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It contains a further circuits, with many of them containing one or more Integrated Circuits ICs. It's amazing what you can do with transistors but when Integrated Circuits came along, the whole field of electronics exploded.

IC's can handle both analogue as well as digital signals but before their arrival, nearly all circuits were analogue or very simple "digital" switching circuits. Let's explain what we mean. The word analogue is a waveform or signal that is changing increasing and decreasing at a constant or non constant rate.

Examples are voice, music, tones, sounds and frequencies. Equipment such as radios, TV's and amplifiers process analogue signals. Then digital came along. Digital is similar to a switch turning something on and off. The advantage of digital is two-fold. Firstly it is a very reliable and accurate way to send a signal. It cannot be half-on or one quarter off. And secondly, a circuit that is ON, consumes the least amount of energy in the controlling device.

In other words, a transistor that is fully turned ON and driving a motor, dissipates the least amount of heat. If it is slightly turned ON or nearly fully turned ON, it gets very hot. And obviously a transistor that is not turned on at all will consume no energy. When two transistors are cross-coupled in the form of a flip flop, any pulses entering the circuit cause it to flip and flop and the output goes HIGH on every second pulse. This means the circuit halves the input pulses and is the basis of counting or dividing.

This is called "logic" and introduces terms such as "Boolean algebra" and "gates. These chips are called Microcontrollers and a single chip with a few surrounding components can be programmed to play games, monitor heart-rate and do all sorts of amazing things. Because they can process information at high speed, the end result can appear to have intelligence and this is where we are heading: AI Artificial Intelligence.

But let's crawl before we walk and come to understand how to interface some of these chips to external components. In this Transistor Circuits ebook, we have presented about interesting circuits using transistors and chips.

In most cases the IC will contain 10 - transistors, cost less than the individual components and take up much less board-space. They also save a lot of circuit designing and quite often consume less current than discrete components. In all, they are a fantastic way to get something working with the least componentry.

A list of of Integrated Circuits Chips is provided at the end of this book to help you identify the pins and show you what is inside the chip. Some of the circuits are available from Talking Electronics as a kit, but others will have to be purchased as individual components from your local electronics store. Electronics is such an enormous field that we cannot provide kits for everything. But if you have a query about one of the circuits, you can contact me. To save space we have not provided lengthy explanations of how the circuits work.

One is to go to school and study theory for 4 years and come out with all the theoretical knowledge in the world but almost no practical experience. We know this type of person. We employed them for a few weeks! The other way is to build circuit after circuit and get things to work. You may not know the in-depth theory of how it works but trial and error gets you there. We know. We employed this type of person for up to 12 years. I am not saying one is better than the other but most electronics enthusiasts are not "book worms" and anyone can succeed in this field by constantly applying themselves with "constructing projects.

It would be nothing for an enthusiast to build 30 - 40 circuits from our previous Transistor eBook and a similar number from this book. Many of the circuits are completely different to each other and all have a building block or two that you can learn from.

Electronics enthusiasts have an uncanny understanding of how a circuit works and if you have this ability, don't let it go to waste. Electronics will provide you a comfortable living for the rest of your life and I mean this quite seriously. 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 and Transistors" 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. As I say in my speeches. What is the difference between a "transistor man" and a "programmer?

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. 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. 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. 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.

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 MHz 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. These are classified as "universal" or "common" NPN and PNP types with a voltage rating of about 25v, mA collector current and a gain of about We simply use Philips types that everyone recognises. You can use almost any type of transistor to replace them and here is a list of the equivalents and pinouts:.

The term AC means Alternating Current but it really means Alternating Voltage as the rising and falling voltage produces an increasing and decreasing current. The output of the following circuits will not be pure DC like that from a battery but will contain ripple.

Ripple is reduced by adding a capacitor electrolytic to the output. The first two transistors form a high-gain amplifier with feedback via the 4u7 to produce a low-frequency oscillator. This provides voltage for the second oscillator across the 1k resistor to drive a speaker. All diodes every type of diode are zener diodes.

They all break down at a particular voltage. The fact is, a power diode breaks down at v or v and its zener characteristic is not useful. But if we put 2 zener diodes in a bridge with two ordinary power diodes, the bridge will break-down at the voltage of the zener. This is what we have done. If we use 18v zeners, the output will be 17v4.

When the incoming voltage is positive at the top, the left zener provides 18v limit and the left power-diode produces a drop of. This allows the right zener to pass current just like a normal diode but the voltage available to it is just 18v.

