ELECTRONIC PLAYGROUND TM and LEARNING CENTER MODEL EP-130 ELENCO® 150 Carpenter Avenue Wheeling, IL 60090 (847) 541-3800 Website: www.elenco.com e-mail: elenco@elenco.com ELENCO ® Wheeling, IL, USA Copyright © 2012, 2009 by Elenco® Electronics, Inc. All rights reserved. REV-A Revised 2012 No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.
Important: If you encounter any problems with this kit, DO NOT RETURN TO RETAILER. Call toll-free (800) 533-2441 or e-mail us at: help@elenco.com. Customer Service • 150 Carpenter Ave. • Wheeling, IL 60090 U.S.A. WARNING: Always check your wiring before turning on a circuit. Never leave a circuit unattended while the batteries are installed. Never connect additional batteries or any other power sources to your circuits. ! WARNING: CHOKING HAZARD - Small parts. Not for children under 3 years.
Ohm’s Law The relationship between voltage, current, and resistance. Ohm, (Ω) The unit of resistance. Oscillator A circuit that uses feedback to generate an AC output. Parallel When several electrical components are connected between the same points in the circuit. Pico- (p) A prefix used in the metric system. It means a millionth of a millionth (0.000,000,000,001) of something. measure for Pitch The musical term for frequency.
BEFORE YOU START THE FUN! As you will notice we refer to a Volt / Ohm Meter (VOM) for making measurements. A VOM or multimeter is a instrument that measures voltage, current (amperes or amps), and resistance (ohms-Ω). You will learn more about these in the upcoming pages. If you really want to learn about electronic circuits, it is vital that that you learn how to measure circuit values - for only then will you really understand electronic circuitry.
DEFINITION OF TERMS WIRING CONNECTIONS AC Common abbreviation alternating current. Provided in your kit are spring terminals and pre-cut wires, make the wires snap together for your use in the numerous projects. To join a wire to a spring terminal, just directly bend the spring over to one side and then install the wire into the opening. Alternating Current for Carbon A chemical element used to make resistors. A current that is constantly changing.
fine screen would keep rocks from falling over), which would prolong the flow of water but not stop it completely. Like rocks are for water, resistors work in a similar way. They regulate how much electric current flows. The resistance, is expressed in ohms (Ω, named in honor of George Ohm), kilohms (kΩ, 1,000 ohms) or megohms (MΩ, 1,000,000 ohms) is a determination of how much resistor resists the flow of electricity.
AND Gate: 29, 36, 39, 40 Data: 47 DTL: 29, 30, 31, 33, 35 Exclusive OR: 33, 44 Flip-flop: 27, 28, 38, 43, 58, 59 Inverting: 70, 72, 73, 74, 85, 95, 109 Line: 46 NAND Gate: 31, 41 NOR Gate: 42 OR Gate: 37, 42, 44, 45 Power Supply: 29, 72, 73, 74, 75 TTL: 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 50, 51, 54, 55, 60, 78, 90, 112, 123 The “8” LED display is mounted on a board and to prevent burning out the display with excess current, permanent resistors have been wired
Antenna: This cylindrical component with a coil of fine wire wrapped around it is a radio antenna. If you’re wondering what the dark colored rod is, it’s actually mostly powdered iron. It’s also known as a “Ferrite Core”, which is efficient for antennas, and used in almost all transistor radios. created by variations of vibrations and then travel across the room. When you hear a sound it is actually your ears feeling the pressure from the air vibrations.
Key: The key is a simple switch—you press it and electricity is allowed to flow through the circuit. When you release it, the circuit is not complete because a break is caused in the circuit’s path. The key will be used in most circuits often times in signaling circuits (you can send Morse code this way as well as other things). EXPERIMENT #130 TWIN-T OSCILLATOR The twin-T type audio oscillator is very popular for use with electronic organs and electronic test equipment because it is very stable.
TROUBLESHOOTING EXPERIMENT #129: SINE WAVE OSCILLATOR WITH LOW DISTORTION You should have no problem with the projects working properly if you follow the wiring instructions. However, if you do encounter a problem you can try and fix it by using the following troubleshooting steps. These steps are comparable to those steps that electronic technicians use to troubleshoot complex electronic equipment. 1.
EXPERIMENT #128: SINE WAVE OSCILLATOR Notes: This oscillator circuit produces a sine wave signal. A sine wave (or sinusoid) is a wave of pure singlefrequency tone. As an example, a 400Hz sine wave is a wave that oscillates 400 cycles in one second and contains no other frequency contents. Non-sine waves (such as square wave or triangular wave signals) have harmonics - waves with frequencies that are multiples of the single-frequency fundamental wave.
EXPERIMENT #1: WOODPECKER EXPERIMENT #127: TRANSISTOR TESTER Transistors are very important, and you may need to test them to be sure they are working. You can’t tell if one is working just by looking at it, but this circuit lets you test them. This circuit also checks whether a transistor is a PNP or an NPN. Notes: For your first experiment you are going to make a circuit that that sounds like a woodpecker chirping. Follow the wiring sequence carefully and observe the drawings.
EXPERIMENT #126: RESISTANCE TESTER EXPERIMENT #2: POLICE SIREN Notes: If you use a meter you can find the exact value of a resistance; but when you only want to know approximate resistance values, you can use this resistance tester. Notes: Here is the first siren you are going to do – don’t be shocked if this experiment becomes the most famous circuit in this kit. This siren sounds like a real siren on a police car! After the wiring is competed press the key.
EXPERIMENT #3: METRONOME EXPERIMENT #125: PULSE TONE GENERATOR Notes: Learning to play a musical instrument? Then you might find this experiment helpful. This is an electronic version of the metronome, used by musical students and musical geniuses alike, worldwide. Notes: This experiment is a pulse-tone oscillator with an adjustable frequency that can obtain a wide range of notes. You can play tunes on it that sound like an electronic organ, but it takes some practice.
EXPERIMENT #124: WATER LEVEL BUZZER Notes: You can use the operational amplifier as a comparator for detecting changes in voltage. In this experiment, you are going to use this comparator function to make a water buzzer that sounds when the wire ends come into contact with water. EXPERIMENT #4: GRANDFATHER CLOCK Does your home lack a grandfather clock? Well not any longer, with this experiment you will make your own electronic grandfather clock.
EXPERIMENT #5: HARP EXPERIMENT #123: AUDIO METAL DETECTOR Have you ever wanted to make music just by waving your hand? Well that is just what you are going to be doing. How does this magic work? Well, the tones change based upon the amount of light that gets to the CdS cell. With a bright light the tone is higher but, if you cover the CdS with your hand, the sound gets lower. Notes: This experiment demonstrates how a metal detector works.
EXPERIMENT #122: AUDIO RAIN DETECTOR EXPERIMENT #6: TWEETING BIRD This circuit works as a rain detector. This circuit stays off and draws no current if the resistance between the long wires is more than about 250kΩ, whether the key is open or closed. The speaker produces a tone when the key is closed and water (or anything else that has a resistance of less than about 250kΩ) is connected to both of the test wires. In this experiment you are going to make a circuit that that sounds like the mockingbird.
EXPERIMENT #7: MEOWING CAT EXPERIMENT #121: AUDIO CONTINUITY TESTER Notes: Are you bothered by mice, do you not have a mousetrap? You should try this next experiment to help you instead—see if the sound of this cat can keep the pests out of your life. Just follow the drawing below and the wiring sequence. To start the experiment switch the set to B. Press down on the key and release it immediately. You will hear the meow from the cat coming from the speaker.
EXPERIMENT #8: CALLIN’ FISH EXPERIMENT #120: SAWTOOTH OSCILLATOR Notes: When you connect the signal from this oscillator to an oscilloscope, it creates a pattern that looks like the teeth of a saw (as shown below). Did you know that many marine animals communicate to each other using sound? I bet you have heard that dolphins and whales use sound for communication, but what you probably don’t know is that they are not the only ones.
