copyright © 2003 by elenco tm electronics, inc. all rights ......experiments 102 - 305 8 - 73 more...

Copyright © 2003 by ElencoTM Electronics, Inc. All rights reserved. No part of this book shall be reproduced by 753098any means; electronic, photocopying, or otherwise without written permission from the publisher.

REV-E Revised 2004

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Table of ContentsBasic Troubleshooting 1Parts List 2MORE About Your Snap Circuits Parts 3MORE DO’s and DON’Ts of Building Circuits 4

MORE Advanced Troubleshooting 5Project Listings 6, 7Experiments 102 - 305 8 - 73More Snap Circuits Projects 74

1. Most circuit problems are due toincorrect assembly, always double-check that your circuit exactlymatches the drawing for it.

2. Be sure that parts withpositive/negative markings arepositioned as per the drawing.

3. Sometimes the light bulbs comeloose, tighten them as needed. Usecare since glass bulbs can shatter.

4. Be sure that all connections aresecurely snapped.

5. Try replacing the batteries.

ElencoTM Electronics is not responsiblefor parts damaged due to incorrectwiring.

Basic Troubleshooting

Note: If you suspect you havedamaged parts, you can follow theAdvanced Troubleshooting procedureon page 5 to determine which onesneed replacing.

How To Use It

WARNING: SHOCK HAZARD - Neverconnect snap circuits to the electricaloutlets in your home in any way!

WARNING: Always check your wiring before turning on a circuit. Never touch the motor whenit is spinning at high speed. Never leave a circuit unattended while the batteries are installed.Never connect additional batteries or any other power sources to your circuits.

The snap circuit kit uses building blocks with snaps to buildthe different electrical and electronic circuits in the projects.Each block has a function: there are switch blocks, lampblocks, battery blocks, different length wire blocks, etc. Theseblocks are in different colors and have numbers on them sothat you can easily identify them. The circuit you will build isshown in color and numbers, identifying the blocks that youwill use and snap together to form a circuit.

For Example:

This is the switch block which is green and has the marking on it.

This is a wire block which is blue and comes in different wirelengths.This one has the number , , , , , or on itdepending on the length of the wire connection required.

There is also a 1-snap wire that is used as a spacer or forinterconnection between different layers.

To build each circuit, you have a power source blocknumber that need two (2) “AA” batteries (not includedwith the snap circuit kit).

A large clear plastic base grid is included with this kit to helpkeep the circuit block together. You will see evenly spacedposts that the different blocks snap into. You do not need thisbase to build your circuits, but it does help in keeping yourcircuit together neatly. The base has rows labeled A-G andcolumns labeled 1-10.

Next to each part in every circuit drawing is a small number inblack. This tells you which level the component is placed at.Place all parts on level 1 first, then all of the parts on level 2,then all of the parts on level 3, etc.

The 2.5V and 6V bulbs come packaged separate from theirsockets. Install the 2.5V bulb in the lamp socket , and the6V bulb in the lamp socket whenever those parts are used.

Place the fan on the motor whenever that part is used,unless the project you are building says not to use it.

Some circuits use the jumper wires to make unusualconnections. Just clip them to the metal snaps or asindicated.

Note: While building the projects, be careful not toaccidentally make a direct connection across the batteryholder (a “short circuit”), as this will damage and/or quicklydrain the batteries.

