CONTENTS

To save space we have not provided lengthy explanations of how the circuits work. This has already been covered in TALKING ELECTRONICS Basic Electronics Course, and can be obtained on a CD for $10.00 (posted to anywhere in the world) See Talking Electronics website for more details: http://www.talkingelectronics.com

MORE INTRO



We have said this before abut we will say it again: There are two ways to learn electronics.

One is to go to school and study theory for 4 years and come out with all the theoretical knowledge in the world but very little practical experience. The other is to "learn on the job."

I am not saying one approach is better than the other but most electronics enthusiasts are not "book worms" and many have been dissuaded from entering electronics due to the complex mathematics surrounding University-type courses.

Our method is to get around this by advocating designing, building, constructions and even more assembly with lots of experimenting and when you get stuck with a mathematical problem, get some advice or read about it via the thousands of free test books on the web.

Anyone can succeed in this field by applying themselves to constructing projects. You actually learn 10 times faster by doing it yourself and we have had lots of examples of designs from students in the early stages of their career.

And don't think the experts get it right the first time. Look at all the recalled electronics equipment from the early days.

The most amazing inventions have come from almost "newcomers" as evidenced by looking through the "New Inventions" website.

All you have to do is see a path for your ideas and have a goal that you can add your ideas to the "Word of Invention" and you succeed.

Nothing succeeds like success. And if you have a flair for designing things, electronics will provide you a comfortable living for the rest of your life.

The market is very narrow but new designs are coming along all the time and new devices are constantly being invented and more are always needed.

Once you get past this eBook of "Chips" you will want to investigate microcontrollers and this is when your options will explode.

You will be able to carry out tasks you never thought possible, with a chip as small as 8 pins and a few hundred lines of code.

In two weeks you can start to understand the programming code for a microcontroller and perform simple tasks such as flashing a LED and produce sounds and outputs via the press of a button.

All these things are covered on Talking Electronics website and you don't have to buy any books or publications. Everything is available on the web and it is instantly accessible. That's the beauty of the web.

Don't think things are greener on the other side of the fence, by buying a text book. They aren't. Everything you need is on the web AT NO COST.

The only thing you have to do is build things. If you have any technical problem at all, simply email Colin Mitchell and any question will be answered. Nothing could be simpler and this way we guarantee you SUCCESS. Hundreds of readers have already emailed and after 5 or more emails, their circuit works. That's the way we work. One thing at a time and eventually the fault is found.

If you think a circuit will work the first time it is turned on, you are fooling yourself.

All circuits need corrections and improvements and that's what makes a good electronics person.Don't give up. How do you think all the circuits in these eBooks were designed? Some were copied and some were designed from scratch but all had to be built and adjusted slightly to make sure they worked perfectly.

I don't care if you use bread-board, copper strips, matrix board or solder the components in the air as a "bird's nest." You only learn when the circuit gets turned on and WORKS!

In fact the rougher you build something, the more you will guarantee it will work when built on a printed circuit board.

However, high-frequency circuits (such as 100MHz FM Bugs) do not like open layouts and you have to keep the construction as tight as possible to get them to operate reliably.

In most other cases, the layout is not critical.

If you just follow these ideas, you will succeed.



A few of the basics are also provided in this eBook, the first is transistor outlines:



TRANSISTORS

Most of the transistors used in our circuits are BC 547 and BC 557. These are classified as "universal" or "common" NPN and PNP types with a voltage rating of about 25v, 100mA collector current and a gain of about 100.

You can use almost any type of transistor to replace them and here is a list of the equivalents and pinouts:

The capacitor C charges via R1 and R2 and when the voltage on the capacitor reaches 2/3 of the supply, pin 6 detects this and pin 7 connects to 0v. The capacitor discharges through R2 until its voltage is 1/3 of the supply and pin 2 detects this and turns off pin7 to repeat the cycle. The top resistor is included to prevent pin 7 being damaged as it shorts to 0v when pin 6 detects 2/3 rail voltage. Its resistance is small compared to R2 and does not come into the timing of the oscillator.