EXPERIMENT #9: STROBE LIGHT EXPERIMENT #119: SQUARE WAVE OSCILLATOR In this experiment you will be creating an oscillator circuit that doesn’t make sound using a speaker or an earphone. Instead the circuit will produce light with an LED. This will give you an idea of how larger strobe lights work. When you press the key, watch LED 1. At certain intervals the light turns on and off. With the 50kΩ control you can control the rate of blinking.
EXPERIMENT #10: SOUND EFFECTS FOR HORROR MOVIES EXPERIMENT #118: RF SIGNAL TRACER Notes: This experiment is a wide band, untuned RF signal tracer. You can use it to check for antenna signals and find sources of RF noise and interference. This circuit is like an untuned crystal set. The 100pF capacitor in the input blocks DC and the 60Hz power line frequency, so the wires can touch almost anywhere without fear of electrical shock. Of course, you should never intentionally probe around high voltage.
EXPERIMENT #11: MACHINE GUN OSCILLATOR EXPERIMENT #117: AUDIO SIGNAL HUNTER Once you finish wiring, press the key to start the oscillator. The 50kΩ resistor is the control; you can swap it out with other resistors to change the sound from a few pulses per second to a dozen or so per second. Also, you can change the frequency of this oscillator circuit by swapping out other capacitors in place of the 10μF.
EXPERIMENT #12: MOTORCYCLE MANIA EXPERIMENT #116: WATER LEVEL ALARM provide the quickest results. This circuit is a radio transmitter/alarm for monitoring rising water levels such as on rivers, dams, and spillways, and sends alarm signals to a standard AM radio. When the water-contact plates or wires are out of the water, the circuit is not complete and nothing happens. When the contacts are touching water, the circuit is activated and transmits a radio signal that can be received by a nearby AM radio.
EXPERIMENT #13: VISION TEST EXPERIMENT #115: WATER LEVEL WARNING Notes: This circuit produces short pulses. After you close the key, the LED display shows 1 for a second and then turns off, even when you keep pressing the key. This experiment uses the LED and an audio oscillator alarm to indicate three different levels of water in a container. The water is used as a conductor to complete the circuits and show the water level. You could create a game with this circuit.
EXPERIMENT #14: PATROL CAR SIREN With this experiment you may want to be careful not to confuse your neighbors. This experiment sounds as like a loud siren just like the real sirens on police cars and ambulances. The tone is initially high but as you close the key the tone gets lower. You are able to control the tone just as the police and ambulance drivers do. Notes: The oscillator circuit being used is the same type used in many other experiments in this kit.
EXPERIMENT #114: MORSE CODE OSCILLATOR WITH TONE CONTROL Notes: Do you want to become an amateur radio ham? Many radio operators started out using an oscillator with a tone control like this one. Listening to the same tone for a long time can be very tiring, so the tone control in this experiment can be very helpful. Simply connect the wires for this circuit and your code practice oscillator is ready for use. Morse Code is a code system that uses dots and dashes, invented by Samuel Morse.
A MAJOR CHANGE EXPERIMENT #113: TWO-TRANSISTOR RADIO Until now, in addition to the wiring sequences you have had drawings to help guide you in the wiring connections. The rest of the projects will have just the schematic diagram without the circuit drawings. Notes: This radio circuit uses two-transistor receiver with enough gain (amplification) to drive the speaker. These simple radios require a good antenna and ground system. Wire the circuit and use terminal 74 as the ground terminal.
EXPERIMENT #15: LIGHT DIMMER EXPERIMENT #112: CRYSTAL SET RADIO Hint: the 10μF capacitor charges when you close the key. Ever thought you could use a capacitor to dim a light? Try this project. After you finish the wiring, set the switch to A. Then the LED segments will light up slowly and show an L. Once the LED reaches its brightest point it will stay on. Move the switch to B and watch as the L fades away.
EXPERIMENT #16: FLIP FLOPPING EXPERIMENT #111: AM RADIO STATION How about we take a break? This circuit is for entertainment. The numbers 1 and 2 will flash on the display in the circuit. This might remind you of some neon signs that have eye-catching advertisements on them. Notes: This AM radio station circuit lets you actually transmit your voice through the air. When you completed wiring the circuit, tune your AM radio a weak station or place with no stations.
EXPERIMENT #17: CAPACITOR DISCHARGE FLASH EXPERIMENT #110: AM CODE TRANSMITTER In this circuit single pulses of high voltage electric energy are generated by suddenly discharging a charged capacitor through a transformer. Automobile ignition systems use a similar capacitor-discharge reaction. This circuit is a simplified but effective code transmitter similar the kind used by military and amateur radio operators around the world.
EXPERIMENT #109: OPERATIONAL AMPLIFIER AM RADIO EXPERIMENT #18: TRANSISTOR ACTION In emergency situations when there is no power, a germanium diode radio can be used. Generally they do not perform well and limited to using and crystal earphone since they have no power source. There are three connections made on a transistor; one of these (the base) controls the current between the other two connections.
EXPERIMENT #19: SERIES AND PARALLEL CAPACITORS smallest capacitor in the series connection. The higher-pitch sound is caused by the lower capacitance. Some of the handiest items in your kit are the capacitors. They store electricity, smooth out pulsing electricity into a steady flow and let some electric current flow while blocking other current. This circuit allows you to compare the effects of capacitors connected in both series and parallel.
EXPERIMENT #20: TRANSISTOR SWITCHING EXPERIMENT #108: COOKING TIMER Wouldn’t you like to make a kitchen timer that you can use for cooking meals? This circuit gives out a buzzer sound for 1 to 2 seconds and automatically stops. Notes: Slide the switch to position B, build the circuit, and set the switch to position A to turn it on. Set the control to position 2 on the dial, and press the key to start the timer. After about 40 seconds, the timer sounds for 1 to 2 seconds and stops.
EXPERIMENT #21: SERIES AND PARALLEL RESISTORS EXPERIMENT #107: TIMER together, and then divide the product by the sum of values. In this case, the total resistance is: In this project, you will discover what happens when you connect resistors in series and in parallel. You will see the LED-1 on the panel flash on and off when you finish wiring. 470 x 100 (470 + 100) See what happens to the LED on side A and then on side B when you slide the switch. There is no change at all.
EXPERIMENT #106: OP AMP THREE-INPUT “AND” GATE Notes: Who says an operational amplifier (op amp) can’t be used to make a digital circuit? Here, you will use one to make an AND gate. The LED display is the output device. If it displays nothing, at least one of the output signals is logical 0 or low; if it displays H, they are all logical 1 or high. EXPERIMENT #22: AMPLIFY THE SOUND Notes: A two-transistor amplifier is used in this circuit.
EXPERIMENT #105: SUPER SOUND ALARM This circuit produces light and sound when it detects your voice or any other sound. The earphone acts as a microphone. IC 1 amplifies sounds picked up by the microphone. Diodes Da and Db rectify the amplified signal - that is, they convert the sound signal from AC to DC. The signal travels through IC 2, the comparator, and activates the LED and the speaker.
EXPERIMENT #23: LED DISPLAY BASICS EXPERIMENT #104 DC-DC CONVERTER Notes: Here’s a DC-DC converter circuit; it can make 5VDC from 3VDC. Assemble the experiment, set the switch to position A, and see how this circuit works. The schematic shows how it works. IC 1 is an oscillator; its output controls transistor Q1. Selfinduction of the transformer coil generates a high voltage current. Diode D1 rectifies this voltage and passes on a high DC voltage current. IC 2 is a comparator that examines the voltage.
EXPERIMENT #24: DIGITAL DISPLAY CIRCUIT FOR THE SEVEN-SEGMENT LED Notes: Wire the circuit as shown to connect the 3V supply to the LED segments and the decimal point (Dp). What numbers and letters do you see displayed? EXPERIMENT #103: LIGHT-CONTROLLED SOUND Notes: This circuit changes the intervals between each sound according to the amount of light falling on the CdS cell. The sound changes continuously as you alter the light intensity.