B1

L1

M12 3 4 5 6

S1

7

L2

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Qty. ID Name Symbol Part # Qty. ID Name Symbol Part #

3 1-Snap Wire 6SC01 1 10µF Capacitor 6SCC3



1 4-Snap Wire 6SC04 1 1kΩ Resistor 6SCR2

1 7-Snap Wire 6SC07 1 5.1kΩ Resistor 6SCR3

1Battery Holder - uses2 1.5V type AA (not Included) 6SCB1 1 10kΩ Resistor 6SCR4

1 Antenna Coil 6SCA1 1 100kΩ Resistor 6SCR5

1Green Light EmittingDiode (LED) 6SCD2 1

High FrequencyIntegrated Circuit 6SCU5

16V Lamp Socket6V Bulb (6.2V, 0.3A)Type 425 or similar

6SCL26SCL2B 1 PNP Transistor 6SCQ1

1 Microphone 6SCX1 1 NPN Transistor 6SCQ2

1Power AmplifierIntegrated Circuit 6SCU4 1 Adjustable Resistor 6SCRV

1 0.02µF Capacitor 6SCC1 1 Variable Capacitor 6SCCV

1 0.1µF Capacitor 6SCC2You may order additional / replacement parts at ourwebsite: www.elenco.com/snapcircuits

D2

A1

B1

7

4

3

2

1

L2

X1

U4

C1

C2

U5

R5

R4

R3

R2

C5

C4

C3

Q1

Q2

RV

CV

Note: There are additional part lists in your other project manuals.

Important: If any parts are missing or damaged, DO NOT RETURN TO RETAILER. Call toll-free (800) 533-2441 or e-mail us at:[email protected]. Customer Service • 150 W. Carpenter Ave. • Wheeling, IL 60090 U.S.A.

Parts List (Colors and styles may vary) Symbols and Numbers

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(Part designs are subject to change without notice).

Note: If you have Model SC-300 or SC-500, there is additionalinformation in your other project manual(s).

The green LED (D2) works the same as the red LED (D1) and the6V lamp (L2) works the same as the 2.5V lamp; these aredescribed in the SC-100 manual.

Resistors “resist” the flow of electricity and are used to control orlimit the electricity in a circuit. Snap circuits includes 100ΩΩ (R1),1KΩΩ (R2), 5.1KΩΩ (R3), 10KΩΩ (R4), and 100KΩΩ (R5) resistors (“K”symbolizes 1,000, so R3 is really 5,100Ω). Materials like metalhave very low resistance (<1Ω) and are called conductors, whilematerials like paper, plastic, and air have near-infinite resistanceand are called insulators.

The adjustable resistor (RV) is a 50KΩ resistor but with a centertap that can be adjusted between 0Ω and 50KΩ. At the 0Ω setting,the current must be limited by the other components in the circuit.

The microphone (X1) is actually a resistor that changes in valuewhen changes in air pressure (sounds) apply pressure to itssurface. Its resistance typically varies from around 1KΩ in silenceto around 10KΩ when you blow on it.

Capacitors are components that can store electrical pressure(voltage) for periods of time, higher values have more storage.Because of this storage ability they block unchanging voltagesignals and pass fast changing voltages. Capacitors are used forfiltering and oscillation circuits. Snap circuits includes 0.02µµF (C1),0.1µµF (C2), 10µµF (C3), 10µµF (C4), 470µµF (C5) capacitors, and avariable capacitor (CV). The variable capacitor can be adjustedfrom .00004 to .00022µF and is used in high frequency radiocircuits for tuning. The whistle chip (WC) also acts like a 0.02µFcapacitor in addition to its sound properties.

The antenna (A1) contains a coil of wire wrapped around an ironbar. Although it has magnetic effects similar to those in the motor,those effects are tiny and may be ignored except at highfrequencies (like in AM radio). Its magnetic properties allow it toconcentrate radio signals for reception. At lower frequencies theantenna acts like an ordinary wire.

The PNP (Q1) and NPN (Q2) transistors are components thatuse a small electric current to control a large current, and are usedin switching, amplifier, and buffering applications. They are easy tominiaturize, and are the main building blocks of integrated circuitsincluding the microprocessor and memory circuits in computers.Projects 124-125 and 128-133 demonstrate their properties. Ahigh current may damage a transistor, so the current must belimited by other components in the circuit.

