
The PCB is designed in the same software that created the schematic diagram. 
The software will have various verification tools to ensure the PCB layout meets the design rules for the PCB process used, and that the PCB matches the schematic.
In general, the smaller the product, and the tighter the components are packed together, the longer it will take to create the PCB layout. 

If your product routes large amounts of power, or offers wireless connectivity, then PCB layout is even more critical and time consuming.
For most PCB designs the most critical parts are the power routing, high-speed signals (crystal clocks, address/data lines, etc.) and any wireless circuits.
Step 4 ᾠGenerate the Final Bill of Materials (BOM)
Although you should have already created a preliminary BOM as part of your preliminary production design, it’s now time for the full production BOM.

The main difference between the two is the numerous low-cost components like resistors and capacitors. 
These components usually only cost a penny or two, so I don’t list them out separately in the preliminary BOM.
But to actually manufacture the PCB you need a complete BOM with every component listed. 
This BOM is usually created automatically by the schematic design software. 

The BOM lists the part numbers, quantities, and all component specifications.
Step 5 ᾠOrder the PCB Prototypes
Creating electronic prototypes is a two-step process. 
The first step produces the bare, printed circuit boards. 

Your circuit design software will allow you to output the PCB layout in a format called Gerber with one file for each PCB layer.
These Gerber files can be sent to a prototype shop for small volume runs. 
The same files can also be provided to a larger manufacturer for high volume production.
The second step is having all of the electronic components soldered onto the board. 

From your design software you’ll be able to output a file that shows the exact coordinates of every component placed on the board. 
This allows the assembly shop to fully automate the soldering of every component on your PCB.
Your cheapest option will be to produce your PCB prototypes in China. 
Although it’s usually best if you can do your prototyping closer to home so as to reduce shipping delays, for many entrepreneurs it’s more important to minimize costs.

which I’ve used extensively to prototype my own designs. 
It takes 1-2 weeks to get assembled boards, unless you pay for rush service which I rarely recommend.
Step 6 - Evaluate, Program, Debug, and Repeat
of the electronics. 

Keep in mind that your first prototype will rarely work perfectly. 
You will most likely go through several iterations before you finalize the design. 
This is when you will identify, debug and fix any issues with your prototype.
This can be a difficult stage to forecast in both terms of cost and time. 

Any bugs you find are of course unexpected, so it takes time to figure out the source of the bug and how best to fix it.
Evaluation and testing are usually done in parallel with programming the microcontroller. 
Before you begin programming though you’ll want to at least do some basic testing to ensure the board doesn’t have major issues. 


Nearly all modern electronic products include a microchip called a Microcontroller Unit (MCU) that acts as the “brainsᾠfor the product. 
A microcontroller is very similar to a microprocessor found in a computer or smartphone.
A microprocessor excels at moving large amounts of data quickly, while a microcontroller excels at interfacing and controlling devices like switches, sensors, displays, motors, etc. 
A microcontroller is pretty much a simplified microprocessor.

The microcontroller needs to be programmed to perform the desired functionality.
Microcontrollers are almost always programmed in the commonly used computer language called ‘Cᾮ The program, called firmware, is stored in permanent but reprogrammable memory usually internal to the microcontroller chip.
Step 7 ᾠCertify Your Product
All electronic products sold must have various types of certification. 

The certifications required vary depending on what country the product will be sold in. 
We’ll cover certifications required in the USA, Canada, and the European Union.
FCC certification is necessary for all electronic products sold in the United States. 
All electronic products emit some amount of electromagnetic radiation (i.e. 

radio waves) so the FCC wants to make sure that products don’t interfere with wireless communication.
There are two categories of FCC certification. 
Which type is required for your product depends on whether your product features wireless communication capabilities such as Bluetooth, WiFi, ZigBee, or other wireless protocols.
Intentional radiator certification will cost you roughly 10 times as much as non-intentional radiator certification.

Consider initially using electronic modules for any of your product’s wireless functions. 
This allows you to get by with only non-intentional radiator certification, which will save you at least $10k.
UL or CSA certification is necessary for all electrical products sold in the United States or Canada that plug into an AC outlet.
Battery-only products that don’t plug into an AC outlet do not require UL/CSA certification. 

However, most major retailers and/or product liability insurance companies will require that your product be UL or CSA certified.
CE certification is needed for the majority of electronic products sold in the European Union (EU). 
It is similar to the FCC and UL certifications required in the United States.
RoHS certification ensures that a product is lead-free. 

RoHS certification is required for electrical products sold in the European Union (EU) or the state of California. 
Since California’s economy is so significant, the majority of products sold in the U.S. 
are RoHS certified.


Do you remember the double recall on the Samsung Galaxy Note 7 because of this issue? Or the stories about various hoverboards bursting into flames?
Because of these safety concerns rechargeable lithium batteries must be certified. 
For most products I recommend initially using off-the-shelf batteries that already have these certifications. 
However, this will limit your choices and most lithium batteries have not been certified. 


This is primarily due to the fact that most hardware companies choose to have a battery custom designed to take advantage of all of the space available in a product. 
For this reason most battery manufacturers don’t bother with getting their off-the-shelf batteries certified.
Part 3 ᾠDevelop the Enclosure

Now we’ll cover the development and prototyping of any custom plastic pieces. 
For most products this includes at least the enclosure that holds everything together.
Development of custom shaped plastic or metal pieces will require a 3D modeling expert, or better yet an industrial designer.
If appearance and ergonomics are critical for your product, then you’ll want to hire an industrial designer. 

For example, industrial designers are the engineers who make portable devices like an iPhone look so cool and sleek.
If appearance isn’t critical for your product then you can probably get by with hiring a 3D modeler, and they are usually significantly cheaper than an industrial designer.
Step 1 - Create 3D Model
The first step in developing your product’s exterior is the creation of a 3D computer

(formerly called Pro/Engineer).
If you want to do your own 3D modeling, and you’re not tied to either Solidworks or PTC Creo, then definitely consider Fusion 360.
Once your industrial or 3D modeling designer has completed the 3D model you can then turn it into physical prototypes. 
The 3D model can also be used for marketing purposes, especially before you have functional prototypes available.

If you plan to use your 3D model for marketing purposes you’ll want to have a photo realistic version of the model created. 
Both Solidworks and PTC Creo have photo realistic modules available.
You can also get a photo realistic, 3D animation of your product done. 
Keep in mind you may need to hire a separate designer that specializes in animation and making 3D models look realistic.

The biggest risk when it comes to developing the 3D model for your enclosure is that you end up with a design that can be prototyped but not manufactured in volume.
Ultimately, your enclosure will be produced by a method called high-pressure injection molding (see step 4 below for more details).
Developing a part for production using injection molding can be quite complex with many rules to follow. 
On the other hand, just about anything can be prototyped via 3D printing.

So be sure to only hire someone that fully understands all of the complexities and design requirements for injection molding.
Step 2 - Order Case Prototypes (or Buy a 3D Printer)
Plastic prototypes are built using either an additive process (most common) or a subtractive process. 
An additive process, like 3D printing, creates the prototype by stacking up thin layers of plastic to create the final product.

Additive processes are by far the most common because of their ability to create just about anything you can imagine.
A subtractive process, like CNC machining, instead takes a block of solid production plastic and carves out the final product.
The advantage of subtractive processes is that you get to use a plastic resin that exactly matches the final production plastic you’ll use. 
This is important for some products, however for most products this isn’t essential.

With additive processes, a special prototyping resin is used, and it may have a different feel than the production plastic. 
Resins used in additive processes have improved significantly but they still don’t match the production plastics used in injection molding.
I mentioned this already, but it deserves to be highlighted again. 
Be warned that prototyping processes (additive and subtractive) are completely different than the technology used for production (injection molding). 

You must avoid creating prototypes (especially with additive prototyping) that are impossible to manufacture.
In the beginning you don’t necessarily need to make the prototype follow all of the rules for injection molding, but you need to keep them in mind so your design can be more easily transitioned to injection molding.
is the company I personally recommend. 
They offer both additive and subtractive prototyping, as well as low-volume injection molding.

You may also consider purchasing your own 3D printer, especially if you think you will need several iterations to get your product right. 
3D printers can be purchased now for only a few hundred dollars allowing you to create as many prototype versions as desired.
The real advantage of having your own 3D printer is it allows you to iterate your prototype almost immediately, thus reducing your time to market.
Step 3 - Evaluate the Enclosure Prototypes
Now it’s time to evaluate the enclosure prototypes and change the 3D model as necessary. 
It will almost always take several prototype iterations to get the enclosure design just right.
Although 3D computer models allow you to visualize the enclosure, nothing compares to holding a real prototype in your hand. 
There will almost certainly be both functional and cosmetic changes you’ll want to make once you have your first real prototype. 

Plan on needing multiple prototype versions to get everything right.
Developing the plastic for your new product isn’t necessarily easy or cheap, especially if aesthetics is critical for your product. 
However, the real complications and costs arise when you transition from the prototype stage to full production.
Step 4 - Transition to Injection Molding
Although the electronics are probably the most complex and expensive part of your product to develop, the plastic will be the most expensive to manufacture. 
Setting up production of your plastic parts using injection molding is extremely expensive.
Most plastic products sold today are made using a really old manufacturing technique called injection molding. 
It’s very important for you to have an understanding of this process.

You start with a steel mold, which is two pieces of steel held together using high pressure. 
The mold has a carved cavity in the shape of the desired product. 
Then, hot molten plastic is injected into the mold.
Injection molding technology has one big advantage ᾠit’s a cheap way to make millions of the same plastic pieces. 

Current injection molding technology uses a giant screw to force plastic into a mold at high pressure, a process invented in 1946. 
Compared to 3D printing, injection molding is ancient!
Injection molds are extremely efficient at making lots of the same thing at a really low cost per unit. 
But the molds themselves are shockingly expensive. 

A mold designed for making millions of a product can reach $100k! This high cost is mostly because the plastic is injected at such high pressure, which is extremely tough on a mold.
To withstand these conditions molds are made using hard metals. 
The more injections required, the harder the metal required, and the higher the cost.
For example, you can use aluminum molds to make several thousand units. 

Aluminum is soft so it degrades very quickly. 
However, because it’s softer it’s also easier to make into a mold, so the cost is lower ᾠonly $1-2k for a simple mold.
As the intended volume for the mold increases so does the required metal hardness and thus the cost. 
The lead time to produce a mold also increases with hard metals like steel. 

It takes the mold maker much longer to carve out (called machining) a steel mold, than a softer aluminum one.
You can eventually increase your production speed by using multiple cavity molds.
They allow you to produce multiple copies of your part with a single injection of plastic.
But don’t jump into multiple cavity molds until you have worked through any modifications to your initial molds. 

It is wise to run at least several thousand units before upgrading to multiple cavity molds.
Conclusion
This article has given you a basic overview of the process of developing a new electronic hardware product, regardless of your technical level. 
This process includes selecting the best development strategy, and developing the electronics and enclosure for your product.
About the Author
interview/ceo-of-shalaka-connected-devices-hrishikesh-kamat-speaks-on-iot-trends-in-india
CEO of Shalaka Connected Devices, Hrishikesh Kamat Speaks on IoT Trends in India

Hrishikesh is the CEO and managing partner of Shalaka Connected Devices LLP, a company focused on developing embedded and IoT solutions for various applications globally. 
It also provides various other services like PCB designing, assembly and testing along with prototype development, MVP development and productisation for large corporates as well as budding startup's.
With massive experience on IoT, his efforts currently revolves around making electronics industry prominent in India and and create an ecosystem for improving the electronics industry. 
Apart from that he is also an advisor at various startup’s in the electronics industry and helping the upcoming engineers to build a career in core engineering and innovation.

“My aim revolves around developing great quality electronics and IoT solutions that would empower our customers to leverage technology for betterment of their organisation.ᾠSays Kamat when asked about his vision. 
We had few more questions to ask him and these were his answers
Shalaka connected devices was started with the hand holding of Shalaka Technologies Pvt Ltd originally started in 2002. 
It got off the ground in 2017 as an independent entity and is now building embedded and IoT solutions for various companies globally. 

Shalaka connected devices started with a team of 3 and now has touched 25 ᾠcompletely bootstrapped with the funding of the founders, and is now growing organically
Shalaka intends to solve the problem of delayed product development especially with embedded systems and hardware development in India. 
Typically a product development cycle can take between 6 months to 1 year based on complexity. 
Shalaka has successfully reduced this time by 25% by using modular libraries and hardware.

Shalaka has helped industries ranging from home automation to manufacturing to automotive in developing products, research samples, or simple realising their ideas for various applications. 
For some clients we have been able to design solutions that have been patented by them and helped them grow business. 
We have also started providing assembly and testing services for our client that helped them get a single window solution for all their electronics need. 
For some companies we have been providing regular support for their electronics needs, thus branding shalaka as a single window solution for all electronic support.

Shalaka plans to focus on product development, manufacturing, assembly and training services for our clients. 
We plan to design at least 10 products a year with a lean team and quick approach. 
We are also focusing on developing mobile applications for their IoT solutions thus providing an end to end service.
For a dairy industry we have been able to design a volume measuring system that is 10 times more accurate and cheaper than the competition thus enabling our client leverage it as a flagship product for their clients.

In another project shalaka has been able to achieve long distance and ultra low battery conserving equipment that can transmit data over a distance of 200-300 meters line of sight for an IoT application. 
We also built a Wi-Fi enabled IoT tracker that is shown below
Currently, shalaka is also working on developing a IOT based home appliance which is in Indian market.
Today people are using IoT Technologies as a very key part of the organisation. 

IoT is being used by almost every SMEs in large Corporates either within the organisation or for their customers. 
In the year 2017 and 18 most companies have invested time and effort in building their first IoT use case. 
This quite shows how much IoT is going to affect various businesses.
Businesses today are running on data that is available from a larger perspective but are going to rely a lot on IoT for obtaining high resolution data. 

Everyone knows that data is the next Big buck and IoT is the primary steps towards achieving it. 
IoT is going to help businesses look deeper into their customers as well as their own operations and focus on improving their products as well as their manufacturing process.
Industry 4.0 is a very large concept and currently most of the companies are struggling with understanding the exact meaning of industry 4.0 and how it can be implemented in their company. 
India currently is in a very infant stage similar to most other developing and developed countries in the world.

is definitely the next industrial revolution because it is a perfect composition of Cyber physical space. 
Which machines interacting better with humans in providing Deep Inside as when is communicating with each other for increase efficiency the surely is going to revolutionize the entire manufacturing and service industry.
Most of the companies have interacted with recently, have a fair idea about industry 4.0. 
They have clear vision about the road map but lack the direction to take the first step. 

So it is the primary duty of any IoT service providing company to educate the market for better use of the technology they are providing. 
India currently lies on the lower size of the innovation curve but accelerating aggressively all leading this innovation sector. 
Industry 4.0 is going to have a very key role in this process.
Everyone should understand that IoT is a combination of various existing Technologies like embedded systems, various types of wired and wireless communication, mobile applications in web applications cloud server Technologies. 

All these Technologies have been present since the last decade while some of them have been present since two or three decades.
More than focusing on reading a book on a white paper it is advised to build a solution a part of the solution the skills that are developed. 
Upcoming engineer should focus on developing one of these skills and becoming a master in it rather than trying to learn the entire IoT system. 
Best place to learn IoT skills is to work in a small company that design these solutions or use them does giving an inside view of the same

The biggest challenge in developing hardware especially for IoT systems is the analytical approach that is required to build an efficient hardware. 
The key for great hardware is focusing on the fundamentals and understanding the key to robustness. 
Reliability of hardware is one thing that engineers especially in the electronics sector have neglected. 
And this becomes the main hurdle for Hardware development.

Another challenge the hardware sector is that it is very time consuming. 
Software is typically easier to debug due to availability of great compilers and tools. 
But hardware requires basic knowledge about electronics and is very time consuming especially with the use of external testing equipments. 
Single mistake in the hardware development phase costs a time loss of 2 to 3 weeks. 

This experimental process is another reason why hardware industry is still not developing in India.
Another challenge in hardware development is the availability of components in short amount of time. 
Usually we have to order components from E-Commerce websites that take around 5 to 7 days for delivery and in case of additional component requirement costs another week off time delay due to unavailability at the local level. 
If majority of two components are available at a local level hardware development can be accelerated with easier testing facilities and lesser risk of time loss.

The upcoming engineers need to focus on one segment of the IoT architecture. 
They should understand the fundamental behind it and focus on building solutions that can be used in the real world. 
Understanding these Technologies at the most fundamental level is very important. 
For this upcoming engineer should focus on getting as much internship as possible.

Engineers at Shalaka has always been passionate about teaching because that is the way better human resources groomed for everyone in the ecosystem. 
Also we believe that teaching is a process of strengthening you are engineering skills. 
This is the very reason why Shalaka has a training wing.
Shalaka provides training to corporate on technology or product levels. 

Just help companies focus on the business and worry less about their Technology wing.
The retail training segment intended towards real life product development rather than lab experiment. 
This training session focuses on developing parts of an IoT solution in understanding the development life cycle via hands on learning. 
Unlike typical training organisations Shalaka focuses on a flexible syllabus on latest technology. 

Shalaka believes that the art of learning is more important in the long run. 
Today most upcoming engineers join training courses with rigid syllabus that is upgraded very rarely. 
Eventually useful skills become obsolete. 
If people are able to embrace the art of learning one is able to stay on the technological curve and grasp upcoming Technologies with minimum effort. 

This is the key focus for the training wing at Shalaka.
Knowingly or unknowingly I have always been with an entrepreneur based mind set. 
I do not know about startup but the right time to do something on your own is now. 
At every age in life we are faced with some challenges that are common to many build a solution to it. 

The scenario can be anywhere around you. 
Set an open mind and a solution oriented perspective one is able to build an activity based organisation that might be run by an individual but solve the problem for many. 
This is somewhere lost today. 
In free time I always suggest everyone to look around for problems and sort them even if they do not provide any monetary benefits.

Start-up does not necessary mean of big organisation but it can be an individual who is working to solve the problem and be successful in doing so. 
Startup is just a term that is defined for the millennial generation but the core essence has been present since centuries. 
Even school kid can develop an entrepreneur mindset by focusing on problems and finding the selection in the most efficient way
NASA space Academy was one of the most interesting parts of my life because it helped me realise my true potential and my drawbacks. 

The entire training focused on activities that real life astronauts and pilots undergo in their training phase. 
It was a mixture of physical and mental activities that made you scratch your brain and stretch your body to its possible limits. 
My most favourite memory is the mark space shuttle simulation that helped us experience the entire Space Shuttle machine process. 
The NASA space Academy experience has played an important role in the overall aptitude towards problem solving that I’ve developed.

Every project has been an experience on its own and it is really hard to separate one as a favourite. 
Every project has been a learning lesson for the next in time and again we have discovered New problems and challenges.
Our work environment is typically very messy but organised since we deal with a lot of hardware, soldering, small components and lot of testing equipment's. 
Our typical work desks are filled with electronics and samples of products we are working on. 

My personal work desk is more organised since most of my work is limited to my laptop and my programming/hardware tasks are done with the team on their work benches.
our small prototype room used only for quick prototyping or experimenting
India is gaining great momentum in the field of electronics and a lot of companies are looking to get their solutions/products designed and manufactured in India which is the biggest plus. 
Since the last 3 years the number of enquiries and opportunities we receive in this segment is growing steadily. 

The hard part is that most of the market is uneducated in terms of challenges and timelines regarding product development in the hardware sector. 
Being a sector that physically involves a lot of hardware design, the process is slow and time consuming ᾠand unlike software industry the results are not quick. 
Also, there is an underdeveloped electronics ecosystem that needs to be developed in order to have quicker support on the various aspects of embedded product development like easier access to components, quicker support from companies for queries and more hardware labs for testing.
My only advice to upcoming aspiring technopreneur, is that they should focus on solving problems starting at their local levels. 

Most aspiring entrepreneurs I have met in the past 3 years are more focused on following a business model that they have observed in an ecosystem/market unlike ours. 
Also, I usually advices them not to jump in the bandwagon just because they see that there is lot of investment being done, because having sufficient technical knowledge about something is as important as running and growing the company.

tutorial/what-is-pwm-pulse-width-modulation

What is PWM: Pulse Width Modulation
, PWMsignals and some parameters associated with it, so that we will be confident in using them in our designs.
What is PWM (Pulse Width Modulation)?
ᾮ

For a PWM signal we need to look at two important parameters associated with it one is the PWM duty cycle and the other is PWM frequency.
Duty cycle of the PWM
As told earlier, a PWM signal stays on for a particular time and then stays off for the rest of the period. 
What makes this PWM signal special and more useful is that we can set for how long it should stay on by controlling the duty cycle of the PWM signal.

The percentage of time in which the PWM signal remains HIGH (on time) is called as duty cycle. 
If the signal is always ON it is in 100% duty cycle and if it is always off it is 0% duty cycle. 
The formulae to calculate the duty cycle is shown below.
Duty Cycle =Turn ON time/ (Turn ON time + Turn OFF time)

(on time + off time) the PWM signal stays on only for 50% of the time period.
ᾮ
Frequency of a PWM
The frequency of a PWM signal determines how fast a PWM completes one period. 

One Period is the complete ON and OFF time of a PWM signal as shown in the above figure. 
The formulae to calculate the Frequency is given below
Frequency = 1/Time Period
Time Period = On time + Off time

Normally the PWM signals generated by microcontroller will be around 500 Hz, such high frequencies will be used in high speed switching devices like inverters or converters. 
But not all applications require high frequency. 
For example to control a servo motor we need to produce PWM signals with 50Hz frequency, so the frequency of a PWM signal is also controllable by program for all microcontrollers.
Some commonly arising questions on PWM
is called as one time period. 
The inverse of one time period is called frequency. 
While the amount of time the PWM signal should remain on in one time period is decide by Duty cycle of the PWM.
and is commonly used where a DAC feature is required. 

The circuit for the same is shown below
In the graph shown above, theYellow coloured one is the PWM signal and the blue colour one is the output analog voltage. 
The value of the resistor R1 and capacitor C1 can be calculated based on the frequency of the PWM signal but normally a 5.7K or 10K resistor and a 0.1u or 1u Capacitor is used.
The output voltage of a PWM signal after converting it to analog will be the percentage of Duty cycle. 

For example if the operating voltage is 5V then the PWM signal will also have 5V when high. 
In such case for a 100% duty cycle the output voltage will be 5V for a 50% duty cycle it will be 2.5V.
Output Voltage = Duty cycle (%) * 5
We have previously used PWM with various microcontroller in many of our projects:

Pulse width Modulation with ATmega32
PWM withArduino Uno
Generating PWM using PIC Microcontroller
Raspberry Pi PWM Tutorial

Servo Motor Control with Raspberry Pi
Pulse width Modulation (PWM) using MSP430G2
Pulse width Modulation (PWM) in STM32F103C8
Servo Motor Control with Raspberry Pi

DC Motor Control with Raspberry Pi
1 watt LED Dimmer
Arduino Based LED Dimmer using PWM


tutorial/what-is-adc-analog-to-digital-converters
What is ADC - Analog to Digital Converters
The Analog world with digital Electronics
Few years back the entire electronics devices that we use today like phones, computers, Televisions etc were analog in nature. 

Then slowly the landline phones were replaced by modern mobile phones, CRT Televisions and monitors were replaced by LED displays, computers with vacuum tubes evolved to be more powerful with microprocessors and microcontrollers inside them and so on..
What is ADC and how to use it?
As said earlier ADC stands for Analog to digital conversion and it is used to convert analog values from real world into digital values like 1’s and 0’s. 
So what are these analog values? These are the ones that we see in our day to day life like temperature, speed, brightness etc. 

But wait!! Can an ADC convert temperature and speed directly into digital values like 0’s and 1’s?
For example to convert temperature values into voltage we can use a Thermistor similarly to convert brightness to voltage we can use a LDR. 
Once it is converted to voltage we can read it with the help of ADC’s.
In order to know how to use an ADC we should first get familiar with some basic terms like, channels resolution, range, reference voltage etc.
Resolution (bits) and channels in ADC
Not every pin on a microcontroller can read Analog voltage, the term 8-channel means that there are 8 pins on this ATmega328 microcontroller which can read Analog voltage and each pin can read the voltage with a resolution of 10-bit. 
This will vary for different types of Microcontrollers.
).

With this if the actual input voltage is 0V then the MCU’s ADC will read it as 0 and if it is 5V the MCU will read 1024 and if it somewhere in between like 2.5V then the MCU will read 512. 
We can use the below formulae to calculate the digital value that will be read by the MCU based on the Resolution of the ADC and Operating voltage.
(ADC Resolution / Operating Voltage) = (ADC Digital Value / Actual Voltage Value)
Reference Voltage for an ADC
meaning you can set this voltage internally to some available value using software (program). 
In an Arduino UNO board the reference voltage is set to 5V by default internally, if required user can set this reference voltage externally through the Vref pin also after making the required changes in the software.
Always remember that the measured analog voltage value should always be less than the reference voltage value and the reference voltage value should always be less than the operating voltage value of the microcontroller.
Example
) different levels, like shown in the below picture:
So if analog voltage is 0.25 then the digital value will be 1 in decimal and 001 in binary. 
Likewise if analog voltage is 0.5 then the digital value will be 2 in decimal and 010 in binary.
, ADC0808.

Below you can find various examples of ADC with different microcontrollers:
How to Use ADC in Arduino Uno?
Raspberry Pi ADC Tutorial
Interfacing ADC0808 with 8051 Microcontroller

0-25V Digital Voltmeter using AVR Microcontroller
How to use ADC in STM32F103C8
How to use ADC in MSP430G2
ADC types and working
To explain how each of these ADC’s work and the difference between them would be out of scope for this article as they are fairly complex. 
But to give a rough idea ADC has an internal capacitor which will get charged by the analog voltage that is to measured. 
Then we measure the voltage value by discharging the capacitor over a period of time.
Some commonly arising questions on ADC
using the link. 
For our above example we should use a 1K resistor and 720 ohm resistor in series to the voltage source and measure the voltage in between the resistors as discussed in the link above.
When using an ADC converter to measure analog voltage the result obtained by the MCU will be in digital. 
For example in a 10-bit 5V microcontroller when the actual voltage that is to be measure is 4V the MCU will read it as 820, we can again use the above discussed formulae to convert the 820 to 4V so that we can use it in our calculations. 

Lets cross-check the same.
(ADC Resolution / Operating Voltage) = (ADC Digital Value / Actual Voltage Value)
Actual Voltage Value = ADC Digital Value * (Operating Voltage / ADC Resolution)
= 820 * (5/1023)

= 4.007
= ~4V
Hope you got a fair idea of ADC and how to use them for your applications. 
If you had any problem in understanding the concepts feel free to post your comments below or write it on our forums.


tutorial/audio-transformer
Audio Transformer
What is a Transformer?
Audio Transformer
) wrapped around a magnetic iron core.
Due to this, the transformer does not alter the voltage or current level. 
It does only create isolation between the Input amplifiers with the output speaker system.

or the current level to drive a load across it. 
Same happens for the Stepdown transformer too. 
It converts the voltage from higher to lower with the increased current output.
When the output of one circuit or device is directly connected to the input of another device, it is very important that the device output impedance and device input impedance both are matched. 

An impedance matching transformer provides this feature and converts higher impedance output to lower impedance to drive a low impedance speaker or feeding to another low impedance device.
Working of Audio Transformer and its Construction
Although an Audio transformer does not have a physical connection between his primary and secondary coil, the transformer provide bidirectional feature between this two windings. 
We can also use the same primary side as secondary and secondary as primary. 

In such case, the transformer provides signal loss in one direction and signal gain in reverse direction or vice versa.
The audio transformer works at frequencies between 20 Hz to 20 kHz. 
So, the operation of an Audio transformer has much wider frequency range.
technique. 

It is very useful for balancing amplifiers and loads (Loudspeaker and other) that use a different input or output impedances for maximum power transfer application.
In modern days, speakers impedances ranges from 4 to 16 ohms, typically 4 ohms, 8 ohms or 16 ohms speakers are available whereas Transistor or Solid state amplifiers use 200 ᾠ300 ohms output impedance. 
If the amplifier is a retro design, such as old Valve or Tube amplifier then the output voltage sometimes reach 300V with 3k impedance. 
We need impedance matching transformer which will convert the High impedance to low impedance and should convert the voltage and current to a level which will directly drive a loudspeaker.

This turns ratio also defines the primary and secondary voltage ratio as the voltage is directly proportional to the primary and secondary winding turns.
So, NP/NS = VP/VS
Audio Transformer Impedance Ratio
is the most important factor for impedance matching transformers. 

For impedance matching transformer the impedance ratio between primary to secondary can be calculated using the primary and secondary turn or the primary and secondary output voltage.
we need to square the transformer turns ratio or the transformer voltage ratio.
is the voltage ratio of the transformer. 
Impedance ratio is the square of turns ratio or voltage ratio. 

So, a transformer with 4:1 turns ratio or voltage ratio could provide 16:1 impedance ratio.
Example
We can calculate some practical values depending on the formulas given above.
Suppose, a transformer with a 25:1 turns ratio is used to balance the power amplifier output with a loudspeaker. 

The Power amplifier provides 100 ohms output impedance, what would be the nominal speaker impedance needed for maximum power transfer?
So, using the 25:1 turn’s ratio transformer across 100Ω power amplifier we could efficiently drive 4Ω Loud Speaker with maximum power transfer.
Types of Audio Transformer
are mainly used for audio related purposes.


Impedance matching Transformer
Step up Audio Transformer with Wide frequency range which is within the audible frequency.
Step down Audio Transformer with Wide frequency range which is within the audible frequency.

There is another specific Audio transformer also available, which are useful for digital audio applications and generally works in high frequency.
Transformers can also have multiple primary and secondary taps, which provide flexibilities to the user to change the output devices without changing the costly audio transformer. 
For example, A transformer can have multiple secondary taps to connect multiple loads with 4 ohms, 8 ohms or even 16 ohms impedance but only one tap need to be connected to the load when working with it. 
Such transformers are generally costly and can be found in retro musical systems or amplifiers.

available in various shapes and sizes depending on their specifications and usages.
Microphone Transformer
A microphone transformer mainly used to balance the impedance between Amplifier system and the microphone. 
It is essential as there will be signal loss due to unbalanced impedance on Amplifier input and microphone output.

A microphone transformer does not reduce Hum noises. 
A microphone transformer needs a twisted pair with ground shielding wires to connect. 
The wire consists of two conductors which are tightly twisted together with surrounded by a conducting braid or foil. 
This wire effectively reduces humming noises and external noise interferences.

In such a configuration, the Amplifier gets a perfect balanced signal.
100V Line Audio Drive Transformer
with poor signal amplitude across the speakers.
The step-up transformer increases the audio output signal voltage to 100V. 

Due to the Formula P(W) = V x A, when a voltage is increased the current decreases for a given power. 
The resistance would not effective for the low signal current. 
The signal will transmit perfectly.
On the other end, across each loudspeaker, a step-down transformer with impedance matching facility, Steps down the 100V to the speaker voltage and increases the current. 

The Transformer also matches the impedance for maximum power transfer.
They have multiple connections in both primary and secondary side. 
In general, primary side taps are used for suitable power level thus the amplification gain can be controlled by tap connections. 
And the secondary side has multiple taps which are useful to connect different impedance speakers to different impedance speaker as per choice and availability.

Many modern Professional Amplifier line transformers provide high power handling capabilities as well as multiple configurations to connect parallel or series, loudspeakers together.

interview/inventor-gaurav-tiwari-speaks-on-how-he-built-and-launched-stridalyzer
Inventor Gaurav Tiwari speaks on how he built and launched Stridalyzer ᾠAn IOT based smart wearable insole

Gaurav Tiwari is the Director of Engineering at ReTisense and the Inventor of Stridalyzer Techonology. 
Being a computer science graduate at GLA University his passion for computers and new technologies has motivated him to work on different freelance projects right from the 1s year of his college.
Today he and his team take the pride for developing and launching Stridalyzer into the market. 
Stridalyzer is a smart IOT based insole with sensors, these insoles sits inside your shoe to analyze your running gait, predict injuries and much more. 

All these data can be easily visualized on your smart phone and unlike most trackers Stridalyzer uses Piezo electric crystals instead of accelerometers to make it battery efficient and that is not where it stops, we have more intriguing information through his interview
ReTiSense plans to be the de-facto leader in Biomechanics platform for Sports and Healthcare by developing breakthrough sensing and analytics for all aspects of human movement.
ReTiSense product line Stridalyzer has two versions.
Stridalyzer Performance: Geared towards helping end-users to understand and improve their running form, avoid running injuries, and improve their running performance.

Stridalyzer INSIGHT: Provide full-loop solutions to patients and healthcare professionals to diagnose, analyze, intervene and track recovery, through the use of patent-pending technologies and intuitive visualizations and reports.

We started a Kickstarter crowd funding campaign, which was a success and then we got some bootstrap funding to start the production.
Sensor fitted insoles (Stridalyzer), can connect to mobile application and used to analyze Running Gait, other sports data, gives the injury prediction. 

Stridalyzer Technology can be used for Rehab (Sports Medicine), Balance Training (Brain Stroke), Foot Ulcer Prediction (Diabetes), Fall Risk Prediction (Elderly) and many other foot problems.
Our Biomechanical modeling and computation algorithms enable real time analysis and guidance in various areas of athletics and sports. 
In addition, our technology is easily integratable with existing footwear, making it attractive for licensing.
Stride means a step and Stridalyzer name comes from analyzer of steps (stride).

The major concernwas the power optimization. 
We have a limited space to put battery in the insole without compromising on comfort. 
We have used 180mah battery, which is small in size and optimized the power usage in many iterations.
We have used 180mah battery and optimized the power consumption over every version of Stridalyzer, which results one full charge can go for 20 hours of run/active time or 3 weeks of standby.

Each insole has a BLE module, which can connect to Stridalyzer app simultaneously using mobile Bluetooth.
My maximum effort goes in actually designing the end-to-end architecture of Stridalyzer features, sometime coding (because I like doing that) and then dealing with customers across the globe.
ReTiSense founded in June 2014, with an idea of Stridalyzer and we had our first functional prototype by January 2015.
You can buy Stridalyzer from below online stores

It was a great feeling. 
We have considered Kickstarter as validation of our idea and go for our first batch production.
Crowdfunding platforms are a good way of validating your product idea. 
Technopreneurs can find an early adaptor for new technology or innovation. 

Selecting a good Crowdfunding platform is very important as it can bring your product specific market PR.
Developing product ischallenging, as it is a niche technology with very few direct competitors, but marketing of these products is more challenging and takes more effort to educate people and build an environment for the products.
There are lots of things that can be done in sports/healthcare like full body biomechanics, prediction and prevention of specific deceases like Parkinson’s.
In wearable tech IoT products, wearable come first. 

Anything, which sits on the body need to be very comfortable, in wearable tech the common problem is to embed technology to wearable without compromising on comfort.
We had a manufacturing partner in Taiwan, for the Stridalyzer first version of manufacturing. 
Now we have moved most of the manufacturing to India.
We started making our own pressure sensors and full insole assembly in India.

Stridalyzer is now a line of products. 
Stridalyzer Performance is an smart insole for runners.
Recently we have launched a new product Stridalyzer INSIGHT, which can be used by Physiotherapists, Rehab (Sports Medicine), Balance Training (Brain Stroke), Foot Ulcer Prediction (Diabetes), Fall Risk Prediction (Elderly) and many other foot problems.
In future we plan to come with full body Biomechanics platform with different devices.

Iot and wearable electronics has improved a lot in last 5 years. 
Iot with integration with machine learning and AI have to go a long way and it’s the future of all connecting devices.
It’s an open friendly environment.
My team is small and has very talented and focused people from different domain.

Anshuman (Founder): He has been in the tech industry in various roles for 18 years. 
An expert in semiconductors and biomechanical analytics.
Anshuman and I met accidentally in a coffee shop and from then we are working on Stridalyzer.
I use many tools and software’s for various purpose like: EasyEDA, WebStorm, pixlr

Yes, We always look for good talents. 
Email ID: careers at retisense dot com
Engineering is the field where learning never stops. 
Develop things that you are proud of.


article/introduction-to-bit-banging-spi-communication-in-arduino-via-bit-banging
Introduction to Bit Banging: SPI communication via Bit Banging
come in to play.
What is Bit Banging?
Bit banging is a technique for serial communication in which the whole communication process is handled via software instead of dedicated hardware. 
To transmit data, the technique involves the use of software to encode the data into signals and pulses which are used to manipulate the state of an I/O pin of a microcontroller which serves as the Tx pin to send data to the target device. 
To receive data, the technique involves sampling the state of the Rx pin after certain intervals which is determined by the communication baud rate. 

The software sets all the parameter needed to achieve this communication including synchronization, timing, levels etc., which are usually decided by dedicated hardware when bit banging is not used.
When to use Bit Banging
Bit-Banging is usually used in situations where a microcontroller with the required interface is not available or when switching to a microcontroller with the required interface might be too expensive. 
It thus provides a cheap way of enabling the same device to communicate using several protocols. 

A microcontroller which is previously enabled for UART communication only, can be equipped to communicate using SPI and 12C via bit banging.
Algorithm for Serial Communication via Bit Banging
While the code to implement bit banging may differ across diverse microcontrollers and may also vary for different serial protocols, but the procedure/algorithm for implementing bit banging is the same across all platforms.
the pseudo-code below is used;

Start
Send start bit
Wait for timing to correspond with the baud rate of receiver
Send data bit

Wait for duration to correspond with the baud rate of receiver again
Check if all data bits have been sent. 
If no, go to 4. 
If yes, goto 7

Send stop bit
Stop
tends to be a little bit more complex, usually an interrupt is used to determine when data is available on the receiver pin. 
This helps ensure the microcontroller doesn’t waste too much processing power. 

Although certain implementations use any of the microcontrollers I/O pins but the chances of noise and errors, if not probably handled, is higher. 
The algorithm to receive data using interrupts is explained below.
Start
Enable interrupt on Rx pin

When interrupt is triggered, obtain start bit
Wait for timing according to the baud rate
Read the Rx pin
Repeat from 4 till all data has been received

Wait for timing according to the baud rate
Check for stop bit
Stop
Bit Banging over SPI
, the base value of the clock is always 0 and data is always sent or received on the rising edge of the clock. 
The timing diagram for the SPI Mode 1 communication protocol is shown below.
To implement this, the following algorithm can be used;
Start

Set the SS pin low to begin communication
Set the pin for Master Out Slave In (MOSI) to the first bit of the data to be sent
Set the clock pin (SCK) high so data is transmitted by the master and received by the slave
Read the state of the Master in Slave Out (MISO) to receive the first bit of data from slave

Set SCK Low, so data can be sent on the next rising edge
Go to 2 till all data bits have been transmitted.
Set the SS pin High to stop transmission.
Stop
Example of Bit Banging: SPI communication in Arduino
to show how data can be bit-banged over SPI using the code below.
to be used.
const int SSPin = 11;

const int SCKPin = 10;
const int MISOPin = 9;
const int MOSIPin = 8;
byte sendData = 64;   // Value to be sent

byte slaveData = 0;  // for storing the  value sent by the slave
function where the state of the pins are declared. 
Only the Master in Slave out (MISO) pin is declared as an input since it is the only pin that receives data. 
All other pins are declared as output. 

After declaring the pin modes, the SS pin is set to HIGH. 
The reason for this is to ensure the process is error free and communication only starts when it’s set to low.
void setup()
{

pinMode(MISOPin, INPUT);
 pinMode(SSPin, OUTPUT);
 pinMode(SCKPin, OUTPUT);
 pinMode(MOSIPin, OUTPUT);

digitalWrite(SSPin, HIGH);
}
Note that this loop will keep sending the data repeatedly.
function which breaks the predefined data into bits and send. 

With this done, we then write the SS pin HIGH to indicate the end of data transmission.
void loop()
{
  digitalWrite(SSPin, LOW);        // SS low

  slaveData = bitBangData(sendData); // data transmission
  digitalWrite(SSPin, HIGH);       // SS high again 
}
is written below. 

The function takes in the data to be sent and breaks it down into bits and sends it over by looping over the code for the transmission as indicated in step 7 of the algorithm.
byte bitBangData(byte _send)  // This function transmit the data via bitbanging
{
  byte _receive = 0;

  for(int i=0; i<8; i++)  // 8 bits in a byte
  {
    digitalWrite(MOSIPin, bitRead(_send, i));    // Set MOSI
    digitalWrite(SCKPin, HIGH);                  // SCK high

    bitWrite(_receive, i, digitalRead(MISOPin)); // Capture MISO
    digitalWrite(SCKPin, LOW);                   // SCK low
  } 
  return _receive;        // Return the received data
}
Disadvantages of Bit Banging
Adopting bit banging should however be a well thought out decision as there are several downsides to bit banging that may make it not reliable for implementation in certain solutions. 
Bit banging increase the power consumed by the microcontroller due to the high processing power consumed by the process. 

Compared to dedicated hardware, more communication errors like glitches and jitters occur when bit banging is used especially when data communication is being performed by the microcontroller at the same time as other tasks. 
Communication via bit banging happens at a fraction of the speed with which it occurs when dedicated hardware is used. 
This may be important in certain applications and may make bit banging a “not so goodᾠchoice.
Bit banging is used for all kinds of serial communications including; RS-232, Asynchronous Serial Communication, UART, SPI, and I2C.
UART via Bit banging in Arduino
One of the popular implementations of bit banging is the Arduino Software Serial library which enables the Arduino to communicate over UART without using the dedicated hardware UART pins (D0 and D1). 
This gives a lot of flexibility as users can connect as many serial devices as the number of pins on the Arduino board can support.


tutorial/synchronous-counter
Synchronous Counter
What is a Counter?
A counter is a device which can count any particular event on the basis of how many times the particular event(s) is occurred. 

In a digital logic system or computers, this counter can count and store the number of time any particular event or process have occurred, depending on a clock signal. 
Most common type of counter is sequential digital logic circuit with a single clock input and multiple outputs. 
The outputs represent binary or binary coded decimal numbers. 
Each clock pulse either increase the number or decrease the number.
Synchronous Counter
generally refers to something which is cordinated with others based on time. 
Synchronous signals occur at same clock rate and all the clocks follow the same reference clock.
Synchronous Up Counter
in the synchronous counter just because all flip-flops or counter stage is in parallel clock source and the clock triggers all counters at the same time.
logic across the Logic 1 signal, change the state of first flip-flop on every clock pulse.
, input pin of J and K is connected across the output of the first Flip-flop. 
For the case of FFC and FFD, two separate AND gate provide the necessary logic across them. 

Those AND gates create logic using the input and output from the previous stage flip-flops.
We can create the same counting sequence used in the Asynchronous counter by making a situation where each flip-flops change its state depending on whether or not all preceding flip-flops output is HIGH in logic. 
But in this scenario, there will be no ripple effect just because all flip-flops are clocked at the same time.
Synchronous Down Counter
, the AND Gate input is changed. 
First Flip-flop FFA input is same as we used in previous Synchronous up counter. 
Instead of directly feeding the output of the first flip-flop to the next subsequent flip-flop, we are using inverted output pin which is used to give J and K input across next flip-flop FFB and also used as input pin across the AND gate. 
Same as like the previous circuit, two AND gates are providing necessary logic to the next two Flip-flops FFC and FFD.
Synchronous Counter Timing Diagram
The counting output across four output pin is incremental from 0 to 15, in binary 0000 to 1111 for 4-bit Synchronous up counter. 
After the 15 or 1111, the counter reset to 0 or 0000 and count once again with a new counting cycle.
For Synchronous down counter where the inverted output is connected across the AND gate, exactly opposite counting step happens. 

The counter starts to count from 15 or 1111 to 0 or 0000 and then get restarted to start a new counting cycle and again start from 15 or 0000.
4 bit-Synchronous Decade Counter
Same as like Asynchronous counter, a Decade counter or BCD counter which can count 0 to can be made by cascading flip-flops. 
Same as like Asynchronous counter, it will also have “divide by nᾠfeature with modulo or MOD number. 

We need to increase the MOD count of the Synchronous counter (can be in Up or Down configuration).
is shown-
Above circuit is made using Synchronous binary counter, which produces count sequence from 0 to 9. 
Additional logics are implemented for desired state sequence and to convert this binary counter to decade counter (base 10 numbers, Decimal). 

When the output reaches count 9 or 1001, the counter will reset to 0000 and again counts up to 1001.
In the above circuit, AND gates will detect the counting sequence reaches 9 or 1001 and change the state of a third flip-flop from the left, FFC to change its state on the next clock pulse. 
The counter then resets to 000 and again starts to count until 1001 is reached.
MOD-12 can be made from the above circuit if we change the position of AND gates and it will count 12 states from 0 (0000 in binary) to 11 (1011 in binary) and then reset to 0.
Trigger Pulse related information
There are two type of edge triggered flip-flops available, Positive edge or Negative edge.
count one single step when the clock input changes its state from Logic 0 to Logic 1, in other term Logic Low to Logic High.
count one single step when the clock input changes its state from Logic 1 to Logic 0, in other term Logic High to Logic Low.

Ripple counters use falling edge or negative edge triggered clock pluses to change state. 
There is a reason behind it. 
It will make easier opportunities to cascade counters together as the Most Significant bit of one counter could drive the clock input of next counter.
Synchronous counter offer carry out and carry in pin for counter linking related application. 

Due to this, there is no propagation delay inside the circuitry.
Advantages and Disadvantage of Synchronous Counter
Now we are familiar with Synchronous counter and what are the difference between the Asynchronous counter and Synchronous counter. 
Synchronous counter eliminates lots of limitations which arrive in Asynchronous counter.

is as follows-
It’s easier to design than the Asynchronous counter.
It acts simultaneously.
No propagation delay associated with it.

Count sequence is controlled using logic gates, error chances are lower.
Faster operation than the Asynchronous counter.
of working with Synchronous counter is that it requires a lot of extra logic to perform.
Use of Synchronous Counter
Few applications where Synchronous counters are used-
Machine Motion control
Motor RPM counter
Rotary Shaft Encoders

Digital clock or pulse generators.
Digital Watch and Alarm systems.

tutorial/asynchronous-counter

Asynchronous Counter
What is a Counter?
A counter is a device which can count any particular event on the basis of how many times the particular event(s) is occurred. 
In a digital logic system or computers, this counter can count and store the number of time any particular event or process have occurred, depending on a clock signal. 

Most common type of counter is sequential digital logic circuit with a single clock input and multiple outputs. 
The outputs represent binary or binary coded decimal numbers. 
Each clock pulse either increase the number or decrease the number.
What is Asynchronous?
Asynchronous stands for the absence of synchronization. 
Something that is not existing or occurring at the same time. 
In computing or telecommunication stream, Asynchronous stands for controlling the operation timing by sending a pulse only when the previous operation is completed rather than sending it in regular intervals.
Asynchronous Counter
possible counting states.
Asynchronous Truncated Counter and Decade Counter
sequences.
To get the advantage of the asynchronous inputs in the flipflop, Asynchronous Truncated counter can be used with combinational logic.

Decade Counters requires resetting to zero when the output reaches a decimal value of 10.
If we count 0-9 (10 steps) the binary number will be ᾍ

Number Count
Binary Number
Decimal Value

0
0000
0
1
0001
1
2
0010
2
3
0011
3

4
0100
4
5
0101
5
6
0110
6
7
0111
7

8
1000
8
9
1001
9

Timing Diagram of Asynchronous Decade Counter and its Truth Table
74LS10D. 
The Asynchronous counter count upwards on each clock pulse starting from 0000 (BCD = 0) to 1001 (BCD = 9). 
Each JK flip-flop output provides binary digit, and the binary out is fed into the next subsequent flip-flop as a clock input. 
In the final output 1001, which is 9 in decimal, the output D which is Most Significant bit and the Output A which is a Least Significant bit, both are in Logic 1. 

These two outputs are connected across 74LS10D’s input. 
When the next clock pulse is received, the output of 74LS10D reverts the state from Logic High or 1 to Logic Low or 0.
In such a situation when the 74LS10D change the output, the 74LS73 J-K Flip-flops will get reset as the output of the NAND gate is connected across 74LS73 CLEAR input. 
When the flip-flops reset, the output from D to A all became 0000 and the output of NAND gate reset back to Logic 1. 

With such configuration, the upper circuit shown in the image became Modulo-10 or a decade counter.
is shown in the next table-

Clock Pulse
Decimal Value
Output - D
Output ᾼU+393C> C
Output ᾼU+393C> B
Output - A

1
0
0
0
0
0
2
1
0
0
0
1
3
2
0
0
1
0
4
3
0
0
1
1

5
4
0
1
0
0
6
5
0
1
0
1
7
6
0
1
1
0
8
7
0
1
1
1

9
8
1
0
0
0
10
9
1
0
0
1
11
0
0
0
0
0


The reset pulse is also shown in the diagram.
Creating the Asynchronous Counter, Example, and Usability
We can modify the counting cycle for the Asynchronous counter using the method which is used in truncating counter output. 
For other counting cycles, we can change the input connection across NAND gate or add other logic gates configuration.

For this, if we want to design a truncated asynchronous counter, we should find out the lowest power of two, which is either greater or equal to our desired modulus.
, if we want to count 0 to 56 or mod ᾠ57 and repeat from 0, the highest number of flip-flops required is n = 6 which will give maximum modulus of 64. 
If we choose fewer numbers of flip-flops the modulus will not be sufficient to count the numbers from 0 to 56. 
If we choose n = 5 the maximum MOD will be = 32, which is insufficient for the count.

formations to get MOD-128 or more specified counter.
frequency divider.
or other combinations as well.
and other combinations as well.
Frequency Dividers
We can reduce high clock frequency down to a usable, stable value much lower than the actual high-frequency clock. 
This is very useful in case of digital electronics, timing related applications, digital clocks, interrupt source generators.
18-bit ripple counter and get 1 Hz stable output which can be used for generating 1-second of delay or 1-second of the pulse which is useful for digital clocks.

can produce precise high frequency other than the signal generators.
Advantages and Disadvantages of Asynchronous Counter
ᾠcounter circuit, which offers much more flexibility on larger counting range related applications, and the truncated counter can produce any modulus number count.
for resynchronizing the flipflops. 

Also, For the truncated sequence count, when it is not equal to , extra feedback logic is needed.
in Asynchronous Counter when high clock frequencies are applied across it.

article/selecting-between-a-microcontroller-and-microprocessor

Selecting Between a Microcontroller and Microprocessor
The brain of an embedded device, which is the processing unit, is a key determinant of the success or failure of the device in accomplishing the task(s) for which it is designed. 
The processing unit is responsible for every process involving from input to the system, to the final output, thus selecting the right platform for the brain becomes very important during the device design as every other thing will depend on the accuracy of that decision.
Microcontroller and Microprocessor
.
on the other hand are general purpose computing devices which incorporate all the functions of the central processing unit on a chip but do not include peripherals like memory and input and output pins like the microcontroller.
Although manufacturers are now changing a lot of things that are blurring the line between microcontrollers and microprocessors like the use of memory on chips for microprocessors and the ability of microcontrollers to connect to an external memory, key differences still exist between these components and the designer will need to choose the best between them for a particular project.
Factors to Consider when Selecting a MPU or MCU
Before making any decision on the direction to go as regards the processing device to use for the design of an embedded product, it is important to develop the design specifications. 
Developing the design specifications provide an avenue for device pre-design which helps identify in details, the problem to be solved, how it is to be solved, highlights the components to be used and much more. 
This helps the designer make informed general decisions about the project and helps determine which direction to travel for the processing unit.
Some of the factors in the design specification that needs to be considered before choosing between a microcontroller and a microprocessor are described below.
1. Processing Power
Processing power is one of the main (if not the main) things to consider when selecting between a microcontroller and a microprocessor. 
It’s one of the main factors that tilt use to microprocessors. 
It is measured in DMIPS (Dhrystone Million of Instructions Per Seconds) and represents the number of instructions a microcontroller or microprocessor can process in a second. 

It is essentially an indication of how fast a device can complete a task assigned to it.
values and the more the maths/numeric computations the device is to perform, the more the design requirements tilt towards the use of a microprocessor due to the processing power required.
It is a desirable thing these days to have colourful and interactive GUIs even for the most basic of applications. 
Most libraries used in creating user interfaces like QT require processing power as much as 80 ᾠ100 DMIPS and the more animations, images and other multimedia contents to be displayed, the more the required processing power. 

However, simpler user interfaces on low resolution screens require little processing power and can be powered using microcontrollers as quite a number of them these days, come with embedded interfaces to interact with different displays
Although most examples given above tend to support the use of a microprocessors, they are generally more expensive compared to microcontrollers and will be an overkill when used in certain solutions, for example using a 500 DMIPS microprocessor to automate a light bulb will make the overall cost of the product higher than normal and could ultimately lead to its failure in market.
2. Interfaces
is one of the factors to be considered before choosing between a microcontroller and a microprocessor. 

It is important to ensure the processing unit to be used has the interfaces required by the other components.
From connectivity and communications stand point for instance, Most microcontrollers and Microprocessors possess the interfaces required to connect to communication devices but when high speed communication peripherals like the super speed USB 3.0 interface, multiple 10/100 Ethernet ports or Gigabit Ethernet port are required, things tilt in the direction of the Microprocessor as the interface required to support these are generally only found on them because they are more capable of handling and processing the large amounts of data and the speed at which those data are transferred.
especially when the system involves the use of an operating system.
3. Memory
These two data processing devices handle memory and data storage differently. 
Microcontrollers for instance come with embedded, fixed memory devices while microprocessors come with interfaces to which memory devices can be connected. 
Two major implications of this are;
The microcontroller becomes a cheaper solution, since it does not require the use of an additional memory device while the microprocessor becomes an expensive solution to be adopted due to these additional requirements.

.
because of the processor core used in them, the fact that the memory is embedded and the firmware used with them is always either an RTOS or bare metal C.
4. Power 
A final point to consider is power consumption. 

While Microprocessors have low power modes, these modes are not as many as the ones available on a typical MCU and with the external components required by a microprocessor based design, it is slightly more complex to achieve low power modes. 
Asides from the low power modes, the actual amount of power consumed by an MCU is a whole lot lower than what a microprocessor consumes, because the larger the processing capability, the more the amount of power required to keep the processor up and running.
such as remote controls, consumer electronics and several smart devices where the design emphasis is on the longevity of battery life. 
They are also used where a highly deterministic behaviour is needed.

, are computation intensive and require high-speed connectivity or a user interface with lots of media information.
Conclusion
are used in applications with huge computation and performance requirements.


interview/manu-madhusudanan-ceo-and-co-founder-of-cooey
Interview - CEO of Cooey speaks on how they are planning to use technology to revolutionize Healthcare industry
Cooey was started after I had the first-hand experience of what many chronic patients go through in India. 
At one point, My daughter caught pneumonia and I also noticed that my mother, who has high blood pressure, would note down her vitals on paper. 

As the healthcare sector requires highly accurate data, I felt that the whole process needed to be digitised, starting from the patients. 
So we tried to conceptualise a solution for the recurring needs of patients.
After market research and speaking to doctors and patients, we launched Cooey as a third platform, engaging patients on the health management system and providing targeted services to them.
“Cooeyᾠis a peculiar cry uttered by the Australian aborigines as a call to attract attention, and also in common use among the Australian colonists.

Cooey’s vision is to use smart technology for high quality, high touch service enablement to provide enhanced long-term care requirements. 
Progressively, it intends to connect the dots between health care institutions with insurance companies and research organizations using real-time patient data and its analytics.The concept of constantly engaging patients with its “engagement moduleᾠis a first of its kind approach in health care space.
Cooey envisions that the above approach would address the future model hospitals which could have only ICU/CCU beds while the rest of the care would be delivered remotely with the aid of devices, data and day-care visits. 
The patient would adopt technologies using biomedical devices and stay connected to his/her care providers.

Cooey has gone through a lot, to bring out the best and to stand tall amid the ocean of different business venture and start-ups. 
The key challenges, as an organization, we faced in the initial stage include cultural fit, especially between Singapore requirements and the US requirements and along with regulatory compliances, and telecommunication infrastructure.
Additionally, there was lack of professionals with right skill sets, high costs of analytics solutions and operational gaps between the stakeholders are the major factors that are hindering the progress of adoption of analytics. 
Cooey achieves its “One-Stop Solutionᾠfor capturing, storage, retrieval, processing, and data analytics services, through constant engagement and continued support system.

We have raised funds from angels investors.
The platform suits any healthcare provider who would like to manage and monitor the recurrent needs of a patient health either remotely or in a facility.
Our typical customer profiles are a) Diabetes Management Company b) Cardiac Care Company c) Rehabilitation & Therapy Company and d) Home Health Agency
India is fast becoming a test bed for technology companies to perfect software solutions that they sell to health care providers in other geographies, especially in the United States, where a new health law has spurred demand for such services. 

The relaxed regulatory framework in India coupled with the willingness of large healthcare providers / hospital chains to experiment has provided the opportunity to iron out wrinkles under real-life conditions. 
Some areas of thrust are digitization of records and remote management of patients.
Cooey stands out with its smart voice assistant 'Maya', which simplifies routine health monitoring tasks with simple voice commands. 
And there is Alexa skills incorporated for bed-side assistance as well.

With the number of installed internet of things (IoT) device units set to go past 26 billion by 2020, machine-to-machine interaction too is going to be dominated by voice. 
And that’s what Maya brings to the table! Your voice-controlled personal assistant with a difference.
Maya simplifies routine health monitoring tasks with simple voice commands. 
Voice interfaces allow its users to ask questions and receive answers through a natural dialogue. 

Maya’s functions are available to use with any device, at any time, to interact with any application. 
With machine learning and cognitive systems as the driving force behind this technology, it’s impact in future applications can be colossal in the days to come.
With Maya around, probably, there is much more you can accomplish to support them and help them enjoy a good quality of life.
Maya empowers you with full device control in addition to using the functions in your installed applications. 

You need not launch a separate application to execute your voice commands. 
Maya wakes up to help you as you see fit, no matter where you are, what you do‐󟠮d she gets the job done for you with simple voice commands.
The ability to get you answers for your routine day to day requests, especially as an elderly patient without using the traditional input methods, have made patient monitoring far too simpler and become effective means to foster strong patient-physician relationship.
Being chronically ill can be embarrassing! Day in and day out, we do see our near and dear ones go through the painful process of logging their health vitals. 

It can add to the worries if you are someone who stays away from them and you realize they have done so much to take care of you and support you.
Both has its own share. 
Dedication, teamwork and workplace synergy is the only way to stand tall amid crucial competition.
Product design & development.

Our team profile has a combined TEAM work experience of about 150 years. 
Combined work experience of 55 years in the US health sector. 
Technologists have worked in products like
Bing, Yahoo.

The goal of our organization is to hit that ground and to come up with the best medical support to the every Indian as per the requirement without being blindly and solely dependent on hospitals. 
Cooey is working relentlessly to achieve the rank to be the forerunner of healthcare revolution.
In the next couple of years, we will be investing heavily on AI & Machine learning. 
We believe in constant engagement and continued support system.

Both places have its own advantages. 
Bangloreans are gentle hearted and they accept every one coming to their land. 
You will be introduced to a whole lot of people from every race and ethnicity. 
Bengaluru is growing rapidly and it has a great heart for people from various diaspora. 

So don’t be surprised if your next door neighbour is Manipuri, Punjabi, Tamilian, Malayalee or even from Japan. 
It might be a little cramped but there is a place for everybody here.
Smart phones are becoming an integral part of information exchange and intuitive mobile applications are becoming enabler for them. 
The use case could vary from everything from pedometers to measure how far you walk, to calorie counters to help you plan your diet, medication regimen that you follow, care advices that you receive. 

Millions of us are now using mobile technology to help us try and live healthier lifestyles. 
Today, you are empowered to share this information with your doctor who will further use it as decision support when you visit them for your healthcare needs. 
This is going to be path breaking, often by partnerships between medical and data professionals, with the potential to identify problems before they happen.
A lot needs to be done in terms of standardizing treatment methodologies. 

In urban and rural India, a standardized patient study showed low levels of provider training and huge quality gaps when it comes to quality of care delivered by private and public providers of primary health care services. 
Big data adoption will be gradual, beginning with early adopters and then to mass market. 
But there is no doubt that the field of health data analytics is one whose time has come and will create immense value to the entire ecosystem in the next decade.
Healthcare cost in India is increasing at 20% every year. 