The simplest Astable uses one resistor and one capacitor. Output pin 3 is used to charge and discharge the capacitor.

LOW FREQUENCY OSCILLATORS
	If the capacitor is replaced with an electrolytic, the frequency of oscillation will reduce. When the frequency is less than 1Hz, the oscillator circuit is called a timer or "delay circuit." The 555 will produce delays as long as 30 minutes but with long delays, the timing is not accurate.

555 ASTABLE OSCILLATORS

Here are circuits that operate from 300kHz to 30 minutes:

(300kHz is the absolute maximum as the 555 starts to malfunction with irregular bursts of pulses at this high frequency and 30 minutes is about the longest you can guarantee the cycle will repeat.)

SQUARE WAVE OSCILLATOR





A square wave oscillator kit can be purchased from Talking Electronics for approx $10.00

See website: Square Wave Oscillator

It has adjustable (and settable) frequencies from 1Hz to 100kHz and is an ideal piece of Test Equipment.

555

LED ZEPPELIN

This circuit is a game of skill. See full article: LED Zeppelin . The kit is available from talking electronics for $15.50 plus postage. Email HERE for details.

The game consists of six LEDs and an indicator LED that flashes at a rate of about 2 cycles per second. A push button is the "Operations Control" and by carefully pushing the button in synchronisation with the flashing LED, the row of LEDs will gradually light up.

But the slightest mistake will immediately extinguish one, two or three LEDs. The aim of the game is to illuminate the 6 LEDs with the least number of pushes.

We have sold thousands of these kits. It's a great challenge.



LED Zeppelin Project - A Game of Skill

LOGIC PROBE USING CD 4001



LOGIC PROBE USING CD 4011

The Knight Rider circuit is available as a kit for less than $15.00 plus postage as Kitt Scanner .



























Here is a simple Knight Rider circuit using resistors to drive the LEDs. This circuit consumes 22mA while only delivering 7mA to each LED. The outputs are "fighting" each other via the 100R resistors (except outputs Q0 and Q5).

This circuit drives 11 LEDs with a cross-over effect:

The circuit can also be constructed with a 40106 HEX Schmitt trigger IC (74C14). The 555 circuit consumes about 30mA when sitting and waiting. The 40106 circuit consumes less than 1mA.

The output of each gate will deliver about 10mA. This is sufficient to drive a LED, but if extra current is required, a transistor BUFFER will be needed. For up to 100mA, a BC547 can be used. For up to 4 amps a BD679 Darlington transistor can be used.

Each gate is a separate "Building Block." It is basically an AMPLIFIER. It is a CURRENT AMPLIFIER and it is different to any other type of amplifier. Here is how it works:

When the input is LOW, the output is HIGH and will deliver 10mA to a load. When the input is HIGH the output is LOW and it will sink 10mA from a load that is connected to rail.

Here is the CURRENT AMPLIFYING part: It takes less than 1 microamp on the input to make the output high or low.

Here's the second feature of the gate:

When the input is LOW (A LOW is from 0v to 25% of rail voltage), it can be increased slowly or up to a frequency of 4MHz, and when the voltage is 66% of rail voltage, the output immediately changes from HIGH to LOW.

When the input is HIGH (from 70% to 100% of rail voltage) and it decreases slowly or up to a frequency of 4MHz, the output immediately changes from LOW to HIGH when the voltage drops to 33% of rail voltage.

This produces a GAP between 33% and 66% called the HYSTERESIS GAP and it prevents noisy input voltages changing the output. The input voltage has to rise and/or fall about 33% of rail voltage for the output to change.

There are 6 of the gates in the IC and they are all internally wired to the power rails. You can think of the input as having infinite impedance (resistance), so it does not put a load on anything connected to this pin.