EXPERIMENT #25: LED DISPLAY WITH CdS AND TRANSISTOR EXPERIMENT #102: WHITE NOISE MAKER Notes: White noise is a noise that has a wide frequency range. One kind of white noise is the static noise you hear when you tune your FM radio to an area with no station. When you play electronic musical instruments, you can use white noise, a normally useless noise, as a sound source. Notes: In this project you will see how to turn on an LED by using a transistor and a CdS cell.
EXPERIMENT #26: SWITCHING THE LED DISPLAY USING TRANSISTOR CONTROL Notes: This project shows how to control the LED display through the use of transistors. EXPERIMENT #101: PULSE FREQUENCY MULTIPLIER Notes: This is a pulse frequency multiplier with one transistor. It doubles the frequency of the input signal, so it is also called a pulse frequency doubler. This circuit is similar to the one in Project 18 (Transistor Action).
EXPERIMENT #100: LISTEN TO ALTERNATING CURRENT Notes: The circuit in this experiment allows you to hear alternating current. You probably know that the electric power running through your home is an alternating current. All your appliances that receive power from electric outlets operate on AC- including lamps. Lamps actually flicker at the rate of 60 times per second, but it looks constant because our eyes see after images. In this experiment you will hear sound converted from light.
EXPERIMENT #27: “FLIP-FLOP” TRANSISTOR CIRCUIT EXPERIMENT #99: RC DELAY TIMER Transistor Q1 turns on when the charge drops to a specific point, the negative voltage from the 47kΩ resistor. Once Q1 turns on, and 100μF quickly starts charging and transistor Q2 turns off. With the Q2 off, its collector voltage rises toward the 9V of the battery supply and thus the LED turns off. The Q1 turns on fully through the fast charging of the 10μF. This flip occurs very fast.
EXPERIMENT #28: “TOGGLE FLIP-FLOP” TRANSISTOR EXPERIMENT #98: RESET CIRCUIT allow the display to light. With the switch in position A, the battery voltage is increased to 9V, and the 100μF capacitor gradually causes the comparator’s positive (+) terminal voltage to increase to about 6V. When this voltage exceeds the reference voltage of 5.4V, the LED display lights 1.
EXPERIMENT #29: “AND” DIODE TRANSISTOR LOGIC WITH LED DISPLAY The base of the PNP transistor turns on when both of the inputs are high and when both diodes supply negative voltage to the base of the PNP transistor. In addition, the NPN transistor turns on and then the current flows to the display to light the LED. In this circuit you will first learn about the AND circuit. When all the connections to its terminals are logic high (receiving voltage), the AND circuit produces a high output.
EXPERIMENT #30: “OR” DTL CIRCUIT WITH DISPLAY Notes: This next circuit is a logic OR circuit. Are you able to guess how this circuit may work? Remember that the AND circuit produces high logic only when inputs A and B are both high. In the OR circuit logic high is produced when A or B receives a logic high input. By connecting either terminal A or B to terminal 119 (logic high terminal) the display will show H. Try connecting each of the terminals to terminal 119; then to terminal 124.
EXPERIMENT #31: “NAND” DTL CIRCUIT WITH DISPLAY Notes: You will not be able to find the word NAND in your dictionary (unless it is a computer or electronic dictionary). This term means inverted or Non-AND function. It creates output conditions that are the opposite of the AND circuits output conditions. When both inputs A and B are high the NAND output is low. If either or both of the inputs are low then the output is high.
EXPERIMENT #95: OP AMP POWER AMPLIFIER EXPERIMENT #32: “NOR” TRANSISTOR CIRCUIT WITH DISPLAY Now you are going to produce a loud sound by combining an operational amplifier with two transistors. After you finish the wiring, set the switch to position A to turn on the power. You hear a loud sound from the speaker when you press the key. It is easy to determine what the NOR (inverted OR) circuit does now that you have built and learned about the NAND (inverted AND) circuit.
EXPERIMENT #33: “EXCLUSIVE OR” DTL CIRCUIT EXPERIMENT #94: TONE MIXER Notes: If you don’t know what an exclusive OR means, don’t worry. An exclusive OR (abbreviated XOR) circuit provides a high output only when one or the other of its inputs are high. Notes: Want to create an amplifier that mixes two tones together? There are many different types of tone mixing circuits, but the operational amplifier is considered one of the best.
EXPERIMENT #93: GET UP SIREN Do you sleep late? Even if you do, don’t fear! Because you can make the siren in this circuit alarm so that wakes you up gradually as the day dawns. Set the switch to position B, construct the circuit, then set the switch to position A to turn it on. You should hear sound from the speaker. Notes: When you expose the CdS cell to light, the siren sounds. The siren sound stops when you cover the CdS.
EXPERIMENT #34: “BUFFER” GATE USING TTL EXPERIMENT #92: BURGLAR BUZZER 1 is the input when the switch is set to A, and 0 is the input when the switch is at B. When the input to the first NAND is 1, its output is 0. But the 0 output of the first NAND is the input to the second. The 0 input to the second makes its output become 1, lighting the LED.
EXPERIMENT #35: “INVERTER” GATE USING TTL EXPERIMENT #91: OP AMP METRONOME Notes: This is the operational amplifier version of the electronic metronome from Project 3 (“Electronic Metronome”). Slide the switch to position B, and connect the wires carefully - this project is more intricate than most of the others. When you complete assembling the circuit, set the control to the 12 o’clock position, and slide the switch to position A to turn on the power.
EXPERIMENT #36: “AND” GATE USING TTL EXPERIMENT #90: CRISIS SIREN Notes: By using your kit’s NAND gates, are you able to figure out how to make an AND gate? To find out let’s experiment! Notes: This siren gives off alternating high and low sounds. Slide the switch to position B and construct the circuit. After you complete the wiring and slide the switch to position A, the power turns on and the speaker creates the sound of a two-pitch siren. As you build this circuit, leave the switch at B.
EXPERIMENT #37: “OR” GATE USING TTL EXPERIMENT #89: ALERT SIREN The sirens in Projects 88 and 89 (“Sweep Oscillator” and “Falling Bomb”, respectively) adjust the pitch only in one direction. This circuit makes a low sound that becomes higher, and goes back to its original low sound. The siren sounds only when you press the key. Notes: Notes: One of the cool things about the quad two-input NAND IC is that to make up other logic circuits all we have to do is combine the four NAND gates.
EXPERIMENT #88: FALLING BOMB EXPERIMENT #38: “R-S FLIP-FLOP” USING TTL Notes: R-S does not mean Radio Shack® flip-flop. As we mentioned earlier circuits that flip-flop alternate between two states. Those who use flip-flop circuits most often are engineers, and they use flip-flop circuits to switch between low (0) and high (1) outputs. We say a circuit is at set status (S) when the output is high or on. We use the word rest (R) when a circuit is off. Notes: Here’s another siren that alters its pitch.
EXPERIMENT #39: “TRIPLE-INPUT AND” GATE USING TTL EXPERIMENT #87: SWEEP OSCILLATOR Notes: The electronic buzzer we built in the previous circuit can only make a continuous beep, but we can make a similar circuit that produces various siren sounds. Your going to make a siren that gives out a sound with a variable pitch. When you move the switch, this siren wails and then creates a continuous highpitched noise. The circuit works this way: connected to the one NAND are both the key and the switch.
EXPERIMENT #40: “AND” ENABLE CIRCUIT USING TTL EXPERIMENT #86: BUZZIN’ WITH THE OP AMP Setting the switch to B blocks the channel from the LED 1 to the LED 2 However, when you set the switch to A, you will find that LED lights and turns off at the same time as LED 1. The two NAND gates produce an AND gate. The operational amplifier (op amp) works well as an oscillator. In this experiment, you will build an electric buzzer that makes a continuous beep.
EXPERIMENT #85: VOICE-CONTROLLED LED Notes: A microphone can be used to detect sound. Here you will make a circuit that lights the LED when the microphone detects sound, using the speaker as a microphone. EXPERIMENT #41: “NAND” ENABLE CIRCUIT USING TTL two inputs to the NAND equivalent to 1 once the switch is set to A. The multivibrator sends 0 and then signals to the other NAND input.