The output of the right zener is 17v4. The same with the other half-cycle. The current is limited by the value of the X2 capacitor and this is 7mA for each n when in full-wave as per this circuit. Theoretically the circuit will supply 70mA but we found it will only deliver 35mA before the output drops. The capacitor should comply with X1 or X2 class. The 10R is a safety-fuse resistor. The problem with this power supply is the "live" nature of the negative rail. When the power supply is connected as shown, the negative rail is 0.

If the mains is reversed, the negative rail is v peak above neutral and this will kill you as the current will flow through the diode and be lethal. You need to touch the negative rail or the positive rail and any earthed device such as a toaster to get killed.

The only solution is the project being powered must be totally enclosed in a box with no outputs. LEDs on vI do not like any circuit connected directly to v mains. However Christmas tress lights have been connected directly to the mains for 30 years without any major problems. Insulation must be provided and the lights LEDs must be away from prying fingers. You need at least 50 LEDs in each string to prevent. As you add more LEDs to each string, the current will drop a very small amount until eventually, when you have 90 LEDs in each string, the current will be zero.

Each LED will see less than 7mA peak during the half-cycle they are illuminated. No rectifier diodes are needed. The LEDs are the "rectifiers. You must have LEDs in both directions to charge and discharge the capacitor. The resistor is provided to take a heavy surge current through one of the strings of LEDs if the circuit is switched on when the mains is at a peak. The LEDs above detect peak current.

The current-capability of a capacitor needs more explanation. In the diagram on the left we see a capacitor feeding a full-wave power supply. This is exactly the same as the LEDs on v circuit above. Imagine the LOAD resistor is removed. Two of the diodes will face down and two will face up. This is exactly the same as the LEDs facing up and facing down in the circuit above.

The only difference is the mid-point is joined. Since the voltage on the mid-point of one string is the same as the voltage at the mid-point of the other string, the link can be removed and the circuit will operate the same.

In the half-wave supply, the capacitor delivers 3. You can use any LEDs and try to keep the total voltage-drop in each string equal. Each string is actually working on DC. It's not constant DC but varying DC.

Because the LEDs turn on and off, you may observe some flickering and that's why the two strings should be placed together. There is one minor fault in the circuit. The 10k should be increased to k to increase the "ON" time. The photo shows the circuit built with surface-mount components:.

The output goes HIGH about 2 seconds after the switch is pressed. The LED turns on for about 0. The circuit will accept either active HIGH or LOW input and the switch can remain pressed and it will not upset the operation of the circuit. The transformer consists of 50 turns 0. The feedback winding is 20 turns 0. The circuit consumes mW but the LEDs are driven with high-frequency, high-voltage spikes, and become more-efficient and produce a brighter output that if driven by pure-DC.

Each LED has a characteristic voltage of 3. By selecting the LEDs we have produced 3 chains of If only 4 LEDs are in series, the characteristic voltage may be as low as Even-up the characteristic voltage across each chain by checking the total voltage across them with an 19v supply and R dropper resistor.

The transformer is shown above. It is wound on a 10mH choke with. This circuit is called a "boost circuit. The LEDs in the circuit are 20,mcd with a viewing angle of 30 degrees many of the LED specifications use "half angle. This equates to approximately 4 lumens per LED. Our design is between 50 - 60 lumens per watt and it is a much-cheaper design.

The effectiveness of a LED array increases when they are spread out slightly and this makes them more efficient than a single 1 watt or 2 watt LED. The two modifications to the circuit make the BC work harder and this is the limit of the inductor. The current consumption is about 95mA. The winding details for the transformer are shown above. They should be graded so that the characteristic voltage-drop across each of them is within 0. The circuit will drive any number from 1 to 20 by changing the "sensor" resistor as shown on the circuit.

The current consumption is about 95mA 12v and lower at 18v. The circuit can be put into dim mode by increasing the drive resistor to 2k2.

The UF is an ultra fast 1N - similar to a high-speed diode. You can use 2 x 1N signal diodes. The circuit will not drive two LEDs in series - it runs out of voltage and current when the voltage across the load is 7v. It oscillates at approx kHz. The photo on the circuit diagram shows the LED mounted on a heatsink and the connecting wires.

A 1-watt demo board showing the complex step-up circuitry. This is a Boost circuit to illuminate the LED and is completely different to our design. It has been included to show the size of a 1 watt LED.

We cannot alter it. This is very difficult to do and so a resistor is normally added in series. But this resistor wastes a lot of energy. So, to keep the loses to a minimum, we pulse the LED with bursts of energy at a higher voltage and the LED absorbs them and produces light. With a Buck circuit, the transistor is turned on for a short period of time and illuminated the LEDs. At the same time, some of the energy is passed to the inductor so that the LEDs are not damaged.