The power amplifier IC (U4) is a module containing an integratedcircuit amplifier and supporting components that are alwaysneeded with it. A description of it is given here for those interested:

MORE About Your Snap Circuits Parts

The high frequency IC (U5) is a specialized amplifier used only inhigh frequency radio circuits. A description of it is given here forthose interested:

INPFIL

(+)OUT

(–)

Power Amplifier IC:(+) - power from batteries(–) - power return to batteriesFIL - filtered power from batteriesINP - input connectionOUT - output connection

See project 242 for example ofconnections.

High Frequency IC:INP - input connection (2 pointsare same)OUT - output connection (–) power return to batteries

See project 242 for example ofconnections.

INP INP(–)

OUT

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MORE DO’s and DON’Ts of Building CircuitsAfter building the circuits given in this booklet, you may wish to experiment on yourown. Use the projects in this booklet as a guide, as many important designconcepts are introduced throughout them. Every circuit will include a powersource (the batteries), a resistance (which might be a resistor, lamp, motor,integrated circuit, etc.), and wiring paths between them and back. You must becareful not to create "short circuits" (very low-resistance paths across thebatteries, see examples below) as this will damage components and/or quicklydrain your batteries. Only connect the ICs using configurations given in theprojects, incorrectly doing so may damage them. ElencoTM Electronics is notresponsible for parts damaged due to incorrect wiring.

Here are some important guidelines:ALWAYS use eye protection when experimenting on your own.

ALWAYS include at least one component that will limit the current through acircuit, such as the speaker, lamp, whistle chip, capacitors, ICs (whichmust be connected properly), motor, microphone, photoresistor, orresistors (the adjustable resistor doesn’t count if it’s set at/nearminimum resistance).

ALWAYS use LEDs, transistors, the high frequency IC, the antenna, andswitches in conjunction with other components that will limit the currentthrough them. Failure to do so will create a short circuit and/or damagethose parts.

ALWAYS connect the adjustable resistor so that if set to its 0 setting, the currentwill be limited by other components in the circuit.

ALWAYS connect position capacitors so that the “+” side gets the higher voltage.

ALWAYS disconnect your batteries immediately and check your wiring ifsomething appears to be getting hot.

ALWAYS check your wiring before turning on a circuit.

ALWAYS connect ICs using configurations given in the projects or as per theconnection descriptions for the parts.

NEVER try to use the high frequency IC as a transistor (the packages are similar,but the parts are different).

NEVER use the 2.5V lamp in a circuit with both battery holders unless you aresure that the voltage across it will be limited.

NEVER connect to an electrical outlet in your home in any way.

NEVER leave a circuit unattended when it is turned on.

NEVER touch the motor when it is spinning at high speed.

For all of the projects given in this book, the parts may be arranged in differentways without changing the circuit. For example, the order of parts connected inseries or in parallel does not matter — what matters is how combinations of thesesub-circuits are arranged together.

Examples of SHORT CIRCUITS - NEVER DO THESE!!!

You are encouraged to tell us about new circuits you create. Upon review,we will post them with your name, age, and hometown in a special sectionon our website. If we use them in future manual revisions, we will sendyou a copy of the manual so you can show your family and friends. Sendyour suggestions to ElencoTM Electronics.

WARNING: SHOCK HAZARD - Never connect snap circuits to theelectrical outlets in your home in any way!

Placing a 3-snap wire directlyacross the batteries is aSHORT CIRCUIT.

This is also aSHORTCIRCUIT.

When the switch (S1) is turned on, this large circuit has a SHORTCIRCUIT path (as shown by the arrows). The short circuit prevents anyother portions of the circuit from ever working.

!

!!

!

NEVERDO!

NEVERDO!

NEVERDO!

NEVERDO!

NEVERDO!!

MORE Advanced Troubleshooting (Adult supervision recommended)

ElencoTM Electronics is not responsible for parts damaged due toincorrect wiring.