EXPERIMENT #42: “NOR” GATE USING TTL EXPERIMENT #84: LOGIC TESTING CIRCUIT Notes: Try to mark 0 and 1 inputs on the schematic and see if this circuit comes up at either a 0 or 1 output. Give it try and don’t peak at the answer. Notes: You know that digital circuits produce low or high (L or H) outputs (0 or 1). Now you’re going to create a logic tester that shows 1 for high level (H) and 0 for low level (L) on the LED display.
EXPERIMENT #83: INITIALS ON LED DISPLAY Notes: The digital LED can’t display all 26 letters of the alphabet, but it’s possible to exhibit many of them. Let’s make an LED display that intersperse shows the initials E and P of our ELECTRONIC PLAYGROUND. You can show other initials too.
EXPERIMENT #44: “EXCLUSIVE OR” GATE USING TTL EXPERIMENT #82: INTRODUCING THE SCHMITT TRIGGER Since we have made up some digital circuits by combining NAND gates, it makes sense that we make XOR gates too. This circuit will show you how. Before you complete this circuit set the switch to B. Connect the terminals 13 and 14, once you have finished the wiring. Does anything happen to LED 1 when you press the key? Release the key now and set the switch to A.
EXPERIMENT #81: SINGLE FLASH LIGHT EXPERIMENT #45: “OR” ENABLE CIRCUIT USING TTL Notes: You’ve built many circuits using the operational amplifier, but there are lots of other ways to use this handy IC. One of them is the single flash multivibrator. With this multivibrator, you can make the LED stay on for a preset amount of time when the key is pressed - a single flash light.
EXPERIMENT #46: LINE SELECTOR USING TTL EXPERIMENT #80: DOUBLE LED BLINKER It isn’t hard to think of some situations where we might want to send input data to two or more different outputs. This experiment shows how we can use a network of NAND gates to help do that. The LED circuits in experiments 78 and 79 (“Operational Amplifier Blinking LED” and “LED Flasher”) each use one LED, but the circuit in this project uses two LEDs that take turns lighting.
EXPERIMENT #47: DATA SELECTOR USING TTL EXPERIMENT #79: LED FLASHER Begin by sliding the switch to position B and wiring the circuit. This LED flasher uses two diodes. As you build this experiment, be sure to connect these diodes in the correct direction. Notes: When you finish assembling the experiment, turn on the power by sliding the switch to position A, and press the key. The LED starts blinking immediately.
EXPERIMENT #78: OPERATIONAL AMPLIFIER BLINKING LED Now you’re going to make a blinking LED circuit using an operational amplifier. In this experiment, an LED continuously lights and turns off slowly. Notes: Slide the switch to position B and connect the wires for this circuit. When you finish connecting the project, slide the switch to position A to turn on the power. After a couple seconds, you’ll see the LED start to blink.
EXPERIMENT #48: BLINKING LEDS EXPERIMENT #77: STABLE-CURRENT SOURCE Notes: In this experiment, we will make a constant current circuit, using an operational amplifier and a transistor. This circuit maintains a constant current even when the input voltage is changed, because more energy is used up in the circuit. Notes: Connect terminals 13 and 14 to turn on the power and finish the wiring sequence for this circuit. You’ll notice that both LED 1 and LED 2 alternate going on and off.
EXPERIMENT #76: MILLER INTEGRATING CIRCUIT EXPERIMENT #49: MACHINY SOUND Notes: Listen to the sound this project makes. Take your time and check your work because there are a lot of wiring steps. Once you’ve finished, set the switch to position A. What are you hearing? From looking at the schematic, can you explain how the circuit produces this sound? Notes: You know that an LED promptly lights when you turn it on. You can also light it up gradually.
EXPERIMENT #75: DUAL-SUPPLY DIFFERENTIAL AMPLIFIER This circuit is simplified by using the speaker as a microphone. To use the earphone as in previous experiments, you would have to make a far more complex circuit. This is the last in the series of microphone amplifiers. Now you will use the operational amplifier as a differential amplifier. It is a two-power source type amplifier, and this time we use the speaker as a microphone. Notes: Slide the switch to position B and construct the circuit.
EXPERIMENT #74: NON-INVERTING AMPLIFIER EXPERIMENT #51: TONE GENERATOR USING TTL Notes: We’ve been constructing tones with audio oscillators for so long that it might seem as if there’s no other way to produce tones from electronic circuits. Multivibrators made from NAND gates do the job just as well. Notes: In Projects 72 and 73 (“Non-inverting Dual Supply Op Amp,” and “Inverting Dual Supply Op Amp,” respectively), we used the operational amplifier with two power sources.
EXPERIMENT #73: INVERTING DUAL SUPPLY OP AMP Notes: This is another two-power source microphone amplifier, but this one is an inverting amplifier. You will use the earphone as a microphone again. Slide the switch to position B and construct the circuit. Once you finish the wiring, slide the switch to position A to turn the power on, adjust the control clockwise, and speak into the “microphone” – the earphone. This project works just like the preceding one.
EXPERIMENT #72: NON-INVERTING DUAL SUPPLY OP AMP EXPERIMENT #53: DARK SHOOTING Notes: Think you have good night vision? This experiment is a game that lets you find out how well you can see in the dark. In a completely dark room, it tests your aim! Notes: In this experiment, you will make a microphone amplifier, using the operational amplifier (op amp) as a non-inverting amplifier with two power sources. The earphone acts as a microphone.
EXPERIMENT #71: CHANGING INPUT VOLTAGE EXPERIMENT #54: A ONE-SHOT TTL 11.8V. However, the actual output voltage will be limited by the available battery voltage, which is 1.5V + 3.0V + 3.0V = 7.5V. After you finish the wiring, set the switch to position B. LEDs 1 and 2 indicate the output voltage of the operational amplifier IC. An LED lights if it is connected to 1.5V or higher. In this experiment, we connect the two LEDs in series, so they only light when connected with about 3V.
EXPERIMENT #55: TRANSISTOR TIMER USING TTL EXPERIMENT #70: OPERATIONAL AMPLIFIER COMPARATOR This is another type of one-shot circuit; in this project you hear the effects of the multivibrator. From the schematic you can see that this experiment uses a combination of simple components and digital electronics. Once you press the key, the 100μF capacitor is charged and lets the NPN translator in the left corner of the schematic operate.
EXPERIMENT #56: LED BUZZIN’ This is another circuit that uses both transistor and NAND type multivibrators. As you hear a sound through the earphone you see LED 1 light up. Notes: Build the circuit, connect the earphone to terminals 13 and 14, and set the switch to position A. Each time the LED lights up you’ll hear a pulse in the earphone. Do you know why? Trace the output from the NAND multivibrator to the transistor multivibrator, assuming the output of the NAND multivibrator is 0.
EXPERIMENT #57: ANOTHER LED BUZZIN’ EXPERIMENT #69: ELECTRONIC ORGAN OSCILLATOR Notes: Carefully compare the schematic for this experiment with the schematic for the last experiment. While they are similar in many ways, but there’s a critical difference. Can you find what it is? Can you tell how the operation will be different? Notes: This circuit has a multivibrator connected to a pulse type oscillator.
EXPERIMENT #68: SLOW SHUT-OFF OSCILLATOR EXPERIMENT #58: SET/RESET BUZZER You have seen how a capacitor’s charge/discharge cycle can be used to delay certain circuit operations. Now let’s slow the oscillator action in this project with a 470μF capacitor. Does anything look familiar about the schematic for this project? This circuit uses an R-S flip-flop circuit made from NAND gates, comparable to the circuit in experiment 38 (R-S Flip-Flop using TTL). Notes: Press and release the key.
EXPERIMENT #59: ANOTHER SET/RESET BUZZER EXPERIMENT #67: PUSHING & PULLING OSCILLATOR Here’s a variant of the last project. This time we use an R-S flip-flop made with transistors and a NAND multivibrator. In this experiment you will make a push/pull, square wave oscillator. This oscillator is known a push/pull because it uses two transistors that are connected to each other. They take turns maneuvering so that while one transistor is “pushing,” the other is “pulling.