When the transistor is turned off, the energy from the inductor also gives a pulse of energy to the LEDs. When this has been delivered, the cycle starts again. A simple power supply can be made with a component called a "3-pin regulator or 3-terminal regulator" It will provide a very low ripple output about 4mV to 10mV provided electrolytics are on the input and output. The diagram above shows how to connect a regulator to create a power supply. The regulators can handle mA, mA and 1 amp, and produce an output of 5v, as shown.

These regulators are called linear regulators and drop about 4v across them - minimum. If the current flow is 1 amp, 4watts of heat must be dissipated via a large heatsink.

If the output is 5v and input 12v, 7volts will be dropped across the regulator and 7watts must be dissipated. The LM regulators are adjustable and produce an output from 1. The LMT regulator will deliver up to 1. The range of regulators are called "fixed regulators" but they can be turned into adjustable regulators by "jacking-up" their output voltage. For a 5v regulator, the output can be 5v to 30v. The LM regulator is adjustable from 1. To make the output 0v to 35v, two power diodes are placed as shown in the circuit.

Approx 0. The circuit can also be called a current-limiting circuit and is ideal in a bench power supply to prevent the circuit you are testing from being damaged. Approximately 4v is dropped across the regulator and 1.

Suppose you want to charge 4 Ni-Cad cells. Connect them to the output and adjust the R pot until the required charge-current is obtained. The charger will now charge 1, 2, 3 or 4 cells at the same current. But you must remember to turn off the charger before the cells are fully charged as the circuit will not detect this and over-charge the cells. The LM 3-terminal regulator will need to be heatsinked. This circuit is designed for the LM series of regulator as they have a voltage differential of 1.

This constant current circuit is designed to drive two 3-watt Luxeon LEDs. Approximately 4v is dropped across the LMT regulator and 1. A 12v battery generally delivers The LM T 3-terminal regulator will need to be heatsinked. This circuit is designed for the LM series of regulator as they have avoltage differential of 1.

It produces a constant 5v mA. You can use any old cells and get the last of their energy. Use an 8-cell holder. The voltage from 8 old cells will be about 10v and the circuit will operate down to about 7. The regulation is very good at 10v, only dropping about 10mV for mA current flow the 78L05 has 1mV drop.

As the voltage drops, the output drops from 5v on no-load to 4. The pot can be adjusted to compensate for the voltage-drop. It can take the place of a 78L05 3-terminal regulator, but it is more efficient. It produces a constant 5v up to mA. The regulation is very good at 10v, only.

This transistor simply allows the current to flow through the collector-emitter leads. The output voltage is maintained by the 3-terminal regulator but the current flows through the "pass transistor. Normally a 2N or TIP is used for this application as it will handle up to 10 amps and creates a 10 amp power supply.

The regulator can be 78L05 as all the current is delivered by the pass transistor. This has very limited application as many circuits do not like this. They supply power to a project for a short period of time. The output voltage gradually dies and this will will produce weird effects with some projects.

Ordinary red LEDs do not work. The output voltage of the LED is up to mV when detecting very bright illumination. When light is detected by the LED, its resistance decreases and a very small current flows into the base of the first transistor.

The transistor amplifies this current about times and the resistance between collector and emitter decreases. The k resistor on the collector is a current limiting resistor as the middle transistor only needs a very small current for the circuit to oscillate.

If the current is too high, the circuit will "freeze. The resistor values on each detector will need to be adjusted changed according to the voltage of the supply and the types of detector being used.

Any number of detectors can be added. See Talking Electronics website for train circuits and kits including Air Horn, Capacitor Discharge Unit for operating point motors without overheating the windings, Signals, Pedestrian Crossing Lights and many more. The LED is called dual colour or tri-colour as it shows red in one direction and green in the other orange when both LEDs are illuminated.

This simple circuit flashes a globe at a rate according to the value of the R and u electrolytic. This is a relay that latches itself ON when it receives a pulse in one direction and unlatches itself when it receives a pulse in the other direction. The following diagram shows how the coil makes the magnet click in the two directions.

To operate this type of relay, the voltage must be reversed to unlatch it. The u gradually charges and the current falls to a very low level. When the input voltage is removed, the circuit produces a pulse in the opposite direction to unlatch the relay. The pulse-latching circuit above can be connected to a microcontroller via the circuit at the left.