If you suspect you have damaged parts, you can followthis procedure to systematically determine which onesneed replacing:

1. - 9. Refer to project manual 1 (projects 1-101) for testing steps1-9, then continue below. Test both lamps (L1, L2) andbattery holders in test step 1, all blue snap wires in step 3,and both LEDs (D1, D2) in step 5.

10. 1KΩΩ (R2), 5.1KΩΩ (R3), and 10KΩΩ (R4) resistors: Buildproject 7 but use each of these resistors in place of the 100Ωresistor (R1), the LED should light and the brightnessdecreases with the higher value resistors.

11. Antenna (A1): Build the mini-circuit shown here, you shouldhear sound.

12. NPN transistor (Q2): Build the mini-circuit shown here. TheLED (D2) must light when thejumper wire is connected andbe off when the jumper isremoved, if otherwise then theNPN is damaged.

13. PNP transistor (Q1): Buildthe mini-circuit shown here.The LED (D2) must light whenthe jumper wire is connectedand be off when the jumper is removed, if otherwise then theNPN is damaged.

14. Adjustable resistor (RV): Build project 261 but use the 1KΩresistor (R2) in place of the photoresistor (RP), the resistorcontrol can turn the LED (D1) on and off.

15. 100ΩΩK resistor (R5) and 0.02µµF (C1), 0.1µµF (C2), and 10µµF(C3) capacitors: Build project 206, it makes sound unless theresistor is bad. Place the 0.02µF capacitor on top of the whistlechip (WC) and the sound changes (pitch is lower). Replace the0.02µF with the 0.1µF and the pitch is even lower. Replace the0.1µF with the 10µF and the circuit will “click” about once asecond.

16. 100µµF (C4) and 470µµF (C5) capacitors: Build project 225,press the press switch (S2) and turn on the slide switch (S1).The LED (D1) should be lit for about 15 seconds then go out(press the press switch again to reset this). Replace the 470µFwith the 100µF and the LED is only lit for about 4 seconds now.

17. Power Amp IC (U4): Build project 293, the sound from thespeaker (SP) should be loud.

18. Microphone (X1): Build project 109, blowing into themicrophone should turn off the lamp (L2).

19. Variable Capacitor (CV): Build project 213 and place it near anAM radio, tune the radio and the capacitor to verify you hear themusic on your radio.

20. High Frequency IC (U5): Build project 242 and adjust thevariable capacitor (CV) and adjustable resistor (RV) until you heara radio station.

Note: If you have the more advanced Model SC-500, there areadditional tests in your 3rd project manual.

ElencoTM

Electronics, Inc.150 W. Carpenter Avenue

Wheeling, IL 60090 U.S.A.Phone: (847) 541-3800

Fax: (847) 520-0085e-mail: [email protected]: www.elenco.com

You may order additional / replacement parts at:www.elenco.com/snapcircuits

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Project # Description Page #102 Batteries in Series 8103 Batteries in Parallel 8104 Spacey Fan 9105 Two-Transistor Light Alarm 9106 Light-Controlled Alarm 9107 Automatic Street Lamp 10108 Voice-Controlled Rays of Light 10109 Blowing Off the Electric Light 10110 Adjustable Tone Generator 11111 Photosensitive Electronic Organ 11112 Electronic Cicada 11113 Light & Sounds 12114 More Light & Sounds 12115 More Light & Sounds (II) 12116 More Light & Sounds (III) 12117 More Light & Sounds (IV) 12118 Motor Speed Detector 13119 Old-Style Typewriter 13120 Space War Sounds 14121 Space War Sounds Controlled by Light 14122 Space War Radio 15123 The Lie Detector 15124 NPN Amplifier 16125 PNP Amplifier 16126 Sucking Fan 17127 Blowing Fan 17128 PNP Collector 17129 PNP Emitter 17130 NPN Collector 18131 NPN Emitter 18132 NPN Collector - Motor 18133 NPN Emitter - Motor 18134 Buzzing in the Dark 19135 Touch Buzzer 19