EXPERIMENT #66: PULSE ALARM Notes: Now you will let one oscillator control another to create an alarm. Here we have a multivibrator-type oscillator controlling a pulse oscillator. The pulse oscillator produces frequency in the audible range (the range that our ears can hear, about 20 to 20k Hertz). The multivibrator circuit on the left side of the schematic should look familiar. The multivibrator commands the pulse oscillator by allowing current to flow to the transistor base.
EXPERIMENT #60: ODE TO THE PENCIL LEAD ORGAN EXPERIMENT #65: HEAT-SENSITIVE OSCILLATOR Notes: This experiment is an oscillator that is controlled in an abnormal way: with a pencil mark! You have caught a glimpse in other oscillator projects how changing the circuit’s resistance can change the sound that is produced. Resistors, such as the ones in your kit, are made of a form of carbon, and so are pencils (we still call them “lead” pencils, even though they are now made with carbon, not lead).
EXPERIMENT #61: DOUBLE-TRANSISTOR OSCILLATOR EXPERIMENT #64: ADJUSTABLE R-C OSCILLATOR Notes: Now you will build an oscillator using two transistors connected directly to each other. As you have witnessed, there are many ways to make an oscillator. This way is easier compared to some. Notes: The “R-C” in this experiment’s name represents resistance-capacitance. You have seen how varying resistance and capacitance can affect the pulsing action of an oscillator.
EXPERIMENT #62: DECIMAL POINT STROBE LIGHT Notes: This circuit is an oscillator with a slow frequency, and you can see the LED lighting and turning off. The off time is longer than the on time, so you observe short pulses of light with long periods between them. The wiring sequence below will make the decimal point light, however you can light any part of the LED display.
EXPERIMENT #63: “THE EARLY BIRD GETS THE WORM” This is the electronic bird circuit that you built for Project 6 (The Woodpecker), but now it has a photoelectric control of the transistor base. This circuit is activated by light, so you can use it as an early bird wake up alarm. Notes: To make the sound of the bird, press the key. You can modify the control so that the right amount of light will set off the bird and wake you up in the morning – not too early and not too late.
EXPERIMENT #64: ADJUSTABLE R-C OSCILLATOR Notes: The “R-C” in this experiment’s name represents resistance-capacitance. You have seen how varying resistance and capacitance can affect the pulsing action of an oscillator. This experiment lets us see the effects when we can alter the strengths of both resistors and capacitors. View the schematic. You can see the switch lets you choose between two different capacitors. Connecting terminals 13 and 14 adds another resistor to the circuit.
EXPERIMENT #65: HEAT-SENSITIVE OSCILLATOR Did you know that a transistor alters its characteristics according to the temperature? This experiment will show you how temperature affects transistor action. Notes: View the schematic. The NPN transistor acts as a pulse oscillator. The 22kΩ resistor and the PNP transistor control the voltage applied to its base. The transistor’s base current and collector current vary with the temperature. Build this experiment and you will hear a sound from the speaker.
EXPERIMENT #66: PULSE ALARM Now you will let one oscillator control another to create an alarm. Here we have a multivibrator-type oscillator controlling a pulse oscillator. The pulse oscillator produces frequency in the audible range (the range that our ears can hear, about 20 to 20k Hertz). The multivibrator circuit on the left side of the schematic should look familiar. The multivibrator commands the pulse oscillator by allowing current to flow to the transistor base.
EXPERIMENT #67: PUSHING & PULLING OSCILLATOR In this experiment you will make a push/pull, square wave oscillator. This oscillator is known a push/pull because it uses two transistors that are connected to each other. They take turns maneuvering so that while one transistor is “pushing,” the other is “pulling. This type of oscillator is called a square wave oscillator because the electrical waveform of the signal has a square shape.
EXPERIMENT #68: SLOW SHUT-OFF OSCILLATOR You have seen how a capacitor’s charge/discharge cycle can be used to delay certain circuit operations. Now let’s slow the oscillator action in this project with a 470μF capacitor. Notes: Press and release the key. The circuit oscillates, but slowly shuts down as the capacitor charges up. When the capacitor is fully charged, no current can flow to the oscillator, and it is off.
EXPERIMENT #69: ELECTRONIC ORGAN OSCILLATOR Notes: This circuit has a multivibrator connected to a pulse type oscillator. Rather than turning the oscillator completely on and off, the multivibrator provides a tremolo effect (a wavering tone). After you build the circuit, use the control to vary the base current supplied to the NPN transistor. This changes the charge/discharge rate of the 0.1μF and 0.05μF capacitors, as well the frequency of the pulse oscillator.
VIII.
EXPERIMENT #70: OPERATIONAL AMPLIFIER COMPARATOR For this section you will need some basic understanding about the operational amplifier integrated circuit. First, we can use separate power sources or we can use one power source for both the circuit and the IC. Notes: The operational amplifier (often called “op amp” for short) can be operated as a non-inverting amplifier, an inverting amplifier, or a differential amplifier.
EXPERIMENT #71: CHANGING INPUT VOLTAGE 11.8V. However, the actual output voltage will be limited by the available battery voltage, which is 1.5V + 3.0V + 3.0V = 7.5V. After you finish the wiring, set the switch to position B. LEDs 1 and 2 indicate the output voltage of the operational amplifier IC. An LED lights if it is connected to 1.5V or higher. In this experiment, we connect the two LEDs in series, so they only light when connected with about 3V.
EXPERIMENT #72: NON-INVERTING DUAL SUPPLY OP AMP In this experiment, you will make a microphone amplifier, using the operational amplifier (op amp) as a non-inverting amplifier with two power sources. The earphone acts as a microphone. Notes: Begin by sliding the switch to position B and finishing the wiring for the circuit. When your wiring is ready, set the switch to position A to turn on the power. Now rotate the control fully clockwise, and lightly tap your “microphone” – the earphone.
EXPERIMENT #73: INVERTING DUAL SUPPLY OP AMP Notes: This is another two-power source microphone amplifier, but this one is an inverting amplifier. You will use the earphone as a microphone again. Slide the switch to position B and construct the circuit. Once you finish the wiring, slide the switch to position A to turn the power on, adjust the control clockwise, and speak into the “microphone” – the earphone. This project works just like the preceding one.
EXPERIMENT #74: NON-INVERTING AMPLIFIER In Projects 72 and 73 (“Non-inverting Dual Supply Op Amp,” and “Inverting Dual Supply Op Amp,” respectively), we used the operational amplifier with two power sources. In this experiment, we will make a single-power source, non-inverting microphone amplifier. Again, the earphone works as a microphone. Notes: Slide the switch to position B and assemble the circuit.
EXPERIMENT #75: DUAL-SUPPLY DIFFERENTIAL AMPLIFIER This circuit is simplified by using the speaker as a microphone. To use the earphone as in previous experiments, you would have to make a far more complex circuit. This is the last in the series of microphone amplifiers. Now you will use the operational amplifier as a differential amplifier. It is a two-power source type amplifier, and this time we use the speaker as a microphone. Notes: Slide the switch to position B and construct the circuit.
EXPERIMENT #76: MILLER INTEGRATING CIRCUIT You know that an LED promptly lights when you turn it on. You can also light it up gradually. In this project, you’ll be able to observe the LEDs slowly get brighter while you hold down the key. Notes: This circuit arrangement is called a Miller integrating circuit. The output of the circuit increases as its input rises. The integrating circuit increases the value of the 100μF capacitor above its actual value.
EXPERIMENT #77: STABLE-CURRENT SOURCE Notes: In this experiment, we will make a constant current circuit, using an operational amplifier and a transistor. This circuit maintains a constant current even when the input voltage is changed, because more energy is used up in the circuit. View the schematic. When the current is modified, the voltage across R1 is also modified. The output of the operational amplifier changes corresponding to the feedback signal from R1.
EXPERIMENT #78: OPERATIONAL AMPLIFIER BLINKING LED Now you’re going to make a blinking LED circuit using an operational amplifier. In this experiment, an LED continuously lights and turns off slowly. Notes: Slide the switch to position B and connect the wires for this circuit. When you finish connecting the project, slide the switch to position A to turn on the power. After a couple seconds, you’ll see the LED start to blink.