The electrolytic can be increased to 1,u to cater for relays with a low resistance. If you want to latch an ordinary relay so it remains ON after a pulse, the circuits above can be used. Power is needed all the time to keep the relay ON. It has 2 coils and requires the circuit at the left. A 5v Latching Relay can be use on 12v as it is activated for a very short period of time. A double-pole ordinary relay and transistor can be connected to provide a toggle action.

The circuit comes on with the relay de-activated and the contacts connected so that the u charges via the 3k3. Allow the u to charge. By pressing the button, the BC will activate the relay and the contacts will change so that the 3k3 is now keeping the transistor ON. The u will discharge via the 1k. After a few seconds the electro will be discharged. If the press-button is now pushed for a short period of time, the transistor will turn off due to the electro being discharged.

A single-coil latching relay normally needs a reverse-voltage to unlatch but the circuit at the left provides forward and reverse voltage by using 2 transistors in a very clever H-design. A normal relay can be activated by a short tone and de-activated by a long tone as shown via the circuit on the left.

This circuit can be found in "27MHz Links" Page 2. When the switch is pressed, the voltage on C1 is passed to Q3 to turn it on. This turns on Q1 and the voltage developed across R7 will keep Q1 turned on when the button is released. Q2 is also turned on during this time and it discharges the capacitor. When the switch is pressed again, the capacitor is in a discharged state and this zero voltage will be passed to Q3 turn it off.

This turns off Q1 and Q2 and the capacitor begins to charge again to repeat the cycle. The following diagrams show how to connect a double-pole double throw relay or switch and a set of 4 push buttons.

The two buttons must be pushed at the same time or two double pole push-switches can be used. See H-Bridge below for more ways to reverse a motor. When the relay is activated, the motor travels in the forward direction and hits the "up limit" switch. The motor stops. This sends a pulse to the latching relay to reverse the motor and ends the short pulse. The train travels to the "down limit" switch and reverses. If the motor can be used to click a switch or move a slide switch, the following circuit can be used:.

When power is applied, the relay is not energised and the train musttravel towards the "up limit. The Normally Open contacts of the relay will close and this will keep the relay energised and reverse the train. When the down limit is pressed, the relay is de-energised. If you cannot get a triple-pole change-over relay, use the following circuit:. The following circuit turns on the red LED below The green LED illuminates above The red LED turns on from 6v to below 11v.

It turns off above 11v and The orange LED illuminates between 11v and 13v. It turns off above 13v and The green LED illuminates above 13v. He wanted a low fuel indicator for his motorbike. The LED illuminates when the fuel gauge is 90 ohms.

The tank is empty at ohms and full at zero ohms. To adapt the circuit for an 80 ohm fuel sender, simply reduce the R to R. The first thing you have to do is measure the resistance of the sender when the tank is amply. When a button is pressed the corresponding globe is illuminated. The Quiz Master globe is also illuminated and the cathode of the 9v1 zener sees approx mid-rail voltage. The zener comes out of conduction and no voltage appears across the R resistor.

No other globes can be lit until the circuit is reset. It has a range of - metres depending on the terrain and the flashing LED turns the circuit ON when it flashes. The circuit consumes 5mA when producing a carrier silence and less than 1mA when off background snow is detected. Two identical circuits will be needed, one for left and one for right.

This is the approximate voltage when the handset is picked up. When the line voltage is above 25v, the BC is turned on and this robs the base of the second BC of the 1. When the line voltage drops, the first BC turns off and the 10u charges via the 47k and gradually the second BC is turned on. This action turns on the BC and the resistance between its collector-emitter leads reduces.

Two leads are taken from the BC to the "rem" remote socket on a tape recorder. When the lead is plugged into a tape recorder, the motor will stop. If the motor does not stop, a second remote lead has been included with the wires connected the opposite way. This lead will work.

The audio for the tape recorder is also shown on the diagram. This circuit has the advantage that it does not need a battery. It will work on a 30v phone line as well as a 50v phone line.

A FET has two advantages over a transistor in this type of circuit. It takes very little current into the gate to turn it on. This means the gate resistor can be very high. This means the motor in the tape recorder will operate at full strength. This circuit has not been tested and the 10k resistor in series with the first 15v zener creates a low impedance and the circuit may not work on some phone systems.

He wanted to have a display on his jacket that ran 9 LEDs then stopped for 3 seconds. The animated circuit shows this sequence:. Note the delay produced by the u and 10k produces 3 seconds by the transistor inhibiting the taking pin 6 LOW. Learn more about the - see the article: "The " on Talking Electronics website by clicking the title on the left index.

See the article on CD Both inputs must not be LOW with the first H-bridge circuit. If both inputs go LOW at the same time, the transistors will "short-out" the supply. This means you need to control the timing of the inputs. In addition, the current capability of some H-bridges is limited by the transistor types. Most touch switches rely on 50Hz mains hum and do not work when the hum is not present.