Add to that, there is a shortage of 1.5 million doctors and 2 million Hospital beds. 
For hospitals, healthcare analytics can impact multiple areas from customer acquisition to operational efficiency to clinical delivery. 
It can be the backbone of marketing teams to target and retain the right type of customers, help operations teams understand where the hospital truly excels in and where it needs to work on to achieve high-cost efficiencies. 
Unlike many software products that are essentially just data repositories and workflow managers, data analytics can enable a doctor to create a better outcome for the patient.

Cooey feels the following are the top reasons for it to grow in the next 3 years:
It is in a niche area of remote monitoring of health vitals and information that is calling for technology adoption.
Chronic disease management companies, assisted & senior living communities, in-home care facilities, long term care & accountable care organizations are the areas that merits technology adoption with respect to remote monitoring opportunities.
Ability to interface with external systems and devices. 

Cooey would project an image that how data analytics can transform every individual and health care organization resulting in benefits to the user.
Cooey approach is a “Service-by-designᾠwhich by default will attract repeat business.
Dedication, teamwork and workplace synergy.


tutorial/switching-buck-regulator-design-basics-and-efficiency
Switching Buck Regulator: Design Basics and Efficiency
regulates the output using a resistive voltage drop and due to this Linear regulators provide lower efficiency and lose power in the form of heat.
use inductor, Diode and a power switch to transfer energy from its source to the output.

There are three types of switching regulators available.
Difference between Buck and Boost Regulator
The difference between the buck and boost regulator is, in the buck regulator the placement of inductor, diode and the switching circuit is different than the boost regulator. 
Also, in case of boost regulator the output voltage is higher than the input voltage, but in buck regulator, the output voltage is lower than the input voltage.

is one of the most used basic topology used in SMPS. 
It’s a popular choice where we need to convert higher voltage to a lower output voltage.
Same as the boost regulator, a buck converter or buck regulator consist of an inductor, but the connection of the inductor is in output stage rather than the input stage used in boost regulators.
So, in many cases, we need to convert lower voltage to the higher voltage depending on the requirements. 

Buck regulator converts the voltage from higher potential to lower potential.
Design Basics of Buck Converter Circuit
In the above image, a simple Buck regulator circuit is shown where an Inductor, diode, Capacitor and a switch are used. 
The input is directly connected across the switch. 

The Inductor and capacitor are connected across the output, thus the load gets smooth output current waveform. 
The diode is used for blocking the negative current flow.
or the switch-off phase (Switch is open).
If we assume that the switch has been in open position for a long time, the current in the circuit is 0 and there is no voltage present.

then the current will increase and the inductor will create a voltage across it. 
This voltage drop minimizes the source voltage at the output, after a few moments the rate of current change decrease and the voltage across the inductor also decrease which eventually increase the voltage across the load. 
Inductor store energy using it’s magnetic field.
The current through the inductor rises at linearly with time. 

The linear current rising rate is proportional to the input voltage less output voltage divided by the inductance
di / dt = (Vin - Vout) / L
(current through the inductor). 
The Current is increasing linearly with time when the switch is closed or ON.

for the load.
The Diode D1 will provide a return path of the current flowing through the inductor during the switch off-state.
Buck Converter Operating Modes
, the inductor never discharged fully, the charging cycle starts when the inductor is partially discharged.

In the above image, we can see, when the switch gets on when inductor current (iI) increase linearly, then when the switch gets off the inductor start to decrease, but the switch again gets on while the inductor is partly discharged. 
This is the Continuous mode of operation.
) / 2
is slightly different than the continuous mode. 

In the Discontinuous mode, the Inductor discharged fully before starting a new charge cycle. 
The Inductor will discharge fully to the zero before the switch became on.
PWM and Duty Cycle for Buck Converter Circuit
As we discussed in previous buckconverter tutorial, varying the duty cycle we can control buck regulator circuit. 

For this, a basic control system is required. 
An Error amplifier and switch control circuit is additionally required which will work in continuous or discontinuous mode.
So, for a complete buck regulator circuit, we need an additional circuitry which will vary the duty cycle and thus the amount of time the inductor receives energy from the source.
In the above image, an Error amplifier can be seen which sense the output voltage across the load using a feedback path and control the switch. 

Most common control technic includes PWM or Pulse Width Modulation technic which is used to control the duty cycle of the circuitry.
The control circuit controls the amount of time the switch remain open or, controlling how much time the inductor charge or discharge.
This circuit controls the switch depending on the mode of operation. 
It will take a sample of the output voltage and to subtract it from a reference voltage and create a small error signal, then this error signal will be compared to an oscillator ramp signal and from the comparator output a PWM signal will operate or control the switch circuit.

When the output voltage changes, the error voltage also affected by it. 
Due to error voltage change, the comparator controls the PWM output. 
The PWM also changed to a position when the output voltage creates zero error voltage and by doing this, the closed control loop system executes the work.
Fortunately, Most modern Switching buck regulators have this thing inbuilt inside the IC package. 

Thus simple circuitry design is achieved using the modern switching regulators.
The reference feedback voltage is done using a resistor divider network. 
This is the additional circuitry, which is needed along with inductor, diodes, and capacitors.
Improve efficiency of Buck Converter Circuit
As energy cannot be created nor destroyed, it can only be converted, most electrical energies loose unused powers converted to heat. 
Also, there is no ideal situation in the practical field, efficiency is a larger factor for selecting Voltage regulators.
for a switching regulator is the diode. 
The forward voltage drop multiply by current (Vf x i) is the unused wattage which is converted to heat and reduces the efficiency of the switching regulator circuit. 

Also, it is the additional cost to the circuitry for thermal/heat management technics using a heatsink, or Fans to cool down the circuitry from dissipated heat. 
Not only the forward voltage drop, Reverse recovery for silicon diodes also produce unnecessary power loss and reduction of the overall efficiency.
efficiency easily.
Despite having Higher efficiency, Stationary design technic, smaller component, switching regulators are noisy than a linear regulator. 

Still, they are widely popular.
Example Design for Buck Converter
where the 5V output is generated from the 12V input voltage. 
MC34063 is the switching regulator which was used in buck regulator configuration. 

We used an Inductor, a Schottky diode, and capacitors.
which is needed for the comparator's PWM and error amplification stage. 
The reference voltage of the comparator is 1.25V.
If we see the project in detail, we can see that 75-78% efficiency is achieved by this MC34063 switching buck regulator circuit. 

Further efficiency can be improved using proper PCB technic and obtaining thermal management procedures.
Dc power source in the low voltage application
Portable equipment
Audio equipment

Embedded hardware systems.
Solar systems etc.

interview/yuki-sato-ceo-and-founder-of-cambrian-robotics

Interview with Yuki Sato ᾠCEO and Founder of Cambrian Robotics Inc.
I feel many people who want to build something, but then development is so hard. 
It’s too complicated for even just turning on a LED from a Smartphone. 
So I started my company. 

I have always been an engineer and founder, so there is no difference between them for me.
Company’s current project Obniz allows people to access hardware via the internet by a clearly-defined API. 
It let people to make things easily. 
For example, People can directly use it through JavaScript in a HTML. 

So it doesn’t require development environment. 
And Obniz is already internet connected. 
Even turning on a LED is done through the internet. 
We are trying to solve the difficulties on building internet connected things. 

Now our product is only Obniz board. 
But we are going to make a tools/kit especially for beginners.
There are so many magazines that are treating new technologies in Japan. 
It is easy to notice a new platform and then learning it is not so hard. 

Once a man learns about one platform, then he will learn a new platform with a very few learning costs. 
Because there are many common things with all the platforms. 
And I love learning. 
I can’t stop it.

I entered a University to learn mechanical engineering because it seems hard to learn myself. 
Before entering, I already have learned electronics and computers by myself. 
I and even you can access the internet. 
So, Today, We can learn as much as we wish. 

For me, iOS and hardware and circuit designing are same thing. 
It’s just “technologyᾮ
Obniz is clearly different compared with other boards. 
A program runs on not obniz. 

People can access an obniz and control it via the internet from their program. 
When you want to make a robot controllable via the internet, you should make (1) firmware (2) communication program in firmware (3) definition of communication (4) inter two machine handshake system (5) other side program which control a robot. 
It’s too complicated. 
With obniz, people can ignore (2)(3)(4). 

And (1) and (5) becomes a single program. 
See HTML example.
You can ignore communications.
By using obniz.js, sdk for javascript, people can use obniz and it’s ios as if simple object in javascript. 

Easy to collaborate HTML parts and hardwares. 
It allows people to make internet connected things more easily. 
And also works everywhere. 
It doesn’t require development tools. 

Just an editor and a browser is needed.
).
We used Pose net with Tensorflow.js to control a puppet through smart phone as shown below
Since Obniz can make use of Phone sensors it can leverage the accelerometer and gyroscope present inside our mobile phone to control external applications like this robot car shown below.

We are surprised. 
But nowadays, combining two or more region technologies tend to be focused. 
Like “AI and carᾠ“food and internetᾮ Our product is “Web and hardwareᾮ Possibly our product tends to be focused.
“Just start nowᾠseems good. 

Supporters will answer your product as funds. 
If the answer is “not goodᾮ Easily, you can try again as possible as you can. 
There is nothing to loose in crowd funding.
Good point is you can reach more customers. 

If a person launch owned EC store, How many people visit it? Kick-starter is good for beginners. 
Its page will be visited by people all over the world. 
Because of that many people watch it. 
You can test if your idea is good or not before you start selling. 

But it takes time. 
You should spend more time with creating kick-starter campaign page and video.
If you were a special engineer who can make circuit, firmware, internet communication, cloud system, then maybe you can do same thing with ESP32. 
With obniz, by just making a simple HTML, you can start IoT development. 

It helps many people even beginners.
ARM architecture is my favour. 
Its design is beautiful, and also development tool is good.
I believe technology is always good for mankind. 

IoT is understandable trends. 
Because Wifi and LTE is almost everywhere. 
There are so many machines. 
There are no reasons the machine should not be connected the internet.

This is taken today.
Yes. 
Because, I need to make obniz parts library. 
To do that, I buy and use new parts more than before. 

But hardwares such as can’t be connected to an obniz.
I’m improving obniz circuit. 
And I make obniz examples. 
So Now I am still designing.

I keep weekends. 
Sunday and Monday I don’t do work. 
I spend the time with my wife and daughter.
Kido is a friend of mine since University. 

We made “papelookᾠtogether. 
And other members from our website “we are searching part-time jobberᾮ
There are so many University. 
It’s not hard to find a person who has good skills for lower payment.

And access through Trains, Bus is good.
But there are few investors compared with U.S.
“Just do itᾮ The cost to start is very low for even a hardware start-up.


tutorial/switching-boost-regulator-circuit-design-basics-and-efficiency
Switching Boost Regulator: Design Basics and Efficiency
regulates the output using a resistive voltage drop, and due to this Linear regulators provide lower efficiency and lose power in the form of heat.
use inductor, Diode and a power switch to transfer energy from its source to the output.

There are three types of switching regulators available.
Design Basics of Boost Converter Circuit
In many cases, we need to convert lower voltage to the higher voltage depending on the requirements. 
Boost regulator boosts the voltage from lower potential to higher potential.

is shown where an Inductor, diode, Capacitor and a switch are used.
The purpose of the inductor is to limit the current slew rate which is flowing through the power switch. 
It will limit the excess high-peak current that is unavoidable by the switch resistance individually.
We will understand how the inductors transfer energy in the upcoming images and graphs.

or the switch off phase (Switch is open).
the Vin is frightened across the inductor. 
The Diode prevents the capacitor discharge through the switch to the ground.
In the upper graph, showing the Charging phase of the inductor. 

The x-axis denotes t (time) and the Y-axis denotes I (current through the inductor). 
The Current is increasing linearly with time when the switch is closed or ON.
is reached.
The Inductor current drop rate with time is directly proportional to the inductor voltage. 

Higher the inductor voltage, faster the current drop through the inductor.
When the switching regulator is in steady-state operating condition, Inductor’s average voltage is Zero during the entire switching cycle. 
For this condition, the average current through the inductor is also in steady-state.
If we assume that the inductor charge time is Ton and the circuit has an input voltage, then there will be a specific Toff or discharge time for an output voltage.

Vin X Ton = Toff x VL
VL = Vin x (Ton / Toff)
We can say that,
Vout = Vin + Vin x (Ton / Toff)

Vout = Vin x ( 1 +  Ton / Toff)
We can also calculate the Vout using duty cycle.
Duty Cycle (D) = Ton / (Ton + Toff)
PWM and Duty Cycle for Boost Converter Circuit
If we control the duty cycle, we can control the steady-state output of the boost converter. 
So, for the duty cycle variation, we use a control circuit across the switch.
So, for a complete basic boost regulator circuit, we need an additional circuitry which will vary the duty cycle and thus the amount of time the inductor receives energy from the source.
can be seen which sense the output voltage across the load using a feedback path and control the switch. 

Most common control technic includes PWM or Pulse Width Modulation technic which is used to control the duty cycle of the circuitry.
controls the amount of time the switch remains open or close, depending on the current drawn by the load. 
This circuit also uses for continuous operation in the steady state. 
It will take a sample of the output voltage and to subtract it from a reference voltage and create a small error signal, then this error signal will be compared to an oscillator ramp signal and from the comparator output a PWM signal will operate or control the switch circuit.

When the output voltage changes, the error voltage also affected by it. 
Due to error voltage change, the comparator controls the PWM output. 
The PWM also changed to a position when the output voltage creates zero error voltage and by doing this, the closed control loop system executes the work.
Fortunately, Most modern Switching boost regulators have this thing inbuilt inside the IC package. 

Thus simple circuitry design is achieved using the modern switching regulators.
The reference feedback voltage is done using a resistor divider network. 
This is the additional circuitry, which is needed along with inductor, diodes, and capacitors.
Improve efficiency of Boost Converter Circuit
Now, If we investigate about the efficiency, It is how much power we provide inside the circuitry and how much we get at the output.
(Pout / Pin) * 100%
As energy cannot be created nor destroyed, it can only be converted, most electrical energies loose unused powers converted to heat. 
Also, there is no ideal situation in the practical field, efficiency is a larger factor for selecting Voltage regulators.

for a switching regulator is the diode. 
The forward voltage drop times current (Vf x i) is the unused wattage which converted to heat and reduces the efficiency of the switching regulator circuit. 
Also, It is the additional cost to the circuitry for thermal/heat management technics using a heatsink, or Fans to cool down the circuitry from dissipated heat. 
Not only the forward voltage drop, Reverse recovery for silicon diodes also produce unnecessary power loss and reduction of the overall efficiency.

efficiency easily.
Also, there is a feature “Skip Modeᾠwhich is being used in many modern devices which allows the regulator to skip switching cycles when there is no need of switching at very light loads. 
It is a great way to improve efficiency in light load condition. 
In skip mode, Switching cycle is initiated only when the output voltage drops below a regulating threshold.

Despite having Higher efficiency, Stationary design technic, smaller component, switching regulators are noisy than a linear regulator. 
Still, they are widely popular.
Example Design for Boost Converter
where the 5V output is generated from the 3.7V input voltage. 

MC34063 is the switching regulator which was used in boost regulator configuration. 
We used an Inductor, a Schottky diode, and capacitors.
In the above image, Cout is the output capacitor and we also used an inductor and Schottky diode which are the basic components for a switching regulator. 
There is also a Feedback network used. 

R1 and R2 resistors create a voltage divider circuit which is needed for the comparator's PWM and error amplification stage. 
The reference voltage of the comparator is 1.25V.
If we see the project in detail, we can see that 70-75% efficiency is achieved by this MC34063 switching boost regulator circuit. 
Further efficiency can be improved using proper PCB technic and obtaining thermal management procedures.


tutorial/inverting-operational-amplifier-op-amp
Inverting Operational Amplifier
section.

pin or Positive. 
An op-amp amplifies the difference in voltage between this two input pins and provides the amplified output across its Vout or output pin.
Inverting Operational Amplifier Configuration
out of phase with respect to input signal. 

Same as like before, we use two external resistors to create feedback circuit and make a closed loop circuit across the amplifier.
, we provided positive feedback across the amplifier, but for inverting configuration, we produce negative feedback across the op-amp circuit.
.
So, In case of inverting op-amp, there are no current flows into the input terminal, also the input Voltage is equal to the feedback voltage across two resistors as they both share one common virtual ground source. 

Due to the virtual ground, the input resistance of the op-amp is equal to the input resistor of the op-amp which is R2. 
This R2 has a relationship with closed loop gain and the gain can be set by the ratio of the external resistors used as feedback.
by following the link.
Gain of Inverting Op-amp
In the above image, two resistors R2 and R1 are shown, which are the voltage divider feedback resistors used along with inverting op-amp. 
R1 is the Feedback resistor (Rf) and R2 is the input resistor (Rin). 
If we calculate the current flowing through the resistor then-
i = (Vin ᾠVout) / (Rin (R2) ᾠRf (R1))

As the Dout is the midpoint of the divider, so we can conclude
As we described before, due to the virtual ground or same node summing point, the feedback voltage is 0, Dout = 0. 
So,
for closed loop gain will be

Gain(Av) = (Vout / Vin) = -(Rf / Rin)
can be used to calculate the gain of an inverting op-amp.
in contrast to the input signal’s phase.
Practical Example of Inverting Amplifier
In the above image, an op-amp configuration is shown, where two feedback resistors are providing necessary feedback in the op-amp. 
The resistor R2 which is the input resistor and R1 is the feedback resistor. 
The input resistor R2 which has a resistance value 1K ohms and the feedback resistor R1 has a resistance value of 10k ohms. 
We will calculate the inverting gain of the op-amp. 

The feedback is provided in the negative terminal and the positive terminal is connected with ground.
The formula for inverting gain of the op-amp circuit-
Gain(Av) = (Vout / Vin) = -(Rf / Rin)
In the above circuit Rf = R1 = 10k and Rin = R2 = 1k

So, Gain(Av) = (Vout / Vin) = -(Rf / Rin)
Gain(Av) = (Vout / Vin) = -(10k / 1k)
So the gain will be -10 times and the output will be 180 degrees out of phase.
Now, if we increase the gain of the op-amp to -20 times, what will be the feedback resistor value if the input resistor will be the same? So,

Gain = -20 and Rin = R2 = 1k.
-20 = -(R1 / 1k)
R1 = 20k
So, if we increase the 10k value to 20k, the gain of the op-amp will be -20times.

.
We also need to check the bandwidth of the op-amp circuit for the reliable operation at high gain.
Summing Amplifier or Op Amp Adder Circuit
or virtual earth mixer.

In the above image, a virtual earth mixer or summing amplifier is shown where an inverted op-amp mixing several different signals across it’s inverting terminal. 
An inverting amplifiers input is virtually at earth potential which provides an excellent mixer related application in audio mixing related work.
As we can see different signals are added together across the negative terminal using different input resistors. 
There is no limit to the number of different signal inputs can be added. 

The gain of each different signal port is determined by the ratio of feedback resistor R2 and the input resistor of the particular channel.
like active low pass or active high pass filter.
Trans-Impedance Amplifier Circuit
is using the amplifier as Trans-Impedance Amplifier.

It can convert the current from Photodiode, Accelerometers, or other sensors which produce low current and using the trans-impedance amplifier the current can be converted into a voltage.
which converts the current derived from the photo-diode into a voltage. 
The amplifier provides low impedance across the photodiode and creates the isolation from the op-amp output voltage.
In the above circuit, only one feedback resistor is used. 

The R1 is the high-value feedback resistor. 
We can change the gain by changing this R1 resistor’s value. 
The high gain of the op-amp uses a stable condition where the photodiode current is equal to the feedback current through the resistor R1.
As we do not provide any external bias across the photo-diode, the input offset voltage of the photodiode is very low, which produce large voltage gain without any output offset voltage. 

The current of the photo-diode will be converted to the high output voltage.
-
Phase shifter
Integrator

In signal balancing related works
Linear RF mixer
Various sensors use inverting op-amp for the output.


article/how-to-select-the-right-microcontroller-for-your-embedded-application
How to Select the Right Microcontroller for Your Embedded Application
A microcontroller is essentially a small computer on a chip, like any computer, it has memory and usually programmed in embedded systems to receive inputs, perform calculations and generate output. 
Unlike a processor, it incorporates the memory, the CPU, I/O and other peripherals on a single chip like shown in the layout below.

is always a complex decision to make because it is the heart of the project and success or failure of the system depends on it.
There are a thousand different type of microcontrollers, each of them with a unique feature or competitive advantage from form factor, to package size, to the capacity of the RAM and ROM that makes them fit for certain applications and unfit for certain applications. 
Thus often times, to avoid the headache that comes with selecting the right one, designers opt for microcontrollers that they are familiar which at times, even they do not really satisfy the requirements of the project. 
Today’s article will take a look at some of the important factors to look at when selecting a microcontroller including the Architecture, the memory, Interfaces and I/O real estate among others.
Important factors to consider when selecting a MCU
The following are some of the important factors to look at when selecting a microcontroller including the Architecture, the memory, Interfaces and I/O real estate among others.
1. Application
The first thing to do before selecting a microcontroller for any project is to develop a deep understanding of the task for which the microcontroller based solution is to be deployed. 

A technical specification sheet is always developed during this process and it will help to determine the specific features that the microcontroller which will be used for the project. 
A good example of how the application/use of the device determines the microcontroller to be used is exhibited when a microcontroller with a floating point unit is adopted for the design of a device that will be used to perform operations involving a lot of decimal numbers.
2. Select Microcontroller Architecture
The Architecture of a microcontroller refers to how the microcontroller is structured internally. 

There are two major architectures used for the design of microcontrollers;
Von Neumann Architecture
Harvard Architecture
The von Neumann architecture features the use of the same bus to transmit data and fetch instruction sets from the memory. 

Therefore data transfer and instruction fetch cannot be performed at the same time and are usually scheduled. 
The Harvard architecture on the other hand features the use of separate buses for the transmission of data and fetching of instructions.
Each of these architectures comes with its own advantage and disadvantage. 
The Harvard architecture for instance are RISC (Reduced instruction Set) computers and are thus able to perform more instructions with lower cycles than the CISC (Complex instruction Set) computers which are based on the von Neumann architecture. 

One important advantage of the Harvard (RISC) based microcontrollers is the fact that the existence of different buses for data and instruction set enables the separation of the memory access and the operations of the Arithmetic and logic unit (ALU). 
This reduce the amount of computational power required by the microcontroller and it leads to reduced cost, low power consumption and heat dissipation which makes them ideal for the design of battery operated devices. 
Many ARM, AVR and PIC Microcontrollers are based on the Harvard architecture. 
Example of microcontrollers that use the Von Neumann architecture include 8051, zilog Z80 among others.
3. Bit Size
A microcontroller can either be 8bits, 16bits, 32bits and 64bits which is the current maximum bit size possessed by a microcontroller. 
The bit size of a microcontroller represents the size of a “wordᾠused in the instruction set of the microcontroller. 
This means in a 8-bit microcontroller, the representation of every instruction, address, variable or register takes 8-bit. 

One of the key implications of the bit size is the memory capacity of the microcontroller. 
In an 8-bit microcontroller for example, there are 255 unique memory locations as dictated by the bit size while in a 32-bit microcontroller, there are 4,294,967,295 unique memory locations, which means the higher the bit size, the higher the number of unique memory locations available for use on the microcontroller. 
Manufacturers these days however, are developing ways to provide access to more memory location to smaller bit size microcontrollers via paging and addressing, so that 8bits microcontroller become 16bits addressable but this tends to complicate programming for the embedded software developer.
The effect of bit size is probably more significantly experienced when developing the firmware for the microcontroller especially for arithmetic operations. 

The various data types have different memory size for different microcontroller bit size. 
For example, using a variable declared as an unsigned integer which due to the data type will require 16bits of memory, in codes to be executed on an 8bit microcontroller will lead to the loss of the most significant byte in the data which at times may be very important to the achievement of the task for which the device on which the microcontroller is to be used, was designed.
It is probably important to note that most application these days are between 32bits and 16 bits microcontrollers due to the technological advancements incorporated on these chips.
4. Interfaces for Communication
Communication between the microcontroller and some of the sensors and actuators that will be used for the project might require the use of an interface between the microcontroller and the sensor or actuator to facilitate the communications. 
Take for instance to connect an analog sensor to a microcontroller will require that the microcontroller has enough ADC (analog to digital converters) or as I mentioned earlier, varying the speed of a DC motor may require the use of PWM interface on the microcontroller. 
So it will be important to confirm that the microcontroller to be selected has enough of the interfaces required including UART, SPI, I2C among others.
5. Operating Voltage
The Operating voltage is the voltage level at which a system is designed to operate. 
It is also the voltage level to which certain characteristics of the system are related. 
In hardware design the operating voltage at times determine the logic level at which the microcontroller communicates with other components that makes up the system.
The 5V and 3.3V voltage level are the most popular operating voltage used for microcontrollers and a decision should be made on which of these voltage level will be used during the process of developing the technical specification of the device. 

Using a microcontroller with a 3.3V operating voltage in the design of a device where most of the external components, sensors and actuators will be operating on a 5V voltage level will not be a very smart decision as there will be a need to implement logic level shifters or converters to enable the exchange of data between the microcontroller and the other components and this will increase the cost of manufacturing and the overall cost of the device unnecessarily.
6. Number of I/O Pins
The number of general or special purpose input/output ports and (or) pins possessed by a microcontroller is one of the most important factors that influences the choice of microcontroller.
If a microcontroller were to have all of the other features mentioned in this article but doesn’t have enough IO pins as required by the project, it cannot be used. 

It is important that the microcontroller has enough PWM pins for instance, to control the number of DC motors whose speed will be varied by the device. 
While the number of I/O ports on a microcontroller can be expanded by the use of shift registers, it cannot be used for all kind of applications and increases the cost of the devices in which it is used. 
Therefore, it is better to ensure the microcontroller to be selected for the design has the required number of general and special purpose I/O ports for the project.
One other key thing to keep in mind when determining the amount of general or special purpose I/O pins required for a project, is the future improvement that may be done to the device and how those improvements may affect the number of I/O pins required.
7. Memory Requirements
There are several types of memory associated with a microcontroller that are designer should look out for when making a selection. 
The most important ones are the RAM, ROM and EEPROM. 
The amount of each of these memories needed might be difficult to estimate until its being used but judging on the amount of work required of the microcontroller, predictions can be made. 

These memory devices mentioned above form the data and program memory of the microcontroller.
The program memory of the microcontroller stores the firmware for the microcontroller so when power is disconnected from the microcontroller, the firmware is not lost. 
The amount of program memory needed depends on the amount of data like libraries, tables, binary files for images etc that are needed for the firmware to work correctly.
The data memory on the other hand is used during run time. 

All variables and data generated as a result of processing among other activities during run-time is stored in this memory. 
Thus, the complexity of computations that will occur during run-time can be used to estimate the amount of data memory needed for the microcontroller.
8. Package Size
of the microcontroller. 

Microcontrollers generally come in packages ranging from QFP, TSSOP, SOIC to SSOP and the regular DIP package which makes mounting on breadboard for prototyping easy. 
It’s important to plan ahead of the manufacturing and envisage which package will be best.
9. Power Consumption
where it is desired that the microcontroller be as low power as possible. 

The datasheet of most microcontrollers contain information on several hardware and (or) software based techniques that can be used to minimize the amount of power consumed by the microcontroller in different modes. 
Ensure the microcontroller you are selecting satisfies the power requirement s for your project.
10. 
Support for Microcontroller
It’s important the microcontroller you choose to work with has enough support including; code samples, reference designs and if possible a large community online. 
Working with a microcontroller for the first time might come with different challenges and having access to these resources will help you overcome them quickly. 
While using latest microcontrollers because of those cool new features it came with is a good thing, it is advisable to ensure that the microcontroller has been around for at least 3-4 months to ensure most of the early problems that may be associated with the microcontroller would have been resolved since various customers would have done plenty of testing of the microcontroller with different applications.
, so you can quickly start building prototype and test out features easily. 

The evaluation kits are a good way to acquire experience, get familiar with the tool chain used for development, and save time during the development of the device.
Selecting the right microcontroller for a project, will continue to be a problem, every hardware designer will have to solve and while there are few more factors that may influence the choice of microcontroller, these factors mentioned above are the most important.

tutorial/non-inverting-operational-amplifier

Non-inverting Operational Amplifier
section.
pin or Positive. 
An op-amp amplifies the difference in voltage between this two input pins and provides the amplified output across its Vout or output pin.

ᾠwith the input signal.
This is generally achieved by applying a small part of the output voltage back to the inverting pin (In case of non-inverting configuration) or in the non-inverting pin (In case of inverting pin), using a voltage divider network.
Non-inverting Operational Amplifier Configuration
provide the small part of the output to the inverting pin of the op-amp circuit. 

These two resistors are providing required feedback to the op-amp. 
In an ideal condition, the input pin of the op-amp will provide high input impedance and the output pin will be in low output impedance.
)
The Voltage divider output which is fed into the non-inverting pin of the amplifier is equal to the Vin, as Vin and voltage divider’s junction points are situated across the same ground node.

as below.
Gain of Non-inverting Op-amp
So, Vin / Vout = R1 / (R1 + Rf)
Or, Vout / Vin = (R1 + Rf) / R1

So, Av = Vout / Vin = (R1 + Rf) / R1
Using this formula we can conclude that the closed loop voltage gain of a Non- Inverting operational amplifier is,
Av = Vout / Vin = 1 + (Rf / R1)
form. 

The gain is directly dependent on the ratio of Rf and R1.
But it is only possible theoretically. 
In reality, it is widely dependent on the op-amp behavior and open-loop gain.
Practical Example of Non-inverting Amplifier
at the output comparing the input voltage.
resistor and will calculate the output voltage after amplification.
So, the value of Rf is,
3 = 1 + (Rf / 1.2k)

3 = 1 + (1.2k + Rf / 1.2k)
3.6k = 1.2k + Rf
3.6k - 1.2k = Rf
Rf = 2.4k

After amplification, the output voltage will be
Av = Vout / Vin
3 = Vout / 2V
Vout = 6V 

than the input.
Voltage Follower or Unity Gain Amplifier
.
So, due to high input impedance, we can apply weak signals across the input and no current will flow in the input pin from the signal source to amplifier. 

On the other hand, the output impedance is very low, and it will produce the same signal input, in the output.
As we know,
Gain (Av) = Vout / Vin
So, 1 = Vout / Vin

Vin = Vout.
where filter stages are isolated from each other using voltage follower op-amp configuration.
etc.
, we can select multiple resistors values and can produce a non-inverting amplifier with a variable gain range.

sectors, as well as in scope, mixers, and various places where digital logic is needed using analog electronics.

article/different-types-of-batteries
Different Types of Batteries and their Applications

A battery is a collection of one or more cells that go under chemical reactions to create the flow of electrons within a circuit. 
There is lot of research and advancement going on in battery technology, and as a result, breakthrough technologies are being experienced and used around the world currently. 
Batteries came into play due to the need to store generated electrical energy. 
As much as a good amount of energy was being generated, it was important to store the energy so it can be used when generation is down or when there is a need to power standalone devices which cannot be kept tethered to the supply from the mains. 

Here it should be noted that only DC can be stored in the batteries, AC current can’t be stored.
are usually made up of three main components;
The Anode (Negative Electrode)
The Cathode (Positive Electrode)

The electrolytes
, so let'sget started.
Types of Batteries
Batteries generally can be classified into different categories and types, ranging from chemical composition, size, form factor and use cases, but under all of these are two major battery types;

Primary Batteries
Secondary Batteries
1. Primary Batteries
once depleted. 

Primary batteries are made of electrochemical cells whose electrochemical reaction cannot be reversed.
They are commonly used in standalone applications where charging is impractical or impossible. 
A good example of which is in military grade devices and battery powered equipment. 
It will be impractical to use rechargeable batteries as recharging a battery will be the last thing in the mind of the soldiers. 

Primary batteries always have high specific energy and the systems in which they are used are always designed to consume low amount of power to enable the battery last as long as possible.
; Pace makers, Animal trackers, Wrist watches, remote controls and children toys to mention a few.
They have a high specific energy and are environmentally friendly, cost-effective and do not leak even when fully discharged. 
They can be stored for several years, have a good safety record and can be carried on an aircraft without being subject to UN Transport and other regulations. 

The only downside to alkaline batteries is the low load current, which limits its use to devices with low current requirements like remote controls, flashlights and portable entertainment devices.
2. Secondary Batteries
, secondary cells unlike primary cells can be recharged after the energy on the battery has been used up.
Although the initial cost of acquiring rechargeable batteries is always a whole lot higher than that of primary batteries but they are the most cost-effective over the long-term. 


This is very important because the chemistry determines some of the attributes of the battery including its specific energy, cycle life, shelf life, and price to mention a few.
that are commonly used.
Lithium-ion(Li-ion)

Nickel Cadmium(Ni-Cd)
Nickel-Metal Hydride(Ni-MH)
Lead-Acid
1. Nickel-Cadmium Batteries
Thenickel–cadmium battery(NiCd batteryorNiCad battery) is a type ofrechargeable batterywhich is developedusing nickel oxide hydroxideand metalliccadmium aselectrodes. 
Ni-Cd batteries excel at maintaining voltage and holding charge when not in use. 
However, NI-Cd batteries easily fall a victim of the dreaded “memoryᾠeffect when a partially charged battery is recharged, lowering the future capacity of the battery.
In comparison with other types of rechargeable cells, Ni-Cd batteries offer good life cycle and performance at low temperatures with a fair capacity but their most significant advantage will be their ability to deliver their full rated capacity at high discharge rates. 

They are available in different sizes including the sizes used for alkaline batteries, AAA to D. 
Ni-Cd cells are used individual or assembled in packs of two or more cells. 
The small packs are used in portable devices, electronics and toys while the bigger ones find application in aircraft starting batteries, Electric vehicles and standby power supply.
Some of the properties of Nickel-Cadmium batteries are listed below.

Specific Energy: 40-60W-h/kg
Energy Density: 50-150 W-h/L
Specific Power: 150W/kg
Charge/discharge efficiency: 70-90%

Self-discharge rate: 10%/month
Cycle durability/life: 2000cycles
2. Nickel-Metal Hydride Batteries
Nickel metal hydride (Ni-MH) is another type of chemical configuration used forrechargeable batteries. 

The chemical reaction at the positive electrode of batteries is similar to that of thenickel–cadmium cell(NiCd), with both battery type using the samenickel oxide hydroxide(NiOOH). 
However, the negative electrodes in Nickel-Metal Hydride use a hydrogen-absorbingalloyinstead ofcadmium which is used in NiCd batteries
effect that NiCads experience.
Below are some of the properties of batteries based on the Nickel-metal hydride chemistry;

Specific Energy: 60-120h/kg
Energy Density: 140-300 Wh/L
Specific Power: 250-1000 W/kg
Charge/discharge efficiency: 66% - 92%

Self-discharge rate: 1.3-2.9%/month at 20oC
Cycle Durability/life: 180 -2000
3. Lithium-ion Batteries
.They are found in different portable appliances including mobile phones, smart devices and several other battery appliances used at home. 

They also find applications in aerospace and military applications due to their lightweight nature.
Lithium-ion batteries are a type ofrechargeable batteryin whichlithium ions from the negativeelectrodemigrate to the positive electrode during discharge and migrate back to the negative electrode when the battery is being charged. 
Li-ion batteries use an intercalated lithiumcompoundas one electrode material, compared to themetalliclithium used in non-rechargeable lithium batteries.
) which provides high energy density and low safety risks when damaged while Li-ion batteries based on Lithium iron phosphate which offer a lower energy density are safer due to a reduced likelihood of unfortunate events happening are widely used in powering electric tools and medical equipment. 

Lithium-ion batteries offer the best performance to weight ratio with the lithium sulphur battery offering the highest ratio.
Some of the attributes of lithium-ion batteries are listed below;
Specific Energy: 100: 265W-h/kg
Energy Density: 250: 693 W-h/L

Specific Power: 250: 340 W/kg
Charge/discharge percentage: 80-90%
Cycle Durability: 400: 1200 cycles
Nominal cell voltage: NMC 3.6/3.85V
4. Lead-Acid Batteries
if you want to know more about the different types of Lead-acid batteries, its construction and applications.
Each of these batteries has its area of best fit and the image below is to help choose between them.
Selecting the right battery for your application
is power, battery life affects the successful deployment of devices that require long battery life and even though several power management techniques are being adopted to make the battery last longer, a compatible battery must still be selected to achieve the desired outcome.
Below are some factors to consider when selecting the right type of battery for your project.
The energy density is the total amount of energy that can be stored per unit mass or volume. 
This determines how long your device stays on before it needs a recharge.

Maximum rate of energy discharge per unit mass or volume. 
Low power: laptop, i-pod. 
High power: power tools.
: It is important to consider the temperature at which the device you are building will work. 

At high temperatures, certain battery components will breakdown and can undergo exothermic reactions. 
High temperatures generally reduces the performance of most batteries.
The stability of energy density and power density of a battery with repeated cycling (charging and discharging) is needed for the long battery life required by most applications.
Cost is an important part of any engineering decisions you will be making. 

It is important that the cost of your battery choice is commensurate with its performance and will not increase the overall cost of the project abnormally.

tutorial/triac-switching-circuit-and-applications
What is TRIAC: Switching Circuit and Applications

, which is a bidirectional device meaning it can conduct in both the direction. 
Due to this property TRIAC is exclusively used where sinusoidal AC supply is involved.
Introduction to TRIAC
but it can conduct in both the directional since it construct by combining two SCR in anti-parallel state. 

The symbol and pin out of TRIAC is shown below.
as listed below
Positive Voltage at MT2 and positive pulse to gate (Quadrant 1)
Positive Voltage at MT2 and negative pulse to gate (Quadrant 2)

Negative Voltage at MT2 and positive pulse to gate (Quadrant 3)
Negative Voltage at MT2 and negative pulse to gate (Quadrant 4)
V-I Characteristics of a TRIAC
The below picture illustrates the status of TRIAC in each quadrant.

Quadrant.
To turn on a TRIAC a positive or negative gate voltage/pulse has to be supplied to the gate pin of the TRIAC. 
When triggered one of the two SCR inside, the TRIAC begins to conduct based on the polarity of the MT1 and MT2 terminals. 
If MT2 is positive and MT1 is negative the first SCR conducts and if the MT2 terminal is negative and MT1 is positive then second SCR conducts. 

This way either one of the SCR always stays on thus making the TRIAC ideal for AC applications.
of the TRIAC. 
So to conclude a TRIAC will remain turned on even after removing the gate pulse as long as the load current is greater than the value of latching current.
A TRIAC will enter into continuous conduction mode only after passing though the holding current and the latching current as shown in the graph above. 

Also the value of Latching current of any TRIAC will always be greater than the value of the holding current.
). 
This type of commutation is called as forced commutation in DC circuits. 
We will learn more about how a TRIAC is turned On and turned Off through it application circuits.
TRIAC Applications
etc. 
Let us look into a simple TRIAC switching circuit to understand how it works practically.
The mains power source is then wired to a small bulb through the TRIAC as shown above. 

When the switch is closed the phase voltage is applied to the gate pin of the TRIAC through the resistor R1. 
If this gate voltage is above the gate threshold voltage then a current flows through the gate pin, which will be greater than the gate threshold current.
and check how it works.
High caution is needed while working with AC power supplies the operating voltage is stepped down for safety purpose The standard AC power of 230V 50Hz (In India) is stepped down to 12V 50Hz using a transformer. 

A small bulb is connected as a load. 
The experimental set-up looks like this below when completed.
at the end of this tutorial.
TRIAC control using Microcontrollers
When TRIACs are used as light dimmers or for Phase control application, the gate pulse that is supplied to the gate pin has to be controlled using a microcontroller. 
In that case the gate pin will also be isolated using an opto-coupler. 
The circuit diagram for the same is shown below.
pin of MOC3021 and the frequency and duty cycle of the PWM signal will be varied to get the desired output. 

This type of circuit is normally used for Lamp brightness control or motor speed control.
Rate Effect ᾠSnubber Circuits
All TRIACs suffer from a problem called Rate Effect. 
That is when the MT1 terminal is subjected to sharp increase in voltage due to switching noise or transients or surges the TRIAC miss-interrupts it as a switching signal and turns ON automatically. 

This is because of the internal capacitance of present between the terminals MT1 and MT2.
In the above circuit, the Resistor R2 (50R) and the Capacitor C1 (10nF) together forms an RC network which acts as a Snubber circuit. 
Any peak voltages supplied to MT1 will be observed by this RC network.
Backlash Effect
Another common problem that will be faced by designers while using TRIAC is the Backlash effect. 
This problem occurs when a potentiometer is used for controlling the gate voltage of the TRIAC. 
When the POT is turned to minimum value, no voltage will be applied to gate pin and thus the Load will be turned off. 
But when the POT is turned to maximum value the TRIAC will not switch on because of the capacitance effect between the pins MT1 and MT2, this capacitor should find a path to discharge else it will not allow the TRIAC o turn ON. 

This effect is called as the Backlash effect. 
This problem can be rectified by simply introducing a resistor in series with switching circuit to provide a path for the capacitor to discharge.
Radio Frequency Interference (RFI) and TRIACs
TRIAC switching circuits are more prone to Radio Frequency interference (EFI) because when the load is turned on, the current raises form 0A to maximum value all of a sudden thus creating a burst of electric pulses which causes Radio Frequency Interface. 

The larger the load current is the worse will be the interference. 
Using Suppressor circuits like an LC suppressor will solve this problem.
TRIAC ᾠLimitations
When required to switch AC waveforms in both the directions obviously TRIAC will be the first choice since it is the only bi-directional power electronic switch. 

It acts just like two SCRs connected in back to back fashion and also share the same properties. 
Although while designing circuits using TRIAC the following limitations must be considered
The TRIAC has two SCR structures inside it, one conducts during positive half and the other during negative half. 
But, they do not trigger symmetrically causing difference in the positive and negative half cycle of the output

Also since the switching is not symmetrical, it leads to high level harmonics which will induce noise in the circuit.
This harmonics problem will also lead to Electro Magnetic Interference (EMI)
While using inductive loads, there is a huge risk of inrush current flowing towards the source, hence it should be ensured that TRIAC is turned off completely and the inductive load is discharged safely through an alternate path


article/wireless-charging-technology
An Overview of Wireless Charging Technology
is the process of recharging battery powered electronic devices without directly tethering them using wires and cables to a power source. 
The process gives users the freedom of charging their phone on the go without the need to plug to power outlet. 

This means wireless charging enabled smartphones and other devices could be charged by simply placing them on a coffee table for instance or even more complex machines like electric cars can be charged by simply parking them in the garage or by wireless charging enabled road. 
It eliminates all the safety issues associated with cord based charging and opens door to a new kind of freedom for users.
to transmit power wirelessly.
How Wireless Power Transmission Works
because it is based on the principle of electromagnetic induction. 
Just like the wireless communication system, wireless charging is achieved via the action of a wireless energy transmitter and receiver. 
The Wireless charging transmitter usually referred to as the charging station is attached to a power outlet and transmits the energy being supplied via the outlet to the receiver which is always attached to the device to be charged and placed in close proximity to the wireless charging station.
, generators and motors, such that the passage of electric current through a coil causes a changing magnetic field around that coil which induces a current in another coupled coil. 

This is the principle behind the transfer of electric energy between the primary and secondary coil in an electric transformer even though they seem electrically isolated. 
In Wireless charging each of the components (the transmitter and the receiver) that make up the system possesses a coil. 
The transmitter coil can be likened to the primary coil while the receiver coil can be likened to the secondary coil of an electric power transformer. 
When a Charging station is plugged into AC power supply, the power supplied is rectified to DC by the rectifier system after which the switching system takes over. 

The reason for the switching is to be able to generate the changing magnetic flux needed to induce charges in the receiver coil.
The receiver coil collects the incoming power and passes it on to the receiver circuit which converts the incoming power to DC and then applies the power received to charge the battery.
like shown in the Image below.
Wireless Charging Standards
Wireless Charging Standards refer to the set of rules governing the design and development of wireless devices. 
There currently two different industry standard for wireless charging being promoted by to different bodies.
1. Rezence Standard
2. QI Standard

standard is based on resonant inductive charging such that charging occurs when both the transmitter and receiver coils are in resonance. 
With this standard, devices can achieve a greater distance between the transmitter and the receiver for charging. 
This standard is being promoted by the Alliance for wireless power (A4WP).
standard, the transmitter and receiver coil are always designed to operate at slightly different frequencies as it is believed more power is delivered using this setup. 

The QI Standard is being promoted by the wireless power consortium which includes members like Apple inc, Qualcomm, HTC to mention a few.
You can select the wireless standard that best suits your application by considering the trade-offs between the EMI, efficiency, and the freedom of alignment between the two standards. 
Nevertheless, certain wireless charging stations are designed to support both the standards, these provide high interoperability between devices.
Simple Wireless Charger Set Design
Before building a wireless charging system the following should be put into consideration.
When equipping a device with wireless charging abilities, the first thing to do is to select the wireless power standard that fits the device and its use cases. 
Certain charging system are based on multiple standards.
The next thing is selecting the right coil type and coil geometry to fit the use case. 

Vendors provide these coils in standard gauges so selection of the appropriate should be based on the recommendation of the datasheet of the wireless charging transmitter IC to be used.
When designing Wireless systems, it is important that the enclosure of the devices is not metal and is of a relatively flat surface to achieve a higher coupling factor between the transmitter and the receiver. 
Metal effectively prevents the energy being transmitted from getting to the receiver and the plastic enclosure must be designed to be ultra-thin.
Design of Transmitter
the Switching circuit is used to generate the alternating signal used in the creation of the changing magnetic field to induce current transfer from the transmitter to the receiver via the transmitter coil.
Design of Receiver
The design of the receiver is similar that of the transmitter except the action takes place in reverse order. 
The receiver consists of a receivercoil, resonance network, and rectifier anda chargerIC which uses the output of the rectifier circuit to charge the connected battery. 

An example of the receiver circuit is shown in the image below with the functional parts Highlighted. 
This example is based on the LTC4120 charging IC.
Applications
Wireless charging is currently being used in many applications including:

Smartphones and wearable
Notebooks and tablets
Power tools and service robots, such as vacuum cleaners
Multicopters and electric toys

Medical devices
In-car charging
In addition to the fancy reasons why you should use wireless charging, like no need to plug in a device and no plug compatibility issues, wireless charging provides safety from hazards related to connecting directly to the mains. 
Furthermore, it’s reliable in harsher environments, such as drilling and mining and allows for seamless on-the-go charging. 

Finally, wireless charging eliminates tangling and other mess created by wires. 
We have only just scratched the face of wireless charging with several novel applications, every product design being done with the future in mind should seek to incorporate wireless charging as its certainly one of the ways we will charge battery powered devices in the nearest future.

tutorial/voltage-controlled-oscillator-vco

Voltage Controlled Oscillator (VCO)
and are very useful in wireless transmission or to perform timing related operations.
is an oscillator which produces oscillating signals (waveforms) with variable frequency. 
The frequency of this waveform is varied by varying the magnitude of the Input voltage. 

For now you can imagine a Voltage Controlled Oscillator (VCO) to be a black box which takes in Voltage of variable magnitude and produces an output signal of variable frequency, and the frequency of the output signal is directly proportional to the magnitude of the input voltage. 
We will learn more about this black box and how to use one in our designs in this tutorial.
Working Principle of Voltage Controlled Oscillator (VCO)
Apart from that there are dedicated IC packages like LM566 LM567 etc. 

which can act as VCO. 
To understand the basic idea of a VCO let us consider a RC oscillator.
the frequency of the output wave depends on the value of the capacitor used in the circuit, since the frequency is given by the formulae
Frequency (f) = 1 / 2πRC

Hence in this case the frequency of oscillation is inversely proportional to the value of capacitance used in the circuit. 
So now to control the output frequency and to make it work as a VCO we have to vary the capacitance of the Capacitor based on the value of the Input voltage. 
This can be achieved with the help of varactor diodes. 
These diodes change the value of capacitance across them based on the voltage applied. 

A sample output graph of a VCO is shown below.
Let us assume the control voltage to be Vc and the output frequency as fo. 
Then under normal operating condition a nominal voltage provided to the VCO for which a nominal Frequency is produced by the VCO. 
As the input voltage (control voltage) is increased the output frequency increases and the vice versa is also possible.
Types of Voltage Controlled Oscillators
There are many types of VCO circuits used in different applications, but they can be broadly classified into two types based on their output voltage.
If the Output waveform of the oscillator is sinusoidal then it is called as harmonic Oscillators. 
The RC, LC circuits and Tank circuits fall into this category. 

These types of oscillators are harder to implement but they better stability than the Relaxation Oscillator. 
Harmonic oscillators are also called as linear voltage controlled oscillator.
If the output waveform of the oscillator is in sawtooth or triangular form then the oscillator is called as Relaxation Oscillator. 
These are comparatively easy to implement and hence most widely used. 

Relaxation Oscillator can further be classified as
Emitter Coupled Voltage Controlled Oscillator
Grounded capacitor Voltage Controlled Oscillator
Delay based ring Voltage Controlled Oscillator
Voltage Controlled Oscillator ᾠPractical Application
As mentioned earlier VCO can be simply construct using RC or LC pair, but in real world application no one really does that. 
There is some dedicated IC which has the ability to generate oscillations based on the input voltage. 
One such commonly used IC is the LM566 from national semiconductor.

and the nominal frequency of this wave can be set by using an external and capacitor and a resistor. 
Later this frequency can also be varied in real time based on the input voltage supplied to it.
is shown below
The IC can be operated either from a single supply or from a dual supply rail with an operating voltage upto 24V. 

The pins 3 and 4 are the output pins which gives us the Square wave and Triangle wave respectively. 
The Nominal frequency can be set by connecting the right value of Capacitor and Resistor to the pins 7 and 6.
based on the output frequency (Fo) is given by the formulae
Fo = 2.4 (Vss - Vc) / Ro+Co+Vss

Where,
using 1.5k and 10k Resistor to supply a constant voltage to pin 5). 
A sample circuit diagram for LM566 is shown below
to check how linear the output frequency varies with respect to the Input control voltage. 

The value of output frequency is adjustable using the Control voltage (on pin 5) with a ratio of 10:1, which helps us in providing a wide range of control.
Applications of Voltage Controlled Oscillators (VCO)
Frequency Shift Keying
Frequency identifiers

Keypad Tone recognizers
Clock/Signal/Function Generators
Used to build Phase Locked Loops.
, why it is important and what a VCO does inside a Phase Locked Loop.
What is a Phase Locked Loop (PLL)? 
and Voltage controlled Oscillator. 
Together these three forms a control system which constantly adjusts the frequency of the output signal based on the frequency of the input signal. 
The block diagram of a PLL is shown below

). 
The main function of a PLL circuit is to produce the output signal with the same frequency of the input signal. 
This is very important in wireless applications like Routers, RF transmission systems, Mobiles networks etc.
) using the feedback path provided. 

The difference in these two signals are compared and given in terms of a voltage value, and is referred as Error voltage signal. 
This voltage signal will also have some high frequency noise coupled with it, which can be filtered by using a Low pass filter. 
Then this voltage signal is provided to a VCO which as we already know varies the output frequency based on the voltage signal (control voltage) provided.
PLL - Practical Application
It is a tone decoder IC, meaning it listens to a particular user configured type of tone on pin 3 if that tone is received it connects the output (pin 8) to ground. 
So basically to listens to all the sound in available in the frequency and keeps comparing the frequency of those sound signals with a preset frequency using the PLL technique. 
When the frequencies match the output pin it turned low. 
The pin of the LM567 IC is shown below, the circuit is highly susceptible to noise so don’t be surprised if you cannot get this IC to work on a breadboard.

pin is used to set the bandwidth of the IC, higher the capacitance lower will be the bandwidth. 
The pins 5 and 6 are used to set the value of set frequency. 
This frequency value can be calculated by using the below formulae
The basic circuit for the LM567 IC is shown below.

The Input Signal whose frequency has to be compared is given to the pin 3 through a filtering capacitor of value 0.01uF. 
This frequency is compared with the set frequency. 
The frequency is set using the 2.4k Resistor (R1) and 0.0033 Capacitor (C1), these values can be calculated according to your set frequency using the above discussed formulae.
which is very useful in audio/wireless related applications.

Hope you got a good idea about VCO’s now, if you have any doubt post them on the comment section or use the forums. 

Also check:
RC Phase Shift Oscillator

Wein Bridge Oscillator
Quartz Crystal Oscillator

tutorial/full-subtractor-circuit-and-its-construction

Full Subtractor Circuit and Its Construction
Full Subtractor Circuit
we seen before.
Let’s see the block diagram,

Full Subtractor Circuit Construction
, On the other hand the Borrow out of Left half Subtractor circuit and the Borrow out of Right Subtractor circuit is further provided into OR logic gate. 
After processing OR logic for two Borrow output bit, we get the final Borrow out of full Subtractor circuit.

The Final Borrow out represents the most significant bit or MSB.
If we see the actual circuit inside the full Subtractor, we will see two Half Subtractor using XOR gate and NAND gate with an additional OR gate.
circuit without the NOT gate.
also updated with three input columns and two output columns.


Borrow In
Input A
Input B
DIFF
Borrow Out
0
0
0
0
0
0
1
0
1
0

0
0
1
1
1
0
1
1
0
0
1
0
0
1
1
1
1
0
0
0

1
0
1
0
1
1
1
1
1
1

So, the Diff is (A XOR B) XOR Borrow in.We can also express it with:

(A ∠B) ∠Borrow in.
Now, for the Borrow out, it is:
which can be further represented by
Cascading Subtractor Circuits
As of now, we described the construction of single bit full-Subtractor circuit with logic gates. 
But what if we want to subtract two, more than one bit numbers?
Here is the advantage of full Subtractor circuit. 
We can cascade single bit full Subtractor circuits and could subtract two multiple bit binary numbers.

while the carry input (LSB) of the full adder circuit is in Logic High or 1, we subtract those two binaries in 2’s complement method. 
The output from the Full-adder (which is now full Subtractor) is the Diff bit and if we invert the carry out we will get the Borrow bit or MSB. 
We can actually construct the circuit and observe the output.
Practical Demonstration of Full Subtractor Circuit
We will use a Full Adder logic chip 74LS283N and NOT gate IC 74LS04. 
Components used-
4pin dip switches 2 pcs
4pcs Red LEDs

1pc Green LED
8pcs 4.7k resistors
74LS283N
74LS04

13 pcs 1k resistors
Breadboard
Connecting wires
5V adapter

is on the right. 
74LS283N is a 4bit full Subtractor TTL chip with Carry look ahead feature. 
And 74LS04 is a NOT gate IC, It has six NOT gates inside it. 
We will use five of them.

is shown in the schematic.
Pin diagram of the IC 74LS283N and 74LS04 are also shown in the schematic. 
Pin 16 and Pin 8 is VCC and Ground respectively,
4 Inverter gates or NOT gates are connected across Pin 5, 3, 14 and 12. 

Those pins are the first 4-bit number (P) where the Pin 5 is the MSB and pin 12 is the LSB.
On the other hand, Pin 6, 2, 15, 11 is the second 4-bit number where the Pin 6 is the MSB and pin 11 is the LSB.
Pin 4, 1, 13 and 10 are the DIFF output. 
Pin 4 is the MSB and pin 10 is the LSB when there is no Borrow out.

SW1 is subtrahend and SW2 is Minuend. 
We connected Carry in pin (Pin 7) to 5V for making it Logic High. 
It’s needed for 2’s complement.
1k resistors are used in all input pins to provide logic 0 when the DIP switch is in OFF state. 

Due to the resistor, we can switch from logic 1 (binary bit 1) to logic 0 (binary bit 0) easily. 
We are using 5V power supply.
When the DIP switches are ON, the input pins get shorted with 5V making those DIP switches Logic High; we used Red LEDs to represent the DIFF bits and Green Led for Borrow out bit.
R12 resistor used for pull up due to the 74LS04 couldn’t provide enough current to drive the LED. 

Also, the Pin 7 and Pin 14 is respectively Ground and 5V pin of 74LS04. 
We also need to convert the Borrow out bit coming from the Full-adder 74LS283N.
for further understanding below, where we have shown subtracting two 4-bit binary Numbers.
Circuit:

Half Adder Circuit
Full Adder Circuit
Half Subtractor Circuit


tutorial/what-is-multiplexer-circuit-and-how-it-works
Multiplexer Circuit and How it Works
or lines and a Digital Multiplexer is a combinational Logic circuit that selects binary information from one of the many input lines and directs it to a single output line.
to check the working on the Hardware.
Basics of Multiplexers:
The best way to understand Multiplexers is by looking at a single pole multi-positioned as shown below. 
Here the switch has multiple inputs D0, D1, D2 and D3 but it has only one Output (Out) pin. 
The Control knob is used to select one of the four available data and this data will be reflected on the output side. 

This way the user can select the required the signal among many available signals.
This is a plain example of a mechanical Multiplexer. 
But in electronic circuit which involves high speed switching and data transfers we should be able to select the required input very fast using digital circuits. 
The Control signals (S1 and S0) does exactly the same, they select one input of the many available ones base on the signal provided to them. 

So the three basic and bare minimum terms on any Multiplexer will be Input Input Pins, Output Pin and Control Signal
These are the available signal pins from which one has to be selected. 
These signals can either be a digital signal or an analog signal.
A multiplexer will always have only one output pin. 

The selected input pin signal will be provided by the output pin.
The Control Pins are used to select the input pin signal. 
The number of Control pins on a Multiplexer depends on the number of input pins. 
For example a 4-input multiplexer will have 2 signal pins.

For understanding purpose, let us consider a 4-input multiplexer that is shown above. 
It has two control signal using which we can select one of the available four input lines. 
The truth Table below illustrates the status of Control pins (S0 and S1) for selecting the required Input pin.
Now, that we have understood the basic of Multiplexers let’s take a look at the 2-Input Multiplexers and 4-Input Multiplexers which are most commonly used in application circuits.
2-Input Multiplexers:
Also it will have only one Control pin to select between the available two Input pins. 
A Graphical representation of a 2:1 Multiplexer is shown below.
Here the input pins are named as D0 and D1 and the Output pin is named as out. 

The user can select one of the inputs that is either D0 or D1 by using the Control Pin S0. 
If S0 is kept low (logic 0) then the Input D0 will be reflected on the output pin and if the Input S0 is kept high (logic 1) then the Input D1 will be reflected on the output pin. 
The truth table representing the same is shown below
is shown below

The logic diagram utilizes only the NAND gates and hence can be easily build on a perf board or even on a breadboard. 
The Boolean expression for the Logic diagram can be given by
Out = S0ᾮD0ᾮD1 + S0ᾮD0.D1 + S0.D0.D1ᾠ+ S0.D0.D1
We can further simply this Boolean expression by using the cancelling out the common terms, so that the logic diagram gets much more simple and easy to construct. 

The simplified Boolean expression is given below.
Out = S0ᾮD0 + S0.D1
Higher Order Multiplexers (4:1 Multiplexer):
These two control lines can form 4 different combinational logic signals and for each signal one particular input will be selected.

The number of control lines for any Multiplexer can be found using the below formulae
2 Number of Control lines = Number of Input lines
= 4. 
Similarly you can calculate for any higher order Multiplexers.

It is also common to combine to lower order multiplexers like 2:1 and 4:1 MUX to form higher order MUX like 8:1 Multiplexer. 
Now, for example let us try to implement a 4:1 Multiplexer using a 2:1 Multiplexer. 
To construct a 4:1 MUX using a 2:1 MUX, we will have to combine three 2:1 MUX together.
MUX as shown below.

is shown below.
As you can see in the table above, for each set of value provided to the Control signal pins (S0 and S1) we get a different Output from the input pins on our output pin. 
This way we can use the MUX to select one among the available four input pins to work with. 
Normally these Control pins (S0 and S1) will be controlled automatically using a digital circuit. 

There are certain dedicated IC which can act as MUX and make the job easy for us, so let us take a look at them.
Practical Implementation of Multiplexer using IC 4052:
is shown below
Here the pins X0, X1, X2 and X3 are the four input pins and the pin X is its corresponding output pin. 

The control pins A and B are used to select the required input to the output pin. 
The Vdd pin (pin 16) has to connect to the supply voltage which is +5V and the Vss and Vee pin should be grounded. 
The Vee pin is for enable which is an active low pin so we have to ground it to enable this IC. 
The MC14052 is an Analog Multiplexer meaning the input pins can also be supplied with variable voltage and the same can be obtained though the output pins. 