EXPERIMENT #79: LED FLASHER Begin by sliding the switch to position B and wiring the circuit. This LED flasher uses two diodes. As you build this experiment, be sure to connect these diodes in the correct direction. Notes: When you finish assembling the experiment, turn on the power by sliding the switch to position A, and press the key. The LED starts blinking immediately.
EXPERIMENT #80: DOUBLE LED BLINKER The LED circuits in experiments 78 and 79 (“Operational Amplifier Blinking LED” and “LED Flasher”) each use one LED, but the circuit in this project uses two LEDs that take turns lighting. Slide the switch to position B and assemble the circuit. Then, turn the power on by sliding the switch to position A and wait for a few seconds. The LEDs light and turn off in rotation. Notes: The operational amplifier works as an astable multivibrator.
EXPERIMENT #81: SINGLE FLASH LIGHT Notes: You’ve built many circuits using the operational amplifier, but there are lots of other ways to use this handy IC. One of them is the single flash multivibrator. With this multivibrator, you can make the LED stay on for a preset amount of time when the key is pressed - a single flash light. Slide the switch to position B and construct the circuit. Turn the power on by sliding the switch to position A. The LED lights, but quickly turns off.
EXPERIMENT #82: INTRODUCING THE SCHMITT TRIGGER Notes: Now you are going to use the operational amplifier as a comparator and as a Schmitt trigger circuit. As long as its input voltage exceeds a certain value, the operational amplifier will produce a signal. View the schematic: can you see how it works? The input level that turns on the output is higher than the level than turns it off. So once a Schmitt trigger circuit turns on, it stays on unless the input drops significantly.
EXPERIMENT #83: INITIALS ON LED DISPLAY Notes: The digital LED can’t display all 26 letters of the alphabet, but it’s possible to exhibit many of them. Let’s make an LED display that intersperse shows the initials E and P of our ELECTRONIC PLAYGROUND. You can show other initials too. Slide the switch to position B and construct the circuit. Once you have completed the wiring, slide the switch to position A to turn on the power, and you’ll observe the letters E and P lighting alternately on the LED display.
EXPERIMENT #84: LOGIC TESTING CIRCUIT Notes: You know that digital circuits produce low or high (L or H) outputs (0 or 1). Now you’re going to create a logic tester that shows 1 for high level (H) and 0 for low level (L) on the LED display. Slide the switch to position B and construct the circuit. When you finish the wiring, slide the switch to position A to turn on the power. The number 0 is on the display because the test terminal (terminal 13) is at low level when no input is exerted.
EXPERIMENT #85: VOICE-CONTROLLED LED A microphone can be used to detect sound. Here you will make a circuit that lights the LED when the microphone detects sound, using the speaker as a microphone. Notes: Slide the switch to position B and construct the circuit. When you finish the wiring, by sliding the switch to position A to turn on the power. Now talk into the “microphone” (the speaker) or tap it lightly; the LED blinks. Observe the schematic.
EXPERIMENT #86: BUZZIN’ WITH THE OP AMP The operational amplifier (op amp) works well as an oscillator. In this experiment, you will build an electric buzzer that makes a continuous beep. By rotating the control you can change the tone of this buzzer. Notes: When you finish the wiring, set the control to the 12 o’clock position and press the key. From the speaker you hear a continuous beep. Turn the control as you press the key; the tone of the buzzer changes.
EXPERIMENT #87: SWEEP OSCILLATOR Notes: The electronic buzzer we built in the previous circuit can only make a continuous beep, but we can make a similar circuit that produces various siren sounds. Your going to make a siren that gives out a sound with a variable pitch. When you move the switch, this siren wails and then creates a continuous highpitched noise. Slide the switch to position B and assemble the circuit. When you complete the wiring, turn the power on by sliding the switch to position A.
EXPERIMENT #88: FALLING BOMB Notes: Here’s another siren that alters its pitch. The siren we built in our last experiment alters pitch from low to high, but this one alters its pitch from high to low and finally stops making any sound. When it stops, press the key and the siren sound will start again. Set the switch to position B and put together the circuit. When you finish the wiring, slide the switch to position A to turn on the power.
EXPERIMENT #89: ALERT SIREN The sirens in Projects 88 and 89 (“Sweep Oscillator” and “Falling Bomb”, respectively) adjust the pitch only in one direction. This circuit makes a low sound that becomes higher, and goes back to its original low sound. The siren sounds only when you press the key. Notes: Set the switch to position B and build the circuit. Turn on the siren by sliding the switch to position A. When you press the key, the siren starts over at the original low pitch.
EXPERIMENT #90: CRISIS SIREN Notes: This siren gives off alternating high and low sounds. Slide the switch to position B and construct the circuit. After you complete the wiring and slide the switch to position A, the power turns on and the speaker creates the sound of a two-pitch siren. This siren is made up of two astable multivibrators. IC 2 provides the normal beep sound. IC 1 produces the signal that alters the pitch of its sound at regular intervals. Let’s execute a small experiment now.
EXPERIMENT #91: OP AMP METRONOME This is the operational amplifier version of the electronic metronome from Project 3 (“Electronic Metronome”). Slide the switch to position B, and connect the wires carefully - this project is more intricate than most of the others. When you complete assembling the circuit, set the control to the 12 o’clock position, and slide the switch to position A to turn on the power. You’ll hear a pip noise from the speaker at fixed intervals.
EXPERIMENT #92: BURGLAR BUZZER This burglar alarm makes a buzzing sound when anyone sneaking into your house trips over a wire and breaks it off or disconnects it from a terminal. Try to figure out how to connect a switch to the door of your house, so that the alarm sounds when a burglar opens the door, instead of stretching out the wire. Notes: Start by sliding the switch to position B and assembling the circuit.
EXPERIMENT #93: GET UP SIREN Do you sleep late? Even if you do, don’t fear! Because you can make the siren in this circuit alarm so that wakes you up gradually as the day dawns. Set the switch to position B, construct the circuit, then set the switch to position A to turn it on. You should hear sound from the speaker. Notes: When you expose the CdS cell to light, the siren sounds. The siren sound stops when you cover the CdS.
EXPERIMENT #94: TONE MIXER Notes: Want to create an amplifier that mixes two tones together? There are many different types of tone mixing circuits, but the operational amplifier is considered one of the best. After you complete the wiring, slide the switch to position A to turn on the power. Note the timbre (the tone) of the sound produced. To mix this tone with another, press the key. You can alter the two separate tones by changing the values for the two 10kΩ resistors.
EXPERIMENT #95: OP AMP POWER AMPLIFIER Now you are going to produce a loud sound by combining an operational amplifier with two transistors. After you finish the wiring, set the switch to position A to turn on the power. You hear a loud sound from the speaker when you press the key. Notes: A capacitor-resistor oscillator is the signal source for this sound. The operational amplifier acts as an inverting amplifier, and transistors Q2 and Q3 cause the speaker to create the sound.
EXPERIMENT #96: VCO VCO? What’s that? VCO stands for voltage controlled oscillator, and as the name implies, this oscillator changes its oscillation frequency according to the voltage applied to the circuit. The circuit creates two different output signals that have triangular and square waves. Notes: When you finish the wiring sequence, slide the switch to position A to turn on the power. Turn the control slowly while you listen to the sound from the earphone.
IX.
EXPERIMENT #97: VOICE POWER METER In this experiment, you will create a voice input power meter. The brightness of the LED in this circuit changes according to the level of voice input that comes from the microphone (the earphone). Since voice levels change quickly, the brightness of the LED should also adjust quickly. In order to show the highest voice input levels, we use a circuit called a peak-level hold circuit.
EXPERIMENT #98: RESET CIRCUIT allow the display to light. With the switch in position A, the battery voltage is increased to 9V, and the 100μF capacitor gradually causes the comparator’s positive (+) terminal voltage to increase to about 6V. When this voltage exceeds the reference voltage of 5.4V, the LED display lights 1. When you set the switch to B, the voltage at the amplifier’s positive (+) terminal discharges through the diode, so the voltage is reduced to 4.1V.