Here is an animation of how the gate works. The input has to be above mid-rail for the output to change and below mid-rail for the output to change back to its originals state.

The next feature to understand is called The time delay circuit is also know as a " TIMING CIRCUIT ," " DELAY CIRCUIT ," or " R-C CIRCUIT ". These names all refer to a CAPACITOR and RESISTOR in series. It does not matter if the capacitor is placed above or below the resistor as the time delay will be the same. (The only difference will be the value of the voltage at the beginning and end of the timing cycle.)

The join of the two components is the point where the voltage is detected and is called the " Detection Point ."

The Detection Point is monitored by a Detection Circuit . This will be the input of one of the Schmitt gates.

The detection circuit must not load the timing circuit. In other words the detection circuit must have a very high input impedance. That's the advantage of this IC. It is ideal for detecting the voltage on a DELAY CIRCUIT.

When voltage is applied to a TIMING CIRCUIT, the capacitor begins to charge. If we monitor the voltage across the capacitor, we can determine when it is at a particular voltage level. It will take a PERIOD OF TIME to reach this level and this is the TIME DELAY we require.

In the animation below we see the capacitor charging via a resistor, with a meter showing the approx voltage across the capacitor. The capacitor does not charge at a constant rate, but this characteristic does not concern us at the moment.

The point to remember is the TIME it takes for the capacitor to charge.

If we add the TIMING CIRCUIT (DELAY CIRCUIT) to the output of a Schmitt gate, we can see the capacitor charging and discharging:

Here is the clever part . Instead of the voltmeter monitoring the voltage across the capacitor, the input of the Schmitt Inverter can be connected to the capacitor.

If the voltage across the capacitor is less than 66% of rail voltage, the output of the gate is HIGH and the capacitor begins to charge. When the voltage reaches 67%, the output goes LOW and the capacitor begins to discharge. When the voltage across it reaches 32% of rail voltage, the Schmitt Inverter changes state and the output goes HIGH.In this way we need only one gate to create an oscillator.

There are two very important things to observe in the animation below.

1. The output is a square wave. In other words the output goes from one state to the other VERY QUICKLY and this produces the characteristic square wave-shape.

2. The voltage across the capacitor is EXACTLY 32% to 67% of rail voltage.

The animation below shows the gate in operation.

You will notice that the diagram does not show the chip connected to the positive and negative rail. It is ASSUMED the chip is connected to the supply voltage and that's how the output produces the HIGH.

Here are the basic oscillator blocks for a 74C14 (40106) IC:

Fig A shows a capacitor - high frequency oscillator

Fig B shows an electrolytic - low frequency oscillator

An oscillator is created by placing a resistor from output to input and a capacitor from input to 0v. The output will be a square-wave and and the mark (high) will be equal to the space (low).

The frequency of the output will depend on the value of R and C. Values of 1k to 4M7 for R and 100p to 100u for C can be used. This is shown in circuits A and B above.



If an unequal HIGH and LOW is required, a diode is placed between output and input:

In figure C the output is output is low for a short period of time as the two resistors R1 and R2 are discharging the capacitor. If R2 is a very low value compared with R1 we can get the low duration to be 10% or less, of the HIGH.

In figure D the diode is reversed compared to figure C and output is high for a short period of time as the two resistors R1 and R2 are charging the capacitor.



Here are some basic building blocks:

Delay

In the diagram above, the input line goes HIGH and remains HIGH. It can be detecting a piece of equipment being turned on, for example.

This action charges capacitor C via resistor R . After a period of time (called the Delay Time), the input of the Schmitt Trigger reaches 67% of rail voltage and the output goes LOW.

The Delay Time is determined by the values of R and C. We are not concerned with the actual values of R and C at this point in time. They can be worked out by experimentation.

The point to note is the placement of the two components to produce a DELAY .