The below GIF image shows how the IC outputs variable input voltage based in the control signals provided. 
The input pins has the voltage 1.5V, 2.7V, 3.3V and 4.8V which is also obtained on the Output pin based on the control signal given.
once build will look something like this below
can also be found at the bottom of this page. 

Hope you understood the working of Multiplexers and know where to use them in your projects. 
If you have any thoughts or doubts leave them in the comment section below and I will try my best to respond to them. 
You can also use the forums to resolve your technical doubts and share your knowledge among other members of this community. 



tutorial/half-subtractor-circuit-and-its-construction
Half Subtractor Circuit and Its Construction
When we use arithmetic subtraction process in our base 10 mathematics, like subtracting two numbers, for an example-
Binary Subtraction:
As in binary number system, 1 is the largest digit, we only produce borrow when the subtrahend 1 is greater than minuend 0 and due to this, borrow will require.
of two bits,


1st Bit or Digit
2nd Bit or Digit
Difference
Borrow
0
0
0
0
1
0
1
0
0
1
1
1

1
1
0
0

along with result 1 because the subtrahend 1 is greater than the minuend 0.
bit.
Half Subtractor:
, which requires only two inputs and provide two outputs.
For making NAND gate, we have used AND gate and NOT gate. 
So we need threegates to construct Half Subtractor circuit:

2-input Exclusive-OR Gate or Ex-OR Gate
2-input AND Gate.
NOT Gate or Inverter Gate
Ex-OR Gate:
is the final output.
This output will be used as Diff Out in half Subtractor circuit.
ᾍ


Input A
Input B
OUT
0
0
0
0
1
1
1
0
1

1
1
0

2-input AND Gate:
bit in the input it will produce an Output.

ᾍ


0
0
0

0
1
0
1
0
0
1
1
1

NOT Gate or Inverter Gate:
Below is the symbol of Inverter Gate:

Input A


0
1
1
0

output.

.
Half-Subtractor Logical Circuit:
gate.
gate.

The Boolean expression of Half Subtractor circuit is-
DIFF = A XOR B
BORROW = not ᾠA AND B (AᾮB)
is as follows-



0
0
0
0
1
0
1
0

0
1
1
1
1
1
0
0

Practical Demonstration of Half Subtractor Circuit:
using these three. 
Below are the pictures of those three ICs.
in the below image-
-

Green LED ᾠ1 pc
Red LED ᾠ1 pc
74LS86
74LS08N

74LS04
1pc 4pin DIP switch
2pcs 4.7k resistor
2pcs 1k resistor

5V wall adapter
Breadboard and hook up wires
and observed the output.
Pin 1 and 2 of 74LS86 are the inputs of the Ex-OR gate and pin 3 is the output from the gate, on the other side pin 1 and 2 of 74LS08 is the input of the AND gate and pin 3 is the output from the gate, pin1 from the 74LS04 is the input of inverter gate and pin2 is the output of inverter gate.

inputs when the DIP switch is in off state.
is given below.
Half Subtractor circuit is used for bit subtraction and logical output related operations in computers.


tutorial/full-adder-circuit-theory-truth-table-construction
Full Adder Circuit and its Construction
.
Full Adder Circuit:
has a major drawback that we do not have the scope to provide ‘Carry inᾠbit for addition. 
In case full adder construction, we can actually make a carry in input in the circuitry and could add it with other two inputs A and B. 
So, in the case of Full Adder Circuit we have three inputs A, B and Carry In and we will get final output SUM and Carry out. 
So, A + B + CARRY IN = SUM and CARRY OUT.
Full Adder Circuit Construction:
Let’s see the block diagram,
, it will produce two outputs, SUM and Carry out. 
First half adder circuit’s SUM output is further provided to the second half adder circuit’s input. 

We provided the carry in bit across the other input of second half order circuit. 
Again it will provide SUM out and Carry out bit. 
This SUM output is the final output of the Full adder circuit. 
On the other hand the Carry out of First half adder circuit and the Carry out of second adder circuit is further provided into OR logic gate. 

After logic OR of two Carry output, we get the final carry out of full adder circuit.
The Final Carry out represents the most significant bit or MSB.
.
also updated with three input columns and two output columns.



0
0
0
0
0
0
1
0
1
0

0
0
1
1
0
0
1
1
0
1
1
0
0
1
0
1
1
0
0
1

1
0
1
0
1
1
1
1
1
1

We can also express the full adder circuit construction in Boolean expression.

For the case of SUM, We first XOR the A and B input then we again XOR the output with Carry in. 
So, the Sum is (A XOR B) XOR C.
We can also express it with (A≂)≃arry in.
Now, for the Carry out, it is A AND B OR Carry in (A XOR B), which is further represented by A.B + (A≂).
Cascading Adder Circuits
As of now, we described the construction of single bit adder circuit with logic gates. 
But what if we want to add two more than one bit numbers?
, Carry out of the each full adder is the Carry in of the next most significant adder circuit. 

As the Carry bit is ripple into the next stage, it is called as Ripple Carry Adder circuit. 
Carry bit is rippled from the left to right (LSB to MSB).
are cascaded together. 
Those three full adder circuits produce the final SUM result, which is produced by those three sum outputs from three separate half adder circuits. 

The Carry out is directly connected to the next significant adder circuit. 
After the final adder circuit, Carry out provide the final carry out bit.
This type of circuit also has limitations. 
It will produce unwanted delay when we try to add large numbers. 

This delay is called as Propagation delay. 
During the addition of two 32 bit or 64 bit numbers, the Carry out bit which is the final output’s MSB, wait for the changes in previous logic gates.
To overcome this situation, very high clock speed is required. 
However, this problem can be solved using carry look ahead binary adder circuit where a parallel adder is used to produce carry in bit from the A and B input.
Practical Demonstration of Full Adder Circuit:
We will use a full adder logic chip and add 4 bit binary numbers using it. 
We will use TTL 4 bit binary adder circuit using IC 74LS283N.
Components used-
4pin dip switches 2 pcs
4pcs Red LEDs
1pc Green LED
8pcs 4.7k resistors

74LS283N
5 pcs 1k resistors
Breadboard
Connecting wires

5V adapter
is shown.74LS283N is a 4bit full adder TTL chip with carry look ahead feature. 
The pin diagram is shown in the schematic below.
Pin 16 and Pin 8 is VCC and Ground respectively, Pin 5, 3, 14 and 12 are the first 4 bit number (P) where the Pin 5 is the MSB and pin 12 is the LSB. 

On the other hand, Pin 6, 2, 15, 11 are the second 4 bit number where the Pin 6 is the MSB and pin 11 is the LSB. 
Pin 4, 1, 13 and 10 are the SUM output. 
Pin 4 is the MSB and pin 10 is the LSB when there are no carry out.
4.7k resistors are used in all input pin to provide logic 0 when the DIP switch is in OFF state. 

Due to the resistor, we can switch from logic 1 (binary bit 1) to logic 0 (binary bit 0) easily. 
We are using 5V power supply. 
When the DIP switches are ON, the input pins get shorted with 5V; we used red LEDs to represent the SUM bits and green Led for Carry out bit.
Also check the Demonstration Video below where we have shown adding two 4-bit binary Numbers.


tutorial/binary-decoder-basics-circuit-truth-tables-applications
Binary Decoders
as well but the number of output lines in a decoder will always be more than the number of input lines. 

We will learn how a decoder works and how we can build one for our project in this tutorial.
Basic Principe of Decoder:
is shown below which takes in 2 Lines as input and converts them to 4 Lines.
=4) which is four in our case. 

The Decoder has 2 input lines and 4 output lines; hence this type of Decoder is called as 2:4 Decoders. 
The two input pins are named as I1 and I0 and the four output pins are named from O0 to O3 as shown above.
which we will learn later in this article. 
The truth table of an ordinary Decoder is shown below

we can write the Boolean expression for each Output line, just follow where the output gets high and form an AND logic based on the values of I1 and I0. 
It is very similar to the Encoder method, but here we use the AND logic instead of the OR logic. 
The Boolean Expression for all four lines are given below, where the symbol (.) represents AND logic and the symbol (ᾩ represents NOT Logic
O0 = I1’.I0’

O1 = I1’.I0
O2 = I1.I0’
O3 = I1.I0
Now that we have all the four expression we can convert these expressions into a combinational logic gate circuit using the AND gates and NOT gates. 

Simply use the AND gates in place of (.) and a NOT gate (inverted logic) in place of a (ᾩ and you will get the following logic diagram.
The two inputs I0 and I1 is provided through a push button and the output is observed through LED lights. 
Once you make the connection on breadboard it would look something like this in the picture below
is shown in the video below

Note that the truth table for each input is displayed at the top left corner and the LED also glows in the same orderly fashion. 
Similarly we can also create combinational logic diagram for all type of Decoders and build them on hardware like this. 
You can also look into the readily available decoder IC’s if your project suits one.
Drawbacks of standard Decoders:
Just like an Encoder the standard Decoder also suffers from the same problem, if both the inputs are not connected (logic X) the output will not remain as zero. 
Instead the Decoder will consider it as logic 0 and the bit O0 will be made high.
Priority Decoder:
is shown below.

is also shown below, here X represents no connection and ᾱᾠrepresents logic high and ᾰᾠrepresents logic low. 
Notice that the enable bit is 0 when there is no connection on the Input lines and hence the output lines will also remain zero. 
This way we will be able to overcome the above mentioned drawback.
As always from the truth table we can drive the Boolean expression for the output lines O0 to O3. 

The Boolean Expression for the above truth table is shown below. 
If you take a closer look you can notice that the expression is as same as that of a normal 2:4 decoder but the Enable bit (E) has been made to AND with the expression.
O0 = E.I1’.I0’
O1 = E.I1’.I0

O2 = E.I1.I0’
O3 = E.I1.I0
The combinational logic diagram for the above Boolean expression can be built using a couple of Inverters (NOT Gates) and 3-input AND gates. 
Just replace the (ᾩ symbol with inverters and the (.) symbol with AND gate and you will get the following Logic diagram.
3:8 Decoders:
which is more commonly used. 
These Decoders are often used in IC packages to complexity of the circuit. 
It is also very common to combine lower order decoders like the 2:4 Decoders to form a higher order Decoder. 

For instance we know that a 2:4 Decoder has 2 Inputs (I0 and I1) and 4 Outputs (O0 to O3) and a 3:8 Decoder has three inputs (I0 to I2) and Eight Outputs (O0 to O7). 
We can use the following formulae to calculate the number of lower order decoders (2:4) required to form a higher order decoder like 3:8 Decoder.
Required number of Lower Order Decoder = m2 / m1
Where,

m2 -> number of outputs for lower order Decoder
m1 -> number of outputs for higher order Decoder
In our case, the value of m1 will be 4 and the value of m2 will be 8, so applying these values in the above formulae we get
Required number of 2:4 Decoder for 3:8 Decoder = 8/4 = 2

Now we know that we will need two 2:4 Decoder to form a 3:8 Decoder, but how should these two be connected to gather. 
The below block diagram shows just that
As you can see the inputs A0 and A1 is connected as parallel inputs for both the decoders and then the Enable pin of the first Decoder is made to act as A2 (third input). 
The Inverted signal of A2 is given to the Enable pin of second decoder to get the outputs Y0 to Y3. 

Here the outputs Y0 to Y3 is referred as Lower four minterms and the outputs Y4 to Y7 is referred as higher four minterms. 
The lower order minterms are obtained from the second decoder and the higher order minterms are obtained from the first decoder. 
Although one noticeable drawback in this type of combinational design is that, the Decoder will not have an Enable pin which makes it susceptible to the problems which we have discussed earlier.
4:16 Decoder:
can also be constructed by combining two 3:8 Decoder. 
For a 4: 16 Decoder we will have four inputs (A0 to A3) and sixteen outputs (Y0 to Y15). 
Whereas, for a 3:8 Decoder we will have only three inputs (A0 to A2).
We have already used the formulae to calculate the number of Decoder required, in this case the value of m1 will be 8 since 3:8 decoder has 8 outputs and the value of m2 will be 16 since the 4:16 decoder has 16 outputs, so applying these values in the above formulae we get

Required number of 3:8 Decoder for 4:16 Decoder = 16/8= 2
Therefore we require two 3:8 Decoder for constructing a 4:16 Decoder, the arrangement of these two 3:8 Decoder will also be similar to the one we did earlier. 
The block diagram for connecting these two 3:8 Decoder together is shown below.
Here the outputs Y0 to Y7 is considered as lower eight minterms and the output from Y8 to Y16 is considered as higher eight minterms. 

The lower right minterms are directly created using the inputs A0,A1 and A2. 
The same signals is also given to the three inputs of the first Decoder, but the Enable pin of the first decoder is used as the fourth input Pin (A3). 
The inverted signal of the fourth input A3 is given to the enable pin of the second Decoder. 
The first decoder outputs the higher eight minterms value.
Applications:
A Decoder is usually used in combination with an Encoder and hence they both share the same applications. 
Without Decoders and Encoders out modern electronics like mobile phone and Laptops would have not been possible. 
Few important applications of Decoders are listed below.

Sequencing Signal Application
Timing Signal Applications
Network lines
Memory elements

Telephone Networks

tutorial/encoder-circuit-basics-truth-table-and-explanations
Binary Encoders

based on the number of inputs and outputs and based on how it operates. 
But every Encoder has one underlying rule, the number of output lines on an Encoder will always be less than number of input lines. 
We will learn more about encoders, what is an encoder, how and why they are used in digital circuits in this article.
Basic Principle of Encoder:
Let us imaginean Encoder to be a black box as shown below which magically reduces the number of Input lines from 4 to just 2 output lines, but still provide the same information without any loss in data.
= 4) four which is exactly the case. 
The four Input Pins are labelled from I0 to I3 and the two output pins are labelled from O0 to O1
below. 

It is also important to know that an ordinary Encoder like the one shown here has a rule that at given time only one input pin should be high so in the following truth table only one input will be high.
Every possible condition of the input the output is shown in the above truth table. 
For instance when only O1 is high (1) and all the other inputs are low (0) then both the output pins will low (0). 
Similarly for each case the output pins will also change its status. 

By using this Output bits status the user will be able to trace back to what input signal would have been given to the Encoder.
Okay, what is fancy about converting 4 lines to 2 lines why do we even need it?
which we will discuss further in this article.
Building Encoders using Combinational Logic Designs 
it is important to know how they are built so that we can make custom encoders for our projects based on the required truth table.
The first in designing the Combinational Logic device is to find the Boolean Expression for the truth table. 
It is very easy and can be easily determined just by looking at the truth table. 
The same truth table that we saw earlier is given below with some illustrations to make you understand better.

The number of expressions will be equal to the number of output lines, here we have two outputs and hence we have two Expressions. 
For the first output O0, just check at which condition it is high (1) and trace the corresponding input pin number which also remains high (1). 
Similarly for all high values of O0 note which input pin number is high and add the pins. 
The input pins corresponding to Output pin O0 is highlighted in red above and for O1 is highlighted in Blue. 

So the Expression for O0 and O1 will be
O1 = I3 + I2
O0 = I3 + I1
Once we obtain the Boolean Expression we just have to draw it in form of Gates. 

Here since we have addition (+) operation we will use the OR gates for constructing our circuits. 
You can also simplify or modify the Boolean expression according to your needs. 
The circuit diagram for the above expression is shown below
as shown below

is shown in the videobelow
As you can see when the first button is pressed the input I0 is made high and hence both the outputs remain low. 
When the second button is pressed the input I1 is turned on and thus one LED goes high to indicate O0 is high. 
Finally when the fourth button is pressed the input I3 is made high and thus both the LED goes high. 

This is a very simple circuit hence we have built it easily on a breadboard but, for practical encoders the circuit will get a bit more complex. 
However Encoders are also available as IC packages which can be purchased if it suits your project.
8:3 Encoders:
The working and usage of 8:3 Encoder is also similar to the 4:2 Encoder except for the number of input and output pins. 

The 8:3 Encoder is also called as Octal to Binary Encoder the block diagram of an 8:3 Encoder is shown below
Here the Encoder has 8 inputs and 3 outputs, again only one input should be high (1) at any given time. 
Since there are 8 inputs it is called as octal input and since there are three outputs it’s also called binary output. 
The truth table of the Encoder is shown below.

Since we have thee outputs we will have three expressions as shown below
O2 = I7 + I6+ I5+ I4
O1 = I7 + I6+ I3+ I2
O0 = I7 + I5+ I3+ I1

Once the Boolean expression is obtained as always we can build the circuit Diagram using the OR gates as shown below.
The circuit uses a 4-input OR gate IC, you can also simplify the Boolean Expression to use other normal 2 input Gate IC’s.
Drawback of Normal Encoders:
These types of Encoders suffer from the following major drawbacks

When none of the input is high the Output will be equal all zero, but this conditions also conflicts with the first bit being high (MSB). 
Hence care should always be taken that at least any one bit stays ON always
When more than one input is high, the output will be collapsed and can give the result for either one of the input which leads to confusion.
To overcome these difficulties we employ a different type of encoder called a Priority Encoder which uses an additional output to determine if the output is valid, and when more than one input is help high the one that goes high starting from the LSD is alone considered while ignoring the other inputs.
Priority Encoder:
as an example to understand how it differs from a normal Encoder and it can overcome the above mentioned two drawbacks. 
The block diagram of a 4:2 Priority Encoder is shown below
A priority 4:2 Encoder also has 4 inputs and 2 outputs, but we will add another output called V which stands for valid bit. 

This valid bit will check if all the four input pins are low (0) if low the bit will also make itself low stating that the output is not valid thus we can overcome the first drawback mentioned above.
The next drawback can be avoided by giving priority to MSB bits, the Encoder will check from the MSB and once it finds the first bit that high (1) it will generate the output accordingly. 
So it does not matter if the other pins are high or low. 
Hence in the truth table below once a 1 is reached the don’t care values are presented by “Xᾮ

Now we have to derive three Expression that is for O0, O1 and V. 
Since the truth table has don’t care items we have to use the K-map method to derive the Boolean Expression for this. 
We are not going to cover how to solve with K-maps since it is out of scope of this article. 
But the Map is shown below so that you can interfere and learn by yourself.

In the above maps, the left one is for O1 and the right one is for O0. 
The output lines are mentioned by y and the input lines are mentioned by x. 
So arranging the equation accordingly we will get the following.
O1 = I3 + I2

O0 = I2 I1ᾠ+ I3
Similarly, for the valid bit “Vᾠthe Boolean expression can be given as
V = I3 + I2 + I1 + I0
The circuit diagram for this project can be build using the Boolean expressions.

The circuit can be build using the basic NOT, AND, and OR gates. 
Here the bits O0 and O1 are considered as outputs while the bit V is use to validate the output. 
Only if the bit V is high, the output will be considered if the value of V is low (0) the output should be ignored, since it implies that all the input pins are zero.


tutorial/half-adder-circuit-and-its-construction
Half Adder Circuit and its Construction
When we use arithmetic summation process in our base 10 mathematics, like adding two numbers
We add each column from right to left and if the addition greater than or equal to 10, we use carry. 

In the first addition 6+4 is 10. 
We wrote 0 and carry the 1 to the next column. 
So, each value has a weighted value based on its column position.
and due to this, carry bit will be passed over next column for addition.
Half Adder Circuit:
Below is the block diagram of a Half-Adder, which requires only two inputs and provide two outputs.
Let’s see possible binary addition of two bits,


1st Bit or Digit
2nd Bit or Digit
Sum of the total<
Carry
0
0
0
0
1
0
1
0
0
1
1
0

1
1
0
1

bit.
Construction of Half Adder Circuit:
We have seen the Block Diagram of Half Adder circuit above with two inputs A,B and two outputs- Sum, Carry Out. 
We can make this circuit using two basic gates
2-input Exclusive-OR Gate or Ex-OR Gate
2-input AND Gate.

Gate produce the carry bit of the same input A and B.
is the final output after adding two numbers.
ᾍ


Input A
Input B
SUM OUT
0
0
0
0
1
1
1
0
1

1
1
0

gate is perfectly fits in this application.
bit in the input it will produce an Output.

-


0
0
0

0
1
0
1
0
0
1
1
1

Half-Adder logical circuit:
can be made by combining this two gates and providing the same input in both gates.
is-
SUM = A XOR B (A+B)

CARRY = A AND B (A.B)
is as follows-



0
0
0
0
1
0
1
0
0
1
1
0
1
1
0
1


Practical Demonstration of Half Adder Circuit:
using this two.
Below is the Pin Diagram for both the ICs:

Circuit Diagram to use these two ICs as a half-adder circuit-
and observed the output.
, the LED will glow.
inputs when the switch is in off state.

is given below.
is constructed.

tutorial/capacitor-in-series-and-parallel-circuits

Capacitor Circuits: Capacitor in Series, Parallel & AC Circuits
made up of waxed paper, mica, ceramic, plastic and etc.
There are many applications of a capacitor in electronics, some of them are listed below:
Energy Storage

Power Conditioning
Power factor Correction
Filtration
Oscillators

? When you connect power supply to the capacitor it blocks the DC current due to insulating layer, and allow a voltage to be present across the plates in the form of electrical charge. 
So, you know how a capacitor works and what are its uses or application, but you have to learn that how to use a capacitor in electronic circuits.
Here, we are going to demonstrate you the connections of a capacitor and effect due to it with examples.
Capacitor in Series

Capacitor in Parallel
Capacitor in AC Circuit
Capacitor in Series Circuit
), because charge stored by a plate of any capacitor comes from the plate of adjacent capacitor in the circuit.

(KVL) in the circuit, we have
VT = VC1 + VC2 + VC3                                 ‐󟤱uation (1)
As we know,
Q = CV

So, V = Q / C
Now, on putting the above values in the equation (1)
(1 / CT) = (1 / C1) + (1 / C2) + (1 / C3)
For n number of capacitor in series the equation will be

(1 / CT) = (1 / C1) + (1 / C2) + (1 / C3) + ‐󬞫 (1 / Cn)
= Total capacitance of the circuit
…n = Capacitors capacitance
Capacitance Equation for two special cases is determined below:

if there are two capacitor in series, with different value the capacitance will be expressed as:
(1 / CT) = (C1 + C2) / (C1 * C2)
Or, CT = (C1 * C2) / (C1 + C2)             ‐󟤱uation (2)
if there are two capacitor in series, with same value the capacitance will be expressed as:

(1 / CT) = 2C / C2 = 2 / C
Or, CT = C / 2
Now, in the below example we will show you how to calculate total capacitance and individual rms voltage drop across each capacitor.
with different values. 

So, the voltage drop across the capacitors is also unequal. 
If we connect two capacitors with same value the voltage drop is also same.
Now, for the total value of capacitance we will use the formula from equation (2)
So, CT = (C1 * C2) / (C1 + C2)

Here, C1 = 4.7uf and C2 = 1uf
CT = (4.7uf * 1uf) / (4.7uf + 1uf)
CT = 4.7uf / 5.7uf
CT = 0.824uf

is:
VC1 = (CT / C1) * VT
VC1 = (0.824uf / 4.7uf) * 12
VC1 = 2.103V

is:
VC2 = (CT / C2) * VT
VC2 = (0.824uf / 1uf) * 12
VC2 = 9.88V
Capacitor in Parallel Circuit
When you connect capacitors in parallel, then the total capacitance will be equal to the sum of all the capacitors capacitance. 
Because the top plate of all the capacitors are connected together and the bottom plate also. 
So, by touching each other the effective plate area is also increased. 

Therefore, the capacitance is proportional to the ratio of Area and distance.
(KCL) in the above circuit,
iT = i1 +i2 + i3
As we know current through a capacitor is expressed as;

i = C (dV / dt)
So, iT = C1 (dV / dt) + C2 (dV / dt) + C3 (dV / dt)
And, 
iT= (C1 + C2 + C3)* (dV / dt)

iT = CT (dV / dt)                      ‐󟤱uation (3)
From equation (3), the Parallel Capacitance equation is:
CT = C1 + C2 + C3
For n number of capacitors connected in parallel the above equation is expressed as:

CT = C1 + C2 + C3 + ‐󞩠Cn
As these capacitors are connected in parallel the equivalent or total capacitance will be equal to the sum of the individual capacitance.
CT = C1 + C2 + C3 
Where, C1 = 4.7uf; C2 = 1uf and C3 = 0.1uf

So, CT = (4.7 +1 + 0.1)uf
CT = 5.8uf
Capacitor in AC circuits
When a capacitor is connected to DC supply, then the capacitor starts charging slowly. 

And, when the charging current voltage of a capacitor is equal to the supply voltage it’s said to fully charged condition. 
Here, in this condition the capacitor works as an energy source as long as voltage is applied. 
Also, capacitors do not allow the current to pass through it after it get fully charged.
Whenever, AC voltage is supplied to the capacitor as shown in above purely capacitive circuit. 

Then the capacitor charges and discharges continuously to every new voltage level (charges on positive voltage level and discharge on negative voltage level). 
The capacitor’s capacitance in AC circuits depends on the frequency of input voltage supplied to the circuit. 
The current is directly proportional to the rate of change of voltage applied to the circuit.
i = dQ / dt = C (dV / dt)

As you see the phasor diagram for AC capacitor in the below image, current and voltage are represent in sine wave. 
On observing, at 0 the charging current is at its peak value because of the voltage increasing in positive direction steadily.
Now, at 90 there is no current flow through the capacitor because the supply voltage reaches to the maximum value. 
At 180 the voltage start decreasing slowly to zero and current reach to maximum value in negative direction. 

And, again the charging reaches to its peak value at 360, because of supply voltage is at its minimum value.
Consider the above circuit diagram, as we know AC input voltage is expressed as,
V = VmSinwt
And, capacitor charge Q = CV,

And, current through a capacitor, i = dQ / dt
So,
i = d (CVmSinwt) / dt
i = C * d (VmSinwt) / dt

i = C*VmCoswt *w
i = w*C*VmSin(wt + π/2)
at, wt = 0
sin(wt + π/2) = 1

hence, im = wCVm
Vm / im = 1 / wC
As we know, w = 2πf
So,

Capacitive Reactance (Xc) = Vm / im = 1 / 2πfC
diagram
Let’s, consider the value of C = 2.2uf and the supply voltage V = 230V, 50Hz
Now, the Capacitive Reactance (Xc) = Vm / im = 1 / 2πfC

Here, C = 2.2uf, and f = 50Hz
So, Xc = 1 / 2*3.1414*50*2.2*10-6
Xc = 1446.86 ohm


tutorial/rc-rl-and-rlc-circuits
RC, RL and RLC Circuits
and they have many applications like from filtering circuits, Tube light chokes, multivibrators etc.. 
So in this tutorial we will learn the basic of these circuits, the theory behind them and how to use them in our circuits.

Before we jump into the main topics lets understand what an R, L and C does in a circuit.
Resistors are denoted by the letter “Rᾮ A resistor is an element that dissipates energy mostly in form of heat. 
It will have a Voltage drop across it which remains fixed for a fixed value of current flowing through it.
Capacitors are denoted by the letter “Cᾮ A capacitor is an element which stores energy (temporarily) in form of electric field. 

Capacitor resists changes in voltage. 
There are many types of capacitors, out of which the ceramic capacitor and the electrolytic capacitors are mostly used. 
They charge in one direction and discharge in opposite direction
Inductors are denoted by the letter “Lᾮ A Inductor is also similar to capacitor, it also stores energy but is stored in form of magnetic field. 

Inductors resist changes current. 
Inductors are normally a coil wound wire and is rarely used compared to the former two components.
and much more it is not possible to cover every aspect in this tutorial, so we will learn the basic behaviour of them in this tutorial.
Basic Principle of RC/RL and RLC circuits:
Before we start with each topic let us understand how a Resistor, Capacitor and an Inductor behave in an electronic circuit. 
For the purpose of understanding let us consider a simple circuit consisting of a capacitor and resistor in series with a power supply (5V). 
In this case when the power supply is connected to the RC pair, the voltage across the Resistor (Vr) increase to its maximum value while the voltage across the capacitor (Vc) stays at zero, then slowly the capacitor starts to build charge and thus the voltage across the resistor will decrease and the voltage across the capacitor will increase until the resistor voltage (Vr) has reached Zero and Capacitor voltage (Vc) has reached its maximum value. 
The circuit and the wave form can be seen in the GIF below

Let us analyse the wave form in the above image to understand what is actual happening in the circuit is. 
A well illustrated waveform is show in the image below.
When the switch is turned on the voltage across the resistor (red wave) reaches its maximum and the voltage across capacitor (blue wave) remains at zero. 
Then the capacitor charges up and Vr becomes zero and Vc becomes maximum. 

Similarly when the switch is turned off capacitor discharges and hence the negative voltage appears across the Resistor and as the capacitor discharges both the capacitor and resistor voltage becomes zero as shown above.
The same can be visualized for inductors as well. 
Replace the capacitor with an inductor and the waveform will just be mirrored, that is the voltage across the resistor (Vr) will be zero when the switch is turned on since the whole voltage will appear across the Inductor (Vl). 
As the inductor charges up the voltage across (Vl) it will reach zero and the voltage across the resistor (Vr) will reach the maximum voltage.
RC circuit:
will consist of only one Resistor and one Capacitor and we will analyse the same in this tutorial
To understand the RC circuit let us create a Basic circuit on proteus and connect the load across the scope to analyse how it behaves. 
The circuit along with the waveform is given below

We have connected a load (light bulb) of known resistance 1k Ohms in series with a capacitor of 470uF to form a RC circuit. 
The circuit is powered by a 12V battery and a switch is used to close and open the circuit. 
The waveform is measured across the load bulb and is shown in yellow colour on the image above.
Initially when the switch is open maximum voltage (12V) appears across the resistive light bulb load (Vr) and the voltage across the capacitor will be zero. 

When the switch is closed the voltage across the resistor will drop to zero and then as the capacitor charges the voltage will reach back to maximum as shown in the graph.
where ⁢€ represents tou (Time constant).
Let us calculate the time taken for our capacitor to charge up in the circuit.
 = RC

   = (1000 * (470*10^-6))
   = 0.47 seconds
T = 5
   = (5 * 0.47)

T = 2.35 seconds.
We have calculated that the time taken for the capacitor to charge up will be 2.35 seconds, the same can also be verified from the graph above. 
The time taken for Vr to reach from 0V to 12V is equal to the time taken for the capacitor to charge from 0V to maximum voltage. 
The graph is illustrated using the cursors in the below image.

Similarly we can also calculate the voltage across the capacitor at any given time and the current through the capacitor at any given time using the below formulas
V(t) = VB (1 – e-t/RC)
I(t) =Io (1 ᾠe-t/RC)
is the output current of the circuit. 

The value of t is the time (in seconds) at which the voltage or current value of the capacitor has to be calculated.
RL circuit:
with only one inductor and one capacitor is shown below
we have to replace the Capacitor with an Inductor. 

The Light bulb is assumed to act as a pure resistive load and the resistance of the bulb is set to a known value of 100 ohms.
When the circuit is open, the voltage across the resistive load will be maximum and when the switch is closed the voltage from the battery is shared between the inductor and the resistive load. 
The inductor charges up quickly and hence a sudden voltage drop will be experienced by the resistive load R.
where ⁢€ represents tou (Time constant).

Let us calculate the time taken for our inductor to charge up in the circuit. 
Here we have used an inductor of value 1mH and the resistor of value 100 Ohms
 = L/R
   = (1 * 10^-3) / (100)

   = 10^-5 seconds
T = 5
   = (5 * 10^-5)
   = 50 * 10 ^-6

T = 50 u seconds.
Similarly, we can also calculate the voltage across the Inductor at any given time and the current through the Inductor at any given time using the below formulas
V(t) = VB (1 – e-tR/L)
I(t) =Io (1 ᾠe-tR/L)

is the output current of the circuit. 
The value of t is the time (in seconds) at which the voltage or current value of the Inductor has to be calculated.
RLC Circuit:
is discussed below

is also called as series resonance circuit, oscillating circuit or a tuned circuit. 
These circuit has the ability to provide a resonant frequency signal as shown in the below image
Here we have a capacitor C1 of 100u and an Inductor L1 of 10mH connected tin series through a switch. 
Since the wire that is connecting the C and L will have some internal resistance, it is assumed that a small amount of resistance is present due to the wire.

Initially, we keep the switch 2 as open and close the switch 1 to charge up the capacitor from the battery source (9V). 
Then once the capacitor is charged the switch 1 is opened and then the switch 2 is closed.
As soon as the switch is closed the charge stored in the capacitor will move towards the inductor and charge it up. 
Once the capacitor is fully dis-charged, the inductor will start discharging back into the capacitor this way charges will flow to and fro between the inductor and the capacitor. 

But since there will be some loss in charges during this process total charge will gradually decrease until it reaches zero as shown in the graph above.
Applications:
The Resistors, Inductors and Capacitors may be normal and simple components but when they are combined to gather to form circuits like RC/RL and RLC circuit they exhibit complex behaviour which makes it suitable for a wide range of application. 
Few of them are listed below

Communication systems
Signal Processing
Voltage/Current magnification
Radio wave transmitters

RF amplifiers
Resonant LC circuit
Variable tunes circuits
Oscillator circuits

Filtering circuits

tutorial/cycloconverter-types-working-circuits-applications
Cycloconverters ᾠTypes, Working and Applications

is one such converter which converts AC power in one frequency into AC power of an adjustable frequency. 
In this article we will learn more about these Cycloconverters their types, working and applications.
What isCycloconverter?
converts a constant voltage, constant frequency AC waveform to another AC waveform of a lower frequency by synthesizing the output waveform from segments of the AC supply without an intermediate DC linkᾍ

One particular property of Cycloconverters is that it does not use a DC link in the conversion process thus making it highly efficient. 
The conversion is done by using power electronic switches likes Thyristors and switching them in a logical manner. 
Normally these Thyristors will be separated into two half, the positive half and the negative half. 
Each half will be made to conduct by turning them during each half cycle of the AC form thus enabling bi-directional power flow. 

For now imagine Cycloconverters as a black box which take in a fixed Voltage fixed Frequency AC power as input and provides a Variable frequency, variable Voltage as output as shown in the illustration below.
We will learn what could possibly be going on inside this black box as we go through the article.
Why do we need Cycloconverters?
Okay, now we know that Cycloconveters convert AC power of fixed frequency to AC Power of variable Frequency. 

But why do we need to do that? What is the advantage of having an AC power supply which variable Frequency?
Cycloconveters are extensively used for driving large motors like the one used in Rolling mills, Ball mills Cement kils etc. 
The out frequency of a Cycloconverters can be reduced upto to zero which helps us to start very large motors with full load at minimum speed and then gradually increase the speed of the motor by increasing the output Frequency. 
Before the invention of Cycloconverters, these large motors has to be unloaded completely and then after starting the motor it has to be loaded gradually which results in time and man power consumption.
Types of Cycloconveters:
Based on the output frequency and number of phase in the input AC power source the Cycloconverters can be classified as below
1. Step-Up Cycloconverters
2. Ste-Down Cycloconverters


Single-Phase to Single-Phase Cycloconverter
Three-Phase to Single-Phase Cycloconverter
Three-Phase to Three-Phase Cycloconverter

Step-Up CCV, as the name suggests this type of CCV provide output frequency greater than that of input frequency. 
But it is not widely used since it not have much particle application. 
Most application will require a frequency less than 50Hz which is the default frequency here in India. 
Also Step-Up CCV will require forced commutation which increases the complexity of the circuit.

Step-Down CCV, as you might have already guessed it well.. 
just provides an output frequency which is lesser then the input frequency. 
These are most commonly used and work with help of natural commutation hence comparatively easy to build and operate. 
The Step-Down CCV is further classified into three types as shown below we will look into each of these types in detail in this article.
Basic Principle behind Cycloconverters:
Although there are three different types of Cycloconverters, the working of them are very similar except for the number of power electronic switches present in the circuit. 
For instance a single phase to Single Phase CCV will have only 6 power electronic switches (SCR’s) while an Three Phase CCV might have upto 32 switches.
The bare minimum for a Cycloconverter is shown above. 

It will have a Switching circuit on either side of the Load, one circuit will function during the positive half cycle of the AC power source and the other circuit will function during the negative half cycle. 
Normally the switching circuit will be demonstrated using SCR as power electronic device, but in modern CCV you can find the SCR’s being replaced by IGBT’s and sometimes even MOSFETS.
The switching circuits will also need a control circuit, which instructs the Power electronic device when to conduct and when to turn off. 
This control circuit will normally be a Microcontroller and might also have a feedback from the output to form a closed loop system .The user can control the value of output frequency by adjusting the parameters in the control circuit.The diodes in the above diagram are used to represent the direction of flow of current. 

The positive switching circuit always sources current into the load and the negative switching circuit always sinks current from the load.
Single Phase to Single Phase Cycloconverters:
The Single Phase to Single Phase CCV is very rarely used, but to understand the operation of a CCV it should be first studied so that we can understand the Three Phase CCV. 
The Single Phase to Single Phase CCV has two pairs of full wave rectifier circuit, each consisting of four SCR. 

One set is placed straight while the other is placed in anti-parallel direction as shown on the picture below.
All the gate terminals of the SCR’s will be connected to a control circuit which is not shown in the circuit above. 
This control circuit will be responsible for triggering the SCRs. 
To understand the working of the circuit let us assume that he input AC supply is of 50Hz frequency and the Load to be a pure resistive load and the firing angle of the SCR (α) to be 0°. 

Since the firing angle is at 0° the SCR when turned on will act like a diode in forward direction and when turned off will act like a diode in reverse direction. 
Let us analyse the wave form below to understand how frequency is stepped down using a CCV
of its value. 
So to do that for the first two cycles of the supply voltage we will use the positive Bridge rectifier and for the following next two cycles we will use the negative bridge rectifier. 

Thus we have four positive pulses in the positive region and then four in the negative region as shown in the output frequency waveform Vo. 
The current waveform for this circuit will be the same as voltage waveform since the load is assumed to be purely resistive. 
Although the magnitude of the waveform will change based on the value of resistance of the load.
of the input frequency, in our case for an input frequency of 50Hz the output frequency will be (1/4 * 50) around 12.5Hz. 

This output frequency can be controlled by varying the triggering mechanism in the control circuit.
Three Phase to Single Phase Cycloconverters:
The Three Phase to Single Phase CCV is also similar to the Single Phase to Single Phase CCV, but in here the input voltage is a 3 Phase supply and the output voltage is a Single Phase supply with variable frequency. 
The circuit also looks very similar except we will need 6 SCR in each set of Rectifier since we have to rectify the 3 Phase AC voltage.

Again the gate terminals of the SCR will be connected to the control circuit for triggering them and the same assumptions are made again to understand the working easily. 
Also there are two kinds of Three Phase to Single Phase CCVs , the first type will have a half wave rectifier for both Positive and Negative Bridge and the second type will have a full-wave rectifier as shown above. 
The first type is not used often because of its poor efficiency. 
Also in a full-wave type both the bridge rectifiers can generate voltages in both the polarity, but the positive converter can supply current (source) only in the positive direction and the negative converter can drain current only in negative direction. 

This allows the CCV to operate in four Quadrants. 
These four quadrants are (+V, +i) and (-V, -i) in rectification mode and (+V, -i) and (-V,-i) in inversion mode.
Three Phase to Three Phase Cycloconverters:
The Three Phase to Three Phase CCV are the most used ones since they can drive Three Phase loads like motors directly. 

The Load for a Three Phase CCV will normally be a Three Phase Star connected load like the stator winding of a Motor. 
This converters take in Three Phase AC voltage with fixed frequency as input and provides Three Phase AC voltage with Variable frequency.
There are two types of Three Phase CCV, the one which has half wave converter and other with full wave converter. 
The Half wave converter model is also called as 18-thyristor Cycloconverters or 3-pulse Cycloconverters. 

The full wave converter is called as 6-pulse Cycloconverters or 36-thyristor Cycloconverters. 
A 3-pulse Cycloconverter is shown in the picture below
Here we have six sets of Rectifiers of which two is allocated for each phase. 
The working of this CCV is similar to single phase CCV except here the rectifiers can rectify only half the wave and the same happens for all the three phases
Applications of Cycloconverter:
Cycloconverters have a large set of industrial application, the following are the few
Grinding Mills
Heavy Washing Machines

Mine Winders
HVDC Power lines
Aircraft Power supply
SVG (Static VAR Generators)

Ship Propulsion system

tutorial/getting-started-with-amazon-aws-for-iot-projects
Getting Started with Amazon AWS for IoT Projects

by creating a thing and then we will test if the thing is working properly using the MQPTT.fx application.
Creating you Amazon AWS account
ᾮ
You will be taken through the sign up procedure. 

During the process of sign up Amazon will ask for your Debit/Credit card details. 
Sadly we need either of one to create an account with AWS. 
But, since you can use it for free for duration of 12 months it should not be a problem. 
Just enter your card details since you will not be charged for 12 months, but make sure to de-activate the account before 12 months if you are not using the account any longer.

You will also be asked for PAN number which is not mandatory, once the sign up process is complete log in to you account.
Create a AWS Thing with Certificate and Policy
In the main page, under AWS services search for “iot coreᾮ You should see the IOT core option being listed as shown below click on it to open the AWS IOT console
You will be greeted with the introductory message from AWS IOT, just click on “get startedᾍ

ᾠoption on the menu which can be found at left side of you screen as highlighted in below picture.
ᾍ
ᾍ
After naming the thing just scroll down and click on next. 

If you are interested you can read through the other options which gives more definition to the things functions, but you can ignore them for now.
ᾍ
button first and then download the three key files and save it on your computer somewhere secure. 
Never share these keys with public, since they can use your AWS account by launching this thing and you will be charged for it.

if it ends with .text change it.
ᾍ
ᾮ We will create a policy in our next step and then attach it.
You will be taken back to the main page, here we have to create a policy so on the left side menu find for an option called secure and then click on policies as shown below

As we know we don’t have any policies yet so click on “create a policy ᾍ
Also make sure the allow button is checked for allowing effect.
Indicates that we can both subscribe and publish to the things with this policy
ᾠbutton on the end of the page to create the policy.

ᾠas shown below.
ᾠoption in the AWS IOT console. 
Before that we need to get the Broker address of the thing we just created.
Getting your AWS thing Details:
After creating a Thing we need to get the details of the thing like its broker address update link etc to access the thing from anywhere using the internet. 
These details can be found in manage option and clicking on the name of the thing.
In the new page click on interact option on the left side of the screen and you will be provided with all the links for accessing your thing. 
As said keep these links confidential. 

For now we need the HTTPS link (Circled in red) for testing if the thing is working properly so just copy it.
Testing the Thing using the AWS:
option. 
This will load the MQTT client which can be used to test our thing.

and you should see the message reflected in your thing as shown below
Using MQTT.fx with AWS IOT:
that we just created.
Make sure you select the correct operating system of your machine.

Open the application and click on the settings icon to configure the MQTT as client. 
The settings icon is shown in the picture below:
section. 
The Broker Port for AWS IOT is 8883 for all users so enter the same. 

Then select SSL/TLS
Now we have to select Self-signed certificates and link the certificates that we downloaded in step 8. 
Also make sure PEM formatted is checked. 
Follow the image below to know which keys you should choose

Finally click on OK and then you will taken back to the main window. 
Now click on the connect button. 
IF everything is working properly then MQTT should be able to connect to our thing and the following screen will be displayed. 
Check for the green circle on the top right corner (en-circled)

tab and give any random name and then click on subscribe. 
Here I have selected bingo as my name. 
After subscribing you will get the following name.
ᾮ Click on the publish button

tab and you should be able to see the message that we just published as shown below
at the bottom to get a better understanding.
In our next tutorials, we will learn how we can use actual hardware things like ESP8266, ESP12, Raspberry Pi etc to use this thing to send/receive information.


tutorial/program-arduino-on-android-phone
How to Program Arduino with an Android device
Sometimes we don’t have any PC or laptop to program our Arduino boards. 
We can still program it using our Android mobile, Thanks to OTG (On the Go) adaptor.

which is completely same as Arduino IDE.
Materials Required:
Arduino Board
OTG cable

Arduino USB cable
Android Device
Let’s start with Installing the ArduinoDroid App:
and install it.

Open the app after installing. 
It will look like as given below:
from menu (shown by three dots on upper right corner).
option, click on it.

Connect your Arduino board with Android device using USB cable and OTG.
In Arduino IDE, if we click on upload button, our program is compiled first and then uploaded. 
But here we have to compile first by clicking Compile button as shown below.
You can see status of compilation in Output window.

button as shown below.
given below.
Also remember that you don’t need to provide any external power to your Arduino board as it will draw power from your Android Smart Phone using OTG cable.


tutorial/getting-started-with-labview
Getting Started with LabVIEW: Glow LED with Button
What is LabVIEW?
(i.e.,) we need not compile it. 

It compiles itself, we only need to execute it.
How it Differ From Other Circuit Designing / Simulation Softwares?
All circuit designing / simulation software’s are a schematics that capture and simulation program that enables you to test the output of various circuits by assembling the components and drawing schematics. 
Whereas, LabVIEW is a virtual workbench for graphical programming by capturing and interfacing of virtual circuits created on any circuit designing / simulation softwares.

whereas, LabVIEW is graphical based programming language.
Why One should prefer LabVIEW?
The one who does not have any basic knowledge about programming can start LabVIEW. 
To do LabVIEW programming one should have practical knowledge and logical thinking capability. 

LabVIEW programmer need not know any programming syntax or any structure of programming like c, c++, java programming languages.
One can prefer LabVIEW, when the program is too large. 
This is as simple connecting hardware components for your project but in a software.
with 1 second of delay.
Launching LabVIEW
Once you launch the software, Getting Started window appears.
Press ctrl+N to open a New Project.
Once you open New Project, you will see front panel and block diagram.

to bring front panel and block diagram side by side like this,
are nothing but the outputs you create, such as led, graphs, etc., I will explain all the entities with an example, to make you understand better.
Data-types in LabVIEW:
Data-types are nothing but the classification of variables. 

The following are the data-types used in LabVIEW and their color specification in the block diagram.


Floating point
Orange

Integers
Blue
Booleans
Green
String
Pink
Polymorphic
Black


- The one which can be any of these above data-types or may not be these.
Example 1: Glowing LED on Button Press
).

Select View >> Controls Palette to have the controls or functions palette permanently on the screen, or right click any blank space in the front panel or block diagram to display it temporarily.
Move the cursor over the icons on the Modern palette to locate the controls that you require (Boolean Controls Palette) .
Click the Boolean controls icon to display the Boolean controls palette.
Click the button control on the Boolean controls palette to attach the control and then add the button to the front panel.

You will use this button control to glow the led.
Thus button control is added to the front panel.
Similarly add button from the Boolean palette. 
Then give connection as shown below,

Select Operate >> Run/Run Continuously.
Or you can use the icons which I have mentioned in the above figure.
To stop the execution again press run continuously icon.
Thus the led glows when you press the button.

of the article.
Example 2: LED ON-OFF
In the below example, instead of button, we will use knob from Boolean palette.
at the end.
Example 3: Blinking LED 
In the above example, I have removed the ok button and added the stop button.
Right click on the block diagram window, Functions palette will appear.
Pick and drag while loop.

Right click over the while loop and select Add Shift Register.
Right click on the block diagram and select Boolean, in that select Boolean not gate.
Similarly, pick and drag delay and add constant to it.
Constants are value that you can change according to your requirement like 1000ms for 1 second.

Give the connections as shown in the above diagram.
NOTE: You can use your own logics to build above examples.
Shortcuts
You can use the below keyboard shortcuts to control LabVIEW.



<ctrl+N>
Open a new, blank VI
<ctrl+H>
Shows or hides the context help window

<ctrl+Space>
Displays he quick drop dialog box.
<ctrl+B>
Deletes all broken wires in a VI
<ctrl+ L>
Displays the error list window.



tutorial/igbt-transistor
IGBT - Insulated Gate Bipolar Transistor
It’s is a semiconductor device used for switching related applications.

which enables large collector emitter currents with almost zero gate current drive.
As discussed, IGBT has the advantages of both MOSFET and BJTs, IGBT has insulated gate same as like typical MOSFETs and same output transfer characteristics. 
Although, BJT is current controlled device but for the IGBT, the control depends on the MOSFET, thus it is voltage controlled device, equivalent to the standard MOSFETs.
IGBT Equivalent Circuit and Symbol
are coming from the PNP transistor.
In the PNP transistor, collector and Emitter is conduction path and when the IGBT is switched on it is conducted and carry the current through it. 
This path is controlled by the N channel MOSFET.
by dividing the output current by the input current.

β = Output Current / Input Current
Due to high current capabilities, the BJT’s high current is controlled by the MOSFET gate voltage.
is very low.
Applications of IGBT:
compared with BJTs and due to this property the IGBT is thermal efficient in high power related application.
IGBTs are used in High power motor control, Inverters, switched mode power supply with high frequency converting areas.
we need to supply constant current across the base of the BJT. 
But in case of the IGBT, same as like MOSFET we need to provide constant voltage across the gate and the saturation is maintained in constant state.

which is the potential difference of the Input (gate) with the Ground / VSS, controls the output current flowing from the collector to emitter. 
The voltage difference between VCC and GND is almost same across the load.
value.
IRL2 = VIN / RS

ᾠstate. 
It is same as like BJT and MOSFET switching.
IGBT I-V Curve and Transfer Characteristics 
is the breakdown voltage of the IGBT.

is shown because IGBT is a voltage controlled device.
is greater than a threshold value depending on the IGBT specification.



tutorial/darlington-transistor-pair
Darlington Transistor Pair
is invented in 1953, by a US electrical engineer and inventor, Sidney Darlington.

Darlington transistor uses two standard BJT (Bi-polar junction transistor) transistors which are connected together. 
Darlington transistor connected in a configuration where one of transistor’s emitter provides biased current to the other transistor’s base.
Darlington Transistor Pair and its Configuration:
configuration.

or where the Push-Pull topologies are needed.
:
Generating Tones by Tapping Fingers using Arduino
Simple Lie Detector Circuit using Transistors

Long Range IR Transmitter Circuit
Line Follower Robot using Arduino
Darlington Transistor Pair Current Gain Calculation:
In the below image we can see two PNP or two NPN transistors are connected together.

will be-
Current gain (hFE) = First transistor gain (hFE1) * Second transistor gain (hFE2)
s base.
is achieve, when the collector current is

β * IB as hFE = fFE1 * hFE2
.
are same.
IB2 = IE1.

We can change this relationship further with
IC1 + IB1
Changing the IC1 as we did previously, we get
β1IB1 + IB1

IB1 (β1 + 1)
Now as previously, we have seen that
IC =  β1IB1 + β2IB2
As, IB2 or IE2 = IB1 (β1 + 1)

IC = β1IB1 + β2 IB1 (β1 + 1)
IC = β1IB1 + β2 IB1 β1 + β2 IB1
IC = {β1 +(β1 + β2) + β2}
So, the total collector current IC is a combinational gain of individual transistors gain.
Darlington Transistor Example:
We will calculate the base current for switching the load.
will be
IL = IC = Power / Voltage = 60 / 15 = 4Amps

(β1 = 30 and β2 = 95) we can calculate the base current with the following equation ᾍ
ᾮ
Darlington Transistor Application:
The application of Darlington transistor is same as normal BJT Transistor.

provide advantage over the response time and thermal performance.
.
What is an Identical Darlington Transistor?
Using the collector current formula the current gain of the Identical Transistor will be-

IC = {{β1 + (β2* β1) + β2} *IB}
IC = {{β1 + (β2* β1) + β1} *IB}
β2 = IB / IC
The current gain will be much higher. 

NPN Darlington pair examples are TIP120, TIP121, TIP122, BC517 and PNP Darlington pair examples are BC516, BC878, and TIP125.
Darlington Transistor IC:
Darlington pair allows users to drive more power applications by few milliamp of current source from micro controller or low current sources.
using this.

dip package. 
As we can see the input and output pin are exactly opposite, due to that it is easier for connecting the IC and making the PCB design more simplistic.
There are seven open collector pins are available. 
One additional pin is also available which is useful for inductive load related application, it can be motors, solenoids, relays, which needs freewheeling diodes, we can make the connection using that pin.

In the upper image the actual Darlington array connection is shown for the each driver. 
It is used in seven drivers, each driver consist this circuit.
and parallel two Darlington pairs for driving higher current loads.
Switching a Motor using ULN2003 IC:
in Darlington Transistor.
stopping the motor. 
The reverse will happen when additional current is applied across the input pin.


tutorial/opto-coupler-types-working-applications
Optocoupler: Its Types and Various Application in DC/AC Circuits
Internal Structure of Optocoupler
or higher.
Types of Optocouplers
are available commercially based on their needs and switching capabilities. 
Depending on the use there are mainly four types of optocouplers are available.
Opto-coupler which use Photo Transistor.

Opto-coupler which use Photo Darlington Transistor.
Opto-coupler which use Photo TRIAC.
Opto-coupler which use Photo SCR.
Photo-Transistor Optocoupler
Often the pin is used to connect with ground or negative using a high value resistor. 
In this configuration, false triggering due to noise or electrical transients can be controlled effectively.
Photo-Darlington Transistor Optocoupler
based opto-coupler is shown.

is two transistor pair, where one transistor controls other transistor base. 
In this configuration the Darlington Transistor provide high gain ability. 
As usual the LED emits infrared led and controls the base of the pair transistor.
are few photo-Darlington based opto-coupler example.
Photo-TRIAC Optocoupler
based opto-coupler is shown.
etc are example of TRIAC based opto-coupler.
Photo-SCR based Optocoupler
etc.
Applications of Optocoupler
From switching other application, same as like where transistor can be used to switch application the Optocoupler can be used. 
It can be used in various microcontroller related operations where digital pulses or analog information needed from a high voltage circuitry, Optocoupler can be used for excellent isolation between this two.

Opto-coupler can be used for AC detection, DC control related operations. 
Let’s see few applications of Opto-transistors.
Optocoupler for Switching DC Circuit:
When the switch will be on, the 9V battery source will provide current to the LED via the current limiting resistor 10k.The intensity is controlled by the R1 resistor. 

If we change the value and make the resistance lower, the intensity of the led will be high making the transistor gain high.
, when the led emit infra-red light the photo transistor will contact and the VOUT will be 0 turning off the load connected across it. 
It is needed to remember that as per the datasheet the collector current of the transistor is 50mA. 
The R2 provide the VOUT 5v. 

The R2 is a pull-up resistor.
in the below video‐󋈍
Optocoupler for Detecting AC Voltage:
The infra-red led is controlled using two 100k resistor. 

The two 100k resistor used instead of one 200k resistor is for extra safety for short-circuit related condition. 
The LED is connected across wall outlet Line (L) & Neutral line (N). 
When the S1 is pressed the led start to emit infra-red light. 
The photo transistor makes a response and converts the VOUT from 5V to 0V.

In this configuration the opto-coupler can be connected across low voltage circuit such as microcontroller unit where the AC voltage detection is required. 
The output will produce square High to Low pulse.
As of now the first circuit is used to control or switching the DC circuit and second is to detect the AC circuit and control or switch DC circuit. 
Next we will see controlling AC circuit using DC circuit.
Optocoupler for Controlling AC Circuit using DC voltage:
, which control the AC LAMP from the 220V AC outlet. 
The 68R resistor is used to Control the BT136 TRIAC which is controlled by the photo-TRIAC inside the opto-coupler unit.
The IL420 is used in the upper schematic which is a photo-TRIAC based Opto-coupler.

Other than this type of circuitry an opto-coupler can be used in SMPS to sending secondary side short-circuit or over current condition information to the primary side.
, check below circuits:
Introduction to Octocoupler and Interfacing with ATmega8
Prepaid Energy Meter using GSM and Arduino

IR Remote Controlled TRIAC Dimmer Circuit
Raspberry Pi Emergency Light with Darkness and AC Power Line Off Detector
IR Remote Controlled Home Automation using PIC Microcontroller


tutorial/quartz-crystal-oscillator
Quartz Crystal Oscillator
In case of RC (Resistor-Capacitor) or RLC (Resistor-Inductor-Capacitor) Oscillators, they are not good choice where stable and accurate oscillations are needed. 
The temperature changes affect the load and power supply line which in turn affects the stability of the Oscillator circuit. 

The stability can be improved to a certain level in case of RC and RLC circuit, but still the improvement is not sufficient in specific cases.
effect. 
When voltage source is applied across it, it will change shape and produce mechanical forces, and the mechanical forces revert back, and produce electrical charge.
effect produces the stable oscillations.
Quartz Crystal and its Equivalent Circuit
In the upper image, left circuit represents the equivalent circuit of Quartz Crystal, shown in the right side. 
As we can see, 4 passive components are used, two capacitor C1 and C2 and one Inductor L1, Resistor R1. 
C1, L1, R1 is connected in series and the C2 connected in parallel.

The series circuit which consists one capacitor, one resistor and one inductor, symbolize the controlled behavior and stable operations of the Crystal and the parallel capacitor, C2 represents the parallel capacitance of the circuit or the equivalent crystal.
of a Quartz Crystal.
Crystal Output Impedance against Frequency
will be:-

XC1 = 1 / 2πfC1
Where,
will be:-
XC2 = 1 / 2πfC2

Where,
the formulas will be:-
we will see the changes in impedance.
point.

The series capacitor C1 and the series Inductor L1 create a series resonance which is equal to series resistor.
So, at this series resonant frequency point, the following things will happen:-
The Impedance is minimum compared in other frequency times.
Impedance is equal to the series resistor.

Below this point the crystal acts as a capacitive form.
Next the frequency gets changed and the slope slowly increased to the maximum point at parallel resonant frequency, at this time, before reaching the parallel resonant frequency point the crystal act as a series inductor.
After reaching the parallel frequency point the impedance slope reaches maximum in value. 
The parallel capacitor C2 and the Series Inductor create a LC tank circuit and thus the output impedance became high.

This is how the crystal behaves as inductor or like a capacitor in series and parallel resonance. 
Crystal can operate in this both resonance frequencies but not at the same time. 
It is need to be tune at any specific one to operate.
Crystal Reactance against Frequency
can be measured using this formula:-
XS = R2 + (XL1 – XC1)2
Where, R is the value of resistance
of the circuit will be:-

XCP = -1 / 2πfCp
The parallel reactance of the circuit will be :-
Xp = Xs * Xcp / Xs + Xcp
If we see the graph it will look like this:-

On the other hand, the crystal will be at capacitive form when the frequency is outside of the fs and fp points.
We can calculate the Series Resonant Frequency and Parallel Resonant frequency using this two formulas ᾍ
Q Factor for Quartz crystal:
Sometimes, the Q factor of a crystal is more than 200,000 also observable.

Q factor of a crystal can be calculated using the following formula ᾍ
Q = XL / R = 2πfsL1 / R
Quartz Crystal Oscillator Example with Calculation
We will calculate a quartz crystals series resonant frequency, parallel resonant frequency and the Quality factor of the crystal when the following points are available-

is ᾍ
, fp is ᾍ
will be-
Colpitts Crystal Oscillator
The transistor Q1 is in common emitter configuration. 
In the upper circuit R1 and R2 is used for the biasing of the transistor and C1 is used as bypass capacitor which protect the base from RF noises.
Capacitor C2 and C3 is used for feedback. 
The crystal Q2 is connected as parallel resonant circuit.

The output amplification is low in this configuration for avoiding excess power dissipation in the crystal.
Pierce Crystal Oscillator 
circuit is shown. 
The C4 provides the necessary feedback in this oscillator circuit. 

This feedback is positive feedback which is 180 degree phase shift at the resonant frequency. 
R3 control the feedback and the crystal provides the necessary oscillation.
The Output sine wave amplitude peak to peak value is limited by the JFET voltage range.
CMOS Oscillator
A basic oscillator which use parallel-resonant crystal configuration can be made using CMOS inverter. 
The CMOS inverter can be used for achieving required amplitude. 
It consists inverting Schmitt trigger like 4049, 40106 or Transistor-Transistor logic (TTL) chip 74HC19 etc.
in inverting configuration. 

The crystal will provide necessary oscillation in series resonance frequency. 
R1 is the feedback resistor for the CMOS and provide high Q factor with high gain capabilities. 
The second 74HC19N is booster to provide sufficient output for the load.
The inverter operate at 180 degree phase shift output and the Q1, C2, C1 provide additional 180 degree phase shift. 