EXPERIMENT #99: RC DELAY TIMER Notes: This circuit is a delayed timer that uses an operational amplifier and the RC time constant. RC stands for resistor/capacitor. A circuit that delays an operation is a time constant. Through resistors RA and RB the negative (–) terminal of the operational amplifier receives a voltage of about 4.5V. This is the comparator’s reference voltage. Connected to capacitor C1 is the positive (+) terminal of the comparator.
EXPERIMENT #100: LISTEN TO ALTERNATING CURRENT The circuit in this experiment allows you to hear alternating current. You probably know that the electric power running through your home is an alternating current. All your appliances that receive power from electric outlets operate on AC- including lamps. Lamps actually flicker at the rate of 60 times per second, but it looks constant because our eyes see after images. In this experiment you will hear sound converted from light.
EXPERIMENT #101: PULSE FREQUENCY MULTIPLIER Notes: This is a pulse frequency multiplier with one transistor. It doubles the frequency of the input signal, so it is also called a pulse frequency doubler. The operational amplifier IC acts as a square-wave oscillator. The output from the oscillator is an AC signal of about 500Hz. When you finish the wiring, set the switch to position A to turn on the power.
EXPERIMENT #102: WHITE NOISE MAKER White noise is a noise that has a wide frequency range. One kind of white noise is the static noise you hear when you tune your FM radio to an area with no station. When you play electronic musical instruments, you can use white noise, a normally useless noise, as a sound source. Notes: When you complete building this circuit, set the switch to position A to turn on the power. Look at the schematic.
EXPERIMENT #103: LIGHT-CONTROLLED SOUND This circuit changes the intervals between each sound according to the amount of light falling on the CdS cell. The sound changes continuously as you alter the light intensity. Notes: Build the circuit, and set the switch to position A to turn on the power. The speaker makes a sound. To change the sound, move your hand over the CdS. You can calculate the approximate value of the frequency of the signal by using the equation 1/2 x C1 x R1.
EXPERIMENT #104 DC-DC CONVERTER Notes: Here’s a DC-DC converter circuit; it can make 5VDC from 3VDC. Assemble the experiment, set the switch to position A, and see how this circuit works. The schematic shows how it works. IC 1 is an oscillator; its output controls transistor Q1. Selfinduction of the transformer coil generates a high voltage current. Diode D1 rectifies this voltage and passes on a high DC voltage current. IC 2 is a comparator that examines the voltage.
EXPERIMENT #105: SUPER SOUND ALARM This circuit produces light and sound when it detects your voice or any other sound. The earphone acts as a microphone. IC 1 amplifies sounds picked up by the microphone. Diodes Da and Db rectify the amplified signal - that is, they convert the sound signal from AC to DC. The signal travels through IC 2, the comparator, and activates the LED and the speaker.
EXPERIMENT #106: OP AMP THREE-INPUT “AND” GATE Who says an operational amplifier (op amp) can’t be used to make a digital circuit? Here, you will use one to make an AND gate. The LED display is the output device. If it displays nothing, at least one of the output signals is logical 0 or low; if it displays H, they are all logical 1 or high. Notes: When you finish the wiring, turn on the power by setting the switch to position A. The LED remains dark. The input terminals are 125, 127, and 129.
EXPERIMENT #107: TIMER Notes: Here’s a timer you can use for taking timed tests or simply for knowing when an amount of time has passed. You can preset this timer for up to approximately 15 minutes. When the time is up, it gives out a continuous buzzer sound until you turn off the power or press the key to reset the circuit. After you build this experiment, set the control to position 2 on the dial and slide the switch to position A to turn on the power.
EXPERIMENT #108: COOKING TIMER Wouldn’t you like to make a kitchen timer that you can use for cooking meals? This circuit gives out a buzzer sound for 1 to 2 seconds and automatically stops. Notes: Slide the switch to position B, build the circuit, and set the switch to position A to turn it on. Set the control to position 2 on the dial, and press the key to start the timer. After about 40 seconds, the timer sounds for 1 to 2 seconds and stops. Use the graph you made in project 107 to preset this timer.
X.
EXPERIMENT #109: OPERATIONAL AMPLIFIER AM RADIO In emergency situations when there is no power, a germanium diode radio can be used. Generally they do not perform well and limited to using and crystal earphone since they have no power source. Notes: In this circuit, we will use an operational amplifier so you can hear the radio through the speaker. This simple IC radio uses the dual operational amplifier as a two-power source, non-inverting amplifier.
EXPERIMENT #110: AM CODE TRANSMITTER This circuit is a simplified but effective code transmitter similar the kind used by military and amateur radio operators around the world. As the key is pressed and released, the transmitter turns on and off in sequence. Notes: The code send out by the transmitter can be received using an AM radio. The radio should be tuned to a weak station. When the transmitter signal mixes with the station’s signal it produce an audio tone, called a beat note.
EXPERIMENT #111: AM RADIO STATION Notes: This AM radio station circuit lets you actually transmit your voice through the air. When you completed wiring the circuit, tune your AM radio a weak station or place with no stations. Place the AM radio close to the circuit since the signal can only transmitted a few feet. As you talk into the speaker adjust the tuning capacitor, until you hear your voice on the radio The audio signals produced as you talk into the speaker are amplified by transistor Q1.
EXPERIMENT #112: CRYSTAL SET RADIO The crystal radio is one of the oldest and simplest radio circuits, which most people in electronics have experimented with. In the days before vacuum tubes or transistors, people used crystal circuit sets to pick up radio signals. Notes: Since the crystal radio signals are very weak, you’ll use a ceramic type earphone to pick up the sounds. These earphones reproduce these sounds well because it is and requires little current.
EXPERIMENT #113: TWO-TRANSISTOR RADIO Notes: This radio circuit uses two-transistor receiver with enough gain (amplification) to drive the speaker. These simple radios require a good antenna and ground system. Wire the circuit and use terminal 74 as the ground terminal. Connect the antenna to terminal 95 or 97. Use the one that gives the best results. The radio’s detector circuit uses a diode and 22kΩ k resistor.
EXPERIMENT #114: MORSE CODE OSCILLATOR WITH TONE CONTROL Notes: Do you want to become an amateur radio ham? Many radio operators started out using an oscillator with a tone control like this one. Listening to the same tone for a long time can be very tiring, so the tone control in this experiment can be very helpful. Simply connect the wires for this circuit and your code practice oscillator is ready for use. Morse Code is a code system that uses dots and dashes, invented by Samuel Morse.
XI.
EXPERIMENT #115: WATER LEVEL WARNING This experiment uses the LED and an audio oscillator alarm to indicate three different levels of water in a container. The water is used as a conductor to complete the circuits and show the water level. Notes: When the water is below all three of the wire connections, only the bottom segment (D) of the LED is on (indicating a low water level).
EXPERIMENT #116: WATER LEVEL ALARM provide the quickest results. This circuit is a radio transmitter/alarm for monitoring rising water levels such as on rivers, dams, and spillways, and sends alarm signals to a standard AM radio. When the water-contact plates or wires are out of the water, the circuit is not complete and nothing happens. When the contacts are touching water, the circuit is activated and transmits a radio signal that can be received by a nearby AM radio.
EXPERIMENT #117: AUDIO SIGNAL HUNTER This experiment is a simple transistor audio amplifier used as an audio signal tracer. You can use this amplifier to troubleshoot transistor audio equipment. You can connect the wires to different terminals in the circuit until you find the stage or component that does not pass the signal along when a circuit is not working correctly. Notes: The 0.1μF input capacitor blocks DC so you can probe around circuits without worrying about damaging the circuit.
EXPERIMENT #118: RF SIGNAL TRACER Notes: This experiment is a wide band, untuned RF signal tracer. You can use it to check for antenna signals and find sources of RF noise and interference. This circuit is like an untuned crystal set. The 100pF capacitor in the input blocks DC and the 60Hz power line frequency, so the wires can touch almost anywhere without fear of electrical shock. Of course, you should never intentionally probe around high voltage.