If the output is required to be the opposite of the circuit above, an inverter is added:

If a diode is added across the input resistor, the capacitor "C" will be discharged when the input goes low, so the "Delay Time" will be instantly available when the input goes HIGH:

Pulse

The following circuit produces a PULSE when the input line goes HIGH:

To invert the output, add an inverter:

To produce a pulse after a delay, the following circuit is required:

Gating

To gate an oscillator via another inverter, a diode is placed between the two gates:

When the push-button is pressed, the input of the first gate goes LOW and the output goes HIGH. The high from the diode prevents the capacitor discharging via the oscillator and it is "jammed" or "frozen" with the output LOW.

The following circuit produces a tone for a short period of time as determined by the pulse section. When the output of the Pulse section is LOW, the oscillator will operate. When the Pulse section is HIGH the oscillator is JAMMED.

To extend the action of a push button, a pulse-extender circuit can be added:

To produce a TOGGLE SWITCH, the following circuit is needed.

The input of the 40106 has a microscopic current availability and over a period of a few hours it will charge the 100n and cause the circuit to re-trigger. That's why the 4M7 is needed.

2 MINUTE TIMER

The relay is energized for a short time, 2 minutes after the push-button is pressed. The push-button produces a brief LOW on pin 1, no matter how long it is pushed and this produces a pulse of constant length via the three components between pin 2 and 3.

This pulse is long enough to fully discharge the 100u timing electrolytic on pin 5.

The 100k and electrolytic between pins 6 and 9 are designed to produce a brief pulse to energize the relay.

Here is another very similar circuit. Use either the active HIGH or Active LOW switch and if the Active LOW switch is used, do not connect the parts or gate between pins 1 and 2 to the rest of the circuit.

Produces a 0.25sec pulse after 0.1sec to 2 seconds

The 74c14 can be used for lots of different circuits. In the following design, the output produces 3mS pulses every second. The circuit is adjustable to a wide range of requirements.

This circuit pulses the pager motor about 2 - 4 seconds after the circuit is turned on:

The following circuit allows a higher voltage to be used and PWM controls the energy to the Pager Motor. The component values will have to be determined by experimentation:

TRIGGER TIMER

The next design interfaces a "Normally Open" and "Normally Closed" switch to a delay circuit.

The feedback diode from the output prevents the inputs re-triggering the timer (during the delay period) the so that a device such as a motor, globe or voice chip can be activated for a set period of time.

The alarm keeps wailing if the door is kept open. It only turns off after 5-10 minutes when the door is opened and closed.

The CD4093 is a quad 2-input NAND gate (with Schmitt Trigger input) and each is wired as an inverter in this circuit. The Schmitt Trigger feature of the input of each gate is not an essential feature in this circuit and you can also use a CD4011 (quad 2-input NAND gate) as it does not have the Schmitt Trigger feature - and may be easier to buy.

The first gate (pins 1, 2 and 3) is a timer and the output does not go HIGH until the 100u charges via the 470k. This is the Exit/Entry delay. When it goes HIGH, the two LEDs are turned ON via the 3k3 resistors. This arms the alarm.

Gate " B " (pins 5, 6 and 4) is an inverter that detects when the Instant input is broken and it charges the 100u via the 3k3 resistor. Gate " C " (pins 8, 9 and 10) detects the charge on the 100u and turns on the BC547 transistor via the 4k7 resistor. The Instant switch can be closed after a second as it has done its job of charging the top 100u via the 3k3 resistor. The circuit is now activated and the siren starts wailing. The 100u and 4M7 provide the 5-10 minutes timer for the "wailing."

The 100u and 2M2 provide the timer for the buzzer when you enter. It will buzz for 20 seconds then turn off as the entry door has opened and closed and charged the lower 100u.The 1N4148 only allows the circuit to charge the 100u and when the door is closed, the voltage on the anode lead drops to a low value but the diode does not allow the 100u to discharge - it only discharges via the 2M2. If the Exit/Entry door is left open, the main siren will wail after 45 seconds. Gate " D " (pins 12, 13 and 11) detects the voltage on the lower 100u and turns ON the buzzer. The input of the gate puts no load on the 100u (as it has a very high impedance) and it is discharged via the 2M2.