During the oscillation process the phase shift always remain 360 degree.
The maximum output frequency is fixed by the switching characteristic of the CMOS inverter. 
The output frequency can be changed using the Capacitors value and the Resistor value. 
C1 and C2 needs to be the same in values.
ProvidingClock to Microprocessor using Crystals
As various use of quartz crystal oscillator includes Digital watches, Timers etc, it is also a suitable choice for providing stable oscillation clock across microprocessor and CPUs.
Microprocessor and CPU needs stable clock input for operation. 
Quartz crystal is widely used for these purposes. 

Quartz crystal provides high accuracy and stability compared to other RC or LC or RLC oscillators.
In general the clock frequency is used for microcontroller or CPU is ranged from KHz to Mhz. 
This clock frequency determines how fast the processor can process data.
To achieve this frequency a series crystal used with two same value capacitors network is used across the oscillator input of the respective MCU or CPU.

In this image, we can see that a Crystal with two capacitor forms a network and connected across Microcontroller unit or Central processing unit via OSC1 and OSC2 input pin. 
Generally all microcontroller or processor consist this two pin. 
In some cases there are two types of OSC pins available. 
One is for primary oscillator for generating the clock and other for the secondary oscillator which is used for other secondary works where secondary clock frequency is needed. 

The capacitor value range from 10pF to 42 pF, anything in between but 15pF, 22pF, 33pF is used widely.

tutorial/kirchhoffs-circuit-law
Kirchhoff’s Circuit Law

Today we will learn about Kirchhoff’s Circuit Law. 
Before going into detail and its theory part, let’s see what actually it is.
.
Kirchhoff’s First Law/ KCL
We will better understand this in the next image.
If you convert this to algebraic summation, the sum of all currents entering the node and the sum of currents leaving the node is equal to 0. For the case of current sourcing, the current flow will be positive, and for the case of current sinking the current flow will be negative.
So,
(Iin1 + Iin2 + Iin3) + (-Iout1 + -Iout2 + -Iout3) = 0.

This idea is called as Conservation of Charge.
Kirchhoff’s second Law/ KVL
ᾮ
Let’s see the diagram.

, where I is the current flow through the resistor. 
In this network, there are four points across each resistors, First point is A which is sourcing the current from the voltage source and supplying the current to the R1. 
Same thing happens for the B, C and D.
, the nodes A, B, C, D where the current is entering and the current is outgoing are the same. 

At those nodes the sum of incoming and outgoing current is equal to 0, as the nodes are common between sinking and sourcing current.
Due to the clockwise current flow, the voltage source is reversed, and due to that reason it is negative in value.
Therefore, the sum of total potential differences is
vAB + vBC + vCD + (-vDA) = 0

One thing we should keep in mind that the current flow should be in clockwise in every node and resistance path, otherwise the calculation will not be accurate.
Common Terminology in DC Circuit Theory:
that using ohm’s law, we can measure currents and voltage across a resistor. 
But, in case of complex circuit like bridge and network, calculating the current flow and voltage drop is become more complex using only ohm’s law. 

In those cases, Kirchhoff’s law is very useful to obtain perfect results.
In the case of analysis, few terms are used for describing the parts of the circuitry. 
These terms are as follows:-


Example to solve Circuit using KCL and KVL:
and also apply ohm’s law when needed.
VR1 + VR2 + (-V1) = 0

Let’s find out the potential difference across the resistors.
VR1 = (i1) x 4
VR1 = 4 (i1)
So,

VR2 = (i1 + i2) x 2
VR1 = 2 {(i1) + (i2)}
VR1 + VR2 + (-V1) = 0
VR1 + VR2 + (-V1) = 0

4 (i1) + 2 {(i1) + (i2)} - 28 = 
4 (i1) + 2 (i1) + 2 (i2) – 28 = 0
6 (il) + 2 (i2) = 28 …………………‐󬬠Equation 1
direction.

VR3 + VR2 + V1 = 0
Let’s find out the potential difference across these resistors.
As per the ohms law V = IR (I = current and R = Resistance in ohms)


VR3 = -(i2) x 1
VR3 = -1 (i2)
,
So,

As per the ohms law V = IR (I = current and R = Resistance in ohms)
VR2 = -(i1 + i2) x 2
VR2 = -2 {(i1) + (i2)}
VR3 + VR2 + V2 = 0

VR3 + VR2 + V2 = 0
-1 (i2) - 2 {(i1) + (i2)} + 7 = 0
-1 (i2) - 2 (i1) - 2 (i2) + 7 = 0
-2 (il) - 3 (i2) = -7 …………………‐󬬠Equation 2

.
As it is the sharing resistor for both loops it is difficult to obtain the result by using only ohm’s law.
So in case of the current flow through the resistor R2:-
iR2 = i1 + i2

= 5A + (-1A)
= 4A
This is how KCL and KVL are useful to determine the current and voltage in complex circuitry.
Steps to Apply Kirchhoff’s law in Circuits:
Labeling all voltage source and resistances as V1, V2, R1, R2 etc, if the values are assumable then the assumptions are needed.
Labeling each branch or loop current as i1, i2, i3 etc
Applying Kirchhoff’s voltage law (KVL) for each respective node.
Applying Kirchhoff’s current law (KCL) for each individual, independent loop in the circuit.

Linear simultaneous equations will be applicable when needed, to know the unknown values.

tutorial/dc-circuit-theory
DC Circuit Theory
What is DC?
In elementary school, we learned that everything is made by atoms. 
This is a product of three particles: Electrons, Protons and Neutrons. 
As the name suggest Neutron does not have any charge whereas Protons are positive and Electrons are negative.

In atom, electrons protons and neutrons stay together in a stable formation, but if by any external process the electrons are separated from atoms they will always want to settle in the previous position thus it will create attraction towards protons. 
If we use these free electrons and push it inside a conductor which forms a circuitry, the potential attraction produces the potential difference.
In case of Direct Current, the polarity will never reverse or changed with respect to time, whereas the flow of current can vary with time.
As in reality, there is no perfect condition. 

In case of the circuit where free electrons are flowing, it is also true. 
Those free electrons do not flow independently, as the conducting materials are not perfect to let the electrons to flow freely. 
It does oppose the flow of electron by a certain rule of restrictions. 
For this issue, every electronics / electrical circuit consist three basic individual quantities which is called as V I R.

Voltage (V)
Current (I)
And Resistance (R)
These three things are the basic fundamental quantities which appear almost in all cases when we see or describe something or making something which is related with Electrical or Electronics. 

They both are well related but they have denoted three separate things in Electronics or Electrical Fundamentals.
What is Current?
1A = 1 C/S
Where, C is denoted as coulomb and S is second.

In practical scenario, the electrons flow from the negative source to the positive source of the power supply, but for better circuit related understanding conventional current flow assumes that the current flows from the positive to the negative terminal.
ᾠetc.
A) etc.
What is Voltage?
Voltage is the potential difference between two points of a circuit. 
It does notify the potential energy stored as electrical charge in an electrical supply point. 
We can denote or measure the voltage difference between any two points in circuit nodes, junction etc.
This Voltage drop or potential difference is measured in Volts with the symbol of V or v. 

More Voltage denotes more capacity and more holds on the charge.
The relationship is as described
V = Potential Energy / Charge
Or

1V = 1 J/C
Where, J is denoted as Joule and C is coulomb.
current of 1 amp flow through resistance of 1 ohm.
1V = 1A / 1R

Where A is Ampere and R is resistance in ohm.
V) etc. 
Voltage is also denoted as negative voltage as well as positive voltage.
It is very important to remember that Voltage can exist without current as it is the voltage difference between two points or potential difference but current cannot flow without any voltage difference between two points.
What is Resistance?
; it is only a positive value.
So, there are materials which have very low resistance and are a good conductor of the electricity. 
Like, copper, Gold, silver, Aluminum etc. 

On the other hand there are several materials which have very high resistance thus a bad conductor of electricity such as Glass, Wood, Plastic, and due to high resistance and bad electricity conducting capabilities, they are mainly used for insulation purpose as an insulator.
, Integrated circuits are made using semiconductor. 
Germanium and silicon are widely used semiconductor material in this segment.
As discussed before resistance cannot be negative. 

But resistance has two particular segments, one is in linear segment and the other is in non-liner segment. 
We can apply specific boundary related mathematical calculation to calculate the resistance capacity of this linear resistance, on the other hand non-linear segmented resistance do not have proper definition or relations between voltage and current flow between this resistors.
Ohms Law and V-I Relationship:
Georg Simon Ohm aka Georg Ohm is a German physicist found a proportional relationship between Voltage drop, Resistance and Current. 

This relationship is known as Ohms Law.
In his finding, it is stated that the current passing through a conductor is directly proportional to the voltage across it. 
If we convert this finding into mathematical formation we will see that
Current (Ampere) = Voltage/ Resistance

I (Ampere) = V / R
If we know any of the two values from those three entities, we can find the third one.
From the above formula, we will find the three entities, and the formula will be:-


Voltage
V = I x R
Output will be Voltage in Volt (V)
Current
I = V / R
Output will be Current in Ampere (A)
Resistance
R = V / I
)


Let’s see the difference of this three using a circuitry where load is resistance and Am-meter is used to measure Current and Volt-meter is used to measure voltage.
In the above image, an Ammeter connected in series and providing the current to the resistive load, on the other hand a volt meter connected across the source to measure voltage.
, and for this to happen, an ideal 0 ohm ammeter is connected in series, but as voltage is the potential difference of two nodes, the voltmeter is connected in parallel.
and then measure the units, we will produce below result:

In this graph If R = 1 then the current and Voltage will increase proportionally. 
V = I x 1 or V = I. 
so if resistance is fixed then the voltage will increase with the current or the vice versa.
What is Power?
Power is either created or consumed, in an electronic or electrical circuitry the power rating is used to provide information about how much power the circuitry consumes to make a proper output of it.
As per the rule of nature, Energy cannot be destroyed, but it can be transferred, like Electrical energy converted to Mechanical Energy when Electricity applied across a Motor, or Electrical energy converted to heat when applied on a Heater. 
Thus a Heater need Energy, which is power, to provide proper heat dissipation, that power is rated power of the heater at maximum output.
Power is the multiplied value of the voltage and current. 

So,
P = V x I
W) etc.
formula. 

Then the power law will be
P = I*R*I
Or
P = I2R

By arranging the same thing we can find the least one thing when other one is not available, the formulas are rearranged in the below matrix:
Electron Flow concept
, But in conventional current flow as we described before we assume that current is flowing from positive to negative terminal. 
In the next image we will understand the flow of current very easily.

and which alternate its direction called as Alternating Current or AC.
Practical Examples
Let’s see two examples to understand the things better.
1. In this circuit, a 12V DC source is connected across a 2Ω load, calculate the power consumption of the circuit?

I = V / R 
I = 12 / 2 = 6 Amperes
As Wattage (W) = Voltage (V) x Ampere (A) the total wattage will be 12 x 6 = 72Watt.
We can also calculate the value without Ampere.

Wattage (W) = Power = Voltage2 / Resistance
Power = 122 / 2 = 12*12 / 2 = 72 watt
Whatever the formula is used, the output will be same.
2. In this circuit total power consumption across the load is 30 Watt, if we connect 15V DC supply, how much current is required?

In this circuitry the total resistance is unknown. 
The input supply voltage is 15V DC so the V = 15V DC and the power flowing through the circuitry is 30W, So, the P = 30W. 
The current flow in the circuitry will be
I = P / V

I = 30 / 15 2 Amperes
So, Powering up the circuitry at 30W, we need 15V DC power source which is capable to deliver 2 Ampere of DC current or more as the circuitry requires 2Amp current.

microcontroller-projects/wein-bridge-oscillator

Wein Bridge Oscillator
and how it is used, let’s see what is Oscillator and what Wein Bridge Oscillator is.
Wein Bridge Oscillator:
by oscillation.

across an amplifier and produce an oscillator circuit.
?
Because of the following points the Wien bridge oscillator is a wiser choice for producing Sinusoidal wave.
It is stable.

The distortion or the THD (Total Harmonic Distortion) is under controllable limit.
We can change the frequency very effectively.
One resistor and one capacitor in series on the other hand one capacitor and one resistor in parallel formation. 
If we construct the circuit the schematic will be just look like this one:-
Wein Bridge Oscillator Output Gain and Phase Shift:
in the above image is very interesting.
When Low frequency is applied the first capacitor (C1) reactance is high enough and block the input signal and resist the circuit to produce 0 output, on the other hand, Same thing happen in a different way for the second capacitor (C2) which is connected in parallel condition. 
C2 reactance is become too low and bypass the signal and again produce 0 outputs.

If we see in depth inside the circuitry we will see that the reactance of the circuit and the Resistance of the circuit is equal if the resonant frequency is achieved.
So, there are two rules applied in such case when the circuit is provided by the resonant frequency across the Input.
If we see the output of the circuitry we will understand those points.
The output is exactly as the same curve as the image showing. 

At Low Frequency from 1Hz the output is less or almost 0 and increasing with the frequency at input upto the resonant frequency, and when the resonant frequency is reached the output is at its maximum peak point and continuously decreasing with the increasing of the frequency and again it’s produce 0 output at high frequency. 
So it is clearly passing a certain frequency range and producing the output. 
That’s why previously it was described as frequency dependable variable Band (Frequency Band) pass filter. 
If we closely look at the phase shift of the output we will clearly see the 0 degree phase margin across the output at the proper resonant frequency.

We will see the output of the filter stage in this simulation video:
as discussed before.
Resonance Frequency and Voltage Output:
If we consider that R1 = R2 = R or the same resistor is used, and for the selection of the capacitor C1 = C2 = C the same capacitance value is used then the resonance frequency will be

Fhz = 1 / 2πRC
The R stands for Resistor and the C stands for the capacitor or capacitance, and the Fhz if Resonance frequency.
we should see the circuit in a different way.
Calculating circuitry resistance in case of AC rather than calculating circuitry resistance in case of DC is a bit tricky.

RC network creates impedance which acts as resistance on an applied AC signal. 
A voltage divider has two resistances, in these RC stages the two resistances is First filter (C1 R1) impedance and the Second filter (R2 C2) impedance.
As there are a capacitor is connected either series or in parallel configuration then the Impedance formula will be:-
Z is the symbol of Impedance, R is the Resistance and the Xc stands for the capacitive reactance of the capacitor.

By using the same formula we can calculate the first stage impedance.
, the formula is same as calculating the parallel equivalent resistor,
Z is the impedance,
R is the Resistance,

X is the Capacitor
The Final Impedance of the circuitry can be calculated using this formula:-
We can calculate a Practical Example and see the Output In such case.
of the input voltage.

If we connect the two stage RC filter output into a non-inverting amplifier input pin or +Vin pin, and adjust the gain to recover the loss the output will produce a sinusoidal wave. 
That is Wien bridge oscillation and the circuitry is Wein Bridge Oscillator circuit.
Working and Construction of Wein Bridge Oscillator:
R1 and R2 is Fixed value resistor whereas the C1 and C2 is a variable trim capacitor. 

By varying the value of those two capacitors at the same time we could get proper oscillation from a lower range to upper range. 
It’s very useful if we want to use the Wein bridge oscillator to produce sinusoidal wave at different frequency from a lower to upper range. 
And the R3 and R4 are used for the op-amp feedback gain. 
The output gain or the amplification is highly dependable on those two value combinations. 

As the two RC stages drop the output voltage at 1/3rd it is essential to recover that back. 
It is also a wiser choice to get at least 3x or more than 3x (4x preferred) gain.
using 1+ (R4/R3) relation.
If we again see the image we can see that the feedback path of the operational amplifier from the output is directly connected to the RC filter input stage. 

As the two stage RC filter has a property of 0 degree phase shift in the resonance frequency region, and directly connected to the op-amp positive feedback let’s assume it is xV+ and the in the negative feedback the same voltage is applied which is xV- with the same 0 degree Phase the op-amp differentiate the two input and rule out the negative feedback signal and due to that continues as the output connected across RC stages the op-amp start to oscillate.
If we use a higher slew rate, higher frequency op-amp the output frequency can be maximized by a wide amount.
Also we need to remember as in previous RC oscillator tutorial we discussed about the loading effect, we should choose the op-amp with high input impedance more than the RC filter to reduce loading effect and ensure proper stable oscillation.
LM318A

LT1192
MAX477
LT1226
OPA838

THS3491 which is 900 mHz High seed op-amp!
LTC6409 which is 10 Ghz GBW Differential op-amp. 
Not to mention this requires special add on circuitry and exceptionally good RF design tactics to achieve this High Frequency output as well.
LTC160

OPA365
TSH22 Industrial grade op-amp.
Practical Example of Wein Bridge Oscillator:
Let’s calculate a practical example value by choosing the Resistor and capacitor value.

As calculating the frequency is easy by the formula of
Fhz = 1 / 2πRC
For the value of C is 1nF and for the resistor is 4.7k the Frequency Will be
Fhz = 33,849 Hz or 33.85 KHz

For the value of C is 50nF and for the resistor is 4.7k the Frequency Will be
Fhz = 677Hz
For the value of C is 100nF and for the resistor is 4.7k the Frequency Will be
Fhz = 339Hz

So the Highest Frequency we can achieve using 1nF which is 33.85 Khz and the lowest frequency we can achieve using 100nF is 339Hz.
is 1+(R4/R3)
R4 = 300k
R3 = 100k

So the Gain = 1+(300k+100k) = 4x
The op-amp will produce 4x gain of the input across the non-inverted “positiveᾠpin.
So by using this way we can produce variable frequency bandwidth Wein Bridge Oscillator.
Applications:
in the field of electronics, from finding the exact value of the capacitor, For generating 0 degree phase stable oscillator related circuitry, due to low noise level it is also a wiser choice for various Audio grade level applications where continuous oscillation is required.

tutorial/rc-phase-shift-oscillator
RC Phase Shift Oscillator
What is Oscillator?
etc.
RC Oscillator and Phase:
See this image:-

like this one we will clearly see that the signal’s starting point is 0 degree in phase, and after that every peak point of the signal from positive to 0 then again negative point then again 0is respectively denotesas 90degree, 180degree, 270degreeand 360degreein phase position.
If we shift the sinusoidal wave starting point other than the 0degreethe phase is shifted. 
We will understand phase shift in the next image.
Phase Shift using RC Oscillator Circuit:
We can simply form a Phase shift Resistor-capacitor network using just only one resistor and one capacitor formation.
canbe produceby a capacitor in series along with a resistor in parallel.
But if we try it in reality and check the phase shift, then we achieve 60degreeto less than90 degreephase shift.It’s dependson thefrequency,and the components tolerances which createadverseeffect in reality. 
As we all know nothing is perfect, there should be some difference than actualso calledor expected values than the reality. 

Temperature and other outer dependenciescreatesdifficulties to achieve exact90 degreephase shift, 45 degree is in general, 60 degree is common depending on the frequencies and achieving 90degreeis a very difficult job in many cases.
As discussed in High pass tutorial we will construct the same circuit and will investigateaboutthe phase shift of the same circuit.
The circuit of that High Pass filter along with the component values is in the below image:-
It will produce 4.9 KHz of Bandwidth. 

If we check the corner frequency we will identify the phase angle at the output of the Oscillator.
Now we can see the phase shift is started from 90 degree which is the maximum phase shift by RC oscillator network but at the point of cornerfrequencythe phase shift is45degree.
The Frequency stability will improve.
Cascading Multiple RC Filters:
By considering this fact that we cannot achieve only achieve 60 Degree phase shift instead of 90degree, we can cascade three RC filters (If the phase shift is 60 degree by RC oscillators) or by cascading four filters in series (If the phase shift is 45 degree by each RC oscillators) and get 180 degree.
andfinallyafter thirdstagewe will get180 degreephase shift.
We will construct this circuitry in simulation software and see the input and outputwave formof the circuitry.
Before getting into the video letsᾠsee the image of the circuitry and will see the oscilloscope connection as well.

pole output
(C / Red channel) and the final output acrossthirdpole (D / Green channel).
and will see the phase change in 60degreeacrossfirstpole,120degreeacrosssecondpole and 180degreeacrossthirdpole.Alsothe amplitude of the signal will minimize step by step.
More we go towardslastpole the decrement ofamplitudeof the signalis decrease.

:-
It is clearly shown that every pole actively changing the phase shifts and at the final output it is shifted to 180 degrees.
RC Phase Shift Oscillator using Transistor:
here.

If we want to change the frequency of this one way to change the capacitors value or use a variable preset capacitor across those three poles individually by eliminatingindividualfixed capacitors.
Frequencyof RC Phase Shift Oscillator:
:-
Where,

R = Resistance (Ohms)
C = Capacitance
N = Number of RC network is / will beuse
and the phase shift will be negative. 

In such case the upper formula will not work for calculating the frequency of the oscillator,differentformula will be applicable.
Where,
R = Resistance (Ohms)
C = Capacitance

N = Number of RC network is / will be use
RC Phase Shift Oscillator using Op-amp:
It is stable for low frequencies.
Just using only oneBJTthe Output wave’s amplitude is not perfect, it is required additional circuitry tostabilizedamplitude of the waveform.

Frequency accuracy is not perfect and it is not immune tonoisyinterference.
Adverse Loading effect. 
Due to cascadeformationthe second pole’s input impedance change the resistors resistance properties of the first pole filter. 
More the filters cascaded more the situation worsen up as it will affect the accuracy ofcalculatedphase shift oscillator frequency.

of the input signal.
we need to recover the loss.
We can also recover that four drawbacks and get more headroom over the control if we use op-amp insteadBJT. 
Due to high input impedance the loading effect also effectively controlled because op-amp input impedance promotes to the overall loading effect.

and see what will be the circuitry or schematic of the RC oscillator using Op-amp.
first pin named asOSCout. 
The R4 is used for the gain compensation of the op-amp. 
We can tweak the circuitry to get high frequency oscillated output but depending on the frequency range bandwidth of the op-amp.

across RC stages.
Let’s see, we will make a circuit with real components value and see what will be the simulated output of the RC phase shift oscillator.
We will use10kohms resistor and500pFcapacitor and determine the frequency of the oscillation. 
We will also calculate the value ofgainresistor.

N= 3, as 3 stages will be used.
R = 10000, as10kohms converted to ohms
C = 500 x 10-12 as capacitor value is500pF
The Output is12995Hzor the relatively close value is 13 KHz.

times the value of the gain resistor is calculated using this formula:-
Gain = Rf / R
29 = Rf / 10k
Rf = 290k

by following the link.
is used and differential audio signal needed but the inverted signal is not available, or if AC signal source needed for any application then RC filter are used. 
Also, signal generator or function generator use RC phase shift oscillator.


tutorial/active-high-pass-filter
Active High Pass Filter
and Active Low Pass Filter, now it is time for Active High pass filter. 
Let’s explore what is an Active High Pass Filter.
What is it, Circuit, formulas, curve?
that its work without any outer interruption or active response.
, we can easily create Active high pass filter. 
Changing the amplifier configuration we can also form different types of high pass filter, inverted or non-inverted or unity gain active high pass filter.

, the op-amp bandwidth is the main limitation of active high pass filter. 
That means the maximum frequency will pass depending on the gain of the amplifier and the open-loop characteristic of the op-amp.

Op-amp
Bandwidth(dB)
Maximum Frequency

LM258
100
1MHz
uA741
100
1MHz
RC4558D
35
3MHz
TL082
110
3MHz

LM324N
100
1MHz

This is a small list about generic op-amp and there voltage gain. 
Also, the voltage gain is largely dependable on the frequency of the signal and the input voltage of the op-amp and how much gain is applied in that op-amp.

Let’s Explore further and understand what is special about it:-
:-
we seen in previous tutorial.
Cut off Frequency and Voltage gain:
fc = 1 / 2πRC
As described in previous tutorial fc is the cut-off frequency and the R is Resistor value and the C is Capacitor value.
These resistors are responsible for the amplification or the gain.
We can also easily calculate the gain of the amplifier using the following equations where we can choose the equivalent resistor value according to gain or it can be vice-versa:-

Amplifier Gain (DC amplitude)(Af) = (1 + R3/R2)
Frequency Response Curve:
Let’s see what will be the output of the Active High pass filter or the Bode plot/Frequency response curve:-
This is the gain curve of the op-amp and the filter connected across the amplifier.

This green curve shows the amplified output of the signal and the red one shows the without amplified output across passive high pass filter.
If we see the curve more accurately then we will find the below points inside this bode plot:-
The red curve increase at 20dB / decade and in the cutoff region the magnitude is -3dB which is 45 degree phase margin.
As discussed before that the maximum frequency response of an op-amp is highly connected with it’s gain or bandwidth (as called open-loop gain Av).

At this frequency the respective op-amp will produce 0dB gain or unity gain decreasing 20dB/decade.
So it is not infinite, after 1 MHz the gain will decrease at the rate of -20dB/decade. 
The Bandwidth of the active high pass filter is highly dependent on bandwidth of the op-amp.
by converting the op-amp Voltage gain.

The calculation is as follows:-
dB  = 20log(Af) Af = Vin / Vout
This Af can be the Dc gain we described before by calculating the resistor value or dividing the Vout with Vin.
applied to the filter (f) and the cut-off frequency (fc). 

Deriving the voltage gain from this two is very simple using this formula =
If we put the value of f and fc we will get the desired voltage gain across the filter.
Inverting Amplifier Filter Circuit:
We can also construct the filter in inverted formation.

The Phase margin can be obtained by the following equation.
The Phase shift is same as seen in Passive high pass filter. 
It is +45 degree at the cutoff frequency of fc.
:-

It is an active High pass filter in inverted configuration. 
The op-amp is connected inversely. 
In the previous section the input was connected across op-amp’s positive input pin and the op-amp negative pin is used to make the feedback circuitry. 
Here the circuitry inverted. 

Positive input connected with ground reference and the capacitor and feedback resistor connected across op-amp negative input pin. 
This is called inverted op-amp configuration and the output signal will be inverted than the input signal.
The resistor R1 is acting as a role of passive filter and also as a gain resistor both at once.
Unity Gain or Voltage Follower Active High Pass Filter:
Till now the circuitry described here is used for voltage gain and post amplification purpose.
Not to mention, it is also an op-amp configuration which often described as voltage follower configuration where the op-amp create exact replica of the input signal.
:-
The gain is 1x. 

It is a unity gain active High pass filter. 
It will produce exact replica of the input signal.
Practical example with Calculation
We will design a circuitry of active High pass filter in non-inverting op-amp configuration.

Gain will be 2x
Cutoff freq will be 2KHz
Let’s calculate the value first before making the circuitry:-
Amplifier Gain (DC amplitude)(Af) = (1 + R3/R2)

(Af) = (1 + R3/R2)
Af = 2
R2= 1k (We need to select one value; we selected 1k for reducing the complexity of the calculation).
By putting the value together we get

(2) = (1 + R3/1)
Now we need to calculate the value of the resistor according to the cut-off frequency. 
As active High pass filter and the passive High pass filter works on the same way the frequency cut-off formula is same as before.
Let’s check the value of the capacitor if the cut-off frequency is 2KHz, we selected the value of the capacitor is 0.01uF or 10nF.

fc = 1/2πRC
By putting all value together we get:-
2000 = 1 / 2π*10*10-9
The nearest value is selected of this resistor 8k Ohms.

Next step is to calculate gain. 
The formula of the gain is same as passive High pass filter. 
The formula of gain or magnitude in dB is as follows:-
As the gain of the op-amp is 2x. 

So the Af is 2.
fc is cut off frequency so the value of fc is 2Khz or 2000Hz.
Now changing the frequency (f) we get the gain.


Gain(dB)
20log(Vout/Vin)
100
.10
-20.01
250
.25
-12.11

500
.49
-6.28
750
.70
-3.07
1,000
.89
-0.97


5,000
1.86
5.38
10,000
1.96
5.85
50,000
2
6.01
100,000
2
6.02


In this table from the 100 Hz the gain is sequentially increased in a pace of 20dB/decade but after the cutoff frequency is reached the gain is slowly increased to 6.02dB and remains constant.
Now as we already calculated the values now it is the time to construct the circuit. 
Let’s add all together and build the circuit:-

or not at the output of the amplifier
The green line is representing Amplified output of the filter which is 2 x gains. 
And the red line representing the filter response across input of the amplifier.
the corner frequency and get 2.0106 KHz or 2 KHz.

As described before the passive filter gain -3dB but as 2x gain of op-amp circuitry added across filtered output, the cutoff point is now 3dB as 3dB added two times.
Cascading and adding More Filters to One Op-Amp 
It’s possible to add more filters across one op-amp like second order active High pass filter. 
In such case just like the passive filter, extra RC filter is added.

is constructed.
In the figure we can clearly see the two filters added together. 
This is the second order high pass filter.
As you can see there is one op-amp. 

The voltage gain is same as previously stated using two resistors. 
As the gain formula is same the Voltage gain is
Af = (1 + R2/R1)
The cut-off frequency is:-

We can add higher order high pass active filter. 
But there is one rule.
Same as like two Second –order filter create fourth order filter and this sums is added up each time.
can be done by as follows:-

Like for the first stage it is 20dB/decade, 2nd Stage it is 20dB + 20dB = 40dB per decade etc. 
Every even number filter consists second order filters, every odd number consists first order and second order filter, first order filter on the first position. 
There are no limitations to how many filters can be added, but it is the accuracy of the filter which decreases when extra filters are added subsequently. 
If the RC filter value i.e. 

Resistor and capacitors are same for each filter, then the cut-off frequency will be same also, the overall gain is remain equal as the frequency components used are same.
Applications
Active High pass filter can be used at multiple places where passive High pass filter cannot be used due to the limitation about gain or amplification procedure. 
Apart from that the active High pass filter can be used in following places:-

High pass filter is widely used circuit in electronics.
Here are few applications:-
Treble equalization before Power amplification
High frequency Video related filters.

Oscilloscope and Function generator.
Before Loud speaker for removing or reducing the Low frequency noise.
Changing the frequency shape at different wave from.
Treble boost filters.


tutorial/active-low-pass-filter
Active Low Pass Filter
What is it, Circuit, formulas, curve?
are as follows:-
The impedance of the circuit creates loss of the amplitude. 
So the Vout is always less than the Vin.
Amplification cannot be done with only passive low pass filter.

Filter characteristics are greatly dependable on the load impedance.
The gain is always equal or lesser than the unity gain.
More the filter stages or filter order added the loss of amplitude become lesser.
, Op-Amp which include a lot of flexibility. 

The choice of component is also dependable on the cost and the effectiveness if it is designed for a mass production product.
For the sake of simplicity, time effectiveness and also the growing technologies in op-amp design, generally an op-amp is used for Active Filter design.
:-
High input impedance.

Due to high input impedance the input signal couldn’t be destroyed or altered. 
In general or in most cases the input signal which is a very low in amplitude could be destroyed if it is used as low impedance circuitry. 
Op-Amp got a plus point in such cases.
Very low component count. 

Only few resistors are needed.
Various type of op-amp is available depending on the gain, voltage specification.
Low noise.
Easier to design and implementation.

But as we know nothing is entirely perfect, this Active filter design also have certain limitation.
The output gain and bandwidth as well as frequency response are dependable on the op-amp specification.
Let’s Explore further and understand what is special about it.
Active Low Pass Filter with Amplification:
Before understanding Active low pass filter design with op-amp, we need to know a little bit about Amplifiers. 
Amplify is a magnifying glass, it produces a replica of what we see but in bigger form to recognize it better.
Here is the simple Low pass filter design:-
Cut off Frequency and Voltage gain:
The Cut off frequency formula is same as used in passive low pass filter.
fc = 1 / 2πRC
As described in previous tutorial fc is cut-off frequency and the R is Resistor value and the C is Capacitor value.
The two resistor connected in the positive node of the op-amp are feedback resistors. 

When these resistors are connected in positive node of the op-amp it is called non-inverting configuration. 
These resistors are responsible for the amplification or the gain.
We can easily calculate the gain of the amplifier using the following equations where we can choose the equivalent resistor value according to gain or it can be vice-versa:-
Amplifier Gain (DC amplitude)(Af) = (1+R2/R3)
Frequency Response Curve:
:-
We will see in detail explanation in next image.
Irrespective of the filter, from the starting point to the cut-off frequency point it is called Bandwidth of the filter and after that, it is called pass band from which the passing frequency is allowed.

by converting the op-amp Voltage gain.
The calculation is as follows
db = 20log(Af)
This Af can be the Dc gain we described before by calculating the resistor value or dividing the Vout with Vin.
Non-inverting and Inverting Amplifier Filter Circuit:
E.g. 
decrease or increase.
.

On the same configuration if we want to invert the output signal then we can choose the inverting-signal configuration of the op-amp and could connect the filter with that inverted op-amp.
:-
Unity Gain or Voltage Follower Active Low Pass Filter: 
Till now the circuitry described here is used for voltage gain and post-amplification purpose.

Not to mention, it is also an op-amp configuration which often described as voltage follower configuration where the op-amp created the exact replica of the input signal.
:-
The gain is 1x. 
It is a unity gain active low pass filter. 

It will produce exact replica of the input signal.
Practical example with Calculation
We will design a circuitry of active low pass filter in non-inverting op-amp configuration.
Input Impedance 10kohms

Gain will be 10x
Cutoff freq will be 320Hz
Let’s calculate the value first before making the circuitry:-
Amplifier Gain (DC amplitude)(Af) = (1+R3/R2) 

(Af) = (1+R3/R2) 
Af = 10
for reducing the complexity of the calculation).
By putting the value together we get

(10) = (1+R3/1) 
Now we need to calculate the value of the resistor according to the cut-off frequency. 
As active low pass filter and the passive low pass filter works on the same way the frequency cut-off formula is same as before.
fc = 1 / 2πRC

By putting all value together we get:-
The formula of the gain is same as passive low pass filter. 
The formula of gain or magnitude in dB is as follows:-
20log(Af)

Now as we already calculated the values now it is the time to construct the circuit. 
Let’s add all together and build the circuit:-
at the input of the active low pass filter and will investigate further to see whether the cutoff frequency is 320Hz or not at the output of the amplifier.
The green line is started from 10Hz to 1500Hz as the input signal is supplied for that range of frequency only.

As we know that the corner frequency will be always at -3dB from the Maximum gain magnitude. 
Here the gain is 20dB. 
So, if we find out the -3dB point will get the exact frequency where the filter stops the higher frequencies.
and not mention the corner frequency will also effected by few Hz.
Second Order Active Low Pass Filter:
It’s possible to add more filters across one op-amp like second order active low pass filter. 
In such case just like the passive filter, extra RC filter is added.
is constructed.

This is the Second order filter. 
In the above figure we can clearly see the two filters added together. 
This is the second order filter. 
It is a widely used filter and industrial application is Amplifier, Musical system circuitry before the Power Amplification.

As you can see there is one op-amp. 
The voltage gain is same as previously stated using two resistors.
(Af) = (1+R3/R2) 
The cut-off frequency is

Confused? May be a schematic will help us.
See the above figure, In this image two op-amp cascaded with individual op-amp. 
In this circuit the Cascaded op amp, If the first one is having 10x gain and the second one is for 5x gain then the total gain will be 5 x 10 = 50x gain.
So, the magnitude of the cascaded op-amp low pass filter circuit in case of two op-amp is:-

dB = 20log(50)
By solving this equation it is 34dB. 
So the gain of cascading op-amp low pass filter gain formula is
TdB = 20log(Af1*Af2*Af3*......Afn)

Where TdB = Total Magnitude
This is how Active low pass filter is constructed. 
On the next tutorial, we will see how Active high pass filter can be constructed. 
But before the next tutorial let’s see what the applications of Active low pass filter are:-
Applications
Active Low pass filter can be used at multiple places where passive low pass filter cannot be used due to the limitation about gain or amplification procedure. 
Apart from that the active low pass filter can be used in following places:-
Low pass filter is widely used circuit in electronics.

Here are few applications of Active Low Pass Filter:-
Bass equalization before Power amplification
Video related filters.
Oscilloscope

Music control system and Bass frequency modulation as well as before woofer and high bass audio speakers for bass out.
Function Generator to provide variable low frequency out at different voltage level.
Changing the frequency shape at different wave from.


tutorial/what-is-matlab-and-how-to-get-started-with-it
Getting started with MATLAB: A Quick Introduction
) is a programming platform developed by MathWorks, which usesit's proprietary MATLABprogramming language. 
The MATLABprogramming language is a matrix-based language which allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages, including C, C++, C#, Java, Fortran and Python. 

It is used in a wide range of application domains from Embedded Systems to AI, mainly to analyze data, develop algorithms, and create models and applications.
MATLAB Main Window
Desktop tools of MATLAB
The desktop tools of MATLAB are Command Window, Command History, Work space, Editor, Help, Array Editor, and Current Directory Browser. 

Here we will explain all the tools one by one.
1. Command Window
Command window is used to entering variables and to run a function and M-file scripts. 
Up (℩ Arrow key is used for recalling a statement which is previously entered. 

After recalling you can edit that function and press enter to run it.
with any number 1, 2, 3, 4, 5 and assigning it to variable ‘xᾬ
  x = [1, 2, 3, 4, 5]
  x =

      1   2   3   4   5
To create the column vector with the number 6, 7, 8, 9, and assigning it to variable ‘yᾬ
  y = [6; 7; 8; 9]
  y =

      6
      7
      8
      9

by the help of a row vector (property of matrix),
 y = [6 7 8 9]
  y =


      6   7   8   9

  y'
 ans =

      6
      7
      8
      9

then we can simply write as
 a = [0:8]
  a =
     0   1   2   3   4   5   6   7   8

then simply write
 u = [0:2:8]
  u =
     0   2   4   6   8

And for decrement by 2
 u = [12:-2:0]
  u =
     12   10   8   6   4   2

Now, for performing simple mathematical operation like addition and subtraction, lets take any two numbers 12 and 14.
 u = 12+14
 ans =
      26

 u = 12-14
 ans =
      -2
2. Command History
Command history means the history of the command window.
It means the function or lines you entered in the Command window is also visible in the Command History window. 
Even we can select any previously entered function or line and execute it. 
Also, you can create an M-file for selected statement. 

M-File is nothing but a text file which contains MATLAB code
3. Workspace
4. Editor Window
Editor is a word processor specifically designed for creating and debugging M-files. 

An M-file consists of one or more commands to execute. 
After saving the M-file, you can even call it directly by typing the file name in command history.
5. HELP 
To open the Help browser, click on the HELP button in the MATLAB desktop tools or alternate for HELP browser is to go to command window and type help browser. 

Use HELP browser for the finding the information, indexing, searching and Demos. 
While reading the documentation, you can bookmark any page, print a page, search for any term in the page and copy or evaluate a selection.
6. Array Editor
In the Workspace Browser double click on a variable to see it in the Array Editor. 

Array editor is used for viewing and editing a visual representation of variables in workspace.
7. Current Directory Browser
MATLAB file operations use search path and current directory as reference point. 
A quick way to browse your MATLAB file is using Current Directory Browser. 

We can use Current Directory Browser for searching, viewing and editing of the M file or MATLAB file.
Now if we save more than two files, in which one is for plotting of graph and the other one is for matrix manipulation in MATLAB file so we can access these saved files by using command window.
Variable in MATLAB
There is no need of any type of declaration or dimension statements in MATLAB. 

When we construct a new variable name in MATLAB, it automatically creates the variable and provides the appropriate amount of storage and save in workspace. 
If the variable with the same name is already present, MATLAB changes its contents and allocate new storage if required. 
Variable name consists of letter and followed by letters, digits or underscore. 
Also, MATLAB is case sensitive it distinguish between lower and upper case.

 x = 0
x =

   0

 y = 1
 y =
    1
We can also create the vector with help of simple variable like this

 x = [0 1 2 3 4 5 6]
x =
    0   1   2   3   4   5   6
M-Files
For example:
 A = [2 4 5 6 7]
in the command window reads the file and creates a variable A, which contains our matrix or the data saved in that M-file.
Graph Plotting 
MATLAB has facilities to display the vector and matrix in the form of graph, depending on the type of input data.
Plot a graph between the ‘xᾠand ‘yᾮ
Let the range of the ‘xᾠis 0 (zero) to π (pi) and the ‘yᾠis the sine function of ‘xᾠwith range of 0 to π (pi)
 x = 0:pi/5: pi;

 y = sin(x);
below command is used for plotting graph in between x and y
 plot(x,y);
For labelling x and y axis

 xlabel('range of y');
 ylabel('sin of x');
And the title of the graph given as
 title('plot of sin(x)');

Let two variables be x, y for plotting the simple y=x straight line,
 x= 0:2:20;
 y = x;
 plot(x,y);

 xlabel('X');
 ylabel('Y');
 title('plot of the y=x straight line');
We can also plot the graph of the any trigonometric function, algebraic function and the graph of matrices manipulation.
Condition Statements in MATLAB
Like we use condition statement in various software’s while programming our microcontrollers, we can also use them in MATLAB programming. 
The several condition statements used in MATLAB are:
for loop

while loop
if statement
continue statement
break statement

switch statement
If statement
are used for execution of alternative groups of statements.
 if a > b

      fprintf (‘greater);
  elseif a == b
            fprintf( ‘equal’ );
    elseif a < b

          fprintf (‘less’);
Else
       fprintf(‘ error’);
end
Switch and Case Statement
In the switch statement the group of statement execute based on the value of variable or expression. 
   
 x = input(‘Enter the no: ᾩ;

switch x
  case 1
    disp('the number is negative')
  case 2

    disp('zero')
  case 3
    disp('the number is positive')
  otherwise

    disp('other value')
end     
BreakStatement
Break statement is used for exit from a while loop or for loop early. 

While it breaks from the innermost loop only in nested loops.
 x = 2;
 while (x < 12)
    fprintf('value of x: %d\n', x);

   x = x+1;
      if(‘ x > 7’)
        break;
     end

end
After the execution of code the result will be:
value of x: 2
value of x: 3

value of x: 4
value of x: 5
value of x: 6
value of x: 7
Continue statement
This statement used inside the loops. 
The control jumps to the start of the loop for next iteration, by skipping the execution of the statement inside the body of the current iteration of the program.
:

 x = 2;
while(x<12)
if x == 7
x = x+1;

continue;
end
fprintf('value of x: %d\n', x);
x = x+1;

end
Hence, the result will be:
value of x: 2
value of x: 3

value of x: 4
value of x: 5
value of x: 6
value of x: 8

value of x: 9
value of x: 10
value of x: 11
For loop
The FOR loop repeats a group of statement in fixed no. 
of times. 
The syntax of the FOR loop is as following:-
for <index = value>

      ……………….
    end
 for x = [2, 1, 3, 4, 5]
disp (x)

end
     2
     1
     3

     4
     5
While loop
loop is repeatedly execute the statement

The syntax of a while loop is as following:-
while <expression>  
<statement>
end

 x = 2;
while( x< 18 )
fprintf('value of x: %d\n', x);
x = x + 1;

end
The result of this loop when code is executed
value of x: 2
value of x: 3

value of x: 4
value of x: 5
value of x: 6
value of x: 7

value of x: 8
value of x: 9
value of x: 10
value of x: 11

value of x: 12
value of x: 13
value of x: 14
value of x: 15

value of x: 16
value of x: 17
This is just a introduction of MATLAB, it has very vast and complex applications. 
A beginner can start MATLAB with below basic projects:

Interfacing Arduino with MATLAB - Blinking LED
GUI Based Home Automation System using Arduino and MATLAB
Servo Motor Control using MATLAB


tutorial/transformer-basics
Basics of Transformer
as distance (length) increases, which means DC power stations had to be placed everywhere, thus the main goal of AC was to solve the transmission issue and without the transformer, that wouldn't have been possible as the losses would still have existed even with AC.
for final distribution within a community without changing the frequency and at the same power that was transmitted from the generating station (P= IV).

To better understand the voltage transformer, it is best to use its most simplified model which is the single-phase transformer.
Single Phase Transformer
and everywhere else.
It is used to describe the operation principle, construction etc of a transformer because other transformers are like a variation or modification of the single phase transformer. 

For example, certain people refer to the three-phase transformer as being made up of 3 single phase transformers.
, thus the two coils only have a magnetic connection between them. 
This ensures that power is transmitted only via electromagnetic induction and also makes the transformers useful for Isolating connections.
Operational Principle of Transformer:
The primary coil always represents the input to the transformer while the secondary coil, the output from the transformer.
, the magnitude of which will be determined by the number of turns of the conductor coil. 
This is the principle with which the secondary coil gets energized.
When a voltage is applied to the primary coil, it creates a magnetic field around the core the strength depends on the applied current. 

The created magnetic field thus induces a current in the secondary coil which is a function of the magnitude of the magnetic field and the numbers of turns of the secondary coil.
then.
Construction of the Transformer
The coils are insulated from each other and also insulated to prevent contact with the core.

The construction of the transformer will thus be examined under the coil and core construction.
The core of the transformer is always constructed by stacking laminated sheets of steel together, ensuring a minimum air-gap exists between them. 
The transformers core in recent times is always made up of laminated steel core instead of iron cores to reduce losses due to eddy current.
There are three major shapes of the laminated steel sheets to choose from, which are E, I, and L.

When stacking the lamination together to form the core, they are always stacked in such a way that the sides of the joint are alternated. 
For example, of the sheets are assembled as front faced during the first assembly, they will be back faced for the next assembly as shown in the image below. 
This is done to prevent high reluctance at the joints.
When constructing a transformer, it becomes very important to specify the type of transformer as either step up or step down as this determines the number of turns that will exist in the primary or secondary coil.
Types of Transformers:
;
1. Step Down Transformers
2. Step Up Transformers

3. Isolation Transformers
, the transformer gives an increased value of the voltage applied to the primary coil, at the secondary coil.
are transformers which gives the same voltage applied to the primary at the secondary and thus basically used to isolate electrical circuits.
Transformer Turns Ratio and EMF Equation:
;
n = Np/Ns = Vp/Vs
where n = turns ratio
Np = Number of turns in primary coil

Ns = Number of turns in secondary coil
Vp = Voltage applied to the primary
Vs = Voltage at the secondary
These relationship described above can be used to calculate each of the parameters in the equation.

Since we said the power remains the same after transformation then;
Which serves as proof that the transformer not only transforms voltage but also transforms current.
EMF Equation:
The number of turns of the coil of either of the primary or secondary coil determines the amount of current it induces or is induced by it. 

When the current applied to the primary is reduced, the strength of the magnetic field is reduced and the same for the current induced in the secondary winding.
E = N (dΦ/dt)
The Amount of voltage induced in the secondary winding is given by the equation:
Where N is the number of turns in the secondary winding.

sinwt
thus
E = N*w*Φmax*cos(wt)
Emax = NwΦmax

The root mean square value of the Induced Emf is gotten by dividing the maximum value of the emf by↲
Where: N is the number of turns in coil winding
f is the flux frequency in hertz
Φ is the magnetic flux density in Weber

with all these values determined, the transformer can thus be constructed.
Electrical Power
Transformers are thus referred to as constant wattage devices, while they may change the voltage and current values, it's always done in such a way that the same power at the input is available at the output.
Thus

Ps = Pp
where Ps is the power at the secondary and Pp is the power at the primary.
Since P = IvcosΦ
then IsVscosΦs =  IpVpcosΦp
Efficiency of a Transformer
The efficiency of a transformer is given by the equation;
Efficiency = (output power / input power) *100%
While the power output of an Ideal transformer should be the same as the power input, most transformers are far from the Ideal transformer and do experience losses due to several factors.

Some of the losses that can be experienced by a transformer are listed below;
1. Copper Losses
2. Hysteresis losses
3. Eddy current losses

R losses. 
These losses are associated with the power dissipated by the conductor used for the winding when current is passed through it due to the resistance of the conductor. 
The value of this loss can be calculated using the formula;
P = I2R

This is a loss related to the reluctance of the materials used for the core of the transformer. 
As the Alternating current reverses its direction, it has an impact on the internal structure of the material used for the core as it tends to undergo physical changes which also uses up part of the energy
This is a loss typically conquered by the use of laminated thin sheets of steel. 
The eddy current loss arises from the fact that the core is also a conductor and will induce an emf in the secondary coil. 

The currents induced in the core according to faradays law will oppose the magnetic field and lead to the dissipation of energy.
Factoring the effect of these losses into the transformer’s efficiency calculations, we have;
Efficiency = (input power - losses / input power )*100%
All parameters expressed in units of power.


electronic-circuits/passive-high-pass-filter
Passive High Pass Filter
, now it is the time to look insight of passive high pass filter.

above the predetermined value, which will be calculated by the formula.
which means no external power, no amplification of the input signal; we will make the circuit using “passiveᾠcomponents which do not requires any external power source. 
The passive components are same as Low pass filter but the connection order will be exactly reversed. 
The passive components are Resistor (R) and

Capacitor (C). 
Again it is a RC filter configuration.
Let’s see what happens if we construct the circuit and check the response or “Bode Plot”‐󋈍
Here is the circuit in this image:

we will see that the position of resistor and capacitor is interchanged.
How High Pass filter works?
Here is the curve how it’s look alike at the output of the capacitor:-
Frequency Response and Cut-Off Frequency
Exactly opposite of Low pass filter.
The formula of Calculating gain is same as we used in our previous tutorial in passive Low pass filter.
Gain(dB) = 20 log (Vout / Vin)
of High pass filter. 

By selecting proper capacitor and proper resistor we could stop Low frequencies, limit signal passing through the filter circuitry without affecting the signal as there is no active response.
As it will allow to pass all signals above the cut-off frequency.
What is the formula of Cut-off Frequency?
The formula of Cut-off frequency is exactly same as like Low Pass filter.

fc = 1 / 2πRC
So, R is resistance and C is capacitance. 
If we put the value we will know the cutoff frequency.
Output Voltage Calculation
Let’s see the first image, the circuitry where 1 resistor and one capacitor are used to form a High pass filter or RC circuit.
When DC signal applied across the circuit it’s resistance of the circuit which creates drop when current is flowing. 
But in case of an AC signal it’s not resistance but impedance is responsible for voltage drop, which measured in Ohms too.
One is resistance and other one is the capacitive reactance of the capacitor. 

So, we need to measure the capacitive reactance of the capacitor first as it will needed to calculating impedance of the circuitry.
, the formula is:-
Xc = 1 / 2πfC
The output of the formula will be in Ohms, as Ohms is the unit of capacitive reactance because it is an opposition means Resistance.

Value of resistor is also a resistance.
So, combining this two opposition we will get the total resistance, which is impedance in RC (AC signal input) circuit.
Impedance denotes as Z
The Formula is:-

until cut-off frequency is reached.
so it is pass the signal. 
Output gain is 1 at that time, that is Unity gain situation and due to unity gain the output voltage is same as the input voltage after the cut-off frequency is reached.
Example with Calculation
As we already know what actually happening inside the circuit and How to find out the value. 
Let’s choose practical values.
Let’s pick up most common value in resistor and capacitor, 330k and 100pF. 
We selected the value as it is widely available and it is easier to calculate.

Let’s see what will be the cut-off frequency and what will be the Output voltage.
Cut off Frequency will be:-
Let’s See whether it is true or not‐󋈍
This is the circuit of the example.

As the frequency response described before that at the cut-off frequency the dB will be
-3dB, Irrespective of the frequencies. 
We will search -3dB at the output signal and see whether it is 4825Hz (4.825Khz) or not.
Here is the frequency response:-

Let’s set the cursor at -3dB and see the result.
Phase Shift
, at -3dB or Cut-Off frequency.
As per the Frequency response of the filter shows us that it could pass all signals above cut-off frequency to the infinity. 

It is just theoretical practice. 
In practical and real world the passband is limited by the limitation of practical components.
The formula of Phase shift is not same as Low Pass filter as in low pass filter the phase became negative, but in high pass filter it is a positive phase shift, so the formula implies as:-
Phase shift φ = arctan (1 / 2πfRC)

Let’s see the phase shift curve of the circuit:-
This is the Phase shift of the circuit, used as practical example.
Let’s Find out the phase shift value at cut-off frequency:-
Time constant
As we already learn before about phase shift and frequency response, the capacitor gets a charging and discharging effect from the input signal frequencies. 
This charging and discharging effect is Time Constant denotes asτ (Tau). 
It is also related with the cut-off frequency.
How?

τ = RC = 1 / 2πfc
Sometimes we need to know the cut-off frequency when we have the time constant value in such case altering the formula we can easily get that:-
fc = 1 / 2πRC
Where RC = τ

fc = 1 / 2πτ
The High Pass filter is a Differentiator. 
If we feed Square Wave and the provide the it on a perfect time domain the output wave form of the filter produce spikes or short duration pulse. 
If the time constant is short durational the filter will produce differentiated square wave. 

We can differentiate a signal using this property of High Pass Filter.
Second Order Low pass filter: Formulas, Calculations and Frequency Curves
When a two first order low pass RC stage circuit cascaded together it is called as second order filter as there are two RC stage networks.
Here is the circuit:-

This is a second order High Pass Filter. 
CAPACITOR and RESISTOR is the first order and CAPACITOR1 and RESISTOR1 is second order. 
Cascading together they form a second order High pass filter.
Here is the response curve:-

This will calculate the cut-off frequency of the second-order High pass circuit.
Just as like Low Pass filter, it’s not so good to cascade two passive High Pass filters as dynamic impedance of each filter order effects other network in same circuitry.
Applications
Low pass filter is widely usedcircuit in electronics.

Here are few applications:-
Audio receiver and Equalizer
Music control system and Treble frequency modulation.
Function Generator

Cathode Ray Television and Oscilloscope.
Square Wave Generator from Triangular wave.
Pulse Generators.
Ramp to Step Generators.


tutorial/ac-circuit-theory-peak-average-and-rms-values
AC Circuit Theory (Part 3): Peak, Average and RMS Values
Today we will be going over some terms and quantities associated with the Alternating Current.
Peak Value of An AC Waveform
or as better known, the peak value.
, the Peak value is always the same for both the positive and negative half cycles that makes a complete cycle (+Vp = -Vp), but this doesn’t hold true for other none sinusoidal waveforms used in representing the alternating current, as different half cycles tend to have different peak values.
Instantaneous Values of Voltage and Current
The Instantaneous value of an Alternating voltage or current is the value of the current or voltage at a particular instant of time during the cycle of the waveform.
Consider the Image below.
The Instantaneous value of voltage is given by the equation;
V = Vpsin2πFt

Where Vp = value of the peak voltage
The instantaneous value of current is also obtained by a similar expression
I = Ipsin2πFt
Average Value of an AC Waveform
The average value or mean value of an alternating current is the average of all instantaneous values during an half cycle. 
It is the ratio of all instantaneous values to the number of instantaneous values selected during a half cycle.
The average value of an AC waveform is giving by the equation;
Where V1...Vn is the instantaneous value of voltage during the half cycle.

The average value is also given by the equation;
Vavg = 0.637 *Vp
Where Vp is the maximum/ Peak value of voltage in that cycle.
This same equation also holds true for current and all we have to do is swap Voltage in the equation for Current.

because the average value of the positive half cycle will cancel out that of the negative half cycle and as a result the expression based on the equation given above will evaluate to zero.
Root Mean Square (RMS) Value of an AC waveform
It is given by the relation;
Where i1 to in represent instantaneous values of current.

Or
Where Ip is the maximum or peak current.
The same set of equations hold for voltage and we just need to replace current with voltage in the equations.
when doing alternating current related calculations except for when performing average power-related calculations. 

The reason for this is the fact that most measuring instruments (multi-meters) used for measuring Alternating voltage and current give their outputs as rms values. 
Thus as much as possible to avoid errors, one should only use Vp to find Ip and Vrms to find Irms and vice versa as this quantities are completely different from one another.
Form Factor
One other quantity associated with an Alternating current that we need to look at is the form factor.

Where Vp is the peak or maximum voltage.
We can also Derive Irms from above equation like:
Form Factor = (0.707 x Vp) / (0.637 x Vp)
1.11 = Irms / Vavg

Irms = 1.11 x Vavg
One other application of form factors is found in digital multimeters used in measuring Alternating current or voltage. 
Most of these meters are generally scaled to display the RMS value of sine waves which they are designed to obtain by calculating the average value and multiplying by the form factor of a sinusoid (1.11) since it can be a little bit difficult to digitally calculate the rms values. 
Thus at times, for AC waveforms which are not pure sinusoidal, the reading from a multimeter may be a little bit inaccurate.
Crest Factor
The last quantity associated with the alternating current that we will be talking about in this article is the Crest Factor.
Mathematically, it is given by the equation;
Where Vpeak is the maximum amplitude of the waveform.

We can also Derive Irms from above equation like:
1.414 = Vpeak / (0.707 x Vpeak)
Vrms = V peak / 1.414
Vrms = 0.707 x Vpeak

The crest factor is majorly an indication of how high the peaks of an alternating quantity are. 
In direct current, for instance, the crest factor is always equal to 1 which is an indication of the lack of peaks in the waveform of a Direct current.
To serve as a sort of the key point below is a table showing the form factors and crest factors of different type of waveforms used in representing AC waveforms.


tutorial/passive-low-pass-filter
Passive Low Pass Filter
, a widely used term in Electronics. 
You will hear or use this ‘technicalᾠterm almost every time in your studies or in your professional career. 

Let’s explore what is special about this technical term.
What is it, Circuit, formulas, curve?
ᾠrest of the 50% we will explore further.
ᾭ In dictionary it means allowing or accepting what happens or what other’s do, without active response.

It is act as same as the traditional water filter which we have in our home/office which block impurities and only pass the clean water.
A traditional low pass filter pass frequency ranging from 30-300Khz (Low Frequency) and block above that frequency if used in Audio application.
As passive means we generally do not apply any outer source to the filtered signal out, it can be made using passive components, which do not required power, so the filtered signal do not gate amplified, the output signal amplitude will not increase at any cost.
for filtering out up to 100Khz but for the rest 100khz-300khz Resistor, Capacitor and Inductor is used (RLC).

Here is the circuit in this image:
capacitor. 
It is a first order filter as there is only one reactive component in the circuitry that is capacitor. 
The filtered output will be available across capacitor.

What actually is happen inside the circuitry is quite interesting.
Here is the curve how it’s look alike at the output of the capacitor:-
Frequency Response and Cut-Off Frequency
Let’s understand this curve further

is the cutoff frequency of the filter. 
The signal line from 0dB/118Hz to 100 KHz it is flat almost.
The formula of Calculating gain is
Gain = 20log (Vout / Vin)

ᾮ
At low frequencies capacitor’s high reactance stops the flowing of current through the capacitor.
If we apply high frequencies above the cut-off limit, the capacitor reactance decrease proportionally when signal frequency increase, resulting lower reactance the output will be 0 as the effect of short-circuit condition across capacitor.
This is the low pass filter. 

By selecting proper resistor and proper capacitor we could stop frequency, limit signal without affecting the signal as there is no active response.
It’s signifying to which the unity gain will applied and signal will be blocked. 
So if it is a 150 Khz low pass filter then the bandwidth will be 150Khz. 
After that bandwidth frequency the signal will attenuate and stop from passing through the circuitry.

fc = 1 / 2πRC
So, R is resistance and C is capacitance. 
If we put the value we will know the cutoff frequency.
Output Voltage Calculation
Let’s see the first image the circuitry where 1 resistor and one capacitor are used to form a low pass filter or RC circuit.
When DC signal applied across the circuit it’s resistance of the circuit which creates drop when current is flowing, but in case of an AC signal it’s impedance, which measured in Ohms too.
One is resistance and other one is the capacitive reactance of the capacitor. 
So, we need to measure the capacitive reactance of the capacitor first as it will needed to calculating impedance of the circuitry.

, the formula is:-
Xc = 1 / 2πfc   
The output of the formula will be in Ohms, as Ohms is the unit of capacitive reactance, because it is an opposition means Resistance.
itself. 

Value of resistor is also a resistance.
, which is impedance in RC (AC signal input) circuit.
Impedance denotes as Z.
ᾠcircuit.

The output voltage of this divider is as follows=
Vout = Vin * (R2 / R1+R2)
R1 + R2 = RT
R1 + R2 are the total resistance of the circuit and this is the same as impedance.

So, combining this total equation we will get
By, solving the above formula we get the final one:-
Vout = Vin * (Xc / Z)
Example with Calculation
.
Cut off Frequency will be:-
By solving this equation the cut-off frequency is 720Hz.
Let’s where it is true or not‐󋈍

This is the circuit. 
As the frequency response described before that at the cut-off frequency the dB will be -3dB, Irrespective of the frequencies. 
We will search -3dB at the output signal and see whether it is 720Hz or not. 
Here is the frequency response:-

If we apply 500Hz signal then the capacitive reactance will be
Then the Vout is when applied 5V Vin at 500Hz:-
Phase Shift
As there is one capacitor associated with the Low pass filter and it’s an AC signal the Phase Angle denotes as φ (Phi) at the output is -45out of phase at -3dB or Cut-Off frequency.