This circuit does not rely on "hum. This is just a diagram to show how the parts are connected. The coils actually sit flat against the slide against the side of the magnet as shown in the diagram:The output voltage depends on how quickly the magnet passes from one end of the slide to the other.

That's why a rapid shaking produces a higher voltage. You must get the end of the magnet to fully pass though the coil so the voltage will be a maximum. Thats why the slide extends past the coils at the top and bottom of the diagram. The circuit consists of two turn coils in series, driving a voltage doubler.

Each coil produces a positive and negative pulse, each time the. The positive pulse charges the top electrolytic via the top diode and the negative pulse charges the lowerelectrolytic, via the lower diode. The voltage across each electrolytic is combined to produce a voltage for the white LED.

When the combined voltage is greater than 3. The electrolytics help to keep the LED illuminated while the magnet starts to make another pass. The k charging and 47k discharging resistors have been chosen to create equal on and off times.

The 10u prevents flicker and the R also reduces flicker. It is a surface-mount bug with 6 legs. The pager motor is driven by an H-Bridge and "walks" to a wall where a feeler consisting of a spring with a stiff wire down the middle causes the motor to reverse. In the forward direction, both sets of legs are driven by the compound gearbox but when the motor is reversed, the left legs do not operate as they are connected by a clutch consisting of a spring-loaded inclined plane that does not operate in reverse.

This causes the bug to turn around slightly. The circuit also responds to a loud clap. The photo shows the 9 transistors and accompanying components:. Hex Bug gearbox consists of a compound gearbox with output "K" eccentric pin driving the legs.

You will need to see the project to understand how the legs operate. When the motor is reversed, the clutch "F" is a housing that is spring-loaded to "H" and drives "H via a square shaft "G". Gearwheel "C" is an idler and the centre of "F" is connected to "E" via the shaft.

When "E" reverses, the centre of "F" consists of a driving inclined plane and pushes "F" towards "H" in a clicking motion. Thus only the right legs reverse and the bug makes a turn. When "E" is driven in the normal direction, the centre of "F" drives the outer casing "F" via an action called an "Inclined Dog Clutch" and "F" drives "G" via a square shaft and "G" drives "H" and "J" is an eccentric pin to drive the legs.

The drawing of an Inclined Dog Clutch shows how the clutch drives in only one direction. In the reverse direction it rides up on the ramp and "clicks" once per revolution. The spring "G" in the photo keeps the two halves together. The frequency is dependent on the k pot and n to give a frequency range from about Hz to Hz. For those who enjoy model railways, the ultimate is to have a fast clock to match the scale of the layout. This circuit will appear to "make time fly" by revolving the seconds hand once every 6 seconds.

The timing can be adjusted by the electrolytics in the circuit. The electronics in the clock is disconnected from the coil and the circuit drives the coil directly. The circuit takes a lot more current than the original clock 1, times more but this is the only way to do the job without a sophisticated chip.

For those who want the circuit to take less current, here is a version using a Hex Schmitt Trigger chip:. The slide switch controls the action. The Darlington transistor will need a heatsink if the motor is loaded.

The second circuit must rise to at least 5. Also the rise and fall times must be very fast to prevent both transistors coming on at the same time and short-circuiting. The third circuit doubles an AC voltage.

The AC voltage rises "V" volts above the 0v rail and "V" volts below the 0v rail. The second 10u is charged via the 5k6 and 33k and when a sound is detected, the negative excursion of the waveform takes the positive end of the 10u towards the 0v rail.

The negative end of the 10u will actually go below 0v and this will pull the two 1N diodes so the anode ends will have near to zero volts on them. As the voltage drops, the transistor in the bi-stable circuit that is turned on, will have 0.

As the anodes of the two signal diode are brought lower, the transistor that is turned on, will begin to turn off and the other transistor will begin to turn on via its u and 47k. As it begins to turn on, the transistor that was originally turned on will get less "turn-on" from its u and 47k and thus the two switch over very quickly.

The collector of the third transistor can be taken to a buffer transistor to operate a relay or other device. The "press-to-talk" switches should have a spring-return so the intercom can never be left ON.

The secret to preventing instability motor-boating with a high gain circuit like this is to power the speaker from a separate power supply! You can connect an extra station or two extra stations to this design. Here is a 12v Warning Beacon suitable for a car or truck break- down on the side of the road.

The key to the operation of the circuit is the high gain of the Darlington transistors. Audio Software icon An illustration of a 3.

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