The piezo buzzer can be a 5v device and a 100R resistor will be needed in series with one lead to reduce the volume.

JUST $3.50 plus $4.00 postage
or email Colin Mitchell: talking@tpg.com.au for details on buying the kit of components for this project. The siren module is too big to ship. You will need to buy the siren from your local alarm components supplier or electronics components store.

Build the circuit on a piece of matrix board (or the Circuit Board included in the kit) and connect the inputs to the screw terminals. 6 separate 2-screw terminals are provided in the kit to make it easy to wire-up the alarm. The alarm takes about 1mA when monitoring a house and about 100mA when activated.

The siren is only activated ONCE for 5 minutes when a break-in occurs as this is the maximum allowable time for a siren to wail in Australia.

If you want the alarm to constantly wail after a break-in, push button A when the alarm is turned on (and the exit beep is being produced). The constantly wailing LED will flash. Push the button again and the 5 minute LED will flash. The button toggles between the two features.

You can use reed switches for the input devices for doors and drawers. You can also trap the burglar by placing money under a clip and have a very thin length of tinned copper wire wound around two pins. When the money is removed, the wire is pulled off the pins. A single strand of wire can be obtained from a length of hook-up flex.

The alarm can be connected to a 12v gell cell with a rating of 1.2AHr and it can be automatically charged using our

Automatic Battery Charger in 101 Transistor Circuits. http://www.talkingelectronics.com/projects/200TrCcts/101-200TrCcts.html#84



Any of the inputs can be used for the Entry/Exit.

It is connected to the door you will use to enter or exit the property. The alarm gives you 45 seconds to exit.

When you enter the property, the buzzer turns on as soon as you open the door and beeps for 45 seconds to allow you to turn off the alarm.

If the alarm is not turned off, the main piezo siren produces a soft tone for 30 seconds and then a piercing wailing sound.

This allows you to turn off the alarm before the loud wailing is produced and is one of the best features of the alarm as the worry of false-triggering an alarm prevents many householders setting their alarm.

Any unused inputs must be connected with a link so the alarm can be set.

When the circuit is turned ON, you have 45 seconds to exit the premises.

The chip then flashes either the 5-min LED or the Constant LED to indicate if the siren will wail for 5 minutes or constantly. You can change the setting by pressing the button. The circuit then beeps for 45 seconds to give you time to exit the property. It then monitors all 4 inputs.

BUY KIT $20.00 plus $6.50 postage

The main chip contains an internal oscillator to drive a piezo diaphragm and also a wailing oscillator for the Piezo Siren. The Piezo Siren is an 80dB piezo diaphragm driven by a BD679 Darlington transistor with a 10mH choke to produce a high voltage for the diaphragm.

The chip operates on 5v and the rest of the circuit uses 12v. A very simple voltage-dropper consisting of 2 LEDs and 1k5 drops the 12v to 5v.

LED DICE - minimum components





LED DICE - using CD4018 5-bit Counter

MAKE ANY RESISTOR VALUE:

If you don't have the exact resistor value for a project, don't worry. Most circuits will work with a value slightly higher or lower.

But if you want a particular value and it is not available, here is a chart.

Use 2 resistors in series or parallel as shown:

There are other ways to combine 2 resistors in parallel or series to get a particular value. The examples above are just one way.

4R7 = 4.7 ohms

MAKE ANY CAPACITOR VALUE:

If you don't have the exact capacitor value for a project, don't worry. Most circuits will work with a value slightly higher or lower.

But if you want a particular value and it is not available, here is a chart.

Use 2 capacitors in series or parallel as shown:

The value "10" in the chart above can be 10p, 10n or 10u. The chart works for all decades (values).