Why?
When the input voltage changes the charge time of the capacitor and due to that scenario output voltage lags behind that of the input signal or sinusoidal.
The relationship as follows:-
Input frequency increase = out of phase margin increase. 

This entire two are proportional to each other.
The formula of Phase shift is
Phase shift φ = -arctan (2πfRC)
Let’s see the phase shift of the circuit

(Red Arrow) and get the result of the cut-off frequency 720Hz (Green Arrow).
Time constant
denotes as τ(Tau). 
It is also related with the cut-off frequency.

How?
τ = RC = 1 / 2πfc
Sometimes we need to know the cut-off frequency when we have the time constant value in such case altering the formula we can easily get that:-
fc = 1 / 2πRC

Where RC = τ
fc = 1 / 2πτ
Second Order Low Pass Filter: Formulas, Calculations and Frequency Curves
When a two first order low pass RC stage circuit cascaded together it is called as second order filter as there are two RC stage networks.

Here is the circuit:-
This is a second order Low Pass Filter. 
R1 C1 is first order and R2 C2 is second order. 
Cascading together they form a second order low pass filter.

Second order filter has a role of slope of 2 x -20dB/decade or -40dB (-12dB/octave).
Here is the response curve:-
The cursor showing -3dB cut-off point in Green signal which is across the first order (R1 C1), the slope at this was seen previously -20dB/ Decade and the red one at the final output which has a slope of -40dB/Decade.
Formulas are:-

This will calculate the gain of the second-order low pass circuit.
In practical the roll-off slope increase as per adding filter stage, the -3dB point and the pass band frequency changes from its actual calculated value above by a determined amount.
This determined amount is calculated by the following equation:-
It’s not so good to cascade two passive filters as dynamic impedance of each filter order effects other network in same circuitry.
Applications
Low pass filter is widely used circuit in electronics.
Here are few applications:-
Audio receiver and Equalizer

Camera filter
Oscilloscope
Music control system and Bass frequency modulation
Function Generator

Power Supply

tutorial/what-is-thyristor-how-it-works
What is Thyristor and How it works?

are the tiny electronic component that changed the world, today we can find them in every electronicdevice like TVs, mobiles, laptops, calculators, earphones etc. 
They are adaptable and versatile, but it doesn’t mean that they can be used in every application, we can use them as amplifying and switching device but they cannot handle higher current, also a transistor required a continuous switching current. 
So, for all these issues and to overcome these problems we use Thyristors. 


Thyristor is also a unidirectional device like a diode, which means it flows current only in one direction. 
It consists of three PN junction in series as it is of four layers. 
Gate terminal used to trigger the SCR by providing small voltage to this terminal, which we also called gate triggering method to turn ON the SCR.

Two Transistor Analogy of Thyristor
is, transistor turns off as the base current is removed while the Thyristor remains ON just by trigger it once. 
For applications like alarm circuit which need to trigger once and stay ON forever, cannot use transistor. 
So, for overcome these problems we use Thyristor.
How Is Thyristor different from MOSFET?
Thyristor and MOSFET both are electrical switches and are most commonly used. 
The basic difference between both of them is that MOSFET switches are voltage controlled device and can only switch DC current while Thyristors switches are current controlled device and can switch both DC and AC current.
are given below in table:


Property
Thyristor
MOSFET
Thermal Run away
Yes
No
Temperature sensitivity
less
high

Type
High voltage high current device
High voltage medium current device
Turning off
Separate switching circuit is required
Not required
Turning On
Single pulse required
No continuous supply is required except during turning On and Off
Switching speed
low
high

Resistive input impedance
low
high
Controlling
Current controlled device
Voltage controlled device

How is Thyristor Different from Transistor?
both are electrical switches but the power handling capacity of Thyristors are is far better than transistor. 
Due to having high rating of Thyristor, given in kilowatts, while of transistor power ranges in watts. 
A Thyristor is taken as a closed couple pair of transistors in analysis. 
The main difference between the transistor and Thyristor is, Transistor need continuous switching supply to remain ON but in case of Thyristor we need to trigger it once only and it remains ON. 

For applications like alarm circuit which need to trigger once and stay ON forever, cannot use transistor. 
So, to overcome these problems we use Thyristor.
are given below in table:



Layer
Four Layers
Three Layers
Terminals
Anode, Cathode and Gate
Emitter, Collector, and Base
Operation over voltage and current
Higher
Lower than thyristor

Turning ON
Just required a gate pulse to turn ON
Required continuous supply of the controlling current
Internal power loss
Lower than transistor
higher

V-I Characteristics of Thyristor or SCR
The basic circuit for obtaining Thyristor V-I characteristics is given below, the anode and cathode of the Thyristor are connected to main supply through the load. 
The gate and cathode of the Thyristor are fed from a source Es, used to provide gate current from gate to cathode.
As per the characteristic diagram, there are three basic modes of SCR: reverse blocking mode, forward blocking mode, and forward conduction mode.
may cause to Thyristor damage.

When anode is made positive with respect to cathode, with gate switch open. 
Thyristor is said to be forward biased, junction J1 and J3 are forward biased and J2 is reversed biased as you can see in figure. 
In this mode, a small current flows called forward leakage current, as the forward leakage current is small and not enough to trigger the SCR. 
Therefore, SCR is treated as open switch even in forward blocking mode.

As the forward voltage is increased with gate circuit remain open, an avalanche occurs at junction J2 and SCR comes into conduction mode. 
We can turn ON the SCR at any moment by giving a positive gate pulse between gate and cathode or by a forward breakover voltage across anode and cathode of the Thyristor.
Triggering Methods of SCR or Thyristor
There are many methods to triggering the SCR like:

Forward Voltage Triggering
Gate Triggering
dv/dt triggering
Temperature Triggering

Light Triggering
Forward Voltage Triggering:
Gate Triggering: 
It is one of the most common, reliable and efficient way to turning ON the Thyristor or SCR. 

In gate triggering, to turning ON an SCR, a positive voltage is applied between gate and cathode, which gives rise to the gate current and the charge gets injected into the inner P layer and forward breakover occurs. 
As higher the gate current will lower the forward breakover voltage. 

By using gate triggering method, as the gate pulse applied the junction J2 breaks, junction J1 and J2 gets forward biased or the SCR comes in conduction state. 

Hence, it allows the current to flow through anode to cathode.
As per the two transistor model, when the anode is made positive with respect to cathode. 
Current will not flow through anode to cathode until the gate pin is triggered. 
When current flows into the gate pin it turns ON the lower transistor. 

As lower transistor conduct, it turns ON the upper transistor. 
This is a kind internal positive feedback, so by providing pulse at gate for one time, made the Thyristor to stay in ON condition. 
When both the transistor turns ON current start conducting through anode to cathode. 
This state is known as forward conducting and this is how a transistor “latchesᾠor stays permanently ON.For turning OFF the SCR, you cannot off it just by removing gate current, at this state Thyristor get independent of gate current. 

So, for turning OFF you have to make switching OFF circuit.
dv/dt Triggering:
In reverse biased junction J2 acquires the characteristic like capacitor because of presence of charge across the junction, means junction J2 behaves like a capacitance. 
If the forward voltage is applied suddenly, a charging current through the junction capacitance Cj lead to turn ON the SCR.

is given by;
iC = dQ/dt = d(Cj*Va) / dt                  (where, Va is forward voltage appears across junction J2)
iC = (Cj * dVa /dt) + (Va* dCj / dt )
as the junction capacitance is nearly constant, dCj / dt is zero, then

iC = Cj dVa / dt
would be more. 
Here, the charging current plays the role of gate current to turn On the SCR even the gate signal is zero.
Temperature Triggering:
When the Thyristor is in forward blocking mode, most of the applied voltage collects over the junction J2, this voltage associated with some leakage current. 
Which increases the temperature of the junction J2. 
So, with the increase in temperature the depletion layer decrease and at some high temperature (within the safe limit), depletion layer breaks and the SCR turns to ON state.
Light Triggering:
(LASCR). 
Sometimes, these SCR triggered using both light source and gate signal in combination. 
High gate current and lower light intensity required to turn ON the SCR.
LASCR or Light triggered SCR are used in HVDC (High Voltage Direct Current) transmission system.


tutorial/ac-circuit-theory-2-waveforms-and-their-properties
AC Circuit Theory (Part 2): AC Waveforms and their Properties
AC Waveform
(Sinusoid waveform) to the extent that in the development of inverters, they distinguish between inverters by describing certain inverters as pure sine wave inverters. 
The reason for this is that the sine wave represents a smooth transition, and rotation of the coil or magnet as the case may be.
representing the AC with all its features (which will be explained later in this article) is shown in the image below.
which states that; the voltage produced by stationary coils as a result of the motion of a rotating magnet is proportional to the rate at which the magnetic flux is changing perpendicular to the coils.

The rate of the magnetic flux cutting the coil is greatest when the magnetic field is positioned in such a way that it cuts more conductor, and least when it is cutting less conductors, this determines the magnitude of the generated current or voltage, and as it continues to rotate, the direction changes.
Other Alternating Waveforms:
Before we dive into the properties of the AC waveform, its important to point out other useful waveform used in representing AC asides the sinusoidal waveform pattern, These wave forms include;
1. Square waves

2. Triangular Waves
3. Sawtooth or Ramp Wave forms
1. Square Waves
The frequency of a square wave is given by:

Frequency = 1 / period
Where, period = tp  + tn
tp = Time taken to complete positive half of a cycle
tn = Time taken to complete the negative half of the same cycle
2. Triangular Waves
Triangular waves have a sharper peak edge compared to the sine wave. 
They have a slow rising and decay time. 
The triangular waves are equally periodic, and have equal rise and fall time. 

A sample of the triangular wave is shown in the image below.
3. Sawtooth waveform
The peak of the sawtooth wave form looks like that of a sawtooth, hence the name. 
Sawtooth waveform are basically of two types; the positive ramp characterized by high steep decay and slow rising time, and the negative ramp wave form characterized by slow steep decay and fast rising time. 

Images to differentiate between the two wave forms are shown below.
are not the only one that can be used in describing AC wave forms, but they are the most popular and common kind of waveform that possesses a name and is deserving of a mention. 
All wave forms used to represent AC have something in common and that’s the periodic change in direction and magnitude this makes the “periodᾠa very important property of AC waveform.
Properties of AC Waveform:
To completely and correctly describe an AC waveform, three properties are involved;
1. Amplitude
2. Frequency (or Period)
3. Phase
1. Amplitude
(or Current).
2. Frequency and Period
The coil or magnet rotates continuously means after the first complete rotation that the waveform repeats itself, this means we could thus select a point irrespective of its location on the waveform and use it as a sort of marker. 

Every time the wave reaches this particular point after repeating itself, the wave is said to have gone through a complete cycle and the number of complete cycle increases as the waveform keeps repeating itself. 
This is most easily explained by selecting the peak of the waveform as our marker, the distance between two successive peaks then describes a complete a cycle.
, but the rate (i.e time) of alternation (or rotation) to achieve the period is described by the property referred to as “Frequencyᾮ
which simply represents the amount of cycles (or period) completed by the waveform in one seconds. 

Frequency is calculated using the formula;
Frequency =  1 / period
and
Period = 1 / frequency

The Frequency of AC supply in most part of the world is usually either 50Hz (Nigeria and Most European Countries) or 60 Hz in EU countries, and most plugged-in devices are always designed to handle this difference in frequency so devices can be used in any of these countries.
3. Phase
measured in degrees is said to exist between them. 
This creates room for calculation without the use of frequency and also makes it easy to compare two waveforms with the same frequency. 

Consider the Images below;
Don’t forget to leave your questions and comments under the comments section.
Till next time,
Cheers!


tutorial/ac-circuit-theory
AC Circuit Theory: What is AC and How its Generated
Introduction
An electrical circuit is a complete conductive path through which electrons flow from the source to the load and back to the source. 
The direction and magnitude of the electrons flow however depend on the kind of source. 
In Electrical Engineering, there are basically two types of voltage or current (Electrical Energy) source which defines the kind of circuit and they are; Alternating Current (or voltage) and Direct Current.
and so on.
AC Circuits
, is one in which the value of either the voltage or the current varies about a particular mean value and reverses direction periodically.
Most present day household and industrial Appliances and systems are powered using alternating current. 
All DC based plugged in appliances and rechargeable battery based devices technically run on Alternating current as they all use some form of DC power derived from AC for either charging of their batteries or powering of the system. 

Thus Alternating current is the form via which power is delivered at the mains.
The Alternating circuit came into being in the 1980s when Tesla decided to solve the long range incapability of the Thomas Edison’s DC generators. 
He sought a way of transferring electricity at a high voltage and then employ the use of transformers to step it either up or down as may be needed for distribution and was thus able to minimize power loss across a great distance which was the main problem of Direct Current at the time.
Alternating Current VS Direct Current (AC vs DC)
differ in several ways from generation to transmission, and distribution, but for the sake of simplicity, we will keep the comparison to their characteristics for this post.
The major difference between the AC and DC, which is also the cause of their different characteristics, is the direction of flow of electric energy. 
In DC, Electrons flow steadily in a single direction or forward, while in AC, electrons alternate their direction of flow in periodic intervals. 
This also leads to alternation in the voltage level as it switches along from positive to negative in line with the current.

Other differences will be highlighted as we go more into exploring Alternating current Circuits.


Energy Transmission Capacity
Travels over long distance with minimal Energy loss
Large amount of energy is lost when sent over long distances

Generation Basics
Rotating a Magnet along a wire.
Steady Magnetism along a wire
Frequency
Usually 50Hz or 60Hz depending on Country
Frequency is Zero
Direction
Reverses direction periodically when flowing through a circuit
It steady constant flow in one direction.
Current
Its Magnitude Vary with time
Constant Magnitude

Source
All forms of AC Generators and Mains
Cells, batteries, Conversion from AC
Passive Parameters
Impedance (RC, RLC, etc)
Resistance Only
Power Factor
Lies between 0&1
Always 1
Waveform
Sinusoidal, Trapezoidal, Triangular and Square
Straight line, sometimes Pulsating.


Basic AC Source (Single Coil AC Generator)
is simple. 
If a magnetic field or magnet is rotated along a stationary set of coils (wires) or the rotation of a coil around a stationary magnetic field, an Alternating current is generated using an AC generator(Alternator).

The simplest form of AC generator consists of a loop of wire that is mechanically rotated about an axis while positioned between the north and south poles of a magnet.
Consider the Image below.
As the armature coil rotates within the magnetic field created by the north and south pole magnets, the magnetic flux through the coil changes, and charges are thus forced through the wire, giving rise to an effective voltage or induced voltage. 
The magnetic flux through the loop is as a result of the angle of the loop relative to the direction of the magnetic field. 

Consider the images below;
The resultant induced voltage is thus sinusoidal, with an angular frequency ω measured in radians per seconds.
The Induced current in the setup above is giving by the equation:
I = V/R

Where V= NABwsin(wt)
Where N = Speed
A = Area
B = Magnetic field

w = Angular frequency.
Real AC generators are obviously more complex than this but they work based on the same principles and laws of electromagnetic induction as described above. 
Alternating current is also generated using certain kind of transducers and oscillator circuits as found in inverters.
Transformers
As at the time when AC came into reckoning, one of the main issues was the fact that DC couldn’t be transmitted over a long distance, thus one of the main issues, AC had to be solved to become viable, was to be able to safely deliver the high voltages (KVs) generated to consumers who use a voltages in the V range and not KV. 
This is one of the reasons why the transformer is described as one of the major enablers of AC and its important to talk about it.
, two coils are wired in such a way that when an Alternating current is applied in one, it induces voltage in the other. 
Transformers are devices which are used to either step down or step up voltage applied at one end (Primary Coil) to produce a lower or higher voltage respectively at the other end (Secondary Coil) of the transformer. 

The Induced voltage in the secondary coil is always equal to the voltage applied at the primary multiplied by the ratio of the number of turns on the secondary coil to the primary coil.
applied at the primary.
Transformers has made the distribution of electric power over long range very possible, cost-effective and practical. 
To reduce losses during transmission, electric power is transmitted from generating stations at high voltage and low current and are then distributed to homes and offices at low voltages and high currents with the aid of transformers.

So we will stop here so as not to overload the article with too much information. 
In part two of this article, we will be discussing AC waveforms and get into some equations and calculations. 
Stay tuned.


tutorial/what-is-shift-register-types-applications
Different Types of Shift Registers and its Applications with Examples 
What is Shift Register:
, capable of storage and transfer of data. 

They are made up of Flip Flops which are connected in such a way that the output of one flip flop could serve as the input of the other flip-flop, depending on the type of shift registers being created.
that can move between two states (0 or 1) and is capable of storing data in bits. 
New data is read into a flip flop with each clock cycle and the previous data sent at the output.
of the flip flop will stay at that value until the next clock cycle, where it will then change again to the value(High or low, 1 or 0) at the input.

which we have used with different microcontrollers to interface a display or sequence of LEDs.
Shift Register with 74HC595 withArduinoto control a sequence of LEDs
Shift Register with ESP32 to interface 7-Segment Display
Shift Register with Raspberry Pi to control multiple LEDs

Shift Register with PIC to control sequence of LEDs
Types of Registers in Digital Electronics
which are listed below although some of them can be further divided based on the direction of data flow either shift right or shift left.
1. Serial in ᾠSerial out Shift Register (SISO)

2. Serial In ᾠParallel out shift Register (SIPO)
3. Parallel in ᾠParallel out Shift Register (PIPO)
4. Parallel in ᾠSerial out Shift Register (PISO)
5. Bidirectional Shift Registers

6. Counters
1. Serial in - Serial out Shift Registers
Serial in ᾠSerial out shift registers are shift registers that streams in data serially (one bit per clock cycle) and streams out data too in the same way, one after the other.
is shown above, the register consists of 4 flip flops and the breakdown of how it works is explained below;

On startup, the shift register is first cleared, forcing the outputs of all flip flops to zero, the input data is then applied to the input serially, one bit at a time.
;
Non-destructive Readout
Destructive Readout

Non-Destructive Readout
mode of operation with an extra line added to allow the switch between the read and write operational modes.
When the device is in the “writeᾠoperational mode, the shift register shifts each data out one bit at a time behaving exactly like the destructive readout version and data is thus lost, but when the operational mode is switched to “readᾬ data which are shifted out at the input goes back into the system and serve as input to the shift register. 
This helps ensure that the data stays longer (as long as it stays in read mode)

Destructive Readout
For destructive readouts, the data is completely lost as the flip flop just shifts the information through. 
Assuming for the 4-bit shift register above, we want to send the word ᾱ101ᾮ After clearing the shift register, the output of all the flip flops becomes 0, so during the first clock cycle as we apply this data (1101) serially, the outputs of the flip flops look like the table below.


FF0
FF1
FF2
FF3
1
0
0
0



FF0
FF1
FF2
FF3
0
1
0
0



FF0
FF1
FF2
FF3
1
0
1
0



FF0
FF1
FF2
FF3
1
1
0
1

2. Serial in ᾠParallel out Shift Register
This means when the data is read in, each read in bit becomes available simultaneously on their respective output line (Q0 ᾠQ3 for the 4-bit shift register shown below).
A 4-bits serial in ᾠParallel out shift register is illustrated in the Image below.
A table showing how data gets shifted out of serial in –parallel out 4 bit shift register is shown below, with the data in as 1001.


Clear
FF0
FF1
FF2
FF3
1001
0
0
0
0
1
0
0
0
0
1
0
0

0
0
1
0
1
0
0
1

which is an 8-bit shift register.

The device features two serial data inputs (DSA and DSB), eight parallel data outputs (Q0 to Q7). 
Data is entered serially through DSA or DSB and either input can be used as an active HIGH enable for data entry through the other input. 
Data is shifted on the LOW-to-HIGH transitions of the clock (CP) input. 
A LOW on the master reset input (MR) clears the register and forces all outputs LOW, independently of other inputs. 

Inputs include clamp diodes. 
This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.
3. Parallel in ᾠSerial out Shift Register
shown below.

although it can also be operated as a serial in ᾠserial out shift register.
The device features a serial data input (DS), eight parallel data inputs (D0 to D7) and two complementary serial outputs (Q7 and Q7ᾩ. 
When the parallel load input (PL) is LOW the data from D0 to D7 is loaded into the shift register asynchronously. 
When PL is HIGH data enters the register serially at DS. 

When the clock enable input (CE) is LOW data is shifted on the LOW-to-HIGH transitions of the CP input. 
A HIGH on CE will disable the CP input. 
Inputs are overvoltage tolerant to 15 V. 
This enables the device to be used in HIGH-to-LOW level shifting applications.

The functional diagram of the shift register is shown below;
The timing diagram for the system is as shown in the image below;
4. Parallel in ᾠParallel out shift register
The input data at each of the input pins from D0 to D3 are read in at the same time when the device is clocked and at the same time, the data read in from each of the inputs is passed out at the corresponding output (from Q0 to Q3).

that is capable of working in most of the modes described by all the types we have discussed so far especially as a parallel in ᾠparallel out shift register.
5. Bidirectional Shift Registers
Shift registers could either perform right or left data shift, or both depending on the kind of shift register and their configuration. 
In right shift operations, the binary data is divided by two. 

If this operation is reversed, the binary data gets multiplied by two. 
With suitable application of combinational logic, a serial shift register can be configured to perform both operation.
Consider the 4-bits register in the image below. 
A couple of NAND gates are configured as OR gates and are used to control the direction of shift, either right or left.

The control line left/write is used to determine the direction to which data is shifted, either right or left.
The register can operate in all the modes and variations of serial and parallel input or output. 
The functional diagram of the 74HC194 highlighting the control line, clock, input and output pins is shown below.
The timing diagram of the device is also shown below. 

It will better help you understand how the control line controls the actions of the register.
6. Counters
Ring counters are basically a type of counter in which the output of the most significant bit is fed back as an input to the least significant bit. 
A 4-bit ring counter is illustrated in the diagram below using D flip flops.

When the clock pulse is applied, the output of each stage is shifted to the next one, and the cycle keeps going. 
When clear is turned high, all the flip flops except the first one (which gets set to 1) is reset to zero.
Applications of Shift registers
Shift registers are used in a lot of applications some of which are;

, where they are used to reduce the number of wires, or lines needed for communication between two devices, since serial communication generally require just two wires compared to parallel which depends on the number of bits being sent.
In modern day electronics, microcontrollers IO pins are referred to as real estates and one needs as much as possible for certain application like turning on 100 leds or reading 100 reed switches with something like an Arduino or the Atmeg328p microcontroller. 
For example, the circuit diagram below illustrates how a serial to parallel shift register can be used to control 8 LEDs, using just three of the microcontrollers IO pins.
Like a finite memory machine, the next state of the device is always determined by shifting and inserting a new data into the previous position.

Shift registers are used for time delay in devices, with the time being adjusted by the clock, or increased by cascading shift registers or reduced by taking the output from a lower significant bit.
The time delay is usually calculated using the formula;
N is the number of flip flop stage at which the output is taken, Fc is the frequency of the clock signal and t which is the value being determined is the amount of time for which the output will be delayed.
for a particular task because of the wide range and type its important to select one that matches your particular need, considering things like, the mode of operation, the bit size (number of flip flops), right or left or bidirectional etc.

are;
74HC 194 4-bit bidirectional universal shift register
74HC 198 8-bit bidirectional universal shift register
74HC595 Serial-In-Parallel-Out shift register

74HC165 Parallel-In-Serial-Out shift register
IC 74291 4-bit universal shift register, binary up/down counter, synchronous.
IC 74395 4-bit universal shift register with three-state outputs.
IC 74498 8-bit bidirectional shift register with parallel inputs and three-state outputs.

IC 74671 4-bit bidirectional shift register.
IC 74673 16-bit serial-in serial-out shift register with output storage registers.
IC 74674 16-bit parallel-in serial-out shift register with three-state outputs.
There are several more, you just have to find which fits your application best.

Thanks for reading, until next time.

tutorial/best-pcb-design-software
How to Choose The Best PCB Design Software

These software are widely used for PCB designing and simulation of the electronicscircuit.
Eagle:
This software was developed by CADSoft Computer in 2016, today EAGLE is procured and maintained by AUTODESK.
is available for download on AUTODESK website.

These features are available in free version.
In this paid version, AUTODESK provides technical support that includes call, mail and online chat support and also provides access to latest software release. 
But for an educational and self-use, the free version of this software will just do more than good.
as shown in the below figure.

which contains a list of the project with schematic and PCB layout file made by the user.
Multisim:
but if you compare for only PCB designing purpose, eagle can be considered as a better platform compared to Multisim.
and industrial purposes.

to get started.
EasyEDA:
It is a web-based tool, so there is no requirement to download or install any software. 
To use EasyEDA, you have to open easyeda.com from any HTML5 capable web browser. 

It doesn’t matter which OS you are using, because it can supportwindows, Linux and MAC. 
All you need is a web browser like Chrome, Firefox, Safari, Internet Explorer or Opera but it is recommended to use this in chrome or firefox for better performance. 
Being an online open-source tool, is the biggest advantage of EasyEDA.
using EasyEDA here at CircuitDigest. 

It has more than 500000 libraries with symbols and footprints of components and you will ever need, there is also a feature to create your own componentsymbol and footprint if needed. 
One more advantage is, it can support other software libraries and schematic which includes Altium, EAGLE, LTspice, and DXF.
this link, it will look like the below screenshot. 
In this editor you can find navigation panel, toolbar, workspace, drawing tools, writing tools andmany more functions. 

Let’s start with navigation panel which contains EELib, design, Parts, Shared, LCSC.
is the EasyEDA libraries that provide lots of components.
is a design manager that is used to check each component on the net easily.
contain schematic symbols and PCB footprints.

if someone sends their project to you than this will appear in the shared tab.
If you want to buy components to finish your PCB project, you should try another website LCSC.com
Sheet setting, line, image, Bezier, arc, text, freehand draw, arrowhead, rectangle, polygon, ellipse, pie, drag and canvas origin.
wire, bus, bus entry, netlabel, net flag VCC, net flag +5V, net port, net flag ground, voltage probe, pin, group/ungroup symbol.
Altium:
Altium Designer is a commercial electronics design package for Windows. 
The Altium Designer UI follows modern design standards that allow engineers to perform complex tasks quickly and efficiently. 
And a major update of the software is available every year, which delivers expanded capabilities, in addition to regular bug fix releases throughout the year.

which also includes some extensive integration with popular mechanical CAD tools on the market. 
This integration allows the entire product development team to work on the product together.
reduces the risk of surprises during manufacturing. 
The hardware-accelerated 3D engine also allows seamless design integration of multi-board projects, as well as boards integrating rigid-flex elements.

as you try to route through gaps, while also maintaining a minimum clearance to other nearby traces. 
When you are routing high-speed designs, such as USB3.0 or DDR, Altium Designer has full support for differential pairs and interactive tuning of net lengths.
making it possible to create a live bill of materials that associates components in the design with real-world supplier parts. 
This association will enable you to rapidly source parts from the lowest priced supplier - taking hours out of the component procurement stage, while also ensuring there are no obsolete or poorly stocked components in the design.

with a reduced feature set, mostly removing the features targeted towards sophisticated or very intricate designs. 
These are:
CircuitStudio, a much lower cost PCB design package that has many of the Altium Designer features.
CircuitMaker, a free version for open source projects.

Altium Upverter, a free web-based tool targeted towards makers/hobbyists.
KiCAD
from its official website.
KiCAD also has it's own library, which contains most of the electrical components. 

This software is also available in 19 different languages and it can run in Windows, Linux and MAC.
;
can convert images to footprint.
are also available on their website.
OrCAD
This software is not freely available, the price of it's license version is starting 2300 USD. 
OrCAD is developed by John Durbetaki, Ken and Keith Seymour.
is used for expertise level PCB design.

PSpice Designer is for industry-standard simulation and contains 33000 parts in the library. 
This version is starting from 1980 USD. 
PSpice designer plus is to analyze for reliability, cost, and yield. 
This version has all features of PCB designer and other unique features like cost analysis, yield analysis, design optimization, system C/C++ modeling and simulation, reliability analysis and HW/SW co-simulation.

from here.
Conclusion:
tutorial/zener-diode-types-applications-and-operational-principle

Zener Diodes
Introduction
is the voltage, on which Zener Diode starts conducting in reverse direction.
Operational Principle of Zener Diode:
, the breakdown voltage is very high and the diode gets damaged totally if a voltage above the breakdown diode is applied, but in Zener diodes, the breakdown voltage is not as high and does not lead to permanent damage of the zener diode if the voltage is applied.
The current increases to a maximum and get stabilized. 
This current remains constant over the wider range of applied voltage and allows the Zener diode to withstand with higher voltage without getting damaged. 
This current is determined by the series resistor.

, consider the two experiments (A and B) below.
, a 12V zener diode is connected in reversed biased as shown in the image and it can be seen that the zener diode blocked the voltage effectively because it was less/equal to the breakdown voltage of the particular zener diode and the lamp thus stayed off.
is shown below.
From the graph, it can be deduced that the zener diode operated in the reverse bias mode will have a fairly constant voltage irrespective of the amount of current supplied.
Applications of Zener Diode:
Zener diodes are used in three main applications in electronic circuits;
1. Voltage Regulation
2. Waveform Clipper

3. Voltage Shifter
1. Zener Diode as Voltage Regulator
This is arguably the most common application of zener diodes.
to a load connected in parallel to it irrespective of variations in the energy drawn by the load (Load current) or variations and instability in the supply voltage.

The Zener diode will provide constant voltage provided current stays within the range of the maximum and minimum reverse current.
is shown below.
Since the zener diode’s reverse bias characteristics are what is needed to regulate the voltage, it is connected in reversed bias mode, with the cathode being connected to the positive rail of the circuit.
, as a small value resistor will result in a large diode current when the loadis connected and this will increase the power dissipation requirement of the diode which could become higher than the maximum power rating of the zener and could damage it.

The value of resistor to be used can be determined using the formula below.
R1 = (Vin – VZ) / IZ
Where;
R1 is the value of the series resistance.

Vin is the input voltage.
Vz which is same as Vout is the Zener voltage
And Iz is the zener current.
By using this formula it becomes easy to ensure that the value of the resistor selected doesn’t lead to the flow of current higher than what the zener can handle.

on the supply rail while making attempts to regulate the input voltage. 
While this may not be a problem for most applications, this problem may be solve by the addition of a large value decoupling capacitor across the diode. 
This helps stabilize the output of the zener.
2. Zener Diode as Waveform Clipper
, producing a differently shaped output signal depending on the specifications of the clipper or clamper.
generically are circuits that are used to prevent the output signal of a circuit from going beyond a predetermined voltage value without changing any other part of the input signal or waveform.
and limiting noise peaks by clipping of high peaks.
when the applied voltage is not equal to the breakdown voltage, they are also thus used in clipping circuits.

regions. 
Although the diode will naturally clip off the other region at 0.7V irrespective of whether it was designed as a positive or negative clipper.
For example, consider the circuit below.
The clipper circuit is designed to clip the output signal at 6.2v, so a 6.2v zener diode was used. 

The zener diode prevents the output signal from going beyond the zener voltage irrespective of the input waveform. 
For this particular example, a 20v input voltage was used and the output voltage on the positive swing was 6.2v consistent with the voltage of the zener diode. 
During the negative swing of the AC voltage however, the zener diode behaves just like the normal diode and clips the output voltage at 0.7V, Consistent with normal silicone diodes.
in such a way that the voltage is clipped at different levels on the positive and negative swing, a double zener clipping circuit is used. 

The circuit diagram for the double zener clipping circuit is shown below.
In the clipping circuit above, the voltage Vz2 represents the voltage on the negative swing of the AC source at which the output signal is desired to be clipped, while voltage Vz1 represents the voltage on the positive swing of the AC source at which the output voltage is desired to be clipped.
3. Zener Diode as Voltage Shifter
and with the ability of the zener diode to maintain steady output voltage in the breakdown region, it makes them Ideal component for the operation.

, the circuit, lowers the output voltage, by a value equal to the breakdown voltage of the particular zener diode that is used. 
The circuit diagram for the voltage shifter is illustrated below.
Consider the experiment below,
The circuit describes a 3.3v zener diode based voltage shifter. 

The output voltage (3.72V) of the circuit is given by subtracting the breakdown voltage (3.3V) of the zener diode from the input voltage (7V).
The voltage shifter as describe earlier on has several applications in modern day electronic circuits design as the design engineer may have to work with up to three different voltage level at times during design process.
Types of Zener Diodes:
Zener diodes are categorized into types based on several parameters which include;

Nominal Voltage
Power Dissipation
Forward drive current
Forward voltage

Packaging type
Maximum Reverse Current
The nominal Operation voltage of a zener diode is also known as the breakdown voltage of the zener diode, depending on the application for which the diode is to be used, this is often the most important criteria for Zener diode selection.
This represents the maximum amount of power the zener current can dissipate. 

Exceeding this power rating leads to excessive increase in the temperature of the zener diode which could damage it and lead to the failure of the things connected to it in a circuit. 
Thus this factor should be considered when selecting the diode with the use in mind.
This is the maximum current that can be passed through the zener diode at the zener voltage without damaging the device.
This refers to the minimum current required for the zener diode to start operating in the breakdown region.

Other parameters that serve as the specification for the diode all need to be fully considered before a decision is made on the type on the kind of zener diode needed for that peculiar design.
Conclusion:
Here are 5 points you should never forget about the zener diode.
A zener diode is like an ordinary diode only that it has been doped to have a sharp a breakdown voltage.

The Zener diode maintains a stable output voltage irrespective of the input voltage provided the maximum zener current is not exceeded.
When connected in forward bias, the zener diode behaves exactly like the normal silicone diode. 
It conducts with the same 0.7v voltage drop that accompanies the use of the normal diode.
The zener diode default operational state is in the breakdown region (reversed biased). 

It means it actually starts to work when the applied voltage is higher than Zener Voltage in reverse biased.
The zener diode is mostly used in applications involving, voltage regulation, clipping circuits and Voltage shifters.

article/what-is-pid-controller-working-structure-applications

PID Controllers: Working, Structure and Tuning Methods
Block diagram of this systems is as shown in below figure-1.
When this error is zero that means desired output is achieved and in this condition output is same as a reference signal.
, dryer will not run for fixed time, it will run until clothes are dry. 

This is the advantage of close loop system and use of controller.
PID Controller and Its Working:
In each application, coefficient of these three actions are varied to get optimal response and control. 
Controller input is error signal and output is given to the plant/process. 

Output signal of controller is generated, in such a way that, output of plant is try to achieve desired value.
which has feedback control system and it compares the Process variable (feedback variable) with set Point and generates an error signal and according to that it adjusts the output of system. 
This process continues until this error gets to Zero or process variable value becomes equal to set point.
In ON/OFF controller, only two states are available to control the system. 

It can either ON or OFF. 
It will ON when process value is less than set point and it will OFF when process value is greater than set point. 
In this controller, output will never be stable, it will always oscillate around the setpoint. 
But PID controller is more stable and precise compare to ON/OFF controller.

Let us understand these three terms individually.
PID Modes of Control:
) is
is increased beyond normal range, process variable starts oscillating at high rate and make system unstable.

y(t) ∝ e(t)
y(t) = ki * e(t)
Here, the resulting error is multiplied with proportionality gain factor (proportional constant) as shown in above equation. 
If only P controller is used, at that time, it requires manual reset because it maintain steady state error (offset).

Because of integration, very small value of error, results very high integral response. 
Integral controller action continues to change until error becomes zero.
y(t) ∝ ∫ e(t)
y(t) = ki ∐󟣨t)

, decrease the speed of response. 
Proportional and Integral controllers are used combined (PI controller) for good speed of response and steady state response.
). 
Generally, Derivative controller is used when processor variables starts oscillating or changes at a very high rate of speed. 

D-controller is also used to anticipates the future behaviour of the error by error curve. 
Mathematical equation is as shown below;
y(t) ∝ de(t)/dt
y(t) = Kd * de(t)/dt

This is a combination of P and I controller. 
Output of the controller is summation of both (proportional and integral) responses. 
Mathematical equation is as shown in below;
y(t) ∝ (e(t) + ∫ e(t) dt)

y(t) = kp  *e(t) + ki  ∐󟣨t) dt
This is a combination of P and D controller. 
Output of controller is summation of proportional and derivative responses. 
Mathematical equation of PD controller is as shown below;

y(t) ∝ (e(t) +  de(t)/dt)
y(t) = kp  *e(t) + kd  * de(t)/dt
This is a combination of P, I and D controller. 
Output of controller is summation of proportional, integral and derivative responses. 

Mathematical equation of PD controller is as shown below;
y(t) ∝ (e(t) + ∫ e(t) dt + de(t)/dt)
y(t) = kp  *e(t) + ki  ∐󟣨t) dt + kd * de(t)/dt
Tuning Methods for PID Controller:
means staying at a given setpoint and command tracking, means if setpoint is change, output of controller will follow new setpoint. 
If controller is properly tuned, output of controller will follow variable setpoint, with less oscillation and less damping.
and getting desired response. 
Methods for tuning controller is as below;

Trial and error method
Process reaction curve technique
Ziegler-Nichols method
Relay method

Using software
Trial and error method is also known as manual tuning method and this method is simplest method. 
In this method, first increase the value of kp until system reaches to oscillating response but system should not make unstable and keep value of kd and ki zero. 
After that, set value of ki in such a way that, oscillation of system is stops. 

After that set the value of kd for fast response.
This method is also known as Cohen-Coon tuning method. 
In this method first generate a process reaction curve in response to a disturbance. 
By this curve we can calculate the value of controller gain, integral time and derivative time. 

This curve is identified by performing manually in open loop step test of the process. 
Model parameter can find by initial step percentage disturbance. 
From this curve we have to find slop, dead time and rise time of curve which is nothing but the value of kp, ki and kd.
In this method also first set the value of ki and kd zero. 

The proportional gain (kp) is increase until it reaches at the ultimate gain (ku). 
ultimate gain is nothing but it is a gain at which output of loop starts to oscillates. 
This ku and the oscillation period Tu are used to derive gain of PID controller from below table.



P

PI

PID
/40


This method is also known as Astrom-Hugglund method. 
Here output is switched between two values of the control variable but these values are chosen in such a way that process must cross the setpoint. 
When process variable is less than setpoint, the control output is set to the higher value. 

When process value is greater than setpoint, the control output is set to the lower value and output waveform is formed. 
The period and amplitude of this oscillatory waveform is measured and used to determine ultimate gain ku and period Tu which is used in above method.
For PID tuning and loop optimization, software packages are available. 
These software packages collect data and make a mathematical model of system. 

By this model, software finds an optimal tuning parameter from reference changes.
Structure of PID controller: 
, proportional, integral and derivative actions are working separately with each other and combine effect of these three actions are act in the system. 
Block diagram of this type of PID is as shown below;

affects all other terms in the equation.
is distributed to all terms same as ideal PID equation, but in this equation integral and derivative constant have an effect on proportional action.
Applications of PID controller:
Let us take an example of AC (air-conditioner) of any plant/process. 

Setpoint is temperature (20  C) and current measured temperature by sensor is 28  C. 
Our aim is to run AC at desired temperature (20  C). 
Now, controller of AC, generate signal according to error (8  C) and this signal is given to the AC. 
According to this signal, output of AC is changed and temperature decrease to 25  C. 

further same process will repeat until temperature sensor measure desired temperature. 
When error is zero, controller will give stop command to AC and again temperature will increase up to certain value and again error will generate and same process repeated continuously.
The I-V characteristic of a PV cell depends on temperature and irradiance level. 
So, operating voltage and current will change continuously with respect to change in atmospheric conditions. 

Therefore, it is very important to track maximum power point for an efficient PV system. 
To find MPPT, PID controller is used and for that current and voltage setpoint is given to the controller. 
If atmospheric conditions will change, this tracker keeps voltage and current constant.
PID controller is most useful in power electronics application like converters. 

If a converter is connected with system, according to change in load, output of converter must change. 
For example, an inverter is connected with load, if load increase more current will flow from inverter. 
So, voltage and current parameter is not fix, it will change according to requirement. 
In this condition, PID controller is used to generate PWM pulses for switching of IGBTs of inverter. 

According to change in load, feedback signal is given to controller and it will generate error. 
PWM pulses are generated according to error signal. 
So, in this condition we can get variable input and variable output with same inverter.


tutorial/fuse-types-and-working
What is Fuse: Types and Working
What are fuses?
in the running cables. 

Here is the basic circuit diagram & symbol of the fuse.
Why do we Need Fuse?
Fuses are used for the prevention of home appliances from the short circuit and damage by overload or high current etc. 
If we don’t use fuses, electrical faults occur in the wiring and it burns the wire andelectric appliances and may starts fire at home. 

The lives of television, computers, radios and other home appliances may also put at risk. 
When the fuse goes, a sudden spark occurs which may lead to turning your home into sudden darkness by disconnecting the power supply which saves any further mishappenings. 
That’s why we need fuses to protect our home appliances from harm.
How Does Fuse work?
It’s made up of thin strip or strand of metallic wire with noncombustible material. 
This is connected between the ends of the terminals. 
Fuse is always connected in series with the electrical circuit.
When the excessive current or heat is generated due to heavy current flows in the circuit, the fuse melts down due to the low melting point of the element and it opens the circuit. 

The excessive flow may lead to the breakdown of wire and stops the flow of current. 
The fuse can be replaced or changed with the new one with suitable ratings. 
The fuse can be made up of the element like zinc, copper, silver &aluminum. 
They also act as a circuit breaker which is used to break the circuit when the sudden fault occurs in the circuit. 

This is not only a protector but it is also used as a safety measure to prevent humans from hazards. 
So, this is how the fuse operates. 
Here is the figure is shown fuse operation, fuse barrel(container), fuse link.
How to choose a Fuse?
Select the fuse, like time-delay fuses for inductive load and fast acting fuses for the resistive load.
Write down the power(watts) of the appliance ᾠusually from the appliance manual,
Write down the voltage rating. 
The voltage must be greater than the circuit voltage for the proper protection of the device.

Use the next highest fuse rating after the calculation. 
For example, if the calculated fuse rating is 8.659 amps, so for this we will use a 9 amp fuse.
Characteristics of Fuses
There are some of the important characteristics of the fuses in the electrical and electronic system which are as follows:-

Current Rating: The continuously conducting maximum amount of current holds the fuse without melting it is termed as current ratings. 
It is the current carrying capacity, which is measured in Amperes. 
This is the thermal characteristics.
Voltage Rating: In this characteristic, the voltage connected in series with fuse does not increase voltage rating. 

i.e.,
I2t Rating: This is the amount of energy which is carried by fuse element whenthere is an electrical fault or some short circuit happens. 
It measures the heat energy(energy due to current flow) of fuse & it is generated when fuse has blown.
Interrupting or Breaking Capacity: It is the maximum rating of current without harm interrupt by the fuse is known as breaking or interrupting capacity of the fuse.

Voltage Drop: When excessive current flows, the fuse element melts and opens the circuit. 
Due to this resistance change and the voltage drop will become lesser.
Temperature: In this, the operating temperature will be higher, therefore the current rating will be lesser, so the fuse melts.
Classification of Fuses
They are divided into two parts AC Fuses & DC Fuses. 
Further, they are divided into many categories given in the flowchart below:-
Different Types of Fuses
are available in the market. 

Generally, there are two types of fuses:-
DC Fuses: DC fuses have larger in size. 
DC supply has constant value above 0V so it is hard to neglect and turn off the circuit and there is a chance of an electric arc between melted wires. 
To overcome this, electrodes placed at larger distances and because of this the size of DC fuses get increased.

AC Fuses: AC fuses are smaller in size. 
They oscillated 50-60 times in every second from minimum to maximum. 
So there is no chance of Arc between the melted wires. 
Hence they can be packed in small size.

AC fuses are further categorized into two parts, i.e., Low voltage fuses and High voltage fuses.
1. Low Voltage Fuses (LV)
Cartridge Type Fuses: It is the type of fuses in which they have totally closed containers & has the contact i.e., metal besides.
Cartridge Type Fuses are of two types:-

D-Type Cartridge Fuses:- It is composed of the cartridge, fuse base, cap & adapter ring. 
The fuse base has the fuse cap, which is fitted with the fuse element with cartridge through adapter ring. 
The circuit is completed when the tip of the cartridge makes contact with the conductor.
Link Type Or HRC(High Rupturing Capacity) Fuses:- In this type of fuse, the flow of current by fuse element is given under normal condition. 

To control the arc which is produced by fuse blown we use the fuse which is made up of porcelain, silver &ceramic. 
The fuse element container filled with silica sand. 
The HRC type is again divided into two parts that are:-
Blade Type/Plug-in Type:- The body of this fuse is made up of plastic and it is easily replaceable in the circuit without any load.

Bolted Type:- In this type of fuse, the conducting plates are fixed to the fuse base.
Rewireable/ Kit-Kat Type:- In this type of fuse, the main advantage is that the fuse carrier is easier to remove without having any electrical shock or injury. 
The fuse base acts as an incoming and outgoing terminal which is made up of porcelain & fuse carrier is used to hold the fuse element which is made up of tin, copper, aluminum, lead, etc. 
This is used in domestic wiring, small industries etc.

Striker Type Fuses:- In this type of fuse, it is used for closing and tripping the circuit. 
They are having enough force and displacement.
Switch Type Fuses:- In this type of fuse, basically metal enclosed of a switch and a fuse and is far used for low and medium voltage level.
Drop Out Fuses:- In this type of fuse, the melting of fuse causes the element to drop under gravity about its lower support. 

They are made for the protection of outdoor transformers.
2. High Voltage Fuses (HV):-
All types of high voltage fuses are used upon the rated voltage up to 1.5 Kv to 138 Kv. 
High voltage fuses are used to protect the instrument transformers & small transformers. 

It is made up of silver, copper & tin. 
When heat generated, the arc produces which causes the boric acid to evolve high amount of gases. 
That’s why these are used in outdoor places.
These are of three types which are as follows:-

Cartridge Type HRC Fuses:- It is similar to low voltage type, only some designing features are different.
Liquid Type HRC Fuses:- These are used for circuit up to 100A rated current& systems up to 132Kv. 
These fuses have the glass tube filled with carbon tetrachloride. 
The one end of the tube is packed and another is fixed by phosphorous bronze wire. 

When fuse operation starts, the liquid uses in the fuse extinguish the arc. 
This increase the short circuit capacity.
Expulsion Type HRC Fuses:- It is the escapable fuse, in which expulsion effect of gases produced by internal arcing. 
In this, the fuse link chamber is filled with boric acid for expulsion of gases.

Resettable Fuses:- It is the type of fuse, commonly known as self-resetting fuses which uses a thermoplastic conductive type thermistor known as Polymeric Positive Temperature Coefficient (PPTC). 
If a fault occurs. 
Current increases, temperature also increase. 
The increase in resistance is due to increase in temperature. 

The applications where it is used are military and aerospace where replacement is not possible.
Applications
Here are some applications in which fuses are used, i.e.,
They are used in home distribution boards, general electrical appliances, and devices.

They are used in gaming consoles andall automobiles such as car, trucks and other vehicles.
They are also used in laptops, cell phones, printers, scanners, portable electronics, hard disk drives.
In the electrical distribution system, you will find fuses in capacitors, transformers, power converters, motor starters, power transformers.
They are used in LCD monitors, battery packs, etc.


tutorial/basics-of-pcb
Basics of PCB
What is PCB? 
, so it will reduce the complexity of the overall circuit design. 
PCB is used to provide electricity and connectivity between the components, by which it functions the way it was designed. 
PCBs can be customised for any specifications to user requirements. 
It can be found in many electronics devices like; TV, Mobile, Digital camera, Computers parts like; Graphic cards, Motherboard, etc. 

It also used in many fields like; medical devices, industrial machinery, automotive industries, lighting, etc.
Types of PCB:
There are several types of PCB available for the circuit. 
Out of these types of PCB, we have to choose the appropriate type of PCB according to our application.

Single-layer PCB
Double-layer PCB
Multi-layer PCB
Flexible PCB

Aluminium backed PCB
Flex-rigid PCB
This type of PCB is simple and most used PCB because these PCBs are easy to design and manufacture. 
One side of this PCB is coated with a layer of any conducting material. 

Generally, copper is used as conducting material for PCB, because copper has very good conducting characteristic. 
A layer of solder mask is used to protect PCB against oxidation followed by silk screen to mark out all of the components on the PCB. 
In this type of PCB, only one side of the PCB is used to connect different types of electrical or electronics components like resistor, capacitor, inductor, etc. 
These components are soldered. 

These PCBs are used in low cost and bulk manufacturing application like calculators, radio, printers and the solid-state drive.
As name suggests, in this type of PCB, a thin layer of conducting material, like copper is applied to both top and bottom sides of the board. 
In PCB, on different layer of board, consist via, which has two pads in corresponding position on different layers. 
These are electrically connected by a hole through the board, which is shown in figure-2b. 

More flexible, relatively lower cost, and most important advantage of this type of PCB board is its reduced size which makes circuit compact. 
This type of PCB is mostly used in industrial controls, converter, UPS system, HVAC application, Phone, Amplifier and Power monitoring systems.
Multilayer PCB has more than two layers. 
It means that, this type of PCB has at least three conductive layers of copper. 

For securing the board glue is sandwiched between the layer of insulation which ensures that the excess heat will not damage any component of circuit. 
This type PCB designing is very complex and used in very complicated and large electrical task in very low space and compact circuit. 
This type of PCB is used in large application like GPS technology, satellite system, medical equipment, file server and data storage.
This type of PCB used flexible plastic material like polymide, PEEK (Polyether ether ketone) or transparent conductive polyester film. 

The circuit board is generally place in folded or twisted. 
This is very complex type of PCB and it also contains different range of layers like single sided flex circuit, double sided flex circuit and multisided flex circuit. 
Flex circuit is used in organic light emitting diode, LCD fabrication, flex solar cell, automotive industries, cellular telephones, camera and complex electronics devices like laptops.
Simple in design and most used and most manufacture PCB is single sided rigid PCB. 

Multi-layer rigid PCB can more compact by containing 9-10 layers.
Combination of Flexible circuit and rigid circuit is most important board. 
Flex-rigid boards consists of multiple layers of flexible PCB attached to a number of rigid PCB layer. 
Flex-rigid board is as shown in figure. 

It is used in cell phones, digital cameras and automobiles etc.
Types of PCBs According to Mounting System 
Through-hole PCB
Surface mounted PCB

In this type of PCB, we have to make hole using drill on PCB. 
In these holes, leads of components are mounted and soldered to pads situated on opposite side of PCB. 
This technology is most useful because it gives more mechanical support to electrical components and very reliable technology for mounting of components but drilling in PCB make it more expensive. 
In single layer PCB, this mounting technology is easy to implement, but in case of double layer and multi-layer PCB making hole is more difficult.

In this type of PCB, components are small in size because these components have very small lead or no leads are required for mounting on the board. 
Here, in this technology, SMD components are directly mounted on the surface of the board and not require to make hole on board.
Different Parts of PCB:
Pad is nothing but a piece of copper on which lead of components are mounted and on which soldering are done. 

Pad provides the mechanical support to the components.
In PCB, components are not connected with the help of wires. 
All components are connected with a conducting material like copper. 
This copper part of PCB which is used to connect all components that is known as trace. 

Trace is looks like below figure.
According to application, cost and available space of circuit, user can choose the layer of PCB. 
Most simple in construction, easy to design and most useful in routine life is single layer PCB. 
But for very large and complex circuit, double layer PCB or Multi-layer PCB is most preferred compared to single layer PCB. 

Now a day, in multi-layer PCB, 10-12 layers can be connected and most critical thing is to communicate between the components in different layer.
Silk layer is used for printing line, text or any art on the surface of PCB. 
Usually, for screen printing epoxy ink is used. 
Silk layer can be used in top and/or bottom layer of PCB according to user requirement which is known as silk screen TOP and silk screen BOTTOM.

In Top layer of PCB, all components are mounted in this layer of PCB. 
Generally, this layer is green coloured. 
In bottom layer of PCB, all components are soldered through the hole and lead of components is known as bottom layer of PCB. 
Sometime, in top and/or bottom layer PCB is coated with green colour layer, which is known as solder mask.

There is one additional layer on the top of copper layer called as Solder Mask. 
This layer generally has green color but it can be of any color. 
This insulating layer is used for to prevent accidental contact of pads with other conductive material on PCB.
PCB Materials:
which is rigid or flexible. 
This dielectric substrate is used with conducting material like copper on it. 
As dielectric material, the glass epoxy laminates or composite materials are used.
FR is stand for FIRE RETARDENT. 

For all type of PCB manufacturing, most common glass laminated material is FR4. 
Based on woven glass-epoxy compounds, FR4 is a composite material which is most useful because it provides very good mechanical strength.



Standard
130
Most common and widely used
Cheapest
With higher glass transition temp.
170-180
Compatible with the lead free reflow technology
Halogen free
--
Compatible with the lead free reflow technology


This material is made from paper and phenol compounds and this material is used for only single layer PCB. 
Both FR1 and FR2 has similar characteristic, the only difference is glass transition temperature. 
FR1 has higher glass transition temperature compared to FR2. 

These materials is also sub divided in standard, halogen free and non-hydrophobic.
These material is made from paper and two layer of woven glass epoxy and phenol compounds and this material is used for Single sided PCB only. 
CEM-1 can used instead of FR4, but price of CEM1 is higher than FR4.
this material is white coloured, glass epoxy compound which is mostly used in double layer PCB. 

CEM-3 has lower mechanical strength compared to FR4, but it is cheaper than FR4. 
So, this is a good alternative of FR4.
This material is used in flexible PCB. 
This material is made from kepton, rogers, dupont. 

This material has good electrical properties, felicity, wide temperature range and high chemical resistance. 
Working temperature of this material is -200 C to 300 C.
Prepreg means pre-impregnated. 
It is a Fiberglass impregnated with resin. 

These resins are pre- dried, so that when it heated, it flows, sticks and completely immersed. 
Prepreg has adhesive layer which gives strength similar to FR4. 
There are many versions of this material according to resin content, SR- standard resin, MR- medium resin and HR- high resin. 
This is chosen according to required thickness, layer structure and impedance. 

This material also available in high glass transition temperature and halogen free.
PCB designing software:
EAGLE is a most popular and easiest way to design PCB. 
EAGLE stands for Easily Applicable Graphical Layout Editor which is previously developed by CadSoft Computer and currently Autodesk is developer of this software. 

For designing circuit diagram, EAGLE has a schematic editor. 
EAGLE file extension is .SCH and different parts and components are define in .LBR extension. 
Board file extension is .BRD.
Multisim is also very powerful and easy learning software. 

Which is originally developed by Electronics Workbench and now it is a division of National Instruments (NI). 
It includes microcontroller simulation (MultiMCU) and integrated import export features to the PCB layout software. 
This software is widely used in academic and also in industry for circuit education.
EasyEDA is a software which is used to design and simulate circuits. 

This software is an integrated tool for schematic capture, SPICE circuit simulation, based on Ngspice and PCB layout. 
Most important advantage of this software is that, it is web based software and used in browser window. 
So, this software is independent from OS.
This software is developed by Australian software company Altium Limited. 

The main feature of this software is schematic capture, 3D PCB design, FPGA development and release/data management. 
This is first software which offer 3D visualization and clearance checking of PCB directly from PCB editor.
This software is developed by jean-pierre charras. 
This software has tools which can create BoM (Bill of Material), artwork and 3D view of PCB as well as all components used in circuit. 

Many components are available in the library of this software and there is feature that user can add their custom components. 
This software is support many human languages.
This software is also developed by Altium. 
Schematic editor of this software includes basic component placement and this software is used to design advanced multichannel and hierarchical schematics. 

All schematic is uploaded to server and these files are available to view by anyone, provided that you need a CircuitMaker account.

article/rs232-serial-communication-protocol-basics-specifications
RS232 Serial Communication Protocol: Basics, Working & Specifications

and how it works.
What is a serial communication?
, which means the data will be transmitted bit by bit. 
While in parallel communication the data is transmitted in a byte (8 bit) or character on several data lines or buses at a time. 

Serial communication is slower than parallel communication but used for long data transmission due to lower cost and practical reasons.
ᾠyou are shooting a target using machine guns, where bullets reach one by one to the target.
- you are shooting a target using a shotgun, where many numberof the bullets reach at the same time.
:

Asynchronous Data Transfer ᾠThe mode in which the bits of data are not synchronized by a clock pulse. 
Clock pulse is a signal used for synchronization of operation in an electronic system.
Synchronous Data Transfer ᾠThe mode in which the bits of data are synchronized by a clock pulse.
:

Baud rate is used to measure the speed of transmission. 
It is described as the number of bits passing in one second. For example, if the baud rate is 200 then 200 bits per Sec passed. 
In telephone lines, the baud rates will be 14400, 28800 and 33600.
Stop Bits are used for a single packet to stop the transmission which is denoted as “Tᾮ Some typical values are 1, 1.5 & 2 bits.

Parity Bit is the simplest form of checking the errors. 
There are of four kinds, i.e., even odd, marked and spaced. 
For example, If 011 is a number the parity bit=0, i.e., even parity and the parity=1, i.e., odd parity.
What is RS232?
Electrical Specifications
Let us discuss the electrical specifications of RS232 given below:
Voltage Levels: RS232 also used as ground & 5V level. 
Binary 0 works with voltages up to +5V to +15Vdc. 

It is called as ‘ONᾠor spacing (high voltage level) whereas Binary 1 works with voltages up to -5V to -15Vdc. 
It is called as ‘OFFᾠor marking (low voltage level).
Received signal voltage level: Binary 0 works on the received signal voltages up to +3V to +13 Vdc & Binary 1 works with voltages up to -3V to -13 Vdc.
Line Impedances: The impedance of wires is up to 3 ohms to 7 ohms & the maximum cable length are 15 meters, but new maximum length in terms of capacitance per unit length.

Operation Voltage: The operation voltage will be 250v AC max.
Current Rating: The current rating will be 3 Amps max.
Dielectric withstanding voltage: 1000 VAC min.
Slew Rate: The rate of change of signal levels is termed as Slew Rate. 

With its slew rate is up to 30 V/microsecond and the maximum bitrate will be 20 kbps.
How RS232 Works?
sources clears the path for receiving the data and gives a signal to send the data. 

This is the whole process through which data transmission takes place.

TXD
TRANSMITTER
RXD
RECEIVER

RTS
REQUEST TO SEND
CTS
CLEAR TO SEND
GND
GROUND


The signals set to logic 1, i.e., -12V. 
The data transmission starts from next bit and to inform this, DTE sends start bit to DCE. 
The start bit is always ᾰᾬ i.e., +12 V & next 5 to 9 characters is data bits. 
If we use parity bit, then 8 bits data can be transmitted whereas if parity doesn’t use, then 9 bits are being transmitted. 

The stop bits are sent by the transmitter whose values are 1, 1.5 or 2 bits after the data transmission.
Mechanical Specification
In DB-25, there are 25 pins available which are used for many of the applications, but some of the applications didn’t use the whole 25 pins. 
So, the 9 pin connector is made for the convenience of the devices and equipments.




1
CD (Carrier Detect)
Incoming signal from DCE

2
RD (Receive Data)
Receives incoming data from DTE
3
TD (Transmit Data)
Send outgoing data to DCE
4
DTR (Data Terminal Ready)
Outgoing handshaking signal
5
GND (Signal ground)
Common reference voltage

6
DSR (Data Set Ready)
Incoming handshaking signal
7
RTS (Request to Send)
Outgoing signal for controlling flow
8
CTS (Clear to Send)
Incoming signalfor controlling flow
9
RI (Ring Indicator)
Incoming signal from DCE


What is Handshaking?
Handshaking is the process which is used to transfer the signal from DTE to DCE to make the connection before the actual transfer of data. 
The messaging between transmitter & receiver can be done by handshaking.

named as:-
:
If there is no handshaking, then DCE reads the already received data while DTE transmits the next data. 
All the received data stored in a memory location known as receiver’s buffer. 