EXPERIMENT #119: SQUARE WAVE OSCILLATOR Multivibrator oscillators produce square waves, and you can use square waves as test signals. You should be familiar with multivibrator circuits from previous experiments. The name square wave comes from the pattern produced by the signal on an oscilloscope (shown below). Notes: Build this circuit and you will hear the sound produced by a square wave signal. You can differ the pitch and the frequency of the signal by modifying the control.
EXPERIMENT #120: SAWTOOTH OSCILLATOR Notes: When you connect the signal from this oscillator to an oscilloscope, it creates a pattern that looks like the teeth of a saw (as shown below). The shape of this wave results from the slow charging of the 0.1μF capacitor through the control and the 100kΩ resistor, and the capacitor’s discharge through the PNP and NPN transistors. The voltage divider - the 470Ω and 100Ω resistors provides about 1.6 volts to the transistors.
EXPERIMENT #121: AUDIO CONTINUITY TESTER This circuit emits a sound if the material you are checking transmits electricity. This is convenient when you are looking at wires, terminals, or other things and cannot look at a signal lamp or LED. Your ears will detect the results of the test while your eyes are busy. Notes: If the component or circuit you are testing conducts electricity, it will complete the circuit for a pulse-type oscillator. You can use this to test most of the components in this kit.
EXPERIMENT #122: AUDIO RAIN DETECTOR This circuit works as a rain detector. This circuit stays off and draws no current if the resistance between the long wires is more than about 250kΩ, whether the key is open or closed. The speaker produces a tone when the key is closed and water (or anything else that has a resistance of less than about 250kΩ) is connected to both of the test wires. Notes: Connect the wires to other wires or metallic plates laid out on an insulated surface.
EXPERIMENT #123: AUDIO METAL DETECTOR This experiment demonstrates how a metal detector works. When the coil gets close to something that is made of metal, the oscillator changes in frequency. This type of metal detector has been used to locate lost treasures, buried pipes, hidden land mines, and so on. These have been used to save many lives by locating mines and booby traps set out by the enemy during wartime.
EXPERIMENT #124: WATER LEVEL BUZZER Notes: You can use the operational amplifier as a comparator for detecting changes in voltage. In this experiment, you are going to use this comparator function to make a water buzzer that sounds when the wire ends come into contact with water. Slide the switch to position B, build the circuit, and then slide the switch to position A to turn on the circuit. You should not hear any sound from the speaker.
EXPERIMENT #125: PULSE TONE GENERATOR Notes: This experiment is a pulse-tone oscillator with an adjustable frequency that can obtain a wide range of notes. You can play tunes on it that sound like an electronic organ, but it takes some practice. To play a tune, modify the control to the proper note and press the key. Readjust the control for the next note and press the key again.
EXPERIMENT #126: RESISTANCE TESTER Notes: If you use a meter you can find the exact value of a resistance; but when you only want to know approximate resistance values, you can use this resistance tester. This circuit converts resistance to electric current and compares it with the comparator’s reference current to tell you the approximate range of resistance. The comparator has a reference voltage of about 0.82V. Build the circuit and set the switch to position A.
EXPERIMENT #127: TRANSISTOR TESTER Transistors are very important, and you may need to test them to be sure they are working. You can’t tell if one is working just by looking at it, but this circuit lets you test them. This circuit also checks whether a transistor is a PNP or an NPN. Notes: You’ll notice that this project has three long wires - one for the emitter, one for the collector and one for the base. The schematic shows the terminals marked for checking PNP transistors.
EXPERIMENT #128: SINE WAVE OSCILLATOR Notes: This oscillator circuit produces a sine wave signal. A sine wave (or sinusoid) is a wave of pure singlefrequency tone. As an example, a 400Hz sine wave is a wave that oscillates 400 cycles in one second and contains no other frequency contents. Non-sine waves (such as square wave or triangular wave signals) have harmonics - waves with frequencies that are multiples of the single-frequency fundamental wave.
EXPERIMENT #129: SINE WAVE OSCILLATOR WITH LOW DISTORTION In this experiment, you build and study a low-distortion sine wave oscillator. Build this experiment after you have built and studied the previous experiment because this one has no transformer; transformers are likely to cause distortion because of their nonlinear characteristics.
EXPERIMENT #130 TWIN-T OSCILLATOR The twin-T type audio oscillator is very popular for use with electronic organs and electronic test equipment because it is very stable. Notes: The resistors and capacitors in the twin-T network determine the frequency of oscillation. The letter T is used because the resistors and capacitors are arranged in the shape of the letter T in the schematic diagram. There are two T networks in parallel across from each other; hence the term twin is used.
INDEX We’ve added this listing to aid you in finding experiments and circuits that you might be especially interested in. Many of the experiments are listed two, three, or four times - since they can be used in many ways. You’ll find some listed as entertainment-type circuits, even through they were not organized that way in the sequence of projects. However, you may find some of these same circuits to be good for other uses too.
LOGIC AND COMPUTER CIRCUITS AND Gate: 29, 36, 39, 40 Data: 47 DTL: 29, 30, 31, 33, 35 Exclusive OR: 33, 44 Flip-flop: 27, 28, 38, 43, 58, 59 Inverting: 70, 72, 73, 74, 85, 95, 109 Line: 46 NAND Gate: 31, 41 NOR Gate: 42 OR Gate: 37, 42, 44, 45 Power Supply: 29, 72, 73, 74, 75 TTL: 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 50, 51, 54, 55, 60, 78, 90, 112, 123 NATURAL SCIENCE PROJECTS Electrical Energy: 52 Fish: 11 OSCILLATORS Blocking: 21 Oscillators: 8, 51 S
PARTS LIST Bar Antenna with Holder PCB for LM358 Battery Box Plastic (2) Resistors 100Ω 5% 1/4W (4) Capacitors 10pF, ceramic disc type 470Ω 5% 1/4W 100pF, ceramic disc type 1kΩ k 5% 1/4W 0.001μF, ceramic disc type 2.2kΩ k 5% 1/4W 0.01μF, ceramic disc type 4.7kΩ k 5% 1/4W 0.02μF, ceramic disc type 10kΩ k 5% 1/4W (2) 0.05μF, ceramic disc type (2) 22kΩ k 5% 1/4W 0.1μF, ceramic disc type 47kΩ k 5% 1/4W 3.
DEFINITION OF TERMS AC Common abbreviation alternating current. Alternating Current for Carbon A chemical element used to make resistors. A current that is constantly changing. Clockwise In the direction in which the hands of a clock rotate. AM Amplitude modulation. The amplitude of the radio signal is varied depending on the information being sent. Coil When something is wound in a spiral. In electronics this describes inductors, which are coiled wires. Amp Shortened name for ampere.
Electric Field The region of electric attraction or repulsion around a constant voltage. This is usually associated with the dielectric in a capacitor. Electricity A flow of electrons between atoms due to an electrical charge across the material. Electrolytic Capacitor A type of capacitor that has high capacitance and is used mostly in low frequency circuits. It has polarity markings. Electron A sub-atomic particle that has an electrical charge.
Ohm’s Law The relationship between voltage, current, and resistance. Ohm, (Ω Ω) The unit of resistance. Oscillator A circuit that uses feedback to generate an AC output. Parallel When several electrical components are connected between the same points in the circuit. Pico- (p) A prefix used in the metric system. It means a millionth of a millionth (0.000,000,000,001) of something. measure for Pitch The musical term for frequency.
IDENTIFYING RESISTOR VALUES Use the following information as a guide in properly identifying the value of resistors. BAND 1 1st Digit Color Black Brown Red Orange Yellow Green Blue Violet Gray White BAND 2 2nd Digit Digit 0 1 2 3 4 5 6 7 8 9 Color Black Brown Red Orange Yellow Green Blue Violet Gray White Multiplier Digit 0 1 2 3 4 5 6 7 8 9 Color Black Brown Red Orange Yellow Green Blue Silver Gold Resistance Tolerance Multiplier 1 10 100 1,000 10,000 100,000 1,000,000 0.01 0.
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