This buffer can only store one bit so receiver must read the memory buffer before the next bit arrives. 
If the receiver is not able to read the stored bit in the buffer and next bit arrives then the stored bit will be lost.
bit is lost.
:

It uses specific serial ports, i.e., RTS & CTS to control data flow.
In this process, transmitter asks the receiver that it is ready to receive data then receiver checks the buffer that it is empty, if it is empty then it will give signal to the transmitter that I am ready to receive data.
The receiver gives the signal to transmitter not to send any data while already received data cannot be read.
Its working process is same as above described in handshaking.

:
In this process, there are two forms, i.e., X-ON & X-OFF. 
Here, ‘Xᾠis the transmitter.
X-ON is the part in which it resumes the data transmission.

X-OFF is the part in which it pauses the data transmission.
It is used to control the data flow and prevent loss during transmission.
Applications of RS232 Communication
RS232 serial communication is used in old generation PCs for connecting the peripheral devices like mouse, printers, modem etc.

Nowadays, RS232 is replaced by advanced USB.
It is also used in PLC machines, CNC machines, and servo controllers because it is far cheaper.
It is still used by some microcontroller boards, receipt printers, point of sale system (PoS), etc.


article/what-is-diode-types-working-pn-junction-theory
Diodes: PN Junction, Types, Construction and Working
What is diode?
History of Diode:
, which was the beginning of the semiconductor era.
Construction of Diode:
These are also called as pure semi-conductors where charge carriers (electrons and holes) are in equal quantity at the room temperature. 
So current conduction takes place by both holes and electrons equally.
Formation of P and N-type semiconductors:
In N-type, semi-conductor electrons are majority charge carriers and holes are minority charge carriers.
In P-type semi-conductor holes are majority charge carriers and electrons are minority charge carriers.
P-N Junction Diode:
Since a junction forms between a P type and N type material it is called as P-N junction.
.
is as follows.
The arrow indicates the flow of current through it when the diode is in forward biased mode, the dash or the block at the tip of the arrow indicates the blockage of current from the opposite direction.
P-N Junction Theory:
We have seen how a diode is made with P and N semi-conductors but we need to know what happens inside it to form a unique property of allowing current in only one direction and what happens at the exact point of contact initially at its junction.
The width of the depletion region in this case depends upon the doping concentration in the materials.
If the doping concentration is equal in both the materials then the immobile ions diffuses into both the P and N materials equally.

What if the doping concentration differs with each other?
Now let’s see the behavior of the diode when proper voltage is applied.
Diode in Forward Bias:
Until these voltages are very less, current flows through the diode (ideally zero).

using below animation:
Diode in forward bias acts as closed switch and has a forward resistance of few ohms (around 20).
Diode in Reverse bias:
using below animation:

because even when the diode is open circuited, current exists in circuit so it is termed as leakage.
Different Types of Diodes:
There are number of diodes whose construction is similar but the type of material used differs. 
For example, if we consider a Light Emitting diode it is made of Aluminium, Gallium and Arsenide materials which when excited releases energy in the form of light. 

Similarly, variation in diode’s properties like internal capacitance, threshold voltage etc are considered and a particular diode is designed based on those.
with their working, symbol, and applications:
Zener diode
LED

LASER diode
Photodiode
Varactor diode
Schottky diode

Tunnel diode
PIN diode etc.
Let’s see the working principle and construction of these devices briefly.
It means when the reverse voltage is applied to the zener diode a strong electric field is developed at the junction which is enough to break the covalent bonds within the junction and causes large flow of current through. 

Zener breakdown is caused at very low voltages when compared to the avalanche breakdown.
generally seen in the normal diode which requires large amount of reverse voltage to break the junction. 
Its working principle is when the diode is reverse biased, small leakage currents pass through the diode, when the reverse voltage is further increased the leakage current also increases which are fast enough to break few covalent bonds within the junction these new charge carriers further breaks down the remaining covalent bonds causing huge leakage currents which may damage the diode forever.
When the electron hole recombination takes places a resultant photon is released which emits light, if the forward voltage is further increased more photons will be released and light intensity also increases but the voltage should not exceed its threshold value else the LED gets damaged.

here.
we can see its light through a camera.
to work properly.
The symbolic representation of a LASER diode is similar to that of LED.

Since capacitance increase with decrease in distance between the plates, the large reverse voltage means the low capacitance and vice-versa.
here.
It exhibits negative resistance region which can be used as an oscillator and microwave amplifiers. 
When this diode is forward biased firstly, since the depletion region is narrow the electrons tunnel through it, the current increases rapidly with a small change in voltage. 

When the voltage is further increased, due to the excess electrons at the junction, the width of the depletion region starts to increase causing the blockage of forward current (where the negative resistance region forms) when the forward voltage is further increased it acts as a normal diode.
In this diode, the P and N regions are separated by an intrinsic semiconductor. 
When the diode is reverse biased it acts as a constant valued capacitor. 
In forward bias condition, it acts as a variable resistance which is controlled by current. 

It is used in microwave applications which are to be controlled by DC voltage.
Its symbolic representation is similar to a normal P-N diode.
Applications of Diodes:
Regulated power supply: Practically it is impossible to generate DC voltage, the only type of source available is AC voltage. 

Since the diodes are unidirectional devices it can be used to convert AC voltage to the pulsating DC and with further filtering sections (using capacitors and inductors) an approximate DC voltage can be obtained.
Tuner circuits: In communication systems at the receiver end since antenna receives all the radio frequencies available in space there is a need to select a desired frequency. 
So, tuner circuits are used which are nothing but the circuit with variable capacitors and inductors. 
In this case a varactor diode can be used.

Televisions, traffic lights, display boards: In order to display images on TVs or on display boards LEDs are used. 
Since LED consumes very less power it is extensively used in lighting systems like LED bulbs.
Voltage regulators: As Zener diode has a very low breakdown voltage it can be used as a voltage regulator when reverse biased.
Detectors in Communications Systems: A well-known detector which uses diode is an Envelope detector which is used to detect the peaks of the modulated signal.


article/humanoid-robots
Humanoid Robots
with state of the art artificial intelligence was given citizenship of Saudi Arabia. 

Who would have thought of this event would be possible when we saw C-3PO in ‘Star Warsᾠmovie Franchise as one of the first and most memorable humanoid robot characters ever seen in the movies.
What is a Humanoid Robot?
provides better grip for regular tasks, better awareness of obstacles and better interaction with humans. 
Most importantly, it is proved immensely helpful for biological advancements in the human body. 

You can find all kinds of robotic applications available from DIY to Integrated with our nervous system. 
The more it amazes you, the costlier it gets. 
If you go for most advanced, just a limb can cost you a hundred thousand dollars.
(AI), the scenario has taken a drastic upside turn for the scope and advancements in this field. 

After the integration of AI, it is practically a Human being. 
It doesn’t only look like a Human being but it has its own thought process, own strategic thinking ability and although they may not be able to feel, but it can acknowledge the possible emotion as well.
go hand in hand.
4000 to whatever you can pour in. 

However, the best one will be the one created by you yourself. 
It covers best of both worlds, Electronics and Computer engineering and gives you a product which is a peerless example of how innovation happens at the edge of two different domains. 
Let’s see how basics are used to create one of the leading advancements in the world today.
Robots like Humans:
We will first understand that how the mechanics of our body and robots can be very similar to a very common and easy DIY Experiment.
You need 4 straws, Cardboard Plank, Glue, Scissors and 10m Thread reel
What did we learn from this architecture? Notice how each finger has its own thread to get pulled, see a single pull gives motion to each phalanx one by one and when we need to use multiple fingers, just pull all together and note that each work together. 
Their action might be delayed and each finger may form curve at different speeds as we are pulling different length of the fingers with the same force, from the same point.

, without an actual limb. 
The nerve used for moving any of the fingers must be passing from the upper hand. 
For someone whose arm is only till the ankle, sensory cords are connected to the lower part of the upper arm and an electronic armature is created to move with respect to the motion of the muscle at that lower part of the arm. 
This way, one can have an arm controlled by our brains just like any other arm.

They are made of 3 Ball joints, 5 joints overall; one ball joint can be considered as a shoulder joint, another ball joint will replace the ankle while the last ball joint forms the wrist. 
The rest of the structure can be considered as upper and lower arm structure which provides strength to the arm structure. 
It is created in such a way that it can cover all the area in its outreach, unlike our hand. 
For example, you cannot bend your hand in the backward direction from the ankle but this structure can do turn in every direction; the only limit is its length.

:
is used for its Torso part which gives protection to the internal circuit and mechanics. 
Legs are created to duplicate the maneuver just like human legs.
is must for regulated outputs and designing the logic.
Main Applications of Humanoids:
There are unlimited possibilities with robots and humanoids from doing a repeated manual task, to think and take a decision using Artificial Intelligence. 
Here I am mentioning few main areas where Humanoids are used:
.

which will be connected to the nervous system of the body. 
A person without hand after elbow can make the hand customized for oneself to be connected to the nerves below the upper arm near the shoulder. 
Each nerve movement and extension of the inner part of the upper arm will give a unique signal to the brain. 
This signal will be corresponding to a specific hand movement; the modular prosthetic limb will recognize the muscle pattern and movement in the hand will take place accordingly. 

Not to forget that each of these things will happen in real time. 
Just by the trigger of a thought, you can move the hand just like it is your own hand. 
It will change the way special people live. 
It will be helpful for the people who went through an accident and lost a limb or other body part. 

The best technology available today also has over 100 sensors in the palm itself, providing sensation capabilities of an actual touch on the surface of the artificial arms and legs which provides successful targeted sensory innervation and feel.
was introduced as one of the options while keeping the recessions and unemployment in mind. 
The government of several countries has shown resistance and placed their thoughts about putting a ban on AI while some of the governments showed interest in restriction of the applications of humanoid robots and them replacing the jobs.
as the great example of Artificial Intelligence with perfect human physical structure.


article/different-types-of-transistors
Different Types of Transistors and Their Working
It is composed of chemical element extract from sand called Silicon. 

Transistors change the theory of electronics radically since it has been designed over half a century before by John Bardeen, Walter Brattain, and William Shockley.
What are Transistors?
These devices are made up of semiconductor material which is commonly used for amplification or switching purpose, it can also be used for the controlling flow of voltage and current. 
It is also used to amplify the input signals into the extent output signal. 

A transistor is usually a solid state electronic device which is made up of semiconducting materials. 
The electronic current circulation can be altered by the addition of electrons. 
This process brings voltage variations to affect proportionally many variations in output current, bringing amplification into existence. 
Not all but most of the electronic devices contain one or more types of transistors. 

Some of the transistors placed individually or else generally in integrated circuits which vary according to their state applications.
What does a transistor made up of?
How Does Transistor Work?
The working concept is the main part to understand how to use a transistor or how it works?, there are three terminals in the transistor:

It gives base to the transistor electrodes.
: Charge carriers emitted by this.
: Charge carriers collected by this.
or the base pin is grounded or having no voltage on it the transistor remain in OFF condition and not allow the current flow from collector to emitter(also called cut-off region).

For the protection of the transistor we connect a resistance in series with it, for finding the value of that resistance we use the formula below:
Different Types of Transistors:
Further we can divide it like below:
Bipolar Junction Transistor (BJT)
are two prime parts of BJTs as we discussed earlier. 
BJT turned on by giving input to base because it has lowest impedance for all transistors. 
Amplification is also highest for all transistors.
are as follows:

In the NPN transistor middle region i.e., base is of p-type and the two outer regions i.e., emitter and collector are of n-type.
In the PNP transistor middle region i.e., base is of n-type and the two outer regions i.e., collector and emitter are of p-type.
What are Transistor Configurations?
Generally, there are three types of configurations and their descriptions with respect to gain is as follows:

: It has no current gain but has voltage gain.
: It has current gain but no voltage gain.
: It has current gain and voltage gain both.
In this circuit, base is placed common to both input and output. 

It has low input impedance (50-500 ohms). 
It has high output impedance (1-10 mega ohms).Voltages measured with respect to base terminals. 
So, input voltage and current will be Vbe & Ie and output voltage and current will be Vcb & Ic.
Current Gain will be less than unity i.e., alpha(dc)= Ic/Ie

Voltage gain will be high.
Power gain will be average.
In this circuit, the emitter is placed common to both input and output. 
The input signal is applied between base and emitter and the output signal is applied between collector and emitter. 

Vbb & Vcc are the voltages. 
It has high input impedance i.e., (500-5000 ohms). 
It has low output impedance i.e., (50-500 kilo ohms).
Current Gain will be high(98) i.e., beta(dc) =Ic/Ie

Power gain is upto 37db.
Output will be 180 degrees out of phase.
In this circuit, collector is placed common to both input and output. 
This is also known as emitter follower. 

It has high input impedance (150-600 kilo ohms).It has low output impedance(100-1000 ohms).
Current gain will be high(99).
Voltage gain will be less than unity.
Power gain will be average.
Field Effect Transistor (FET):
It has mainly high input impedance in mega ohms with low frequency conductivity between drain and source controlled by electric field. 
FETs are highly efficient, vigorous & lesser in cost.
Junction Field Effect Transistor (JFET)
The junction field effect transistor has no PN junction but in place of high resistivity semiconductor materials, they form n& p type silicon channels for flow of majority charge carriers with two terminals either drain or a source terminal. 
In n-channel, flow of current is negative whereas in p-channel flow of current is positive.
There are two types of channels in JFET named as: n-channel JFET & p-channel JFET
Here we have to discuss about principal operation of n-channel JFET for two conditions as follows:

Channel between drain and source acts as resistance. 
Let n-channel be uniform. 
Different voltage levels set up by drain current Id and moves from source to drain. 
Voltages are highest at drain terminal and lowest at source terminal. 

Drain is reverse biased so depletion layer wider here.
where current Id remains same & JFET acts as a constant current source.
Apply negative Vgs and Vds varies. 
The width of depletion region increases, channel becomes narrow and resistance increases. 

Lesser drain current flows & reaches upto saturation level. 
Due to negative Vgs, saturation level decreases, Id decreases. 
Pinch –off voltage continuously drops. 
Therefore it is called voltage controlled device.

The characteristics shown different regions which are as follows:
: Vgs=0, depletion layer small.
: Also known as pinch off region, as channel resistance is maximum.
: Controlled by gate source voltage where drain source voltage is lesser.

: Voltage between drain and source is high cause breakdown in resistive channel.
p-channel JFET operates same as n-channel JFET but some exceptions occurred i.e., Due to holes, channel current is positive &Biasing voltage polarity needs to be reversed.
Drain current in active region:
Metal Oxide Field Effect Transistor (MOSFET):
Metal Oxide Field Effect Transistor is also known as voltage controlled field effect transistor. 
Here, metal oxide gate electrons insulated electrically from n-channel & p-channel by thin layer of silicon dioxide termed as glass.
It is a three terminal device i.e., gate, drain & source. 
There are two types of MOSFET by functioning of channels i.e., p-channel MOSFET & n-channel MOSFET.

There are two forms of metal oxide field effect transistor i.e., Depletion Type & Enhancement Type.
It requires Vgs i.e., gate-source voltage to switch off & depletion mode is equal to normally closed switch.
Vgs=0, If Vgs is positive, electrons are more & if Vgs is negative, electrons are less.
: It requires Vgs i.e., gate source voltage to switch on & enhancement mode is equal to normally open switch.

used in grounding.
Modes of Biasing For Transistors:
whereas depending on biasing, there are four different circuits of biasing as follows:
:

In the figure, the base resistor Rb connected between the base and the Vcc. 
The base emitter junction is forward biased due to voltage drop Rb which leads to flow Ib through it. 
Here Ib is obtained from:
Ib=(Vcc-Vbe)/Rb

This results in stability factor (beta +1) which leads to low thermal stability. 
Here the expressions of voltages and currents i.e.,
Vb=Vbe=Vcc-IbRb
Vc=Vcc-IcRc=Vcc-Vce

Ic = Beta Ib
Ie=Ic
In this figure, the base resistor Rb connected across collector and base terminal of transistor. 
Therefore base voltage Vb and collector voltage Vc are similar to each other by this

Vb =Vc-IbRb
Where,
Vb=Vcc-(Ib+Ic)Rc
reducing.

Here, (beta +1) factor will be less than one and the Ib leads to reduce amplifier gain.
So, voltages and currents can be given as-
Vb=Vbe
Ic= beta Ib

Ie is almost equals to Ib
In this figure, it is the modified form over the collector feedback basing circuit. 
As it has additional circuit R1 which increases stability. 
Therefore, increase in base resistance leads to the variations in beta i.e., gain.

Now,
I1=0.1 Ic
Vc= Vcc-(Ic+I(Rb)Rc
Vb=Vbe=I1R1=Vc-(I1+Ib)Rb

Ic= beta Ib
Ie is almost equals to Ic
In this figure, it is same as fixed bias circuit but it has an additional emitter resistor Re connected. 
Ic increases due to temperature, Ie also increases which again increases the voltage drop across Re. 

This results in reduction in Vc, reduces Ib which brings iC back to its normal value. 
Voltage gain reduces by presence of Re.
Now,
Ve=Ie Re

Vc=Vcc – Ic Rc
Vb=Vbe+Ve
Ic= beta Ib
Ie is almost equals to Ic

In this figure, there are two supply voltages Vcc & Vee are equal but opposite in polarity.Here,Vee is forward biased to base emitter junction by Re & Vcc is reverse biased to collector base junction.
Now,
Ve= -Vee+Ie Re
Vc= Vcc- Ic Rc

Vb=Vbe+Ve
Ic= beta Ib
Ie is almost equal to Ib
Where, Re>>Rb/beta

Vee>>Vbe
Which gives a stable operating point.
In this figure, it uses both collector as feedback & emitter feedback for higher stability. 
Due to flow of emitter current Ie, the voltage drop occur across emitter resistor Re, therefore the emitter base junction will be forward bias. 

Here, the temperature increases, Ic increases, Ie also increases. 
This leads to a voltage drop at Re, collector voltage Vc decreases & Ib also decreases. 
This results that the output gain will be reduced. 
The expressions can be given as:

Irb=0.1 Ic=Ib+I1
Ve=IeRe=0.1Vcc
Vc=Vcc-(Ic+Irb)Rc
Vb=Vbe+Ve=I1R1=Vc-(I1+Ib0Rb)

Ic=beta Ib
Ie is almost equal to Ic
In this figure, it uses voltage divider form of resistor R1 & R2 to bias the transistor. 
The voltage forms at R2 will be base voltage as it forward biases the base-emitter junction. 

Here, I2= 10Ib.
This is done to neglect voltage divider current and changes occur in value of beta.
Ib=Vcc R2/R1+R2
Ve=Ie Re

Vb=I2 R2=Vbe+Ve
Ic resist the changes in both beta & Vbe which results in a stability factor of 1.In this, Ic increases by increase in temperature, Ie increases by increase in emitter voltage Ve which reduces the base voltage Vbe. 
This results in decrease base current ib and ic to its actual values.
Applications of Transistors
Transistors for the most of the parts are used in electronic application such as voltage and power amplifiers.
Used as switches in many circuits.
Used in making digital logic circuits i.e., AND, NOT etc.
Transistors are inserted in everything i.e., stove tops to the computers.

Used in the microprocessor as chips in which billions of transistors are integrated inside it.
In earlier days, they are used in radios, telephone equipment’s, hearing head’s etc.
Also, they are used earlier in vacuum tubes in big sizes.
They are used in microphones to change sound signals into electrical signals as well.


article/communication-between-two-computers-using-xbee-modules
Communication Between Two Computers using XBee Modules
Detecting attached XBee module in Computer: 
You can detect your XBee radio module in Linux and Mac OSX, by opening a Terminal, you can type a few commands to see if the module is recognized by your computer. 
Additionally while connected to more than one module we can see you have to be a bit more careful. 
After opening terminal you need to use the following command lines to see if your device is properly recognized by your system or not.
, you need to type

dmesg | tail
ls/dev/tty (mac users must enter ls/dev/tty.*)
As shown in image above you will see /dev/ttyUSB0, ensure that you have not connected other USB devices in that case the USB1, 2 or x. 
This directory would be very useful while communicating XBee with python.

in the devices as shown below in case you are using putty or using python. 
Alternatively now you can use XCTU for the same.
Connecting XBee module to Computer for communication:
as it is compatible with Windows and MAC, the software is free and available for all the OSes like MAC, Windows, Linux.

Drag the CoolTermMac folder from Downloads folder to Applications folder and CoolTerm icon will appear on the Launchpad automatically.
once you get the COM port set the:
baud rate as 9600,
Databits 8,

Parity None and
Stop bits 1.
and then click on OK.
button as shown in the image below, after clicking

Type +++ (don't press enter) if you get OK as a response appear then proceed. 
If not then wait for more than 10 seconds and retype +++ to renter command
Type ATSH and hit enter and you can see as shown below the higher address 32 bit address which is static address assigned by digi.
Now you can type other commands to see the parameters,

If you get problem in connecting XBee with your computer then:
Check settings like baud rate settings.
Reconnect your module and check if it is properly connected.
Try to update firmware which may solve if it is not working due to do some previous settings.

Reset the settings incase if it is sleeping mode.
Linux user can simply install putty using terminal in Linux (debian versions)
sudo apt-get install putty
For other distribution download the source file and go to the directory using terminal and type following commands

sudo make
sudo install
radio button and enter text into text box ᾯdev/ttyusb0ᾠas shown in the below image. 
And set the baud rate 9600.

change the settings as shown in settings above, change
3. Then on terminal type ᾫ++ᾠ(Without pressing enter) then after getting OK you may type other AT Commands as shown below.
, extract it and then click on the coolterm.exe you are good to go.
A simple project of communicating two XBee modules
The idea is to send text information in ASCII values from one computer and send it to other computer. 
We will use XCTU console modem.
to proceed:
Two XBee modules in our case its XB24-ZB family

Two XBee adapter boards
Two PC’s with serial communication terminals
But before proceeding we need to configure our XBee module and add the XBee radio modules. 
Now follow the steps to communicate with other XBee:

First let us update the firmware for our coordinator, just open configuration mode, Then in Radio Configuration menu update firmware by clicking on the image as shown below:
After noting down the address at the back of the radio module i.e ᾰ013A200–Higher XXXXXXXX-Lower (your radio’s address)ᾮWe have to configure using commands as listed below in table



PAN ID
ATID
1001 (any address from 0 to FFFE will do)
Destination address high
ATDH
0013A200
Destination address low
ATDL
module)
Write function
ATWR
NA


(Enter key substitute) you need to repeat the same procedure for every command except ᾫ++ᾠ.
The order of the commands to be added shown below:
As shown below add packets and make a sequence this will save your time as you can reuse by saving these packets for later use, After adding packets in sequence as shown below, set the transmit interval to 1000ms.

Open the serial connection with XBee radio module in console Now Click on the button at the bottom of the console “Start sequenceᾬ your console session may look as shown in image below.
+++OK
ATID 1000
OK

ATDH 0013A200
OK
ATDL 40ADFB32
OK

ATID
1000
ATDH
13A200

ATDL
40ADFB32
ATWR
OK

Similarly you need to configure your router using following parameters as listed in the table below:

Function
Command
Parameter
PAN ID
ATID
1001 (any address from 0 to FFFE will do)

Destination address high
ATDH
0013A200
Destination address low
ATDL
module)
Write function
ATWR
NA


will look like this:
Router
+++OK
ATID 1000

OK
ATDH 0013A200
OK
ATDL 40A78409

OK
ATID
1000
ATDH

13A200
ATDL
40A78409
ATWR

OK
Sending Text from One PC to other using XBee:
Now time for some action, download CoolTerm/Putty or even XCTU in two PC’s, plug your XBee with adapter board to them, here we as shown below we are using CoolTerm. 
Now open serial connection and connect your XBee module as you learned early in this tutorial.

nsole write any character you will see the same character popping in other console window also. 
Here one XBee module works as Transmitter and other as Receiver.
, we have till now covered basics of XBee architecture and networking keeping in mind XBee ecosystem, we also acquired knowledge of AT commands and using terminals. 
In this tutorial we have learned how a XBee module can be interfaced with computer for communication between two computers. 

We can now communicate with our friends in nearby rooms using XBee radios!!! The next topic will be based on application of Arduino and XBee as an.
Do-it-Yourself
Download python IDE from: https://www.python.org/ftp/python/2.7.8/python-2.7.8.msi, download serial libraries of python and send AT commands using python.
Use AT commands to hook up LEDs at Digital I/O and control them remotely.

Configure an XBee module to get Analog inputs from a Potentiometer http://examples.digi.com/sensors/802-15-4-analog-input-with-a-potentiometer
Using python’s Tkinter you can make an interactive application to track motion by using an accelerometer and XBee, to make get gestures.
Plug in XBee module and receive the data of your grass using humidity sensor you can extend this project by plotting the data in using pythons Matplotlib.


article/zigbee-introduction-architecture-at-commands
Introduction to ZigBee: Architecture, Networks and AT Commands
is a product that supports various wireless communication protocol, including ZigBee, Wi-Fi (Wi-Fly module), 802.15.4, 868 MHz module etc. 
Here we are mainly focused on Xbee/Xbee-PRO ZB RF module which consists of ZigBee firmware.

Just think of a calculator in computer, where complex calculations are performed with user friendly interface. 
The task would have been very difficult and tedious if only hardware would have been available. 
So, at highest level, the availability of software makes problem solving process easier. 
Whole process is divided into layers of the software by the actual hardware which is called by higher levels.

We even use the concept of layers in our daily life. 
For example, sending courier/letter to your friend’s house, sending email from one point of world to another. 
Similarly, most modern network protocols even employ a concept of layers to separate different software components into independent modules that can be assembled in different ways. 
One may have to get his hands dirty for getting the in depth understanding of Xbee architecture, but we will make the things very simple for you.

to avoid collision you can learn more about CSMA using this link. 
Basically in it the nodes talk in the same way that human conversation; they briefly check to see that no one is talking before they start to send data.
the transmitter. 
The flow of data must not be allowed to overwhelm the receiver radio. 

Any receiving radio has a limited speed at which it can process incoming data and a limited amount of memory in which to store incoming data.
ZigBee Architecture:
in ZigBee stack which are physical layer, Media access layer, Network layer and application layer.
defines various addressing objects including profiles, clusters, and endpoints. 

You can see theZigBeestack layers in the figure above.
: It adds routingcapabilities that allows RF data packets to traverse multiple devices (multiple "hops") to route data from source to destination (peer to peer).
manages RF data transactions between neighboring devices (point to point). 
The MAC includes services such as transmission retry and acknowledgment management and collision avoidance techniques.

It defines how devices are connected to make a network; it defines the output power, number of channels and transmission rate. 
Most ZigBee applications operate on the 2.4 GHz ISM band at a 250kbps data rate.
Most XBee families have flow control,I/O,A/Dand indicator lines built in which can be configured using appropriate commands. 
Analog samples are returned as 10-bit values. 

The analog reading is scaled such that 0x0000 represents 0V, and 0x3FF = 1.2V. 
(The analog inputs on the module cannot read more than 1.2V)
To convert the A/D reading to mV, do the following:
AD (mV) = (A/D reading * 1200mV) / 1023
Data Transmission in ZigBee
You can call a network as combination of software and hardware which is capable of sending data from one location to another. 
Hardware is responsible for carrying the signals from one point of network to another. 
Software consists of instruction sets that make it possible to work as we expect.

are propagated in the whole network such that all nodes receive the transmission. 
To accomplish this, the coordinator and all routers that receive a broadcast transmission will retransmit the packet three times.
Unicast transmissions in ZigBee route data from one source device to another destination device. 
The destination device could be an immediate neighbor of the source device, or it could have several hops in between the way. 

An example is shown below in the figure explaining mechanism for recognizing the reliability of the bi-directional link.
Basics of network for Xbee routers and Coordinator
is unique universally; it is firmed inside the Xbee module by the manufacturer. 
No other ZigBee radio on earth will have that same static address, on back of every xbee module you can see this address as shown below, and notably the higher part of address ᾰ013A200ᾠis same for every xbee module.

which should be unique locally, when it joins a ZigBee network. 
The 16-bit address 0x0000 is reserved for the coordinator. 
All other devices receive a randomly generated address from the router or coordinator device that allows the join. 
The 16-bit address can change when two devices are found to have the same 16-bit address or a device leaves the network and later joins (it can receive a different address).

is set of characters i.e. 
strings which can be more human friendly way of addressing a node in a network.
Each network is defined with a unique PAN identifier (PAN ID). 
This identifier is common among all devices of the same network. 

ZigBee supports both a 64-bit and a 16-bit PAN ID. 
Both PAN addresses are used to identify a network uniquely. 
Devices on the same ZigBee network must share the same 64-bit and 16-bit PAN IDs. 
If multiple ZigBee networks are operating within range of each other, each should have unique PAN IDs.

The 16-bit PAN ID is used to address MAC layer in all RF data transmissions between devices in a network. 
But, due to the limited addressing space of the 16-bit PAN ID (65,535 possibilities), there may be chance that multiple ZigBee networks (within range of each other) can have the same 16-bit PAN ID. 
To resolve these conflicts, the ZigBee Alliance created a 64-bit PAN ID. 
ZigBee defines three different device types: coordinator, router, and end device.

for charging of setting up the network. 
So, it can never sleep. 
It is also responsible for selecting a channel and PAN ID (both 64-bit and 16-bit) to start the network. 
It can allow routers and end devices to join the network. 

It can assist in routing data in a network.
in a network. 
One router can get signals from other routers/EPs (End Points). 
It can also never sleep. 

It must join a Zigbee PAN before it can transmit, receive, or route data. 
After joining, it can allow routers and end devices to join the network. 
After joining, it can also assist in routing data. 
It can buffer RF data packets for sleeping end devices.

There can be multiple End Points as well. 
It can go in sleep mode to save power. 
It must join a ZigBee PAN before it can transmit or receive data and it cannot even allow devices to join the network. 
It is dependent on parent for transmit/receive data.

Since the end device can go in sleep mode, the parent device must buffer or hold incoming data packets until the end device wakes up and receive the data packets.
Different Network Topology in ZigBee
Network topology refers to the way in which network has been designed. 
Here, the topology is geometric representation of relationship of all the links and linking devices (Coordinator, Router and End devices) to one another.

, every node is connected with each other node expect the end device because end devices can’t communicate directly. 
To enable simple communication between two ZB radios, you'll need to configure one with the coordinator firmware, and one with router or endpoint firmware. 
Main advantage of Mesh network is that if one of the links becomes unusable, it does not incapacitate the entire system.
, each device has a dedicated point-to-point connection to a central controller (Coordinator). 

All the devices are not directly linked to each other. 
Unlike a mesh topology, in star topology one device can’t send anything directly to another device. 
The coordinator or hub is there for exchange: If one device wants to send data to another, it sends the data to the coordinator, which further sends the data to the destination device.
are those networks which contains two or more types of communication standards. 

Here, hybrid network is combination of star and tree network, few end devices are connected directly to the coordinator node and other end devices needs the help of parent node to receive the data.
, routers forms the backbone and end devices generally clustered around each router. 
It’s not very different from a mesh configuration except the fact that there routers are not interconnected you can visualize these networks using figure shown above.
Xbee firmware
The XBee Programmable module is equipped with a Free scale application processor. 
This application processor comes with a supplied boot loader. 
This XBee ZV firmware is based on Embernet 3.x.x ZigBee-PRO stack, XBee-Znet 2.5 modules can be upgraded to this functionality. 
You can check the firmware using ATVR command which we will discuss later in the chapter. 

XBee version numbers will have 4 significant digits. 
A version number can also be seen using ATVR command. 
The response returns 3 or 4 numbers. 
All numbers are hexadecimal and can have a range from 0-0xF. 

A version is reported as "ABCD". 
Digits ABC are the main release number and D is the revision number from the main release. 
The API discuss in chapter 4 and AT commands are almost same for Znet 2.5 and ZB firmware.
In telecommunications, the entire Hayes command is a language specific commands developed for the Hayes modem Smart Modem, 1981 they were a series of short words to control the modem making communication and setting of up of a modem simple in those days.

XBee also works on command mode and has set off AT Commands which stands for ATTENTION, these commands can be sent to XBee via terminals XBee and AT configured XBee radios have two modes of communication
The radio only passes the information it receives to the remoter radio address it has been configured to. 
The data sent through serial port is received by XBee as it is.
This mode is used to talk to radio and configure some preconfigured modes, we communicate to the modules while in this modes and change configuration.

You can type +++ and wait one second without pressing any other buttons, the message OK should then appear as the image of the terminal just up. 
By OK, the XBee tells us he spent in COMMAND mode and is ready to receive configuration messages.
XBee AT Commands:
This is the test command to check if the module is responding an OK as reply confirms the same.

Destination Address High. 
To configure the upper 32 bits of the 64-bit destination address DL and DH combined gives you 64 bit destination address.
Destination Address Low. 
This again for configuring the lower 32 bits of the 64-bit destination address.

This command changes the PAN ID (PersThe ID is 4 bytes of hexadecimal and can range from 0000 to FFFF
Write. 
Write parameter values to non-volatile memory so that parameter modifications persist through subsequent resets.
Note: Once WR is issued, no additional characters should be sent to the module until

After the "OK\r" response is received.
Restores factory settings to the module, is very useful if the module does not responds.

article/different-types-of-switches

Know About Different Types of Switches and Their Applications
Switch is nothing but a device which is used to turn ON and OFF the equipment. 
Most probably this equipment is electrical equipment like fan, TV etc. 
To flow current from a circuit it must require a close path (loop). 

If switch is OFF, that means circuit is open and current cannot flow through the conductor and equipment is de-energise (OFF state). 
To make it energise, we have to turn ON switch, it makes a complete circuit and close path. 
So, current can flow through the equipment and it can turn ON. 
So, function of switch is to make (switch is ON) and break (switch is OFF) the circuit.

Mechanical switches require physical or manual contact with switch for operation. 
Electrical switches not require physical or manual contact, it has ability to perform operation. 
Electrical switches operate under the action of semiconductors.
Mechanical Switches:
based on number of poles and throughs. 
Poles means the number of input circuit (power circuit) available to the switch. 
Throws means the number of output circuit (number of path in which current can flow) available to the switch.
Single pole single throw (SPST)

Single pole double throw (SPDT)
Double pole single throw (DPST)
Double pole double throw (DPDT)
Two poles six throw (2P6T)

Momentary operation switch / Momentary control switch

Push button
Pressure switch

Temperature switch
Toggle switch
Rotary switch
for the current to flow and separate each other to open circuit for the current to interrupt.

This switch is simplest example of switch. 
Generally, this switch used in single loop, means circuit requires to control only one close path. 
Symbol of single pole single throw switch is as shown in figure-1a. 
This switch is connected in series with the equipment, source or elements as shown in figure-1b.

This switch consists of four terminals; two input terminal (pole) and two output terminal (throw) as shown in figure-3a. 
This switch is very similar to two SPST switches. 
Both switches are connected with single liver so, both switches operate at a single time. 
These switches used when we want to control two circuit for same time as shown in figure-3b.

This switch consists of six terminals; two input terminals (pole) and two terminals for each pole, so total four output terminal (throw) as shown in figure-4a. 
Operation of this switch is similar to the two separate SPDT switches operate at a same time. 
In this switch, two terminal of input (pole) are connected with one set (two) of output (throw-1) in position-1 of switch. 
If we change the position of switch, it will connect this input with second set of output (terminal-2) as shown in figure-4b. 

Here as shown in example, let us assume that, in position-1 if motor is rotating in clockwise direction, if we change to position-2 motor will rotate in anti-clockwise direction.
is used for change-over in circuit with common input terminal.

Push button switch: when you press the switch, contacts of switch is closed and make circuit close to flow the current and when you remove pressure from the button, contacts of switch is open and break the circuit. 

So, this switch is momentary contact switch which is able to control the circuit by making and breaking its contact. 
In push button switch, when you remove pressure from the switch, there is an arrangement of spring to open contact.
Pressure switch: This type of switch consists of C-shape diaphragm. 
According to pressure, this diaphragm is indicating pressure. 

These switches are used to sense pressure of air, water or oil, in industrial application. 
This switch operates, when pressure of system is increase or decrease from set point.
Temperature switch: This type of switches consists of temperature sensing devices like RTD (resistance temperature device). 
This switch operates according to the value of measured temperature.

Toggle switch: This type of switch is commonly used in household application to ON and OFF electrical appliances. 
It has a lever by which we can move up or down to ON and OFF appliances.
Rotary switch: This type of switch is used to connect one line with one of the many lines. 
Nob of multi-meter, channel selector, range selector metering device band selector in communication devices are the examples of this type of switch. 

This switch is same as single pole multi throw switch. 
But the arrangement of this switch is different.
Electrical Switches:
is used in integrated circuits (ICs), electrical motor drives, HVAC application and also widely used as digital output (DI) of controller.

Relay
Bipolar transistor
Power diode
MOSFET

IGBT
SCR
TRIAC
DIAC

GTO
bipolar junctions transistor has three terminals; base, emitter and collector. 
Transistors are work on three regions; cut-off, saturation and active region. 
Symbol of transistor is as shown in figure-6. 

For switching purpose, active region is not used. 
If sufficient amount of current is available at base terminal, transistor enter in to saturation region and current will flow through collector-emitter path and transistor act as a ON switch. 
If base current is not sufficient, circuit is open and current cannot flow through the collector-emitter and transistor enters in to cut-off region. 
In this region, transistor act as OFF switch. 

Transistor are used as an amplifier in electronics application and it also used to make a gate like AND, NOT in digital circuits and transistor is also used as a switching device in integrated circuit. 
Transistors are not useful in high power application because it has more resistive loss compared to MOSFET.
Power diode have two terminals; anode and cathode. 
Diode is made up of p and n type semiconductor material and make pn-junction, which is known as diode. 

Symbol of power diode is as shown in figure-7. 
When diode is in forward bias current can flow through the circuit and in reverse bias blocks current. 
If anode is positive with respect to cathode, diode is in forward bias and act as a switch ON. 
Similarly, if cathode is positive with respect to anode, diode is in reverse bias and act as a switch OFF. 

Power diodes are used in power electronics application like, rectifier, voltage multiplier circuit and voltage clamper circuit, etc.
IGBT- Insulated Gate Bipolar Transistor. 
IGBT is a combination of BJT and MOSFET. 
IGBT has a high input impedance and high switching speeds (characteristic of MOSFET) as well as low saturation voltage (characteristic of BJT). 

IGBT has three terminals; Gate, Emitter and Collector. 
IGBT can control with the use of gate terminal. 
It can be switched ON and OFF by triggering and disabling its gate terminal. 
IGBT can block both positive and negative voltage same as GTO. 

IGBT is used in inverter, traction motor control, induction heating and switched mode power supplies.
SCR- Silicon Controlled Rectifier. 
SCR has three terminals; Gate, Anode and Cathode. 
Working of SCR is same as diode, but SCR start conduction when it is in forward bias (cathode is negative and anode is positive) and positive clock pulse at the gate is also required. 

In forward bias, if clock pulse of gate is zero, SCR turned off by forced commutation and in reverse bias SCR is remains in OFF state same as diode. 
SCRs are used in motor control, power regulators and lamp dimming.
DIAC- Diode AC switch. 
DIAC has two terminals. 

This switch can operate in both direction. 
Symbol of DIAC is as shown in figure-12. 
DIAC works on two regions; forward blocking or reverse blocking region and avalanche breakover region. 
When applied voltage is less than breakover voltage DIAC works in forward blocking or reverse blocking region. 

In this region DIAC act as OFF switch. 
When applied voltage is greater than breakover voltage, avalanche breakdown occurs and DIAC act as ON switch. 
DIAC cannot switch sharply for low voltage and low current application as compared to TRIAC and SCR. 
DIAC used in light dimming, control of universal motor and heat control circuit.

GTO has three terminals; Gate, Anode and Cathode. 
As name suggest, this device can turn OFF through gate terminal. 
In symbol of GTO consists of two arrows on the gate terminal, which shows the bidirectional flow of current through the gate terminal. 
This device can turn ON by applying a small positive gate current and turn OFF by negative pulse from the gate terminal. 

GTO used in inverters, AC & DC Drives, induction heater and SVC (static VAR compensation). 
GTO cannot use for turning inductive loads off, without the help of the snubber circuit.

article/what-is-wheatstone-bridge

Wheatstone Bridge
The below table shows different bridges with their uses:

S.No.
Name of Bridge
Parameter to be determine

1.
Wheatstone
measure an unknown resistance
2.
Anderson
measure the self-inductance of the coil
3.
De-sauty
measuring very small value of Capacitance
4.
Maxwell
measure an unknown inductance

5.
Kelvin
used to measure unknownelectrical resistorsbelow 1ohm.
6.
Wein
measurement of capacitance in terms of resistance and frequency
7.
Hay
measurement of unknown inductor of high value


helps in measuring the resistance in a simple way. 
But the advantage of Wheatstone bridge over this is to provide the measurement of very low values of resistance in the range of milli-ohms.
Wheatstone bridge
forming a bridge. 

The four resistance in circuit are referred as arms of bridge. 
The bridge is used for finding the value of an unknown resistance connected with two known resistor, one variable resistor and a galvanometer. 
To find the value of unknown resistance the deflection on galvanometer made to zero by adjusting the variable resistor. 
This point is known as balance point of Wheatstone bridge.
Derivation
As we can see in figure, R1 and R2 are known resistor. 
R3 is variable resistor and Rxis unknown resistance. 
The bridge is connected with the DC source (battery).

value when bridge is in the Balanced condition (no current flow between point C and D).
V = IR (by ohm's law)
VR1 = I1 * R1         ... 
equation (1)

VR2 = I1 * R2         ... 
equation (2)
VR3 = I2 * R3         ... 
equation (3)

VRx = I2 * Rx         ... 
equation (4)
I1 * R1 = I2 * R3      ... 
equation (5)

I1 * R2 = I2 * Rx      ... 
equation (6)
On dividing equation (5) and equation (6)
R1 / R2 = R3 / Rx

Rx = (R2 * R3) / R1
So, from here we get the value of Rx which is our unknown resistance and hence this is how Wheatstone bridge helps in measurement of an unknown resistance.
Operation
Getting zero current through galvanometer gives high accuracy, as a minor change in variable resistance can disrupt the balance condition.

As shown in the figure, there are four resistance in the bridge R1, R2, R3 and Rx. 
Where R1 and R2are the unknown resistor, R3is the variable resistance and Rxis the unknown resistance. 
If the ratio of known resistors is equal to the ratio of adjusted variable resistance and unknown resistance, in that condition no current will flow through the galvanometer.
At balanced condition,

R1 / R2 = R3 / Rx
and R3so it’s easy to find the value of Rxfrom the above formula.
From the above condition,
Rx = R2 * R3 / R1

Hence, the value of unknown resistance is calculated through this formula, given that current through Galvanometer is Zero.
Given below:
Example
, as we take an unbalanced bridge to calculate the appropriate value for Rx (unknown resistance) to balance the bridge. 

As we know if the difference of voltage drop across point C and D is zero then the bridge is in balance condition.
According to the circuit diagram,
For the first arm ADB,
Vc = {R2 / (R1 + R2)}* Vs

On putting the values in the above formula,
Vc = {80 / (40 + 80)}* 12 = 8 volts
For the second arm ACB,
Vd = {R4 / (R3 + R4)}* Vs

Vd = {120 /(360+ 120)}*12 = 3 volts
So, the voltage difference between point C and D is:
Vout = Vc - Vd = 8 - 3 = 5 volts
If the difference of voltage drop across C and D is positive or negative (positive or negative shows the direction of unbalance), it shows that the bridge is unbalanced and for making it balance we need a different value of resistance in replacement ofR4.

The value of resistor R4 required for balance the circuit is:
R4 = (R2 * R3) / R1 (condition of balance bridge)
R4 = 80 * 360 / 40
R4 = 720 ohm

Hence, the value ofR4 required to balance the bridge is 720 , because if the bridge is balance the difference of voltage drop across C and D is zero and if you can use a resistor of 720  the voltage difference will be zero.
Applications
Mainly used in measuring of very low value of unknown resistance having range of milli-ohms.
If using a varistor with Wheatstone bridge we can also identifies the value of some parameters like capacitance, inductance and impedance.

By using Wheatstone bridge with operational amplifier it helps in measuring different parameters like temperature, strain, light etc.

article/bionic-eye
Bionic Eye

We are living a life with full of colors and pictures we daily see, a life without sight is dark. 
And blind people are alive with the dark lives. 
It’s not like just helping a blind person to cross the road we have to do something more for them as a human being. 
As we belong to the community of engineers - nothing is impossible for us if we try. 

If scientists generate ideas then its engineers who put life in those ideas. 
Today we are having all the machines in our hand, it’s our turn to return what mankind gives us.
In this a video camera is integrated with a pair of glasses which will capture and process images. 
The images are wirelessly sent to small processor which converts it into electronic signal and these signal further transmitted to a retinal implant or electrode which send visual signal to brain for further processing. 

So by this even blind people also have vision.
The Human Eye
When a light ray reflected from an object an reaches to our eye then signals are sent to brain then brain decodes the signal in order to optimize the appearance, location and movements of the object we are seeing at. 
The whole process is performed due to light only, without light there is no world which means we are not able to see anything.

The main part of an eye is retina. 
The retina is an inside wall of eye which works as film of a camera to capture the light signals and transmit them to brain via optic nerves to create vision.
The Bionic Eye
which provide visual sensations to the brain. 

It consist of electronic systems having image sensors, microprocessors, receivers, radio transmitters and retinal chips. 
Technology provided by this help the blind people to get vision again.
It consist of a computer chip which is kept in the back of effected person eye and linked with a mini video camera built into glasses that they wear. 
Then an image captured by the camera are focused to the chip which converts it into electronic signal that brain can interpret. 

The images produced by Bionic eye were not be too much perfect but they could be clear enough to recognize. 
The implant bypasses the diseased cells in the retina and go through the remaining possible cells.
Working of Bionic Eye
The device consists of 3,500 micro photodiodes which are set at the back part of the retina. 

The electrical signal which is sent to brain is obtained from these miniature solar cells array as they converts the normal light to electrical signal.
and further transfer it to the receiver, it send signals through a very tiny cable to an electrode panel implanted by the doctors on the back wall of eye which is also called as retina. 
Electrode panel generate pulses which travel through the optic nerve to the brain, the optic nerve of a blind person is sometimes damaged then we use some devices which are capable of bypassing the signal from the possible ways, then only the signal is able to reach the brain. 
As the signal reaches the brain, brain start the decoding the signal and we are able to identify what the subject is, this process is too fast that we are able to see in similar to human eye.
Available Bionic Eye System
approved FDA in United States. 
Retinal Prosthesis is a biomedical implant used to partially restore the useful vision for those who have lost their sight due to this disease. 
According to a survey in every 5,000 people there is one suffered from that disease. 

It used to provide pulse signal to the brain by using the retinal implant for the blinded person. 
As it is having a mini video camera to get the data which is wirelessly transferred to a video processing unit which converts the data into electronic signal and then the signals transferred to electrodes which generate impulse to interpret with the brain and a blind person is able to see like an normal human, but the vision is not 100% perfect.
Future of Bionic Eyes
In the future we are able to increase higher numbers of electrodes that are capable of producing sharper, colored and more functional vision for people who are blind from retinitis pigmentosa and other retinal diseases, including macular degeneration.

Scientists are are testing devices with even more electrodes so that it can bypass the retina and move the signals to the brain directly. 
The next generation of Argus II retinal stimulator is going to design with 60 controllable electrodes which provide subjects beamed with higher resolution images.
How It Looks Like to See Through a Bionic Eye
Bionic eye provides a vision differ from the vision a human used to have. 

It does not restore full vision it’s not fully perfect or clear. 
A trial taken by the manufacturing company, about half of the blind person were able to read very large letters it’s about 9 inches high viewed from 1 foot away or about 23 centimeters high viewed from 0.3 meters away. 
A few blind person were able to read smaller letters it’s about 1-2 inches high viewed from 1 foot away or about 2.5-5 centimeters high viewed from 0.3 meters away and short words. 
After the test, it is found that the majority of blind person received a benefit from the Argus II System.
Limitations
At last, it’s all about the cost for Bionic Eye, for a pair of Eye it would cost something around $30,000which is not a favorable amount for the affected person.
Not every type of eye disease affected person will be treated by this like it will not be helpful for glaucoma patients, mainly it help the person affected from retinitis pigmentosa.
An artificial replacement for a human body is a risky task as it may cause death or some serious situations may occur.

As we know it’s not a human eye it’s a bionic eye so an affected one would not be able to get 100% of perfect vision.

article/what-is-hoverboard-how-does-it-work
What is a Hoverboard and How does it work?

They include Accelerometer, Gyroscope and Magnetometer; all three sensors have 3-axis each.
Measures Position in Linear 3 dimensions (Cartesian Coordinates) using variable capacitance. 
Here, we have capacitors for each dimension where one of the plates of capacitor is kept constant and other is allowed to vary its position (They are very sensitive to change in position). 
The change in distance between these plates will cause change in capacitance and thereby, voltage, giving us a quantifiable value we can monitor and use it where needed.

It’s the most important component, so much that the other name for this vehicle is ‘Gyro scooterᾮ Gyroscope basically measures Angular change by shift of mass within the gyro. 
A mechanical gyroscope consists of concentric metal rims with a rotor at the center while an electronic gyroscope, which is used for most applications including this one, is a little different. 
It uses Coriolis Effect: when a mass is moving in a particular direction with a particular velocity and when an external angular velocity is exerted whose axis is perpendicular to the motion, then a Coriolis force will occur which will be perpendicular to both, causing perpendicular displacement of the mass. 
This displacement will cause change in the Capacitance and thereby, Voltage giving us a quantifiable value corresponding to a particular angular rate.

Magnetometer: 
It measures magnetic field with respective to earth’s magnetic field by using Hall Effect principle. 
Although, we haven’t included this one in our list of components below to make your own Hoverboard.
Required Components to build Hoverboard:
If you are planning to build your own Hoverboard then the most important and minimum components required are:
Two Wheels,
Two Motors, Two IR Sensors,
Two Gyroscopes,

Two tilt/speed sensors,
A Logic Board,
A Battery pack,
A Power Switch,

A Plastic Shell and
A strong Frame with central Pivot (preferably steel),
Charging port (recommended, if not available, external charging will be needed every time)
How Hoverboard works?
They are generally placed below the frame where rider places the feet. 
Once the rider places the feet on the board, Gyroscope provides data to the logic board when the rider tilts ahead or backward. 
When the rider is not tilting, the IR sensor, which is positioned below the Foot placement, gives data to the logic board to not move and not run the motor. 
This how they sense the pressure on the foot pads and move these self-balancing scooters accordingly.

More tilt will give you more speed.
, left feet should be moved ahead for the tilt. 
In order to move in circles, tilt anyone leg ahead. 
It is not very productive but it is fun J

are very common sensors which uses Infrared rays in order to get the reflected data from the object to measure its presence and distance from the sensor which can be used for many applications.
measure the speed of the wheels in motion in rpm (Revolutions per minute) and send the data to gyroscope and logic board in order to control the speed.
as main component. 
It sends and receives data from all sensors, sends the processed data with its logic to the motors for the required movement which provides continuous adjustments, giving you a balancing and centered vehicle. 

It also manages the power from the batteries and also takes care that it doesn’t burn out.
are readily available and there are various choices available for this component but most commonly used battery for this application is a 36V 4400mAH battery. 
You can also make your own battery pack using the battery of an old Laptop (Although, it is not recommended as you’ll need to handle it with utmost care!)
Specifications of Hover Boards:
of weight and its price is in the range of USD200- USD300.
, Look for Good quality ones, the ones having‐󋈍
Better rim over the wheels because in order to stay still, pushing your feet against the rim will be helpful to keep them steady.
Better battery quality as there has been couple of cases where the battery exploded due to poor insulation, so check the safety standards of the battery thoroughly as they don’t have any protection for over-charging

Better software and logic program so that you can make the complete use of the sensors and have an accurate device for yourself. 
Specifically check if there are lagging issues because the whole process of data flow should be in sharp real-time in order to get the best result.
Wheels of proper size, as big wheels will need more torque and power to move them. 
Also, They shouldn’t be too small or they won’t be able to carry the weight resulting in poor speed and power management

Fog-lights can be added to light up your pathway, LEDs to show you certain data like Green for all-good data flow and Red if any sensor or board is not working properly and the board needs to be restarted, Suspensions can be added and also battery quality can be increased.
Trend of Hover Boards:
is now available in the market. 
Not as in demand as it once was, but it is there and popular among kids and teens. 

Ideal for the people (especially working class) who want to travel short distances and look cool while at it, Hover boards have re-emerged successfully and promises to stay as a commoner’s vehicle for a longer time.

article/what-is-lifi-how-it-works
Light Fidelity ᾠLi-Fi

(IoT), Industrial Automations, Smart Home systems etc.. 
the demand for internet is also growing exponentially. 
The technology has evolved so much that everything from our car to our refrigerator needs a connection to the internet. 
This raises other questions like; Will there be enough bandwidth for all these devices? Will these data be secure? Will the existing system be fast enough for all these data? Will there be too much conjunction on network traffic?

The term Li-Fi stands for “Light Fidelityᾮ This is believed to be the next generation of internet, where Light will be used as a medium to transport data. 
Yes you read it right; it is the same Light that you use in your homes and offices which, with some modifications can be used to transmit data to all your devices that requires internet.
Is it even possible? How does LiFiwork? Could it be expected in near future?... 
The answer to all these questions will be found in this article
What is the existing technology and why do we need a change?
Right from the origin of internet we have been using the RF medium to transmit the data from one end to another wirelessly. 
The RF medium uses Radio Waves, the data to be transmitted will be modulated into these waves and then demodulated on the receiver side. 
We started by transmitting few kilo bytes of data per second and have made sufficient advancements that now the average global internet speed is around 7.2 Mbps (Mega bytes per second), which sounds to be enough for most of us. 

But, this technology of using an RF medium for transferring data suffers from a lot of drawback like
There is too demand for the internet that could not met by the current method, which leads to the effect called Spectrum crunch.
There is demand for high bandwidth since a higher network speed it required.
RF medium is not safe to be used in Hospitals, Power Plants, Aeroplanes etc.. 

and these places will also need internet connectivity for the modern era.
Radio frequency is not safe, since you data can escape through walls and cannot be contained within a particular area.
lets understand how it works
Fun Fact: Did you know that, todays most used wireless internet (WiFi) was actually invented accidentally by Dr John O'Sullivan. 

He was actually trying to experiment with exploding mini black holes, but it lead to the invention of WiFi in 1991 which now contributes to 60% of global internet traffic.
How Li-Fi Works
As told earlier Li-Fi uses light to transmit data unlike Radio waves. 
This idea was first coined by Prof. 

Harald Haas in one of his TED talk in 2011. 
The definition for Li-Fi can be given as “LiFi is high speed bi-directional networked and mobile communication of data using light. 
LiFi comprises of multiple light bulbs that form a wireless network, offering a substantially similar user experience to Wi-Fi except using the light spectrumᾍ
So, yes wherever you have a light bulb you will have an internet connection but here, the term light bulb does not refer to ordinary incandescent lights in our house, these are specially modified LED lights which can transmit data. 

As we know LED is a semiconductor device and like all semiconductors it has switching properties. 
This switching property is used to transmit data. 
The below image explains how a data is transmitted using light.
Every LED lamp should be powered through an LED driver, this LED driver will get information from the Internet server and the data will be encoded in the driver. 

Based on this encoded data the LED lamp will flicker at a very high speed that cannot be noticed by the human eyes. 
But the Photo Detector on the other end will be able to read all the flickering and this data will be decoded after Amplification and Processing.
The data transmission here will be very fast than RF. 
As we all know light travels faster than air that is the light is ten thousand times faster than Radio waves since the frequency of Radio waves are just 300 Giga hertz but light can go up to 790 Tera hertz

Perhaps, the technology of transmitting data through light might seem new but we have been using it for a long time. 
Don’t trust me? Read further...
Every time we pressed a button on our Television remote the IR LED in the Remote pulses very fast this will be received by the Television and then decoded for the information. 
But, this old method is very slow and cannot be used to transmit any worthy data. 

Hence with LiFi this method is made sophisticated by using more than one LED and passing more than one data stream at a given time. 
This way more information can be passed and hence a faster data communication is possible.
Fun Fact: The global internet consumption is growing exponentially that the amount of data consumed in the 2016 is higher than the entire data consumed right from the birth of internet. 
It is also estimated that there will be 20 billion internet connected devices by the end of 2018, whereas the world population itself is just 7.6 billion
How far are we from enjoying Li-Fi?
which are ready to offer Li-Fi service for your Home or Office through their Li-Fi dongle which could just be plugged into your laptop USB and read data from any Li-Fi enabled light. 
So we are not far away from using our reading lamps not only to illuminate or desk but also to Provide internet connection.
Building your own Li-Fi
to transmit audio signal from one end to other.
and a speaker on the output side and you will be able to receive and play the transmitted audio signal.

article/how-to-use-a-digital-multimeter

Newbie Guide - How to Use a Digital Multimeter
is a very essential instrument for engineers who are interested in working with electronics. 
Perhaps this would be the first instrument that we get introduced to when starting to explore things related to electronics.
and how this will help us in our journey with electronics, this will be a very basic article which will take your through the different operations of a multimeter will illustrative pictures and videos. 

At the end of this article you will learn how to measure voltage with multimeter, measure DC current, check for continuity, measure resistance and also check if few components like LED and diodes are in working state. 
Pheww... 
sounds like a big list isn’t it! But trust me they will be very useful when you are trying out stuff on your own. 
Hence sit back and read through, while I will try making this article as intresting as possible.
How to Measure Voltage with Multimeter:
There are two different Voltages in general that can be measured by the Multimeter. 
One is DC voltage and the other being AC Voltage. 
All most all electronics devices work on DC voltage (Conventional AC will be converted to DC) and hence DC voltage is the most measured parameter.

Our Multimeter can measure both AC and DC voltages. 
Let us start with DC voltage.
How to MeasureDC Voltage with Multimeter:
This position will change only if we are measuring current.

So, to measure a voltage the black test lead should be in COM slot and red lead should be in V slot. 
Now we have to select the Mode by using the regulator like knob in the centre of the multimeter. 
We should look for the DC voltage symbol (shown in picture below) and select a range under it. 
By default the range will be like 200mV, 2V, 20V, 200V and 600V. 

Based on the voltage level that you are planning to measure you can select the range. 
And don’t worry it is not going to blow up if you select a lesser range you can always hit and try. 
For example if you are measuring 35V and if you place it at 20V range then you meter will read simply read 1, this means that you should select a high voltage range in this case 200V. 
In the below picture I have set the meter to read DC Voltage that is within 20V range.
How to MeasureAC Voltage with Multimeter:
While AC voltage is rarely measured using Digital Multimeter it is still important at places where AC mains are involved. 
To measure AC voltage place the Red lead at V slot and Black lead at COM slot as shown in the picture below. 
Now set the mode by using the knob, we have to place it at AC voltage symbol (shown in picture below). 

Normally we will have two ranges for AC voltages, they are 200V and 600V. 
For measuring AC voltage in India which is 220V we have to place it in 600V mode as shown in the picture below.
How to MeasureDC Current with Multimeter:
Do not try measuring AC current with your DC multimeter it might damage the meter permanently.

To measure DC current the black Probe should be placed in COM slot and the red probe should be placed in the A slot as shown in the picture below. 
This is done because current should always be measured in series. 
Also note that some meters might have two A slot based on the range so make sure to read the symbol before connecting. 
Then we can select the mode by turning the knob to the dc current symbol (shown in picture). 

Again we have ranges from 200 micro amps to 10A we can select the required range. 
In the below image the meter is set to read DC current at 2mA.So I am using the same V slot. 
But if the current is 10A then I should have changed the slot.
through a wire that is powering the LED.
How to CheckContinuity with Multimeter:
, place the Black probe on the COM slot and the Red probe on the V slot, then turn the knob to the continuity symbol (shown in picture below). 
To check continuity between terminals say terminal A and terminal B, place one probe (any probe) on terminal A and the other on Terminal B. 
If there is connection between terminal A and terminal B then the meter will read zero and you will also get a “beepᾠsound. 

If there is not connection you won’t get the beep sound.
How to MeasureResistance with Multimeter: 
One of the most use and unavoidable component in electronics are Resistors. 
There are a wide range of resistors available based on their power rating and resistance value, the value of each resistor will be mentioned with the help of colour codes. 

It is important to learn how to read a resistors value using colour code, but there might be certain cases it’s hard to read the colour. 
In those cases we can use a multimeter to read the resistance value of the resistor easily.
make sure the black probe is on the COM slot and the red probe in on the V slot. 
Now, turn the knob to the Resistance symbol. 

Again we have ranges from 200 to 2M, select the one that you desire, here in the below picture I am placing it on 20k value. 
You can always try different ranges to get the right range that suits for your resistor.
The value measured will not be accurate; this can just be used as an approximation. 
Also if the resistor is placed inside a circuit then we should not measure the resistance using multimeter, since it will show wrong values.
How to CheckComponents using Diode Mode:
Another interesting mode in the multimeter is the Diode mode. 
Ever wondered if the LED/Diode in your circuit is in working condition, or what color your LED might glow when powered! Think no more get your multimeter place it in diode mode and check it in no time. 
You check the polarity of your LED and even make it glow to check for its working.

To use the diode mode, make sure your black probe is in the COM slot and the red probe is in the V slot. 
Now, adjust the regulator knob to the diode symbol as shown in the picture below. 
The diode mode and the 2K mode resistance mode use the same place so don’t worry about it. 
Now place the Red probe on the Anode and the Black probe on the cathode of the LED and it should make the LED glow. 

This works because LED is also a form of diode, if you reverse the polarity the LED will not glow the same can be used to check the working of a diode.
condition. 
Again this technique is not advisable to be used when the components are in a circuit, because the existing connections might cause a bad/wrong result.


article/relay-working-types-operation-applications
Basic Working Principle of Relay - Construction and Types 
and take a deeper look intoits construction
What is Relay?
fits only for the electromechanical relay.
Construction of Relay and its operation:
The following figure shows how a Relay looks internally and how it can be constructed,
the normally closed pin is connected to the armature or the common terminal whereas the normally opened pin is left free (when the coil is not energized). 

When the coil is energized the armature moves and is get connected to the normally opened contact till there exists flow of current through the coil. 
When it is de-energized it goes to its initial position.
is as shown in the figure below
What is inside a Relay - Teardown
below. 
All these are arranged logically to form into a relay.

:

It is a metal which doesn’t have magnetic property but it can be converted into a magnet with the help of an electrical signal. 
We know that when current passes through the conductor it acquires the properties of a magnet. 
So, when a metal winded with a copper wire and driven by the sufficient power supply, that metal can act as a magnet and can attract the metals within its range.
A movable armature is a simple metal piece which is balanced on a pivot or a stand. 

It helps in making or breaking the connection with the contacts connected to it.
These are the conductors that exist within the device and are connected to the terminals.
It is a small metal piece fixed on a core in order to attract and hold the armature when the coil is energized.
Few relays don’t need any spring but if it is used, it is connected to one end of the armature to ensure its easy and free movement. 

Instead of a spring, a metal stand like structure can be used.
Relay Working Principle
Now let'sunderstand how a relay works in a normally closed condition and normally open condition.
When no voltage is applied to the core, it cannot generate any magnetic field and itdoesn’t act as a magnet. 

Therefore, it cannot attract the movable armature. 
Thus, the initial position itself is the armature connected in normally closed position (NC).
When sufficient voltage is applied to the core it starts to create a magnetic field around it and acts as a magnet. 
Since the movable armature is placed within its range, it gets attracted to that magnetic field created by the core, thus the position of the armature is being altered. 

It is now connected to the normally opened pin of the relay and external circuit connected to it function in a different manner.
The functionality of the external circuit depends upon the connection made to the relay pins.
So finally, we can say that when a coil is energized the armature is attracted and the switching action can be seen, if the coil is de-energized it loses its magnetic property and the armature goes back to its initial position.
in below given animation:
Different Types of Relay:
that work on different principles. 
Its classification is as follows
When two different materials are joined together it forms into a bimetallic strip. 

When this strip is energized it tends to bend, this property is used in such a way that the bending nature makes a connection with the contacts.
With the help of few mechanical parts and based on the property of an electromagnet a connection is made with the contacts.
Instead of using mechanical parts as in electrothermal and electromechanical relays, it uses semiconductor devices. 
So, the switching speed of the device can be made easier and faster. 

The main advantages of this relay are its more life span and faster switching operation compared to other relays.
It is the combination of both electromechanical and solid-state relays.
These are similar to the electromechanical relays but there exists both permanent magnet and electromagnet in it, the movement of the armature depends on the polarity of the input signal applied to the coil. 
Used in telegraphy applications.

The coil in these relays doesn’t have any polarities and its operation remains unchanged even if the polarity of the input signal is altered.
Pole and Throw combinations:
can be considered as an output terminal. 
Its classification is as follows

It consists of only one pole and one throw. 
Generally, the path is either closed or opened (remains untouched to any terminal). 
A push button is the best example of this type. 
When we push the button, the contact is in the closed position and when released the contact is in the open position, which can be understood from the below image.

This type of switches consists of only one pole but has two throws. 
So, the contact is always made to either of the terminals. 
A slide switch can be considered as its example. 
The slider is always connected to either of the contacts i.e., a closed path always exists all the time if both the terminals are connected to a circuit.

It has two poles and a throw. 
The contacts of it are either opened or closed which is done simultaneously. 
Toggle switch works on this property. 
When the switch is toggled from one position to another, both the contacts are moved simultaneously.

This type of switches has two poles but the individual pole has two throws. 
So, it is named as double throw and the switching action is done similarly and simultaneously for both the poles. 
A switch on a standard trimmer is of DPDT because while we are charging the trimmer and when the switch on the trimmer is in the ON state, it automatically stops charging means the switches are internally opened in the charging circuit.
Applications of Relay:
are limitless, its main function is to control the high voltage circuit (230V circuit AC) with the low voltage power supply (a DC voltage).
Relays are not only used in the large electrical circuits but also used in computer circuits in order to perform the arithmetic and mathematical operations in it.
Used to control the electric motor switches. 
To turn ON an electric motor we need 230V AC supply but in few cases/applications, there may be a situation to switch ON the motor with a DC supply voltage. 

In those cases, a relay can be used.
Automatic stabilizers are one of its applications where a relay is used. 
When the supply voltage is other than the rated voltage, set of relays sense the voltage variations and controls the load circuit with the help of circuit breakers.
Used for the circuit selection if there exists more than one circuit in a system.

Used in Televisions. 
An old picture tube television’s internal circuitry works with the DC voltage but the picture tube needs a very high AC voltage, in order to turn on the picture tube with a DC supply we can use a relay.
Used in the traffic signal controllers, temperature controllers.


article/lifi-vs-wifi
LiFi vs WiFi
Just like the invention of wheel for automobiles the invention of wireless internet has revolutionized internet since then. 
Today every average household has a minimum of 5 devices that gets connected to internet and it is estimated that by 2020 we will have 50 billion devices connected to the internet sending and receiving information wirelessly. 

Today, be it a highly complex workstation or an ordinary smart LED lamp we use the technology called WiFi to connect it to the internet.
What is this new term Li-Fi and how does it differ from a Wi-Fi? Can we expect Li-Fi to replace Wi-Fi in near future? Let’s find answers to all these questions in this article.
Michael Yardney a strategists says that there will be 3,810 new devices that gets connected to internet every couple of minutes (approx). 
With this rate we are sure to attain 50 billion devices by 2020
What is Wi-Fi and Li-Fi?
both are different technologies that are used to send and receive data wirelessly. 
With Wi-Fi we use Routers and Radio Frequency (RF) waves to transmit data whereas with Li-Fi we use LED bulbs (yes the one we use to light our house/office) and Light signals to transmit and receive data.



The term Wi-Fi stands for “wireless fidelityᾍ
The term Li-Fi stands for “Light fidelityᾍ
Invented on 1991 by NCR corporation
Coined by Prof. 
Harald Haas in one of his TED talk in 2011

Utilizes modems and RF signal for wireless data communication
Utilizes LED bulbs and light signal for wireless data communication
Ranges from 150Mbps to maximum of 2Gbps
About 1 Gbps (that’s a lot of fun)
Varies based on power of antenna, an average of about 32 meters
About 10 Meters only
LED bulb, LED driver and photo detector
Routers, Modems and access points

Can easily pass through Walls hence has higher range
Covers more distance
Most of the existing hardware supports Wi-Fi
Does not use RF, hence no interface issues
Extremely faster than Wi-Fi

Data theft can be minimised
Since RF is not used can be used under sea, hospitals power plants etc
Will have interference issues with neighbouring routers and other wireless access points
Slower than Li-Fi

Since signal is not confined data can be easily stolen
Affected by Sunlight, cannot be used in bright day light
Covers less distance than Wi-Fi
Can used only when user is present under the coverage of light



Both Wi-Fi and Li-Fi has its own advantages and limitations, although Li-Fi seems to be temptingly faster many people believe that Li-Fi will just remain as an alternative to Wi-Fi and might not replace it completely

A bit more about Wi-Fi:
Li-Fi might knock our doors sooner or later but let’s understand how Wi-Fi works so that we would be able to feel how this change would be.
When the web of internet started spreading all over the world they were all wired connections. 
Believe me or not, we still use underwater cables to cover 99% of the world since they are more reliable. 
But later the evolution of mobile phones and PD’s brought in the need of wireless internet. 

So at the delivering end of our internet we used Wi-Fi as shown in the picture below
As you can see every Wi-Fi signal needs a Wi-Fi router to send and receive a data packet. 
These routers are again connected by wires to the Internet providers through a modem. 
Wi-Fi works with the help of Radio waves and so for every device that gets connected to internet we need to provide an additional piece of hardware that could send and receive RF signals.

When Wi-Fi was first invented it was mainly indented to use for cashier systems and they named in WaveLAN only years later it was given its iconic name Wi-Fi.
A bit more about Li-Fi:
Li-Fi uses light to transmit data unlike Radio waves. 
This idea was first coined by Prof. 

Harald Haas in one of his TED talk in 2011. 
The definition for Li-Fi can be given as “LiFi is high speed bi-directional networked and mobile communication of data using light. 
LiFi comprises of multiple light bulbs that form a wireless network, offering a substantially similar user experience to Wi-Fi except using the light spectrumᾍ
So, yes wherever you have a light bulb you will have an internet connection but here, the term light bulb does not refer to ordinary incandescent lights in our house, these are specially modified LED lights which can transmit data. 

As we know LED is a semiconductor device and like all semiconductors it has switching properties. 
This switching property is used to transmit data. 
The below image explains how a data is transmitted using light.
Every LED lamp should be powered through an LED driver, this LED driver will get information from the Internet server and the data will be encoded in the driver. 

Based on this encoded data the LED lamp will flicker at a very high speed that cannot be noticed by the human eyes. 
But the Photo Detector on the other end will be able to read all the flickering and this data will be decoded after Amplification and Processing.

article/ssd1306-oled-display

OLED Display, its Types and Working
it uses the same technology that is used in most of our televisions but has fewer pixels compared to them. 
It is real fun to have these cool looking display modules to be interfaced with the Microcontrollers since it will make our projects look cool.
There are a lot of OLED display modules available in the market, each with its own classification. 

So before you buy one make sure which one would suit your project much better. 
The most commonly used types are classified below
is the fastest mode of communication and the default one.
Pinouts and Function:
As said earlier the module we are using will have 7-pins, the picture of the same is shown below.
There are lots of vendor for these modules and hence your board might look slightly different than mine. 
Also the naming might also be differed. 
The pins and its functions are explained in the table below.



Gnd
Ground
Ground pin of the module
Vdd
Vcc, 5V
Power pin (3-5V tolerable)

SCK
D0,SCL,CLK
Acts as the clock pin. 
Used for both I2C and SPI
SDA
D1,MOSI
Data pin of the module. 
Used for both IIC and SPI

RES
RST,RESET
Resets the module (useful during SPI)
DC
A0
Data Command pin. 
Used for SPI protocol
CS
Chip Select
Useful when more than one module is used under SPI protocol


The above shown module can operate in all three modes. 
When you purchase one, your module will be set to work in 4-Wire SPI mode by default. 
You can change it to work in I2C or 3-Wire SPI by changing the position of the Resistors as shown in the Bottom Layer silkscreen of the board.
Working of an OLED display:
present in the OLED module. 
This SSD1306IC will then update each pixel present on our OLED display.
:


article/pnp-transistor
PNP Transistors
ᾠ2N3906 and PN2907A, shown in the images above.

Based on the fabrication process the pin configuration may change and these details are available in corresponding datasheet of the transistor. 
Mostly all PNP transistors are of above pin configuration. 
As the power rating of the transistor increases necessary heat sink need to be attached to the body of transistor. 
An unbiased transistor or a transistor without potential applied at the terminals is similar to two diodes connected back-to-back as shown in figure below. 

The most important application of PNP transistor is high side switching and Class B combined amplifier.
The diode D1 has a reverse conducting property based on the forward conduction of diode D2. 
When a current flows through the diode D2 from emitter to base, the diode D1 senses the current and a proportional current will be allowed to flow in the reverse direction from emitter terminal to collector terminal provided ground potential is applied at the collector terminal. 
The proportional constant is the Gain (β).
Working of PNP Transistors:
As discussed above, the transistor is a current controlled device which has two depletion layers with specific barrier potential required to diffuse the depletion layer. 
The barrier potential for a silicon transistor is 0.7V at 25°C and 0.3V at 25°C for a germanium transistor. 
Mostly the common type of transistor used is silicon because it is the most abundant element on the earth after oxygen.

Internal operation:
The construction of pnp transistor is that the collector and emitter regions are doped with p-type material and the base region is doped with small layer of n-type material. 
The emitter region is heavily doped when compared with collector region. 
These three regions form two junctions. 

They are collector-base junction(CB) and base-emitter junction.
When a negative potential VBE is applied across Base-Emitter junction decreasing from 0V, the electrons and holes start to accumulate at the depletion region. 
When the potential further decreases below 0.7V, the barrier voltage is reached and the diffusion occurs. 
Hence, the electrons flow towards the positive terminal and the base current flows (IB) is opposite to the electron flow. 

Besides, the current from emitter to collector starts to flow, provided the voltage VCE is applied at collector terminal. 
The PNP transistor can act as a switch and an amplifier.
Operating region versus Mode of operation:
1. Active region, IC=β×IBᾠAmplifier operation

2. Saturation region, IC= Saturation current ᾠSwitch operation (Completely ON)

3. Cut-off region,IC= 0 ᾠSwitch operation (Completely OFF)
Transistor as switch :
has been selected. 
The first important thing to bear in mind to use a current limiting resistor at base. 
Higher base currents will damage a BJT. 
From the datasheet the maximum continuous collector current is -600mA and corresponding gain(hFE or β) is given in datasheet as test condition. 

The corresponding saturation voltages and base currents are also available.
1. Find the collector current wiz the current consumed by your load. 
In this case it will be 200mA (Parallel LEDs or loads) and resistor = 60 Ohms.
2. In order to drive the transistor into saturation condition sufficient base current has to be drawn out such that the transistor is completely ON. 

Calculating the base current and the corresponding resistor to be used.




For complete saturation the base current is approximated to 2.5mA (Not too high or too low). 

Thus below is the circuit with 12V to base same as that to emitter with respect to ground during which the switch is OFF state.
Theoretically the switch is completely open but practically a leakage current flow can be observed. 
This current is negligible since they are in pA or nA.For better understanding on current control, a transistor can be considered as a variable resistor across collector(C) and emitter(E) whose resistance varies based on the current through the base(B).
Initially when no current is flowing through base, the resistance across CE is very high that no current flows through it. 

When an potential difference of 0.7V & above appears at base terminal the BE junction diffuses and causes the CB junction to diffuse. 
Now current flows from emitter to collector proportionately to that of current flow from emitter to base, also the gain.
Now let us see how to control the output current by controlling the base current. 
Fix IC= 100mA in spite of load being 200mA, the corresponding gain from datasheet is somewhere between 100 & 300 and following the same formula above we get






The variation of practical value from calculated value is because of the voltage drop across transistor and the resistive load that is used. 
Also, we have used a standard resistor value of 13kOhm instead of 12.5kOhm at base terminal.
Transistor as amplifier:
Amplification is the converting a weak signal into usable form. 
The process of amplification has been an important step in many applications like wireless transmitted signals, wireless received signals, Mp3 players, mobile phones, and etc., The transistor can amplify power, voltage and current at different configurations.
Some of the configurations used in transistor amplifier circuits are
1. Common emitter amplifier

2. Common collector amplifier
3. Common base amplifier
Of the above types common emitter type is the popular and mostly used configuration. 
The operation occurs in active region, Single stage common emitter amplifier circuit is an example for it. 

A stable DC bias point and a stable AC gain are important in designing an amplifier. 
The name single stage amplifier when only one transistor is being used.
Above is single stage amplifier where a weak signal applied at base terminal is converted into β times the actual signal at collector terminal.
Part purpose:

CIN is the coupling capacitor which couples the input signal to the base of the transistor. 
Thus this capacitor isolates the source from transistor and allows only ac signal to pass through. 
CE is the bypass capacitor which acts as the low resistance path for amplified signal. 
COUT is the coupling capacitor which couples the output signal from the collector of the transistor. 

Thus this capacitor isolates the output from transistor and allows only ac signal to pass through. 
R2 and RE provides the stability to amplifier whereas the R1 and R2 together ensures the stability in DC bias point by acting as a potential divider.
In case of PNP transistor, the word common indicates the negative supply. 
Hence, emitter will be negative when compared with collector. 

The circuit operates instantaneously for each time interval. 
Simply to understand, when the ac voltage at base terminal increases the corresponding increase in current flows through the emitter resistor.
Thus, this increase in emitter current increases the higher collector current to flow through the transistor which decreases the VCE collector emitter drop. 
Similarly when the input ac voltage reduces exponentially the VCEvoltage starts to increase due to the decrease in emitter current. 

All these change in voltages reflect instantaneously at the output which will be inverted waveform of the input, but amplified one.


Voltage gain
High
Medium
Low

Current gain
Low
Medium
High
Power gain
Low
Very High
Medium

Based on the above table, the corresponding configuration can be utilized.


article/npn-transistors
NPN Transistors
- BC547A and PN2222A, shown in the images above.

as shown in figure below.
The diode D1 has a reverse conducting property based on the forward conduction of diode D2. 
When a current flows through the diode D2, the diode D1 senses the current and a proportional current will be allowed to flow in the reverse direction from collector terminal to emitter terminal provided a higher potential is applied at the collector terminal. 
The proportional constant is the Gain (β).
Working of NPN Transistors:
As discussed above, the transistor is a current controlled device which has two depletion layers with specific barrier potential required to diffuse the depletion layer. 
The barrier potential for a silicon transistor is 0.7V at 25°C and 0.3V at 25°C for a germanium transistor. 
Mostly the common type of transistor used are silicon type because silicon is the most abundant element on the earth after oxygen.

is that the collector and emitter regions are doped with n-type material and the base region is doped with small layer of p-type material. 
The emitter region is heavily doped when compared with collector region. 
These three regions form two junctions. 
They are collector-base junction(CB) and base-emitter junction.

When a potential VBE is applied across Base-Emitter junction increasing from 0V, the electrons and holes start to accumulate at the depletion region. 
When the potential increases above 0.7V, the barrier voltage is reached and the diffusion occurs. 
Hence, the electrons flow towards the positive terminal and the base current flows (IB) is opposite to the electron flow. 
Besides, the current from collector to emitter starts to flow, provided the voltage VCE is applied at collector terminal. 

The transistor can act as a switch and an amplifier.
1.Active region, IC = β×IB ᾠAmplifier operation
2. Saturation region, IC = Saturation current ᾠSwitch operation (Completely ON)
3. Cut-off region, IC = 0 ᾠSwitch operation (Completely OFF)
Transistor as switch :
To explain with a PSPICE model BC547A has been selected. 
The first important thing to bear in mind to use a current limiting resistor at base. 
Higher base currents will damage a BJT. 

From the datasheet the maximum collector current is 100mA and corresponding gain(hFE or β) is given.
Steps to select components,
1. Find the collector current wiz the current consumed by your load. 
In this case it will be 60mA (Relay coil or Parallel LEDs) and resistor = 200 Ohms.

2. In order to drive the transistor into saturation condition sufficient base current has to be supplied such that the transistor is completely ON. 
Calculating the base current and the corresponding resistor to be used.
For complete saturation the base current is approximated to 0.6mA (Not too high or too low). 
Thus below is the circuit with 0V to base during which the switch is OFF state.

a)PSPICESimulation of BJT as Switch, and b) equivalentSwitch Condition
Theoretically the switch is completely open but practically a leakage current flow can be observed. 
This current is negligible since they are in pA or nA. 
For better understanding on current control, a transistor can be considered as a variable resistor across collector(C) and emitter(E) whose resistance varies based on the current through the base(B).

Initially when no current is flowing through base, the resistance across CE is very high that no current flows through it. 
When an potential of 0.7V & above is applied at base terminal the BE junction diffuses and causes the CB junction to diffuse. 
Now current flows from collector to emitter based on the gain.
a)PSPICESimulation of BJT as Switch, and b) equivalentSwitch Condition

Now let us see how to control the output current by controlling the base current. 
Considering IC = 42mA and following the same formula above we get IB = 0.35mA ; RB = 14.28kOhms ⇠15kOhms.
a)PSPICESimulation of BJT as Switch, and b) equivalentSwitch Condition
The variation of practical value from calculated value is because of the voltage drop across transistor and the resistive load that is used.
Transistor as amplifier :
Amplification is the converting a weak signal into usable form. 
The process of amplification has been an important step in many applications like wireless transmitted signals, wireless received signals, Mp3 players, mobile phones, and etc., The transistor can amplify power, voltage and current at different configurations.
Some of the configurations used in amplifier circuits are

Common emitter amplifier
Common collector amplifier
Common base amplifier
Of the above types common emitter type is the popular and mostly used configuration. 

The operation occurs in active region, Single stage common emitter amplifier circuit is an example for it. 
A stable DC bias point and a stable AC gain are important in designing an amplifier. 
The name single stage amplifier when only one transistor is being used.
where a weak signal applied at base terminal is converted into β times the actual signal at collector terminal.
Part purpose:
CIN is the coupling capacitor which couples the input signal to the base of the transistor. 
Thus this capacitor isolates the source from transistor and allows only ac signal to pass through. 
CE is the bypass capacitor which acts as the low resistance path for amplified signal. 

COUT is the coupling capacitor which couples the output signal from the collector of the transistor. 
Thus this capacitor isolates the output from transistor and allows only ac signal to pass through. 
R2 and RE provides the stability to amplifier whereas the R1 and R2 together ensures the stability in DC bias point by acting as a potential divider.
The circuit operates instantaneously for each time interval. 

Simply to understand, when the ac voltage at base terminal increases the corresponding increase in current flows through the emitter resistor. 
Thus, this increase in emitter current increases the higher collector current to flow through the transistor which decreases the VCE collector emitter drop. 
Similarly when the input ac voltage reduces exponentially the VCE voltage starts to increase due to the decrease in emitter current. 
All these change in voltages reflect instantaneously at the output which will be inverted waveform of the input, but amplified one.


Characteristics
Common Base
Common Emitter
Common Collector
Voltage gain
High
Medium
Low
Current gain
Low
Medium
High

Power gain
Low
Very High
Medium

Based on the above table, the corresponding configuration can be utilized.


article/beginners-guide-for-getting-started-with-3d-printing
A Beginners Guide for Getting Started with 3D Printing
, how one could get benefited from it and how it is going to change things in future.
So!! What is 3D printing and how does it work?
3D printing or additive manufacturing is a process of making three dimensional solid objects from a digital file. 
It uses a printer like machine which melts a material (commonly plastic) and pours it on a base in a predefined manner thus creating successive layers to make it 3 dimensional. 
To put it simple the printer builds a loaf of bread slice by slice.
because it is more affordable compared to others.

A 3D file is checked by software to see if it is printable.
The software then slices the file and sends it to a machine.
A plastic filament is fed through the printing head.
The filament melts and the head then deposits it on a build platform.

The head moves around depositing the material so that it makes up the bottom slice of the object.
The head returns to its starting position and the build platform is lowered.
The head then builds the new layer on top of the first and this is repeated until the object is done.
Is 3D printing new to the market?
was coined, it was basically used for Rapid prototyping. 
But later around 2014 with the rise of low-cost 3D printers, the technology has turned into a disruptive movement for hobbyists, learners, technopreneurs, inventors, teachers, research peoples and whom not. 
Thus it is getting a wide market and great scope for future.
3D printers where originally made to help astronauts. 

It was hard for the team to pack up every tools and materials that they would need in the space to work on their project. 
Having surplus tools will increase the weight of the shuttle which eventually increases fuel consumption. 
So they came up with this idea where the 3D printer will be sent to space along with the astronauts, when they need any tools or materials to work with, they simply have to click through the STL file and print it. 
If any emergency and new design is to be made, the design will be made in base station and sent to the crew to print it. 

But as technology advanced things changed, now it is affordable for every home to have a printer.
How can one get started with 3D printers?
, for any print to take place the following are the four simple steps to be followed:
1. 3D CAD modelling

2. Slicing and other settings.
3. Layer - wise printing
4. Complete part
Yes, in order to print something with your printer you have to design them modelling software.

you can use any of your modelling software that has the ability to save a file in .STL(Stereolithography) or .OBJ(object). 
Once the design is created is can be taken to the slicing stage. 
Here you are free to alter, edit or tweak your desing the way you like since the complete design is made by you.
then there are tons of free open source software available which can be used the design in your mind. 

It would just be like placing building block. 
If your design is too good you will also paid by some online communities.
, and has no idea how to design a 3D model Worry not!.. 
There are lots of websites which provide free STL files. 

These files are tested and printed by persons who designed it hence it is reliable and will be easy to print. 
The only limitation to these files is that they come in .STL formats (Mostly). 
This format cannot be customized the way we like but even then it can be resized with the help of slicing software. 
If you are an absolute beginner then we would recommend you by starting with some designs available in the market.

Once the design is made the work of 3D modelling software is over. 
The files are now sent to Slicing software where it gets ready for the printer to print it.
The models that are designed have to be converted into a series of code called the G-Code for the printer to recognize it and start printing. 
This part is called Slicing. 

The quality of the print depends on the settings that are made here. 
Before we jump into this lets us get familiar of how simple a 3D printer really is!!!!
3D printing is not magic!
s, trust me it is not a rocket science. 

There are lot of students who have tried building a 3D printer for themselves successfully.In the next few paragraphs I will explain the parts of a basic 3D printer that will help you understand the Printers much better.
The typical parts of a 3D printer are shown in the picture below.
There many types of filament and a lot more come into the market every month. 
Each filament has its diameter and printing temperature, the most used one PLA which has temperature of 180-210 deg C.

this software was mainly created for the printer called Ultimaker. 
But since it was made free and open source most of the printers out there have started using Cura.
In this software the print settings are sent just like we do for our laser printer. 
Here we can Scale, align, and orient our print model. 

Other crucial settings like the temperature, retraction speed, flow of the filament nozzle diameter etc are fed to the printer using this Software.
Based on the settings the Print time and material length required for the print will be displayed by the software itself, as shown in the picture below. 
Here the print time is 1 hour 14 minutes and the material used will 10 gram. 
The other settings for this print can also be found in the picture

Once the STL file is loaded and settings are done, this software can be used to visualize how our print will be made using the layers option, as shown in the picture below. 
This how or print will look like when it printing the 78th layer of this print. 
The blue color line indicates the path of our extruder. 


Once this is done the file can be converted into a G-Code which can be fed to the printer for printing. 
That is it, you model will be printed in the time mentioned.
Was it that hard?
What is the future for 3D printing?
3D printing however does have its own set of challenges. 
It suffers from slow operating speed, mechanical defects in products and limited material choices (mostly Plastic). 
Due to slow operating speed of 3D printers, manufacturing companies might lose out to competitions with inefficient go to market strategy. 
But hopefully this field is evolving as you are reading this article, and has a great scope ahead. 

It all depends on how one decides to use this technology.

article/design-electronic-circuits-online-with-easyeda
Design Your Circuits Online for Free with EasyEDA

for the same. 
It’s basically a tool that is used to design projects. 
As told its online software, so one need not to download any application for this, you can simple Sign Up or Login to the website and play along, as you please. 
As its online tool, that makes its platform independent and can be run on any OS (Windows/Linux/Mac) and Browser (Internet Explorer/ Firefox/ Chrome/ Safari).

As no software is being downloaded, no need to be afraid of malware and virus. 
Once a project is designed, we need not to worry about misplacing it because it will be stored at EasyEDA website. 
So we can access the file anytime. 
With many features being added day by day, the EasyEDA website can be depicted as a promising tool for Electronic Hobbyist and Engineers.
Getting Started with EasyEDA:
The website is shown in the figure.
Then hit on LOGIN button to create an account. 
You can create a new Account on EasyEDA or you can Login with your Google or QQ account. 

Here we are Login with Google Account:
Login with your Gmail details (assuming you already have a Gmail account), and you will see your name on upper right corner.
Drawing the Schematic using EasyEDA:
Once you enter the drawing board pick up all the components that are needed from the libraries. 

If you cannot find the component, click on MORE LIBRARIES option and then search for your component, as shown below.
Pick all the components from the left panel and draw the schematic as shown in below figure. 
Click on the desired component to select and again click on the canvas to Drop that component. 
Right click or Esc button to exit after placing component. 

Wiring can be simply done by dragging the wire between end points of components, like we do in most of the Circuit drawing softwares like Proteus. 
Also to change the properties or attributes of any components, just click on that component, and change the attributes from the Right side panel.
After the drawing is completed, Save the schematic under your project name so that you can do the simulation.
Simulating the Circuit in EasyEDA:
After saving the circuit, click on “Green Buttonᾠon top of screen for Simulation and choose “Run the documentᾮ
After that you have to configure the simulation you want to run. 
As shown in below figure, you have five type of simulation.
For now we will stick with transient, as told before we are designing inverter circuit here, the AC output provided by the inverter is to drive home appliances. 

For that to happen, the inverter circuit should be operated at 50Hz frequency as it is the AC line frequency. 
We will choose the appropriate START and STOP TIME for the simulation graph to be understandable.
Once the simulation completes you can see the graph at the chosen terminal. 
The terminal should be chosen by bringing the probe to that point. 

You can select the probe as shown below; drag it to the point where you want to see the graph.
as shown below. 
These waveforms can be saved and exported in different formats like JPG, PDF, PNG etc.
,
PCB layout conversion using EasyEDA:
After we go to schematic board, click on the “PROJECT TO PCBᾠoption as shown in below figure. 
Once you click on that you will enter to PCB design board. 
In case if there are any components on the schematic which don’t have PCB traces, you will be asked to choose the most appropriate one to proceed. 

Choose the appropriate one based on your view and submit it.
After entering the PCB design, all the components will be distributed around the PCB model board as shown below.
Arrange all the components in the orderly fashion as we arrange the books in a shelf. 
Once everything is arranged you should be having input at one end and output on the other, as shown below.

Now trace the light blue lines on the board without intercepting one another, you can do as many loops as you want. 
These traces must not be too close to one another.
Once the tracing is completed you will have something as below,
After that choose PRINT in the FILE menu, to get the PCB board trace. 

Print the appropriate layer by selecting the option, since we are using a single layer, we can leave the configuration as it is.
Once you print it you will have a document as,
You can print the picture on to glossy paper for PCB etching or you can give the module to PCB manufacturers for mass production.


article/arduino-vs-raspberryp-pi-difference-between-the-two
Arduino vs Raspberry Pi: Differences between the two
version is also available for Pi. 
Like a computer, It has memory, processor, USB ports, audio output, graphic driver for HDMI output and as it runs on Linux, most of the linux software applications can be installed on it. 

It has several models and revisions like Raspberry Pi, Raspberry Pi 2, Raspberry Pi Model B+ etc.
, Arduino PRO, Arduino MEGA, Arduino DUE etc.
Although they are quite different but there are some similarities in terms of their inception. 
They both are inve-nted in European countries, like Raspberry Pi is developed by Eben Upton in UK and Arduino is developed by Massimo Banzi in Italy. 

Both the inventors are teachers and they develop these hardware platforms as a design learning tool for their students. 
Raspberry pi was first introduced in year 2012 while Arduino in 2005.
, we adopted an approach where we will discuss the merits and demerits of both the hardwares over each other. 
So first we are starting with:
Advantages of Arduino over Raspberry Pi:
and other electronic components with Arduino, with just few lines of code. 
While in Raspberry pi, there is much overhead for simply reading those sensors, we need to install some libraries and softwares for interfacing these sensors and components. 
And the coding in Arduino is simpler, while one needs to have knowledge of Linux and its commands for using the Raspberry pi.

which can be turned ON and OFF at any point of time, without any risk of damage. 
It can start running the code again on resuming the power.
can easily be powered using a battery pack.
than Raspberry Pi, Arduino costs around $10-20 depending on the version, while price of Raspberry is around $35-40.
Advantages of Raspberry Pi over Arduino:
One can think that Arduino is the best, after reading its merits over Raspberry Pi, but wait, it’s completely depends on your project that which platform should be used. 
Raspberry Pi’s power and its easiness is the main attraction of it, over Arduino. 
Below we will discuss some of its advantages over Arduino:

at a time like a computer. 
If anyone wants to build a complex project like an advanced robot or the project where things need to be controlled from a web page over internet then Pi is the best choice. 
Pi can be converted into a webserver, VPN server, print server, database server etc. 
Arduino is good if you just want to blink a LED but if you have hundreds of LEDs needs to be controlled over web page, then Pi is the best suited.

ᾠneeds to be plugged in, to make Arduino, as functional as Pi, with a proper coding to handle them.
For Arduino you definitively need a electronic background, and need to know about embedded programming languages. 
But to start with Pi you don’t need to dive into the coding languages and a small knowledge of electronics and its components is enough.
on the single Raspberry Pi board. 

Pi uses SD card as flash memory to install the OS, so just by swapping the memory card you can switch the operating system easily.
Example:
We can understand the need of Arduino or Pi through example. 
Like if you want answer any phone call automatically with a prerecorded message, then Arduino is the way. 

But at the same time if you want to block the robocallers or spam callers then? Then Raspberry Pi comes into picture, which can either filter the spam calls using spam callers database over the internet or it can also put a captcha type of verification for human callers.
, where machines will directly interact and control another machines, without human intervention.
Conclusion:
Some people say that Arduino is best for beginners but I am not agree with it, a beginner can start with any one of them. 

Choice is just depend on your project and your background. 
I am concluding it with, how to make choice between these two, for your next project:
if:
You are from electronics background or if you are a beginner and really want to learn about electronics and its components.

Your project is simple, especially networking is not involved.
Your project is more like a electronics project where software applications are not involved, like Burglar alarm, voice controlled light.
You are not a computer geek who is not much interested in softwares and Linux.
If:

Your project is complex and networking is involved.
Your project is more like a software application, like a VPN server or Webserver
Don’t have good knowledge of electronics.
Have good knowledge about Linux and softwares.

Although they both have their own pros and cons, but they can also be used together to make the best out of them. 
Like Pi can collect the data over the network and take decisions, and command the Arduino to take the proper action like rotate a motor.

ten-examples-of-internet-of-things-iot

10 Real Life Examples of Internet of Things
ᾠis the latest ongoing talk of innovation in the world.
you must know about:
Smart thermostats:
Nest thermostat not only controlled from anywhere but also it learns by itself by following your daily routing and change the temperature of your home without bothering you, Like if you have set low temperature at night continuously for 7 days, then this device learns that and automatically lowers the temperature at night. 
This is very helpful device for saving the energy.
Mimo Monitor:
are not only affordable but also presents a new technology. 

Used for several business purposes, this loT has been making things easier, simpler and is said to be very productive. 
But now Mimo Monitors offers something unique and unexpected. 
The technology now enables you get updated to your baby’s body position, their breathing level, body temperature, response to activities and health. 
The information collected is intimated to you through your mobile phones. 

Further the above expained, “Nest Learning Thermostatᾬ can automatically change the temperature of your baby’s nursery, according to the data, got by Mimo meter. 
The main goal behind it is to provide the best safety measure available to avoid SIDS (Sudden Infant Death Syndrome).
Philips-Hue Bulbs:
have now stepped into a new stage of innovation with these smart bulbs. 

Linked with your mobile phones, you can now actually control the intensity of lights on your fingertips. 
The combination of bulb with mobile technology is next thing for your home. 
Instead of going for different watt of bulbs to suit the mood and the environment, simply change the intensity from dim to medium to full using your phone. 
These bulbs can be programmed to get dim at night, also it can work as a alarm by setting it in blinking mode on any intruder detection. 

The lighting can be dynamically change according to the environment, like a different lighting when watching a movie. 
ON and OFF timer can also be set for these bulbs to automatically ON and OFF after a particular time.
Ralph Lauren Polotech Shirt:
for athletes and become a pioneer to bring IoT in clothing industry. 

This Shirt can record the biometric readings of Athletes like Heart rate, calories burned, activity levels, breathing depths etc. 
and can help him to deliver the best performance. 
It can be connected to the Apple watch or an iPhone, and can track & record all the activities in your iPhone. 
So this Polotech Shirt along with the iPhone can become your complete fitness tracker or we can say fitness trainer.
Apple Watch and HomeKit:
is the example of how advanced the technology is at Apple. 
Apart from time and date, the Apple watch enables you to keep a track record of your health and daily activities. 
Also the voice activation allows you to get notifications in instant. 

View maps, listen to music and take care of your calls just by a single watch. 
Surprised at what a watch can do? Well, it’s has lot more features for you to explore and make life easier.
, which enables Siri (voice assistant in Apple’s iOS) to communicate with the devices and accessories at your home, so that they can be controlled remotely.
Smart Refrigerator: 
are there, which not only inform you about the consumed items or empty bottles in the fridge but also order them online before they runs out. 
These refrigerators can do much more than this although the production has not started at big scale yet.
Smart Phones:
are the most common example of IoT or we can say Smart Phone is one of the first few “Thingsᾠin the ‘Internet of Thingsᾮ All the devices explained above can be controlled using your smart phone and smart phone is become the center of this network like the stick of the magician. 

Like a magician do the magic by moving his stick, Smart Phone can do the “Real magicᾠby just few touches.
Smart cars:
is really a big achievement in this field. 
Imagine that a car automatically opens the garage door before you arrive at home and you can remotely control the temperature, lights, charging of the car. 

Tesla car have all these feature, it also have a App framework where you can build your own app to control the car and know its speed, location, battery status from anywhere. 
The car can upgrade itself automatically by downloading and installing the latest firmware and software. 
It has 18 sensors to automate the things, and it can fix a service schedule at the car service station by itself.
Microchips:
We are hearing about microchips for a long time and have their applications in some of the sensitive and dangerous fields like defense. 
But now one of the most integrated circuit have found its way to our day-to-day life. 
Microchips are generally used in the forms of tracer as the radar detectors can detect data about various things. 
Now with ioT, you can fit a microchip on collars of pet or attach it to them to keep a track of their movement without being physically looking for them. 

There is more freedom to your pets now and this also enables you to keep a record of their health too.
Google Glass:
it is more like repeating history for the company. 
A headset designed with optical-head display, if only you knew eyeglasses could be this much efficient. 

You can now wear it and together with voice activation you can interact, see, surf the net, click pictures and do many others things in a Smartphone-like-hands-free form. 
This Google glass is the result of ‘Project Glassᾠfrom Google.
The internet of Things has many other innovative devices to introduce to the world which will simply leave you amazed and thrilled. 
We are talking about technology that a decade from now will be marvelous amazement of science playing a yet another important role in our lives.


article/top-5-smart-wearable-gadgets
5 Interesting Wearable Tech Gadgets You Should Know About
gadget that provides information regarding everything that your smartphone gives, without looking at the smartphone.

capable of doing anything, like providing information regarding injury, health, safety helmet, relaxation gadget, and many more. 
With these wearable gadgets one can perform all sort of task with great ease. 
Let’s have a look at the top 5 wearable tech gadgets of this year worth trying.
1. Google Glass
Now take HD photos and videos with the innovative Google Glass forming the best substitute for a smartphone. 
Besides this, the technology also allows you to send messages and visualize the information on what’s trending currently on social media without checking the phone again and again. 
It has a small screen and a touch panel to control it. 
So this wearable headset forms a perfect replacement of a smartphone that does everything that a smartphone could do.
2. Apple Watch
This wearable gadget is basically iPhone supported one. 
The most attractive product you can wear on your wrist. 
Apple watch can be paired with the iPhone via Bluetooth. 

And then you can make and respond to calls directly from your wrist but capability of contact addition is not available, for which one needs to head towards the smartphone.
Health conscious? Then track your fitness level with this wearable product that informs the user regarding its heart rate, amount of calories burnt, including steps. 
But no GPS is enabled for fitness.
iPhone compatible apps are available within the smartwatch like messaging, games, Gmail, and many more. 

We can get push notifications like facebook messages, alerts etc. 
directly on Smartwatch. 
It lacks in the text message edition capability.
The gadget is not compatible with other smartphones and for full functioning of gadget, iPhone needs to be nearby the gadget. 

Although other companies have also launched their Smartwatches which can be paired with their Mobile phones.
3. Skully AR-1 Helmet
The technology has advanced so much that not only wearable smartwatches has emerged but there are other wide variety of wearable technology also. 
One such is Skully AR-1 bike helmet.

This smart wearable guides you with GPS and 180 degree rear view camera navigation making your journey easier by equipping the features of Google Glass. 
Now make a hand-free navigation with this smart technology.
Does your phone and music sound louder while riding? Control it from your helmet without risking the use of phone. 
Protect yourself from sun’s reflection with the help of sun shaded screen just away at the touch of a button.

The most disadvantage of this technology is the weight of the technology. 
This might act as a burden on your head as it is heavier than normal ones.
4. Muse
Set the head sensing headband right above your ears to meditate with great ease. 

Experience the great relaxing sense while meditation like never before for a healthy inner peace.
The app brings the nature to you irrespective of where you are with the amazing ear bud feature that plays musical rhythm of rainforest, waves on the beach, providing you great relaxation.
It can helpboost up your energy with the great meditation headband ever. 
It also controls you from diverting your focus to other things by increasing the intensity of the sounds. 

So whenever you go out of rhythm and tend to think about something else the app senses it and brings you back to focus. 
So get a deeper relaxation like never before with the muse gadget and notice the change by yourself.
5. First V1sion
Are you a sports lover? Then the must have wearable gadget is FirstV1sion. 

This wearable gadget is formed by fusing a t-shirt with a HD camera to relive the filed vision of an athlete as a viewer.Relive the emotion, vertigo, or sense the speed, and many more of an athlete just by watching the match. 
Mic feature for the better audio clarity.
Low latency video with delay less than 2 milliseconds is sent to the viewers for great visualization by the use of RF transmission technology.
This could be a greattechnology to be emerged to broadcast any live sports.
Oculus Rift
which is developed by Oculus VR Company. 
Now Oculus VR is acquired by Facebook.
Oculus Rift change the whole viewing experience whether you are playing a game or watching a movie. 

It brings you in that environment virtually like you are the part of the game or can act lively like a player. 
Other than playing Games you can take any kind of virtual experience like a space flight, deep forest tour, flying in the sky etc, there are huge number of things you can experience with Oculus. 
Because of its usability, it can be used in many fields like education, learning, training etc other than the entertainment. 
This device has great potential and can be a breakthrough in the world of Tech.

It is scheduled to be launched in beginning of year 2016.

article/16x2-lcd-display-module-pinout-datasheet
16x2 LCD Display Module

is named so because; it has 16 Columns and 2 Rows. 
There are a lot of combinations available like, 8×1, 8×2, 10×2, 16×1, etc. 
But the most used one is the 16*2 LCD, hence we are using it here.
:



1
Pin 1
Ground
Source Pin
This is a ground pin of LCD
Connected to the ground of the MCU/ Power source
2
Pin 2
VCC
Source Pin
This is the supply voltage pin of LCD
Connected to the supply pin of Power source

3
Pin 3
V0/VEE
Control Pin
Adjusts the contrast of the LCD.
Connected to a variable POT that can source 0-5V
4
Pin 4
Register Select
Control Pin
Toggles between Command/Data Register
Connected to a MCU pin and gets either 0 or 1.
0 -> Command Mode
1-> Data Mode

5
Pin 5
Read/Write
Control Pin
Toggles the LCD between Read/Write Operation
Connected to a MCU pin and gets either 0 or 1.
0 -> Write Operation
1-> Read Operation
6
Pin 6
Enable
Control Pin
Must be held high to perform Read/Write Operation
Connected to MCU and always held high.

7
Pin 7-14
Data Bits (0-7)
Data/Command Pin
Pins used to send Command or data to the LCD.
Only 4 pins (0-3) is connected to MCU
All 8 pins(0-7) are connected to MCU
8
Pin 15
LED Positive
LED Pin
Normal LED like operation to illuminate the LCD
Connected to +5V
9
Pin 16
LED Negative
LED Pin
Normal LED like operation to illuminate the LCD connected with GND.
Connected to ground


It is okay if you do not understand the function of all the pins, I will be explaining in detail below. 
Now, let us turn back our LCD:
These black circles consist of an interface IC and its associated components to help us use this LCD with the MCU. 

Because our LCD is a 16*2 Dot matrix LCD and so it will have (16*2=32) 32 characters in total and each character will be made of 5*8 Pixel Dots. 
A Single character with all its Pixels enabled is shown in the below picture.
So Now, we know that each character has (5*8=40) 40 Pixels and for 32 Characters we will have (32*40) 1280 Pixels. 
Further, the LCD should also be instructed about the Position of the Pixels.

from the MCU and process them to display meaningful information onto our LCD Screen.
Let’s discuss the different type of mode and options available in our LCD that has to be controlled by our Control Pins.
we send the data nibble by nibble, first upper nibble and then lower nibble. 
For those of you who don’t know what a nibble is: a nibble is a group of four bits, so the lower four bits (D0-D3) of a byte form the lower nibble while the upper four bits (D4-D7) of a byte form the higher nibble. 

This enables us to send 8 bit data.
we can send the 8-bit data directly in one stroke since we use all the 8 data lines.
Now you must have guessed it, Yes 8-bit mode is faster and flawless than 4-bit mode. 
But the major drawback is that it needs 8 data lines connected to the microcontroller. 

This will make us run out of I/O pins on our MCU, so 4-bit mode is widely used. 
No control pins are used to set these modes. 
It's just the way of programming that change.
As said, the LCD itself consists of an Interface IC. 

The MCU can either read or write to this interface IC. 
Most of the times we will be just writing to the IC, since reading will make it more complex and such scenarios are very rare. 
Information like position of cursor, status completion interrupts etc. 
can be read if required, but it is out of the scope of this tutorial.

There are some preset commands instructions in LCD, which we need to send to LCD through some microcontroller. 
Some important command instructions are given below:



0F
LCD ON, cursor ON
01
Clear display screen
02
Return home
04
Decrement cursor (shift cursor to left)

06
Increment cursor (shift cursor to right)
05
Shift display right
07
Shift display left
0E
Display ON, cursorblinking

80
Force cursor to beginning offirst line
C0
Force cursor to beginning of second line
38
2 lines and 5×7 matrix
83
Cursor line 1 position 3

3C
Activate second line
08
Display OFF, cursor OFF
C1
Jump to second line, position 1
OC
Display ON, cursor OFF

C1
Jump to second line, position 1
C2
Jump to second line, position 2

Check our LCD interfacing Articles with different Microcontrollers:

LCD Interfacing with 8051 Microcontroller
Interfacing LCD with ATmega32 Microcontroller
LCD Interfacing with PIC Microcontroller
Interfacing 16x2 LCD with Arduino

16x2 LCD Interfacing with Raspberry Pi using Python

article/how-to-make-a-pcb-at-home
How to make a PCB at home?

asthey are easily found intelevision sets,computers and in every electronic device. 
PCB is widely accepted and most commonly used in Electronics industry. 
PCB is very cost effective, it assembles the complex circuits in small space and eliminates the risk of loose connections, it has pre designed copper tracks to connect the components in effective and clean way.
quite easily. 

Only you need to follow some steps for making your own PCB. 
Before we start you need to get some tools and materials:
Tools and materials required
Drill machine

Cloth Iron
Laser Printer
Photo paper / Glossy paper
Gloves

Ferric Chloride (Etching solution)
PCB board
Black permanent Marker
Sand paper or Steel wool

Soldering Iron
Step 1
, to convert the circuit schematic diagram into PCB layout. 
There are lot of paid and free softwares available for this purpose, some open source software are Cadsoft Eagle, Fritzing, PCBWizard etc. 

Here we are using Dip Trace software of PCB designing. 
By using this software we can design schematic and PCB layout for any project.
for line follower robot.
In this PCB layout we have designed a circuit board for line follower robot and 2 sticks for placing IR sensors.
Step 2
of the PCB layout. 
Print should be taken on Glossy paper/Photo Paper using the Laser Printer.
Step 3
In this step we need a Copper clad Board and we need to cut that copper clad in required size, according to our PCB layout design.
Step 4
Now rub it by using sand paper or steel wool. 
It will remove the oxide layer from the board as well as makes the board rough so that paper can stick properly.
Step 5
In this step, place this copper clad by the side of printed side of photo paper, and fold the paper.
OR put copper board upon the Printed layout, with copper side down towards the printed layout and plastic side up. 
Then fold the paper.

OR You can cut out PCB layout from the photo paper and put it on Copper board, with printer side down towards the copper board. 
And use the cello tape at the corners, to properly stick it with the board.
Step 6
Now take a hot iron and start ironing slowly for 5-10 minutes or tightly press the hot iron for some time. 

Heating the paper will transfer the ink to the copper board. 
Now allow copper plate to be cool down, and open the folded paper. 
If paper gets stuck to the plate, use warm water to remove the paper properly.
At some places ink does not get properly transferred to the copper plate, or gets fainted during the removing of paper, so use a Black permanent marker and complete the missing lines and tracks.

If you are very good at drawing or the circuit schematic is very simple, then you can get rid from printing the circuit on paper and transfer it to the copper board by ironing it. 
You can directly draw the whole PCB layout on copper board using Black Permanent marker. 
First draw it using pencil and then use marker over the pencil sketch. 
But for complex circuits this method is not recommended.
Step 7
Now we have our circuit layout under the black ink and we only need copper tracks under these black lines. 
So we need to remove all the other copper except the black lines. 


Put the PCB in this solution for approx. 
half an hour. 
Now Ferric chloride will react and remove the exposed copper and won’t react with the masked copper under the Black lines. 
And we get copper track as per our PCB lay out.

, either use Plier of use gloves to take out the PCB from the solution. 
Ferric chloride solution is vey dangerous and toxic.
Finally take the PCB out from the solution and wash it with cold walter.
To make the Etching process faster, you can either stir the solution (with PCB dipped) in every 2-3 minutes or you can use some warm water to make the solution.
Step 8
Now rub the PCB with the steel wool or fine sand paper to remove the black ink, or you can use thinner (Acetone) on a piece of cotton to remove Black ink. 
Now you can see the shiny copper tracks clearly as per our printer PCB layout.
Step 9
).
Step 10
Now it’s time to solder components on this Printed Circuit Board (PCB).
Step 11
Now slice the printed circuit board. 
Means cut the component’s unwanted legs by using cutter.
do take the extra care when Ironing the PCB and while working with Ferric Chloride solution.


article/easyeda-for-circuit-design
EasyEDA for Electronic Circuit Design
are made in your web browser. 
EasyEDA has all the featuresyou expect and easily take your design from conception through to production. 

EasyEDA aims to bring every electronic hobbyist an easier EDA experience. 
That’s why EasyEDA comes to the world and named EasyEDA.
EasyEDAFeatures
Here is how EasyEDA introduces its online PCB creation tool. 

The main features of the tool are as follows:
Draw diagrams quickly in your browser using the available libraries. 
The updates will be applied automatically.
Check analog, digital and mixed circuits with sub-circuits and SPICE models!

With multiple layers, thousands of blocks, you can always work quickly and smoothly arrange your cards.
Steps applied to the creation of a blinking LED with 555 IC
)
:

On the left side of the screen, you find symbols that you select when you click on it. 
On the right side you can choose to draw a schematic or directly a PCB (printed circuit board).
? I largely use it during my career, I will use it this time again.
And as output I use a LED to see what happen‐󋈍
Drawing the schematic
The interface already seen a little higher is very simple to use. 
Select a component in the left column by clicking it. 
Move the mouse in the drawing window. 

Click, you release the component. 
Click again, you release another one... 
The space bar and the R key are used to rotate the components. 
The numbers increment automatically. 

Here is the diagram that I realized.
Circuit simulation
You will have to set the parameters in order to observe the curves generated by the simulator. 
After a few tries, the simulation result appears.

We can see the charge / discharge of the capacitor and the output voltage. 
To better see the results I enlarged the image by adjusting the time (μs/div).
If you look at the 555 calculator a little higher, you will see that the period should be worth 15.385 microseconds ... 
not bad, right?

Once verified the proper operation of the circuit, click on the printed circuit card icon and you start the creation of the PCB.
The first step is the generation of the net where the components are connected by direct wires.
From this net, move the components on the board according to your placement constraints (here I did not have any )
Well ... 

we begin to see what will look like the circuit ... 
You can now route the tracks.
You click on the icon representing printed circuit tracks and go!. 
The first window asks you information on the size of the tracks. 

You can also avoid routing some tracks as the ground for example, if you are planning to use ground plane ... 
At first simply confirm by clicking on RUN.
With the 555 diagram, routing takes only a few seconds ... 
it certainly will not be the case with a more complex schematic.

The color of tracks indicates whether they are above or below the circuit.
We can add tracks, change the width, move some tracks by clicking on the active points, for example I shifted the blue one that passes under R4 and that seemed too close to the pad. 
I also do a U-turn to LED D1 (bottom right) because the tracks crossed. 
In this case you must restart the routing and lose your changes to the tracks width. 

It is therefore necessary to redo tracks width modification. 
Please ensure that all components are correctly positioned before changing tracks width !
You can insert an image, a logo on the PCB :
The different layers of the board are displayed using a color code. 

Here the yellow color indicates that we visualize the top silk layer printed on the top of the circuit.
We can finally see a photographic view of the circuit to have an idea of what it will look like.
More advanced examples
Well, okay, my basic 555 circuit is not very representative ... 

It allowed me to test the workflow and verify the operation of this free tool.
Of course with a little more time (and a lot more experience) you can produce circuits quite professional, examples of which are available on the website:
4 ports Switch
STM32 board :
Use open source modules
EasyEDA also provides component libraries that allow you to directly integrate components from multiple vendors :
To illustrate this I have chosen an LED equipped module (SeeedStudio). 
It is possible to integrate this module to your project :

in all forms such as R3:
Create the PCB
When you are satisfied with your circuit, Fabrication Output icon directs you to the page where you can choose to download the Gerber files (if you want them manufactured by another manufacturer) or continue by ordering the printed circuit to EasyEDA.
Tutorial on How to Use EasyEDA
describes how to use the simulator.
The tutorial is completed with videos that explain the operations, such as the diagram creation :
One can also create professional schematics:
Conclusion
During my tests, which lasted several hours, EasyEDA proved stable, reliable and relatively easy to learn as it is pretty intuitive. 
One regret though, is that when you have routed and then retouched widths tracks, it requires to restart the routing ... 
and to redo the track widths modifications. 
No matter if it was a small circuit like mine. 

A little annoying if you have a complex drawing !
The availability of a large number of open source modules is more significant, as well as access to thousands of shared projects such as clocks or speed controllers ...
The availability of a tutorial and an ebook for the simulator facilitate the handling of this online app.
Completely free for electronics engineers, educators, students, makers and enthusiasts. 

Why not try this free and powerful circuit design software. 
You will find it is interesting and unique.

article/voltage-multiplier-circuits

Voltage Multipliers
Multimeter only reads the RMS (root mean voltage) value of AC voltage, we need to multiply RMS value to 1.414 (root 2), to get the Peak value.
Generally transformers are there to step-up the voltage, but sometimes transformers are not feasible because of their size and cost. 
Voltage multiplier circuits can be built using few diodes and capacitors, hence they are low cost and very effective in comparison with Transformers. 

Voltage multiplier circuits are quite similar to rectifier circuits which are used to convert AC to DC, but voltage multiplier circuits not only convert AC to DC but can also generate very HIGH DC voltage.
These circuits are very useful where High DC voltage needs to be generated with Low AC voltage and low current is required, like in microwave ovens, CRT (Cathode ray tubes) monitors in TV and computers. 
CRT monitor requires high DC voltage with low current.
Full wave Voltage Doubler
is very simple:
During the positive half cycle of Sinusoidal wave of AC, Diode D1 get forward biased and D2 get reversed biased, so capacitor C1 charges through the D1, to the peak value of sine wave (Vpeak). 
And during the negative half cycle of sine wave, D2 is forward biased and D1 revered biased, so capacitor C2 get charge through the D2, to Vpeak.
Now both the capacitors are charged to Vpeak so we get the 2 Vpeak (Vpeak + Vpeak), across the C1 and C2, with no Load connected. 

It has named after the Full wave rectifier.
Half Wave Voltage Doubler Circuit
During the first positive half cycle of Sinusoidal wave (AC), Diode D1 get forward biased and capacitor C1 get charged through the D1. 
Capacitor C1 get charged up to the peak voltage of AC i.e. 

Vpeak.
During the negative half cycle of the sine wave, Diode D2 conducts and D1 reverse biased. 
D1 blocks the discharging of capacitor C1. 
Now the capacitor C2 charge with the combined voltage of capacitor C1 (Vpeak) and the negative peak of the AC voltage that is also Vpeak. 

So the capacitor C2 charge up to 2Vpeak volt. 
Hence the voltage across capacitor C2 is two times the Vpeak of AC.
In the next positive cycle, capacitor C2 discharged into the load, if load is connected, and gets recharged in the next cycle. 
So we can see that it gets charged in one cycle and discharged in next cycle, so the ripple frequency is equal to the input signal frequency i.e. 

50 Hz (AC Mains ).
Voltage Tripler Circuit
, we just need to add 1 more Diode and capacitor to the above Half wave Voltage Doubler circuit according to the circuit diagram Below.
that, in first positive half cycle capacitor C1 gets charged to Vpeak and and capacitor C2 charged to 2Vpeak in the negative half cycle.

Now during the second positive half cycle, Diode D1 and D3 conducts and D2 get reverse biased. 
In this way capacitor C2 charges the capacitor C3 up to the same voltage as itself, which is 2 Vpeak.
Now the capacitor C1 and C3 are in series and voltage across C1 is Vpeak and voltage across C3 is 2 Vpeak, so the voltage across the series connection of C1 and C3 is Vpeak+2Vpeak = 3 Vpeak, and we get Triple the voltage of Input Vpeak volt.
Voltage Quadruple Circuit
(4 times the input voltage).
We have seen in voltage Tripler circuit, that capacitor C1 charged to Vpeak in first positive half cycle, C2 charged to 2Vpeak in negative half cycle and C3 also charged to 2Vpeak in second positive half cycle.
Now during the second negative half cycle Diode D2 and D4 conducts, and capacitor C4 is charged to the 2Vpeak, by the capacitor C3 which is also at 2 Vpeak. 
And we get four times Vpeak (4Vpeak), across the capacitor C2 and C4, as both the capacitors are at 2 Vpeak.

, practically the voltage is not exactly the multiple of the Peak voltage, resulting voltage is less than the multiples because of some voltage drop across the Diodes, so the resulting voltage would be:
Vout = Multiplier*Vpeak ᾠvoltages drop across diodes
is High Ripple frequency and it’s very difficult to smooth the output, although using the large value of capacitors can help reduce rippling. 
And the advantage of the circuit is that we can generate very high voltage from a Low voltage power source.

We can generate much higher voltage and can get 5 times, 6 times, 7times and more, the voltage of the Peak AC voltage, by adding more diodes and capacitors. 
We can also generate the High negative voltage by just reversing the polarity of Diodes and Capacitors in this circuit. 
Theoretically we can multiply the voltage infinitely but practically it’s not possible because of capacitance of capacitors, low current, high rippling and many other factors.
Video:
Notes:
Voltage won’t multiple instantaneously but it will increase slowly and after some time, it will set to the Thrice of input voltage.
Voltage rating of capacitors should be at least twice the input voltage.
The output voltage is not exactly the Multiple of Peak input voltage, it will be less than Input voltage.


article/difference-between-lcd-and-led-displays
LCD vs. LED Displays
in a discreet manner and you must go through the whole article in order to come across this important information about both the display technologies.
A Little about LCD and LED Displays
in order to improve luminosity and video definition of the display. 
Though this is the major difference between LCD and LED displays, it improves the overall picture quality of LED displays and make them superior than LCDs. 
Lets check the major aspects of both the display.

LED displays does not behave like LCD displays which start to get diminished if goes across 30 degree from the centre point. 
The viewing angles of displays has no limit in LED displays since it’s loaded with larger viewing angle. 
LED displays is known for having better viewing angles in comparison of LCD displays.
If you are looking for excellent colour accuracy, choose only LED displays. 

Though there is no great difference between the colour accuracy of LED and LCD, but no one can deny that LED displays goes with great colour accuracy. 
LED displays is loaded with RGB LEDs.
When it comes about better contrast ratio, LED displays emerges first. 
It’s excellent to cover dark areas of the image on the screen and make the audience able to see every detailing of the image without getting irritated. 

LED displays holds better contrast in comparison of LCD displays. 
The LCD displays is not able to create the dark areas of the images on the screen which lead to loss of image quality. 
And that’s why it counts one of the major drawbacks of it. 
In order to have better contrast and more detailed image in the dark areas, LED is the best.

Size also matters if you are stepping out to buy. 
LCD come in the size range from 15inches to 65 inches, while LED displays are available between 17inches to 70inches. 
If wishes a bigger size, you can prefer LED displays.
Thebacklightsof LCD displays contain mercury which poses a risk to environment. 

Some studies suggest that due to brokenbacklightsin LCD panels, mercuryvaporis released in environment which is hazardous to health.LED displays is environment friendly since Mercury has not been used in it.
LED displays is equipped with a faster response rate time factor to have a better experience while watching fast action video. 
For a great displays go for only LED displays since it keeps you away from blurring images, motion lag etc.
LED displays aremore expensive than LCDs.


article/what-are-the-different-types-of-capacitors
Different Types of Capacitors
We will discuss some of them in this article.

Based on the design, capacitors are categorized in these different types:
Electrolytic type.
Polyester type.
Tantalum type.

Ceramic type.
For most of applications we use Electrolytic type Capacitors.Theyare very important for an electronic student as they are easy to get and to use, and they are inexpensive too.
As shown in figure, they are available in different sizes and colors. 
But they all do the same function.

An electrolytic capacitor is usually labeled with these things:
1. Capacitance value.
2. Maximum voltage.
3. Maximum temperature.

4. Polarity.
For an electrolytic capacitor, the capacitance is measured in micro Farad. 
Based on requirement the appropriate capacitor is chosen. 
With higher capacitance, the size of capacitor also increases.

An electrolytic capacitor contains a dielectric material inside; this material has a break down voltage. 
This voltage is represented on label. 
This is the maximum operating voltage for that capacitor. 
If any voltage higher than labeled voltage applied across that capacitor, it gets damaged permanently. 

For a higher voltage the dielectric material breaks down.
Electrolytic capacitor has a limit for is environmental temperature. 
This means it cannot be operated or stored at temperatures higher than labeled. 
If happened, the device will be damaged permanently.

These type of capacitors are dangerous to touch at terminals until discharged completely. 
If discharge is not done completely, they can deliver a lethal shock.Under no circumstances these should be touched until discharged completely.
Electrolytic capacitor has polarity. 
As shown in figure, the negative terminal of a electrolytic capacitor is marked.This polarity must be followed and the capacitor should be connected accordingly. 

Otherwise the capacitor will be damaged permanently.With this polarity one can conclude, the electrolytic capacitors are for DC power only. 
These are not to be used in AC power applications.
and so these can be connected in any way. 
These can be operated in both AC circuit and DC circuits.

; theyare available in low capacitances only. 
But the operating voltages for these capacitors are high. 
The capacitances for these capacitors are found the same way as ceramic type capacitors. 
And these are also mentioned in pico Farad.

have no polarity and so these can be connected in any way. 
These can be operated in both AC circuit and DC circuits.
They have low capacitance but very high breakdown voltage. 
These capacitors have no polarity and can be operated any way.

These capacitors are used in low capacitance applications.The label is marked with:
1. Capacitance value.
2. Maximum voltage.
3. Maximum temperature.

4. Polarity.
Unlike electrolytic, the tantalum capacitor positive terminal is marked instead of negative.
; they havevalues up to 10μF. 
Some of them are polarized. 

The positive terminal for the polarized ones is marked. 
These are seen in embedded circuits.
are manufactured in stripes as shown in figure. 
These are placed on PCB by pick and place machine.


article/difference-between-c-and-embedded-c
C Language vs. Embedded C
as they do not find much difference between both.

Well actually there isn’t wide difference between both, they differ in small aspects and owe more similarities than differences.
In starting stages, assembly language were used to write codes and programs and then fused into the EPROMS for the microprocessor based systems. 
But due to lack in code portability feature and high cost in software development, the use of assembly language programming was prohibited and then was the time when c programming language came into the picture.
With the advancement in the technology, embedded systems were associated with the processors which make use of embedded software. 

This type of system moved on to C and became the most widely used programming language for embedded processors.
Embedded processors are nothing but the processors that are associated with microcontrollers. 
C is basically a middle level language and for this reason it is widely used than any other languages like Pascal, FORTRAN etc. 
as C also provides similar benefits as those by high level language.
So what are the differences between C and Embedded C?
The most widely used system programming language is C. 
It is the simple programming language that uses free-format source code. 
It has been used in applications formerly built in assembly language. 

The embedded C is the extension of C language that finds its application in the embedded system to write embedded software.
Embedded C was developed to overcome the limitations that exist inthe C languageto program for variousmicrocontrollers.Since the development of code, programming is different on a computer system than for an Embedded system, there are few characteristics which draws the advantage of using Embedded C over C. 
They are:
Due to the usage of small and less power consuming components in embedded system.

Embedded system have limited ROM & RAM and less processing power, so one should take care of limited resources while writing the program in embedded C, whereas in C language, desktop computers have access to system OS, memory, etc.
Most of the syntax and some library functions used by Embedded C are same as that of C, like variable declaration, conditional statements, arrays and strings, macros, loops, main () function, global declaration, operational function declaration, structures and unions, and many more.
, that supports the embedded system programming.
Clear picture of both can be drawn from the below points though there are much similarities than differences between both:

A set of language extension for C is called Embedded C whereas desktop computer language is generally called C programming language.
C directly run program from OS terminal whereas embedded C needs to create the file first then download to the embedded system where the compiling process is carried out.
OS system is must for C programming whereas it’s an option for Embedded C.
See output on your desktop with C programming whereas no output can be observed on desktop with Embedded C, i.e. 

Embedded C runs in real time constraints.
Programming languages like C++, JavaScript, Perl, Python, and many more are directly or indirectly influenced by C language whereas Embedded C is developed only for the required microprocessor/microcontroller.
Embedded C is used for microcontrollers like TV, washing machines, etc. 
whereas C finds applications in simple yet logical programs, OS based software, etc.

Based on microcontroller orprocessor, Embedded C comes with different formats while C programming comes with free-format source code.
As mentioned before, Embedded C has limited source constraints like limited RAM/ROM etc. 
whereas C can make use of all computer resources.
No data can be input in embedded C while running, due to its predefined data whereas C can easily intake program data while programming.

is its coding speed and code size. 
Besides, it’s even simple and easy to learn and understand.
just the difference lies in the way you use the resources and the programming code effectively.


article/using-5v-dc-power-supply-from-computer-usb
5V DC Power Supply from Computer USB
, Servo etc., it’s difficult to run them with a normal 9v battery, especially when battery have gotten weak. 
These motors require comparatively high current to rotate and we can easily draw approx. 

500mA from Computer’s USB.
are used for Power supply.
So you can use these two wires for your bread board or PCB circuits or you can properly solder two jumper wires to them.You can also measure the voltage from Multimeter, it would be 5v approx.


article/what-are-industrial-manipulators
Industrial Manipulators or Robotics Manipulators 
are machines which are used to manipulate or control material without making direct contact. 
Originally it was used to manipulate radioactive or bio-hazardous object which can be difficult for a person to handle. 

But now they are being used in many industries to do task like lifting heavy objects, welding continuously with good precision etc. 
Other than industries they are also being used in hospitals as surgical instruments. 
And now a day’s doctors extensively use robotics manipulators in their operations.
, I would like to tell you about joints.

A joint has two references. 
The first one is the regular reference frame that is fixed. 
The second reference frame is not fixed, and will move relative to the first reference frame depending on the joint position (or joint value) that defines its configuration.
We will learn about two joints which are used in manufacturing different types of Industrial Manipulators.

They have one degree of freedom and describe rotational movements (1 degree of freedom) between objects. 
Their configuration is defined by one value that represents the amount of rotation about their first reference frame's z-axis.
Here we can see revolute joint between two objects. 
Here follower can have rotational movement around its base.

Prismatic joints have one degree of freedom and are used to describe translational movements between objects. 
Their configuration is defined by one value that represents the amount of translation along their first reference frame's z-axis.
Here you can see various prismatic joint in one system.
Different types of Industrial Manipulators
In industries many types of industrial manipulators are used according to their requirements. 
Some of them are listed below.
Cartesian coordinate robot: 
In this industrial robot, its 3 principle axis have prismatic joints or they move linear thorough each other. 

Cartesian robots are best suited for dispensing adhesive like in automotive industries. 
The primary advantage of Cartesians is that they are capable of moving in multiple linear directions. 
And also they are able to do straight-line insertions and are easy to program. 
The disadvantages of Cartesian robot are that it takes too much space as most of the space in this robot is unused.

SCARA Robot: 
The SCARA acronym stands for Selective Compliance Assembly Robot Arm or Selective Compliance Articulated Robot Arm. 
SCARA robots have motions similar to that of a human arm. 
These machines comprise both a 'shoulder' and 'elbow' joint along with a 'wrist' axis and vertical motion. 

SCARA robots have 2 revolute joints and 1 prismatic joint. 
SCARA robots have limited movements but it is also its advantage as it can move faster than other 6 axis robots. 
It is also very rigid and durable. 
They are mostly used in purpose application which require fast, repeatable and articulate point to point movements such as palletizing, DE palletizing, machine loading/unloading and assembly. 

Its disadvantages are that it has limited movements and it is not very flexible.
Cylindrical robot: 
It is basically a robot arm that moves around a cylinder shaped pole. 
A cylindrical robotic system has three axes of motion ᾠthe circular motion axis and the two linear axes in the horizontal and vertical movement of the arm. 

So it has 1 revolute joint, 1 cylindrical and 1 prismatic joint. 
Today Cylindrical Robot are less used and are replaced by more flexible and fast robots but it has a very important place in history as it was used for grappling and holding tasks much before six axis robots were developed. 
Its advantage is that it can move much faster than Cartesian robot if two points have same radius. 
Its disadvantage is that it requires effort to transform from Cartesian coordinate system to cylindrical coordinate system.

PUMA Robot: 
The PUMA (Programmable Universal Machine for Assembly, or Programmable Universal Manipulation Arm) is the most commonly used industrial robot in assembly, welding operations and university laboratories. 
It is more similar to human arm than SCARA robot. 
It has great flexibility more than SCARA but it also reduces its precision. 

So they are used in less precision work like assembling, welding and object handling. 
It has 3 revolute joints but not all the joints are parallel, second joint from the base is orthogonal to the other joints. 
This makes PUMA to compliant in all three axis X, Y and Z. 
Its disadvantage is its less precision so it can’t be used in critical and high precision needed applications.

Polar Robots: 
It is sometimes regarded as Spherical robots. 
These are stationary robot arms with spherical or near-spherical work envelopes that can be positioned in a polar coordinate system. 
They are more sophisticated than Cartesian and SCARA robots but its control solution are much less complicated. 

It has 2 revolute joints and 1 prismatic joint to make near spherical workspace. 
Its main uses are in handling operations in production line and pick and place robot.
In term of wrist design it has two configurations:
Pitch-Yaw-Roll (XYZ) like the human arm and Roll-Pitch-Roll like spherical wrist. 

The spherical wrist is the most popular because it is mechanically simpler to implement. 
It exhibits singular configurations that can be identified and consequently avoided when operating with the robot. 
The trade between simplicity of robust solutions and the existence of singular configurations is favorable to the spherical wrist design, and that is the reason for its success.


article/servo-motor-working-and-basics
What is a Servo Motor? - Understanding the basics of Servo Motor Working
What is a Servo Motor?
.Apart from these major classifications, there are many other types of servo motors based onthe type of gear arrangement and operating characteristics. 

A servo motor usually comes with a gear arrangement that allows us to get a very high torque servo motor in small and lightweight packages. 
Due to these features, they are being used in many applications like toy car, RC helicopters and planes, Robotics, etc.
Servo motors are rated in kg/cm (kilogram per centimeter) most hobby servo motors are rated at 3kg/cm or 6kg/cm or 12kg/cm. 
This kg/cm tells you how much weight your servo motor can lift at a particular distance. 

For example: A 6kg/cm Servo motor should be able to lift 6kg if the load is suspended 1cm away from the motors shaft, the greater the distance the lesser the weight carrying capacity. 
The position of a servo motor is decided by electrical pulse and its circuitry is placedbeside the motor.
Servo Motor Working Mechanism
It consists of three parts:

Controlled device
Output sensor
Feedback system
It is a closed-loop system where it uses a positive feedback system to control motion and the final position of the shaft. 

Here the device is controlled by a feedback signal generated by comparing output signal and reference input signal.
Here reference input signal is compared to the reference output signal and the third signal is produced by the feedback system. 
And this third signal acts as an input signal to the control the device. 
This signal is present as long as the feedback signal is generated or there is a difference between the reference input signal and reference output signal. 

So the main task of servomechanism is to maintain the output of a system at the desired value at presence of noises.
Servo Motor Working Principle
A servo consists of a Motor (DC or AC), a potentiometer, gear assembly, and a controlling circuit. 
First of all, we use gear assembly to reduce RPM and to increase torque of the motor. 

Say at initial position of servo motor shaft, the position of the potentiometer knob is such that there is no electrical signal generated at the output port of the potentiometer. 
Now an electrical signal is given to another input terminal of the error detector amplifier. 
Now the difference between these two signals, one comes from the potentiometer and another comes from other sources, will be processed in a feedback mechanism and output will be provided in terms of error signal. 
This error signal acts as the input for motor and motor starts rotating. 

Now motor shaft is connected with the potentiometer and as the motor rotates so the potentiometer and it will generate a signal. 
So as the potentiometer’s angular position changes, its output feedback signal changes. 
After sometime the position of potentiometer reaches at a position that the output of potentiometer is same as external signal provided. 
At this condition, there will be no output signal from the amplifier to the motor input as there is no difference between external applied signal and the signal generated at potentiometer, and in this situation motor stops rotating.
Interfacing Servo Motors withMicrocontrollers:
which is most commonly used for RC cars humanoid bots etc. 
The picture of MG995 is shown below:
Thecolorcoding of your servo motor might differ hence check for your respective datasheet.

All servo motors work directly with your +5V supply rails but we have to be careful on the amount of current the motor would consume if you are planning to use more than two servo motors a proper servo shield should be designed.
Controlling Servo Motor: 
All motors have three wires coming out of them. 
Out of which two will be used for Supply (positive and negative) and one will be used for the signal that is to be sent from the MCU.

Servo motor is controlled by PWM (Pulse with Modulation) which is provided by the control wires. 
There is a minimum pulse, a maximum pulse and a repetition rate. 
Servo motor can turn 90 degree from either direction form its neutral position. 
The servo motor expects to see a pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns. 

For example, a 1.5ms pulse will make the motor turn to the 90° position, such as if pulse is shorter than 1.5ms shaft moves to 0° and if it is longer than 1.5ms than it will turn the servo to 180°.
High speed force of DC motor is converted into torque by Gears. 
We know that WORK= FORCE X DISTANCE, in DC motor Force is less and distance (speed) is high and in Servo, force is High and distance is less. 
The potentiometer is connected to the output shaft of the Servo, to calculate the angle and stop the DC motor on the required angle.

of proper width, to its Control pin. 
Servo checks the pulse in every 20 milliseconds. 
The pulse of 1 ms (1 millisecond) width can rotate the servo to 0 degrees, 1.5ms can rotate to 90 degrees (neutral position) and 2 ms pulse can rotate it to 180 degree.
All servo motors work directly with your +5V supply rails but we have to be careful about the amount of current the motor would consume if you are planning to use more than two servo motors a proper servo shield should be designed.

To learn more about servo motorworking principleand practicaluses,please check below applications where controlling of servo motor is explained with the examples:
Servo motor tester circuit
Servo motor interfacing with 8051 microcontroller
Servo motor control using Arduino

Servo control with Arduino Due
Servo Control with Flex Sensor
Raspberry Pi Servo Motor Tutorial


article/what-is-oled-display-technology
Understanding OLED Display Technology
Let’s dream about a high definition television that is even less than a quarter inch thick, curved and about 80 inches wide. 
Moreover, it consumes lesser power than your normal TV set and it can be rolled up if you don’t want to use it. 

You can also carry that TV around wherever you like. 
What if we could have a display monitor inbuilt in our clothing? Does it look real or just a dream? Well, these devices can be existent in near-term using the recent technology of OLEDs.
is a recently developed display technology in which alayer of organic compoundemits light when electric current runs through it along with a combination of filters and color refiner to produce high definition images. 
It packs in carbon based sheets between two charged electrodes, comprising of a metallic cathode and a transparent anode. 

The organic based films surround hole transparent layer, emissive and electron transport layer inside it. 
When current is applied to the OLED cell, the positive and negative charges remerge in the emissive layer and creates an electro luminous light. 
OLED displays are emissive devices and they work on emitting light rather than modulating or reflecting the light.
Although "LED" and "OLED" both uses"light-emitting diode" technology the design process of each is actually quite different. 

WhileLED displays use an array of LEDs as the backlight on traditional LCD displays, in OLED displays,the organic layer creates its own light source for each pixel. 
This results in an improved clarity and color of images.
A glimpse on OLED technology
The sheets used in OLED devices are prepared from organic carbon based materials thatilluminateswhen current is applied through them. 

They are much more efficient and simpler to use than LCDs as they are not dependent upon backlight and filters. 
They provide a beautiful picture quality with amazing clarity. 
They also provide brilliant colour features; have a relatively fast response rate and a wider range of viewing angles. 
They are also used for making OLED lightings.

This technology was made-up in early 1980s. 
It was further developed to replace LCD technique because OLED technology is comparably brighter, thinner and lighter than LCDs. 
They also consume lesser power than LCDs and offers higher contrast features. 
The most attractive advantage that it possesses over LCDs is that they are comparably cheaper to manufacture and hence it is cost effective.

Working of OLED
OLED technologyworks on a very simple principle. 
Whenever a current is applied to the electrodes, an electric field gets developed around it as a result, the charges start moving in the device. 
Electrons escape from the cathode and holes move from anode in reverse direction. 

The electrostatic force brings the electrons and the holes together and they form a photon which is a bound state of electron and hole. 
This recombination of charges develops photon with a given frequency that is given by the energy gap that gets formed between the LUMO and HUMO levels of the emitting molecules. 
This electrical power that is applied to the electrodes gets converted into light that is radiated out from the device.
Different materials are used to produce different colours of light and the colours combine to form a white source of light.Generally, the anode material is made up of Indium tin oxide because it is transparent to the visible light and has a high work function. 

The material helps to promote injection of holes into the HOMO level of organic layer. 
Materials like barium and calcium are commonly used for making cathode electrodes as they have lower work function and they can promote injection of electrons into the LOMO level of organic layer. 
These materials also required to be coated by metals like aluminium as they are very reactive in nature and often need a protective sheet over them.
Materials used in OLEDs

The basic structure of an OLED contains a cathode for introducing electron, an emissive layer and an anode for removing electron out of it. 
Although the modern OLEDs contain many more layers, yet the elementary functionality remains the same in all the types of OLEDs. 
There are several types of OLED materials that are used in manufacturing of OLED. 
The most fundamental division is of small molecule OLEDs and large molecule OLEDs. 

All the commercially utilised OLEDs are small molecule based, which is called SMOLED. 
They perform better and efficiently. 
The emitter materials that are used in OLEDs are fluorescent or phosphorescent. 
The fluorescent materials have a longer lifespan although they are less resourceful than the later one. 

Most of the OLEDs use phosphorescent materials as they provide better services and longer run. 

AMOLED and PMOLED are the terms related to the display of an OLED. 
A PMOLED has limited range and resolution although they are economical than AMOLED. 

These displays are very complicated to manufacture but they are efficient to use and can also be given larger dimensions. 
PMOLED displays are utilized in producing smaller devices while AMOLED displays are used in television sets, tablets and smartphones.
Applications of OLEDs
OLED technology is used in commercial applications of mobile phones, digital media players, car radios, digital camera, television etc. 

Portable displays are used in the mechanism so the lower lifespan is no more an issue in this purpose. 
It can also be used for all-purpose illumination as well as for displays and rear light sources in LCD displays, traffic signals, emergency signals or automotive applications.
Advantages of OLED technology
OLED technology has really opened a widen gates for many advancements and developments in the field of machinery, tools and electronic equipments. 

Itoffers following benefits:
It does not use any liquid material and comprises of solid construction, as a result it offers a better resistance.
They can be viewed from any angle and gives a wide range of enjoying the view. 
In spite of this, we never feel any distortion in the screen and any drawback in the quality.

It can possess thickness as low as 1 mm which is even less than half of the thickness of LCDs. 
As a result, they are lighter in weight.
The response time of OLEDs is 1/1000 of LCDs.
It can work in lowest temperature possible even if it is minus 40 degree.

It is cost efficient as the manufacturing is reasonable as well.
They give brighter light and consume lower power.
It offers higher efficiency and larger area sources.
Flexible display and tuneable emission.

Disadvantages of OLED technology
With the countless advantages, we have some flaws and drawbacks of the technology as well that are mentioned hereunder:
The colour purity crisis is an inadequacy in the device as it finds difficult to display fresh and rich colours.
It can get easily damaged by water.

Large quantity productions of large size screens are not obtainable.
It usually comes up with life span of 5000 hours which is much lower than LCDs.
The most prominent drawback of OLEDs are they cannot be seen in the presence of direct sunlight.
The developers have tried making positive changes in these drawbacks and thus have developed OLEDs having longer lifespan. 

Red and green OLED has lifespan of 46000 to 230000 hours while blue OLEDs have lifespan of around 14000 hours. 
Larger OLED panels have also been produced.
Challenges faced by OLEDs
Although the technology has taken a great leap in the recent times, there are still several challenges that are being faced by OLED industries. 

They are listed as follows:
Material lifespan of OLEDs
Soluble OLED performance
The lighting capacity expansion of OLEDs

Colour balance.
Water damage.
The recent developments in OLED technology 
OLED technology has been widely used in recent years and it is quite successful as per the study. 

Samsung is the leading producer of AMOLED displays today. 
It is making over 200 million of displays every year and is about to enlarge the production capability of their manufacturing very soon. 
It is focussing on smaller displays of 5-10 inch which are used in smartphones and tablets these days.
LG is also manufacturing OLEDs of larger display panels. 

It has used OLEDs for producing Television units of 55 to 77 inch display.
Even if both the companies have produced enough number of OLEDs every year, still the production volume has been relatively slower. 
As reported by both the companies about expanding their production capacities, the expectations for larger production of OLEDs have been widened and the public is also expectant about any new product launch.


article/introduction-to-3d-printers
Introduction to 3D Printers
is a revolutionary technology that have created a buzz recentlybecause of their ingenious concept that has been utilised in their invention, and the hugepotential to impact the current manufacturing process. 
Being an incomparable device that is utilised to craft a three dimensional object from a digital file; 3D printers have created marvels in the digital world of printers.The practice of making a three dimensional entity makes the use of the chemical approach and additive processes where an object is manufactured by organizing a range its coatings one over the other until the intact object is shaped. 

Each of these coatings is very finely sliced horizontal piece of a final object that is required to be made by the printer.
What is a 3D printer?
How do 3D printers work?
These printers first formulate the fundamental design of the object that you desire to form. 

This plan is made through a CAD file which applies 3D modelling program which is used to make a new project or it can also use 3D scanner which duplicates the exact model of the object and also builds a 3D digital file of the object. 
These scanners put together different techniques for making 3D models. 
For making a digital file for printing, the software used in 3D modelling splits the final model into millions of layers. 
When these slices are uploaded in the printer, a final object can be created by layering one above the other. 

The 3D printer studies every 2D slice of the image and crafts a final object, making a three dimensional model of the image.is
This video explains the complete process of 3D printing.
Technology used in the 3D printers
and many more.
3D Modelling
The printable 3D models can be shaped using CAD package or 3D scanner that uses plain digital camera and photogrammetric software. 
3D scanning procedure evaluates and saves digital data and makes it materialize as a shape of a real object. 
Based on this technique, three dimensional models can be produced. 

Irrespective of the 3D modelling software used, this 3D model gets converted into .STL or .OBJ format to allow the software that prints the object to make it readable.
The file must be examined for multiple errors before printing a 3D model from an STL file. 
This step is called fix up. 
STL files can have many errors that are generated from the process of 3D scanning and these errors are first needed to be fixed before slicing the layers of the file. 

After it’s done, the .STL file needs to be developed by the software that translates the model into multiple thin layers and converts into a file that has specific instructions labeled to it. 
The 3D printer tracks this file and the directions affixed to it and it lays down multiple layers of liquid, powder or paper material to craft the model from series of cross section. 
There are several materials that can be applied via the print nozzle like plastic, sand, metal or sometimes even chocolate. 
These layers which correspond to various cross sections of the CAD model are then connected or merged automatically to give them a final shape.
Applications of 3D printers
3D printing finds many applications in varioussectors of industries from automotiveto aerospaceand aviation to bio-printing and healthcare instruments. 
3D printing can also be of great use in creating objects of day to day use, and personal projects.
The most brilliant advantage of these printers is they can craft almost any shape and geometry of any entity. 

Well, the time taken to print the 3D model of any object largely depends only upon the size and structure of the object to be printed. 
It can take several hours to even days to print any entity. 
It also depends upon the method that has been used by the printer and how complex the model is. 
The technology of additive system can deduct your time from being wasted and help to print the object in few hours.
3D Printing Services
3D printersare expensive and not everyone can afford itfor their individual purposes, and so there are various companies and firms that offer 3D printing services. 
There are also online 3D printing serviceswhich deliver3D printing services at economical price range and can print and deliver any object from a digital file that you upload to their website.


article/7-segment-display
7 Segment Display Units
A seven-segment display (SSD) is a widely used electronic display device for displaying decimal numbers from 0 to 9. 
They are most commonly used in electronic devices like digital clocks, timers and calculators to display numeric information. 

As its name indicates, it is made of seven different illuminating segments which are arranged in such a way that it can form the numbers from 0-9 by displaying different combinations of segments. 
It is also able to form some alphabets like A, B, C, H, F, E, etc.
LED used to illuminate DOT in7 segment display.We can refer each segment as a LINE, as we can see there are 7 lines in the unit, which are used to display a number/character. 
We can refer each segment "a,b,c,d,e,f,g" and for dot character we will use "h". 

There are 10 pins, in which 8 pins are used to refer a,b,c,d,e,f,g and h/dp, the two middle pins are common anode/cathode of all he LEDs. 
These common anode/cathode are internally shorted so we need to connect only one COM pin.
There are two types of 7 segment displays: Common Anode and Common Cathode:
In this all the Negative terminals (cathode) of all the 8 LEDs are connected together (see diagram below), named as COM. 

And all the positive terminals are left alone.
In this all the positive terminals (Anodes) of all the 8 LEDs are connected together, named as COM. 
And all the negative thermals are left alone.
How to Display Numbers on 7 Segment Display?
If we want to display the number ᾰᾬ then we need to glow all the LEDs except LED which belongs to line “gᾠ(see 7 segment pin diagram above, so we need a bit pattern 11000000. 
Similarly to display ᾱ”we need to glow LEDs associated with b and c, so the bit pattern for this would be 11111001. 
A table has been given below for all the numbers while using Common Anode type 7 segment display unit.



0
11000000
C0
1
11111001
F9
2
10100100
A4

3
10110000
B0
4
10011001
99
5
10010010
92
6
10000010
82

7
11111000
F8
8
10000000
80
9
10010000
90


To learn more about 7 segment display units,read below tutorials which explains the practical applications to use 7 segment displays:

article/what-is-gps
GPS (Global positioning System)

GPS is a navigation technology which, by use of satellites, tells the precise information about a location.Basically a GPS system consists of group of satellites and well developed tools such as receiver. 
The system, however, should comprise at least four satellites. 
Each satellite and the receiver are equipped with stable atomic clock. 
The satellite clocks are synchronised with each other and ground clocks. 

GPS receiver also has a clock but it is not synchronized and is not stable (less stable). 
Any deviation of actual time of satellites from ground clock should be corrected daily. 
Four unknown quantities (three coordinates and clock deviation from satellite time) are required to be computed from the synchronized network of satellites and the receiver. 
The work of the GPS receiver is to receive signals from the network of satellites to compute three basic unknown equations of time and position.

A GPS signal includes a pseudorandom codes and time of transmission and satellite position at that time. 
The signal broadcasted by GPS is also called carrier frequency with modulation. 
Further, a pseudorandom code is a sequence of zeros and ones. 
Practically, the receiver position and the offset of receiver clock relative to receiver system time are computed simultaneously, using the navigation equations to process time of flight (TOFs). 

TOF is the four values that the receiver forms using time of arrival and time of transmission of the signal. 
The location is usually converted to latitude, longitude and height relative to geoids (essentially, mean sea level). 
Then the coordinates are displayed on the screen.
Elements of GPS
The structure of the GPS is a complex one. 
It consists of three major segments of a space segment, a control segment and a user segment. 
Launching the satellite into medium earth orbit is a strenuous job. 
The space segment comprises 24 to 32 satellites or space vehicles in the same orbit, 8 each in three circular orbits. 

At least six satellites are always in line of sight from almost everywhere on earth’s surface.
Next to space segment is control segment. 
In control segment there is a master control station, an alternate master control station, ground antennae and monitor station. 
The user segment is composed of thousands of civil, commercial and military positioning service. 

A GPS receiver or devise consists of an antenna, tuned to the frequency transmitted by satellites. 
It also includes display screen to provide location and time.
A GPS receiver is classified on the number of satellites it can monitor simultaneously, that is number of channels. 
Receivers generally have four to five channels but recent advancements have shown that up to 20 channels have also been made. 


Satellite frequency: All satellite broadcast frequencies. 
The frequency band comprises five types such as L1, L2, L3, L4, and L5. 
These bands have frequency ranges between1176MHz to 1600 M Hz.
How GPS works
GPS satellites rotate all around the earth two times in a day. 
It revolves around in a very accurate course and sends out indication and information to the earth. 
The receivers of GPS get all the information and apply triangulation to discover the accurate location of the user. 

Fundamentally, the receiver of GPS contrasts the duration at which a signal was spread by a satellite and allots the time it was received. 
The time difference formulates how far the receiver is away from the satellites of the GPS. 
It measures the exact distance with few more satellites and the receiver determines the position of the user and displays it on the map of the electronic appliance.
The receiver must be locked to the signal with at least three satellites to produce a two dimensional position and also tracks the movement of the user. 

By using four or more satellites, the receiver can determine the three dimensional position of the user which consists of altitude, latitude and longitude. 
After determining the position of user, the GPS unit calculates other information such as speed, bearing, track, distance, destination, sunrise, and sunset time.
How accurate is GPS?
The receivers of the GPS are very accurate because of the parallel multi channel design. 

The parallel channels are very quick and precise although certain factors like atmospheric noise and disturbances can perturb and affect the accuracy of GPS receivers at large sometimes. 

Users can also get improved precision with Differential GPS (DGPS), which corrects GPS signals to surrounded by a regular of three to five meters. 
The U.S. 

Coast Guard operates the most common DGPS correction service. 
The system contains an arrangement of towers that obtain GPS signals and broadcast an exacted signal by beacon transmitters. 
With the aim of getting the exact signal, users must have a differential beacon receiver and beacon antenna apart from having a GPS.
Sources of GPS signal errors
Factors that can corrupt the precision of GPS signals and thus influence accurateness incorporate the following:
Ionosphere and troposphere delays - The satellite signal slows down as it crosses the layers of atmosphere. 
The GPS system uses a built in model that is used to calculate the regular duration of hindrance required to correct this type of inaccuracy.
Signal multipath- This error is occurred when the signal is reflected from the objects like taller buildings and larger rocks before it reaches the receiver. 

This increases the overall time duration of the travel of signal and causes errors and inaccuracy.
Orbital errors ᾠThese errors are also known as ephemeris errors which are used to calculate the inaccuracies of the location of the satellite.
Number of satellites visible- accuracy depends on the exact number of satellites that a GPS receiver can see. 
The factors like buildings, terrain, electronic interference blocks the signal accuracy and reception which causes error in position and sometimes no reading in signals. 

It typically does not work indoors, underwater and underground.
Applications
Not only for military use is a GPS machine widely known for its use in civil and commercial services. 
Some civilian applications are:

Used in Astrometry and celestial mechanics calculations.
: It is also used in automated vehicles (driverless vehicles) to apply locations for cars and trucks.
: Modern mobile phones come equipped with GPS tracking software. 
It is present because one can know one’s position and can also track nearby utilities such as ATMs, coffee shops, restraints, etc. 

The first cell phone enabled GPS was launched in 1990s. 
In cellular telephony it is also used in detection for emergency calls and many other applications.
: In case of any natural disaster, a GPS is a best tool to identify the location. 
Even prior to the disasters like cyclones, GPS helps in calculating the estimated time.

5. Fleet tracking: GPS is a developer tool known for its potential to track military ships during the war time.
: A GPS enabled car makes it easier to track its location.
In geo fencing, we use GPS to track a human, an animal or a car. 
The devise is attached to the vehicle, person or on animal’s collar. 

It provides continuous tracking and updating.
: one of the major applications is geotagging meaning applying local coordinates to digital objects.
: Uses centimetre-level positioning accuracy.
: helps in determining location of nearby point of interests.

: Surveyors make use of Global Positioning System to plot maps.

article/difference-between-optical-and-laser-mouse
Optical Mouse vs. Laser Mouse
Difference between Optical and Laser Mouse
Although it is difficult to differentiate these two kinds of mouse by merely noticing or using, as the differences are not noticeable for most of users.Tracking Method, DPI and Cost are three major factors that differentiateOptical and Laser Mouse. 
All are being described below.
Optical Mouse uses LED lights to track the movements. 

Soitcan only be used on opaque surfaces. 
On the other hand, Laser mouse uses Laser light to track the movements. 
As the laser light is narrow and more targeted Laser mouseare more accurate and precise in tracking the movements. 
Also it makes the laser mouse to be used nearly on all types of surfaces, while optical mouse may face difficulties in accurate tracking on black or shiny surfaces.

DPI stands for Dots-Per-Inch. 
An ordinary optical mouse comes with around 200 ᾠ800 dpi which is fine if you’re using only Internet and casually using your computer. 
But for gaming, it comes Laser Mouse as it comes up to 4000 dpi for better sensitivity and accuracy. 
DPI can be reached to 8000+ as per the different range of Laser Mouse.

Laser mouse are available in the modern market at a higher price in comparison of regular optical mice. 
Although, some kind of optical mouse comes with excellent features like wireless, Bluetooth and macro buttons, which raise the value of it as much as a laser mouse.



LED Lights
Laser
Less Expensive
Comparatively Expensive
1980 (Mouse Systems Corporation and Xerox)
1998 (Sun Microsystems)
Microsoft (1999)
Logitech MX 1000 (2004)

Opaque surfaces, mouse pads, non-glossy surfaces
Can be used on glass, no mouse pad required
Lower resolution (up to 3000 dpi)
Higher resolution (up to 6000 dpi), superior surface tracking



article/what-is-4g-technology
What is 4G Technology?
You must have been hearing about the wireless technologies like 2G, 3G, 4G, etc. 
The latest in the sequence is 4G, which is the 4th generation of wireless telecommunication technologies. 

So basically what is 4G techology and how it is different from its predecessor technologies like 2G and 3G? Answers to these questions are coveredin this article.
Fourth generation of the mobile telecom services are offering better services as compared to its predecessor technologies withfaster data transfer rates. 
Along with a peak download speed of 1 Gbps and peak upload speed of 500 Mbps, theourth generation (4G) technology will be offering much advancement to the current wireless communication including low latency, efficient spectrum use and low-cost implementations. 
The latest integration alsooffers not only the high speed but also high-quality voice and high-definition video.

With impressive network capabilities, 4G enhancement promise to bring the wireless experience to an entirely new level with impressive user applications, such as sophisticated graphical user interfaces, high-end gaming, high-definition video and high-performance imaging.Consumer expectations for mobile handsets and similar products are becoming more and more sophisticated.
History of various communication technologies like 2G, 3G and 4G
The predecessor technologies to it are 1G, 2G and 3G technologies, 5G technology is also set up in the sequence with expected to hit the market by 2020. 
Here is the timeline for various communication technologies.


Mobile technology
Year
Generation
Early 1980’s
Generation
Late 1980’s

Generation
Early 2000’s
Generation
Late 2000’s
Generation
Expected by 2020


Along with these major ivolvements in wireless communication technologies, there have been some intermediate inventionslike 2.5G GPRS (General Packet Radio Service), which stands for "second and a half generation," is a cellular wireless technology developed in between its predecessor, 2G, and its successor, 3G and also 2.75 ᾠEDGE (Enhanced Data rates for GSM Evolution)
Key 4G Technologies
The 4g technologies have brought about many changes when compared to the previous technology. 
The 4Gtechnologies are required to work on the frequency range between 2 to 8 GHz. 

Despite having the same bandwidth ranging between 5-20 MHz the data transfer rates have rushed up by almost 10 times making it as fast as 20 Mbps. 
It makes it superior in areas like imaging and processing power tosupport future 4G applications like three dimensional (3D) and holographic gaming, 16 megapixel smartcameras and high-definition (HD) camcorders.
With the previous technologies using both types of switching the data transfer rates are pushed up choosing only the packet switching instead of choosing both packet switching and circuit switching methods. 
Packet-switched networks move data in separate, small blocks or packets based on the destination address in each packet. 

When received, packets are reassembled in the proper sequence to make up the message. 
Circuit-switched networks require dedicated point-to-point connections during calls. 
A circuit-switched network is good for certain kinds of applications with limited points to go. 
If you're doing voice applications solely, it's great. 

But if you have multiple locations to get to and large amounts of data to transmit, it's better to break it down into packets.
Current Stats of uses of 4G
Here is a list of countries depicting the penetration of 4G networks in their country and the frequency used by them for 4G network.


COUNTRY
PENETRAION
FREQUENCY
SOUTH KOREA
62%
800MHz, 1800MHz
JAPAN
21.3%

AUSTARLIA
21.1%


UNITED STATES
19%

SWEDEN
14%

CANADA
8%

UNITED KINGDON
5%
800MHz, 1800MHz, 2600MHz

GERMANY
3%

RUSSIA
2%
2600MHz
PHILIPPINES
1%


4G offers a lot of benefits
High bandwidths,
Low cost of network and equipment
The use of license-exempt spectrum

Higher capacity and quality of service enhancement
Access to the broadband multimedia services with lower cost
Inter-network roaming
Difference between 3G and 4G


Practically up to 3.2 Mbps
Practically between 2-8 Mbps
5 Mbps
500 Mbps

Circuit switching and packet switching
Packet switching and message switching.
Wide area cell based
LAN, WAN
CDMS 2000, EDGE, UMTS
LTE Advance and Winmax2
Turbo codes for error correction
Concatenated codes for error correction

100 Mbps
1 Gbps
1.8-2.5 GHz
2-8 GHz

Future of Wireless Communication Technologies
ITU (International Telecommunication Union) has established the overall roadmap for the development of 5G mobile and defined the term it will apply to it as “IMT-2020ᾮ The ITU-R Radio communication Assembly, which meets in October 2015, is expected to formally adopt the term “IMT-2020ᾮ

article/what-is-the-internet-of-things
Internet of Things  ᾠBasics, Current Trends and Future Scope

ᾮ
One of the most buzzing words in current world of technology is IoT, A concept with a huge potential to change our entire way of living and working. 
But what exactly is the “Internet of Thingsᾠand how is it going to impact our life? Let’s have a look at the basics of IoT, current trends and the future scope.
What is IoT?
Internet of Things is basically a concept to connect all the things (devices, gadgets, home appliances, vehicles, phones, computers, etc.) with the internet and make them able to communicate with each other and provide the required data, information to perform smoother operations.
The most exciting part of this technology is its endless possibilities. 
It can connect not only devices and gadgets but people, animals and objects to internet and assign a unique IP address to make it distinguishable and able to communicate. 
For example, a person with heart monitor implant or with wearable circuits, or a farm animal with biochip transponder, plants, an automobile with built-in sensors, street lights, and environment, all could be a part of IoT network.
What are the applications of IoT?
Once you have an understanding of what is basically the Internet of Things, you would know that in fact there are numerous applications of IoT ᾠacross almost all industries and sectors. 
From building and home automation to wearable devices, IoT has its importance in every aspect of our life. 
These are few key areas where IoT is going to play an important role:

Buildings and home automation
News and Media
Environmental Monitoring
Manufacturing

Medical and Healthcare Industry
Transportation
Energy Management
Smart Cities
What is the Future Scope of IoT
With the easy availability of internet and more and more devices like computers, smart phones, smart watches, smart wearable devices, etc. 
are being made with Wi-Fi functionalities; the network of internet connected devices is increasing rapidly. 
According to the recent data, there are over 12 billion devices that are able to connect with internet, and it is expected that the number of such devices will be more than 26 billion by 2020. 

This perfectly predicts an era of IoT where communication will not only be restricted to people to people or people to things but one step ahead with a worthwhile communication between things to things.

article/555-timer-ic
Understanding 555 Timer IC

This tutorial covers different aspects of 555 Timer IC and explains its working in details. 
So lets first understand what are astable, monostable and bistable vibrators.
This means there will be no stable level at the output. 
So the output will be swinging between high and low. 

This character of unstable output is used as clock or square wave output for many applications.
This means there will be one stable state and one unstable state. 
The stable state can be chosen either high or low by the user. 
If the stable output is selected high, then the timer always tries to put high at output. 

So when a interrupt is given, the timer goes low for a short time and since the low state is unstable it goes to high after that time. 
If the stable state is chosen low, with interrupt the output goes high for a short time before coming to low.
This means both the output states are stable. 
With each interruption the output changes and stays there. 

For instance the output is considered high now with interruption it goes low and it stays low. 
By the next interruption it goes high.
Important Characterstics of 555 Timer IC
NE555 IC is a 8 pin device. 

The important electrical characteristics of timer are that it should not be operated above 15V, it means the source voltage cannot be higher than 15v. 
Second,we cannot draw more than 100mA from the chip. 
If don't follow these, IC would be burnt and damaged.
Working Explanation
The timer basically consists of two primary building blocks and they are:
1.Comparators (two) or two op-amp
2.One SR flip-flop (set reset flip-flop)
comparator is simply a device that compares the voltages at the input terminals (inverting (- VE) and non-inverting (+VE) terminals). 

So depending on the difference in the positive terminal and negative terminal at input port, the output of the comparator is determined.
For example consider positive input terminal voltage be +5V and negative input terminal voltage be +3V.The difference is, 5-3=+2v. 
Since the difference is positive we get the positive peak voltage at the output of the comparator.
For another example, ifpositive terminal voltage is +3V and negative input terminal voltage be +5V.The difference is +3-+5=-2V, since the difference input voltage is negative. 

The output of comparator will be negative peak voltage.
If for an example consider the positive input terminal as INPUT and the negative input terminal as REFERENCE as shown in above figure.So the difference of voltage between INPUT and REFERNCE is positive we get a positive output from the comparator. 
If the difference is negative then we will get negative or ground at the comparator output.
The flip-flop is a memory cell, it can store one bit of data. 

In the figure we can see the truth table of SR flip-flop.
There are four states to a flip-flop for two inputs; however we need to understand only two states of the flip- flop for this case.

S
R
Q
Q' (Q bar)

0
1
0
1
1
0
1
0

Now as show in the table, for set and reset inputs we get the respective outputs. 

If there is a pulse at the set pin and a low level at reset, then flip-flop stores the value one and puts high logic at Q terminal. 
This state continues until the reset pin gets a pulse while set pin has low logic. 
This resets the flip-flop so the output Q goes low and this state continues until the flip-flop is set again.
By this way the flip-flop stores one bit of data. 

Here another thing is Q and Q bar are always opposite.
In a timer the comparator and flip-flop are brought together.
Consider 9V is supplied to the timer, because of the voltage divider formed by the resistor network inside the timer as shown in the block diagram; there will be voltage at the comparator pins.So because of the voltage divider network we will have +6V at the negative terminal of the comparator one. 
And +3V at the positive terminal of the second comparator.

One another thing is comparator one output is connected to reset pin of flip-flop, so it the comparator one output goes high from low then the flip-flop will reset. 
And on the other hand the second comparator output is connected to set pin of flip-flop, so if the second comparator output goes high from low the flip-flop sets and stores ONE.
Now if we observe carefully, for a voltage less than +3V at the trigger pin (negative input of second comparator), the output of the comparator goes low from high as discussed earlier. 
This pulse sets the flip-flop and it stores a value one.

Now if we apply a voltage higher than +6V at the threshold pin (positive input of comparator one) , the output of comparator goes from low to high. 
This pulse resets the flip-flop and the flip-flip store zero.
Another thing happens during reset of flip-flop, when it resets the discharge pin gets connected to ground as Q1 gets turned on. 
Q1 transistor turns on because the Qbar is high at reset and is connected to Q1 base.

In astable configuration the capacitor connected here discharges during this time and so the output of timer will be low during this time.In astable configuration the time during the capacitor charges the trigger pin voltage will be less than +3V and so the flip-flop will store one and the output will be high.
In an astable configuration as shown in figure,
The output signal frequency depends on RA, RB resistors and capacitor C. 
The equation is given as,

Frequency(F) = 1/(Time period) = 1.44/((RA+RB*2)*C).
Here RA, RB are resistance values and C is capacitance value. 
By putting the resistance and capacitance values in above equation we get the frequency of output square wave.
High Level logic time is given as, TH= 0.693*(RA+RB)*C

Low Level logic time is given as, TL= 0.693*RB*C
Duty ratio of the output square wave is given as, Duty Cycle= (RA+RB)/(RA+2*RB).
555 Timer Pin Diagram and Descriptions
Now as shown in figure, there are eight pins for a 555 Timer IC namely,

1.Ground.
2.Trigger.
3.Output.
4.Reset.

5.Control
6.Threshold.
7.Discharge
8.Power or Vcc

This pin has no special function what so ever. 
It is connected to ground as usual. 
For the timer to function, this pin must and should be connected to ground.
This pin also has no special function. 

It is connected to positive voltage. 
For the timer to function to work, this pin must be connected to positive voltage of range +3.6v to +15v.
As discussed earlier, there is a flip-flop in the timer chip. 
The output of flip-flop controls the chip output at pin3 directly.

Reset pin is directly connected to MR (Master Reset) of the flip-flop. 
On observation we can observe a small circle at the MR of flip-flop. 
This bubble represents the MR (Master Reset) pin is active LOW trigger. 
That means for the flip-flop to reset the MR pin voltage must go from HIGH to LOW. 

With this step down logic the flip-flop gets hardly pulled down to LOW. 
So the output goes LOW, irrespective of any pins.
This pin is connected to VCC for the flip-flop to stop from hard resetting.
This pin also has no special function. 

This pin is drawn from PUSH-PULL configuration formed by transistors.
The push pull configuration is shown in figure. 
The bases of two transistors are connected to flip-flop output. 
So when logic high appears at the output of flip-flop, the NPN transistor turns on and +V1 appears at the output. 

When logic appeared at the output of flip-flop is LOW, the PNP transistor gets turned on and the output pulled down to ground or –V1 appears at the output.
Thus how the push-pull configuration is used to get square wave at the output by control logic from flip-flop. 
The main purpose of this configuration is to get the load off flip-flop back. 
Well the flip-flop obviously cannot deliver 100mA at the output.

Well until now we discussed pins that do not alter the condition of output at any condition. 
The remaining four pins are special because they determine the output state of timer chip, we will discuss each of them now.
The control pin is connected from the negative input pin of comparator one.
Consider for a case the voltage between VCC and GROUND is 9v. 

Because of the voltage divider in the chip as observed in figure3 of page8, The voltage at the control pin will be VCC*2/3 (for VCC = 9, pin voltage=9*2/3=6V ).
The function of this pin to give the user the directly control over first comparator. 
As shown in above figure the output of comparator one is fed to the reset of flip-flop. 
At this pin we can put a different voltage, say if we connect it to +8v. 

Now what happens is, the THRESHOLD pin voltage must reach +8V to reset the flip-flop and to drag the output down.
For normal case, the V-out will go low once the capacitor gets charge up to 2/3VCC (+6V for 9V supply). 
Now since we put up a different voltage at control pin (comparator one negative or reset comparator).
Capacitor should charge until its voltage reaches the control pin voltage. 

Because of this force capacitor charging, the turn on time and turn off time of signal changes. 
So the output experiences a different turn on torn off ration.
Normally this pin is pulled down with a capacitor. 
To avoid unwanted noise interference with theworking.

Trigger pin is dragged from the negative input of comparator two. 
The comparator two output is connected to SET pin of flip-flop. 
With the comparator two output high we get high voltage at the timer output. 
So we can say the trigger pin controls timer output.

Now here what to observe is, low voltage at the trigger pin forces the output voltage high, since it is at inverting input of second comparator. 
The voltage at the trigger pin must go below VCC*1/3 (with VCC 9v as assumed, VCC*(1/3)=9*(1/3)=3V). 
So the voltage at the trigger pin must go below 3V (for a 9v supply) for the output of timer to go high.
If this pin is connected to ground, the output will be always high.

Threshold pin voltage determines when to reset the flip-flop in the timer. 
The threshold pin is drawn from positive input of comparator1.
Here the voltage difference between THRESOLD pin and CONTROL pin determines the comparator 2 output and so the reset logic. 
If the voltage difference is positive the flip-flop gets resetted and output goes low. 

If the difference in negative, the logic at SET pin determines the output.
If the control pin is open. 
Then a voltage equal to or greater than VCC*(2/3) (i.e.6V for a 9V supply) will reset the flip-flop. 
So the output goes low.

So we can conclude that THRESHOLD pin voltage determines when the output should go low, when the control pin is open.
This pin is drawn from the open collector of transistor.Since the transistor (on which discharge pin got taken, Q1) got its base connected to Qbar. 
Whenever the ouput goes low or the flip-flop gets resetted, the discharge pin is pulled to ground. 
Because Qbar will be high when Q is low, So the transistor Q1 gets turns ON as base of transistor got power.

, so the name DISCHARGE.

article/what-is-a-microcontroller
What is a Microcontroller?

Microcontrollers are integral part of embedded systems. 
A microcontroller is basicallycheap and small computer on a single chip that comprises a processor, a small memory, and programmable input-output peripherals. 
They are meant to be used in automatically controlled products and devices to perform predefined and pre-programmed tasks. 
To get a better idea of what actually is a microcontroller; let’s see an example of a product where microcontroller is used. 

A digital thermometer that displays the ambient temperature uses a microcontroller which is connected to a temperature sensor and a display unit (like LCD). 
The microcontroller here takes the input from temperature sensor in raw form, process it and display it to a small LCD display unit in a human readable form. 
Similarly a single or multiple microcontrollers are used in many electronic devices according to requirement and complexity of applications.
Where they are used?
Microcontrollers are used in embedded systems, basically a variety of products and devices that are combination of hardware and software,and developed to perform particular functions. 
A few examples of embedded systems where microcontrollers are used, could be ᾠwashing machines, vending machines, microwaves, digital cameras, automobiles, medical equipment, smart phones, smart watches, robots and various home appliances.
Why do we use microcontrollers?
Microcontrollers are used to employ automation in embedded applications. 

The major reason behind immense popularity of microcontrollers is their ability to reduce size and cost of a product or design, compared to a design that is build using separate microprocessor, memory and input/output devices.
As microcontrollers have features like in-built microprocessor, RAM, ROM, Serial Interfaces, Parallel Interfaces, Analog to Digital Converter (ADC), Digital to Analog Converter (DAC) etc. 
that makes it easy to build applications around it. 
In addition, microcontrollersᾠprogramming environment offers vast possibilities to control the different types of applications as per their requirement.
What are the different types of microcontrollers?
There is a wide range of microcontrollers available in the market. 
Various companies like Atmel, ARM, Microchip, Texas Instruments, Renesas, Freescale, NXP Semiconductors, etc. 
manufacture different kinds of microcontrollers with different kinds of features. 

Looking into various parameters like programmable memory, flash size, supply voltage, input/output pins, speed, etc, one can select the right microcontroller for their application.
according to these parameters.
When classified according to the bit-size, most of the microcontrollers range from 8-bit to 32 bit (higher bit microcontrollers are also available). 
In an 8-bit microcontroller its data bus consists of 8 data lines, while in a 16-bit microcontroller its data bus consists of 16 data lines and so on for 32 bit and higher microcontrollers.

Microcontrollers need memory (RAM, ROM, EPROM, EEPROM, flash memory, etc) to store programs and data. 
While some microcontrollers have inbuilt memory chips while others require an external memory to be connected. 
These are called embedded memory microcontrollers and external memory microcontrollers respectively. 
Inbuilt memory size also varies in different types of microcontrollers and generally you would find microcontrollers with memory of 4B to 4Mb.

Microcontrollers vary according to the number of input-output pin sizes. 
One can choose a specific microcontroller as per the requirement of application.
There are two types of instruction sets - RISC and CISC. 
A microcontroller can use RISC (Reduced Instruction Set Computer) or CISC (Complex Instruction Set Computer). 

As name suggests, RISC reduces the operation time defining the clock cycle of an instruction; while CISC allows applying one instruction as an alternative to many instructions.
There are two types of microcontrollers ᾠHarvard memory architecture microcontrollers and Princeton memory architecture microcontrollers.
8051 series of microcontrollers (8-bit)
AVR microcontrollers by Atmel (ATtiny, ATmega series)

Microchip’s PIC series microcontrollers
Texas Instrumentsᾠmicrocontrollers like MSP430
ARM Microcontrollers
Features of Microcontrollers
Microcontrollers are used in embedded systems for their various features. 
As shown in the below block diagram of a microcontroller, it comprises of processor, I/O pins, serial ports, timers, ADC, DAC, and Interrupt Control.
Processor is the brain of a microcontroller. 
When provided the input through input pins and instructions through programs, it process the data accordingly and provide at the output pins.

Memory chips are integrated in a microcontroller to store all the programs and data. 
There could be different types of memory integrated in microcontrollers like RAM, ROM, EPROM, EEPROM, Flash memory, etc.
Every microcontroller has input output ports. 
Depending on the types of microcontrollers, the number of input output pins may vary. 

They are used to interface with external input and output devices like sensors, display units, etc.
They facilitate microcontrollers serial interface with other peripherals. 
A serial port is a serial communication interface through which information transfers in or out one by one bit at a time.
Sometimes embedded systems need to convert data from digital to analog and vice versa. 

So most of the microcontrollers are incorporated with inbuilt ADC (Analog to Digital Converter) and DAC (Digital to Analog Converters) to perform the required conversion.
Timers and counters are important parts of embedded systems. 
They are required for various operations like pulse generation, count external pulses, modulation, oscillation, etc.
Interrupt control is one of the powerful features of microcontrollers. 

It is a sort of a notification which interrupts the ongoing process and instructs to perform the task defined by interrupt control.
To summarize all this up, microcontrollers are sort of compact mini computers which are designed to perform specific tasks in embedded systems. 
With a wide range of features, their importance and use are vast and they can be found in products and devices across all industries.
]


article/various-types-of-resistors
Different Types of Resistors
We will discuss some of them below.

Resistors are differentiated based on power dissipation, application, and design.
1/8 watt resistors
1/4 watt resistors
1/2 watt resistors

1 watt resistors
2 watt resistors
SMD (Surface Mount Devices) resistors
Through hole type

High power dissipation
Carbon coating type.
Wire wound type.
For most of application we use  watt-Through hole-Carbon coating type resistors.These are very important forelectronic students and hobbyistsas they are easy to get and to use. 

And they are cheap.
These are a quarter watt resistor that means these types of resistors can not dissipate more than quarter watt through body in normal room conditions. 
So these can drive a current ( ↰.25/R). 
If this limit crossed the resistor gets damaged.

These resistors are abundantly used as they are cheap. 
These are also breadboard friendly resistors and so an electronic student finds ease in designing circuits with these resistors.
These are a half watt resistor that means these types of resistors can not dissipate more than half watt through body in normal room conditions. 
So these can drive a current ( ↰.5/R). 

If this limit crossed the resistor gets damaged.
The above picture shows one watt-through hole-carbon type resistor. 
These resistors are used occasionally as they are not so cheap. 
These are not breadboard friendly resistors and are not preferred while designing.

These are one watt resistor that means these types of resistors cannot dissipate more than one watt through body in normal room conditions. 
So these can drive a current ( ↱/R). 
If this limit crossed the resistor gets damaged.
These are SMD (Surface Mount Device) type resistors. 

These can be found in PC mother boards, mobile phone or any embedded circuits. 
These are used when the driving currents are limited to 1-2 milliAmperes any current higher than that will damage the device.
These are used while making mass production circuits. 
These are not breadboard friendly. 

They are the cheapest of all types.
board by pick and place machine, and these soldered to board by over flow or by oven method.

article/what-is-the-difference-between-microprocessor-and-microcontroller

What is the difference between microprocessor and microcontroller?
is that a Microprocessor IC only has a CPU inside it while a Microcontroller IC also has RAM, ROM, and other peripherals associated with it. 
Some popular examples of the microprocessor are Intel core i7, AMD Athlon, Broadcom BCM2711 (Raspberry Pi) etc, and some example for microcontrollers are ATmega328 (Arduino UNO), STM32, PIC16F877A etc.To understand in detail we have to take a look at the general architecture of a Microprocessor and Microcontroller, which is exactly what we are going to do in this article.
What is a Microcontroller?
series of microcontroller.
you can check out the article linked.
What is a Microprocessor?
Microprocessor has only a CPU inside them in one or few Integrated Circuits. 

Like microcontrollers it does not have RAM, ROM and other peripherals. 
They are dependent on external circuits of peripheralsto work. 
But microprocessors are not made for specific task but they are required where tasks arecomplex and tricky like development of software’s, games and other applications that require high memory and where input and output are not defined. 
It may be called heart of a computer system. 

Some examples of microprocessor are Pentium, I3, and I5 etc.
From this image of architecture of microprocessor it can be easily seen that it have registers and ALU as processing unit and it does not have RAM, ROM in it.
Microprocessor VsMicrocontroller
As now you are basically aware of what is a microcontroller and microprocessor, it would be easy to identify the major differences between a microcontroller and microprocessor.

1. Key difference in both of them is presence of external peripheral, where microcontrollers have RAM, ROM, EEPROM embedded in it while we have to use external circuits in the case of microprocessors.
2. As all the peripheral of microcontroller are on single chip it is compact while microprocessor is bulky.
3. Microcontrollers are made by using complementary metal oxide semiconductor technology so they are farcheaper than microprocessors. 
In addition the applications made with microcontrollers are cheaper because they need lesser external components, while the overall cost of systems made with microprocessors are high because of the high number of external components required for such systems.

4. Processing speed of microcontrollers is about 8 MHz to 50 MHz, but in contrary processing speed of general microprocessors is above 1 GHz so it works much faster than microcontrollers.
5. Generally microcontrollers have power saving system, like idle mode or power saving mode so overall it usesless power and also since external components are low overall consumption of power is less. 
While in microprocessors generally there is no power saving system and also many external components are used with it, so its power consumption is high in comparison with microcontrollers.
6. Microcontrollers are compact so itmakes them favorable and efficient system for small products and applicationswhile microprocessors are bulky so they are preferred for larger applications.

7. Tasks performed by microcontrollers are limited and generally less complex. 
While task performed by microprocessors are software development, Game development, website, documents making etc. 
which are generally more complex sorequire more memory and speed so that’s why external ROM, RAM are used with it.
8. Microcontrollers are based on Harvard architecture where program memory and data memory are separate while microprocessors are based on von Neumann model where program and data are stored in same memory module.
article.