Project # Description Page #136 High Frequency Touch Buzzer 19137 High Frequency Water Buzzer 19138 Mosquito 19139 High Sensitivity Voice Doorbell 20140 Louder Doorbell 20141 Very Loud Doorbell 20142 Doorbell with Button 20143 Darkness Announcer 20144 Musical Motion Detector 20145 Radio Music Alarm 21146 Daylight Music Radio 21147 Night Music Radio 21148 Night Gun Radio 21149 Radio Gun Alarm 21150 Daylight Gun Radio 21151 Blow Off a Space War 22152 Series Lamps 22153 Parallel Lamps 22154 Fire Fan Symphony 23155 Fire Fan Symphony (II) 23156 Fan Symphony 23157 Fan Symphony (II) 23158 Police Car Symphony 24159 Police Car Symphony (II) 24160 Ambulance Symphony 24161 Ambulance Symphony (II) 24162 Static Symphony 25163 Static Symphony (II) 25164 Capacitors in Series 25165 Capacitors in Parallel 25166 Water Detector 26167 Salt Water Detector 26168 NPN Light Control 27169 NPN Dark Control 27

Project # Description Page #170 PNP Light Control 27171 PNP Dark Control 27172 Red & Green Control 28173 Current Controllers 28174 Current Equalizing 28175 Battery Polarity Tester 28176 Blow Off a Doorbell 29177 Blow Off a Candle 29178 Blow On a Doorbell 29179 Blow On a Candle 29180 Screaming Fan 30181 Whining Fan 30182 Light Whining 30183 More Light Whining 30184 Motor Than Won’t Start 30185 Whiner 31186 Lower Pitch Whiner 31187 Hummer 31188 Adjustable Metronome 31189 Quiet Flasher 31190 Hissing Foghorn 32191 Hissing & Clicking 32192 Video Game Engine Sound 32193 Light Alarm 33194 Brighter Light Alarm 33195 Lazy Fan 33196 Laser Light 33197 Water Alarm 34198 Drawing Resistors 34199 Pitch 35200 Pitch (II) 35201 Pitch (III) 35202 Flooding Alarm 35203 Make Your Own Battery 36

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Project Listings

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Project # Description Page #204 Make Your Own Battery (II) 36205 Make Your Own Battery (III) 36206 Tone Generator 37207 Tone Generator (II) 37208 Tone Generator (III) 37209 Tone Generator (IV) 37210 More Tone Generator 38211 More Tone Generator (II) 38212 More Tone Generator (III) 38213 Music Radio Station 39214 Alarm Radio Station 39215 Standard Transistor Circuit 39216 Motor & Lamp by Sound 40217 Fading Siren 40218 Fast Fade Siren 40219 Laser Gun with Limited Shots 41220 Symphony of Sounds 41221 Symphony of Sounds (II) 41222 Transistor Amplifiers 42223 Pressure Meter 42224 Resistance Meter 42225 Auto-Off Night-Light 43226 Discharging Caps 43227 Changing Delay Time 43228 Morse Code Generator 44229 LED Code Teacher 44230 Ghost Shriek Machine 44231 LED & Speaker 44232 Dog Whistle 44233 Mind Reading Game 45234 Enhanced Quiet Zone Game 46235 Capacitor Charge & Discharge 46236 Sound Wave Magic 47237 Space War Amplifier 47

Project # Description Page #238 Trombone 48239 Race Car Engine 48240 Power Amp 49241 Electronic Kazoo 49242 AM Radio 50243 Fire Engine Symphony 51244 Fire Engine Symphony (II) 51245 Vibration or Sound Indicator 51246 Two-Finger Touch Lamp 52247 One-Finger Touch Lamp 52248 Space Battle 53249 Space Battle (II) 53250 Multi-Speed Light Fan 53251 Light & Finger Light 53252 Storing Electricity 54253 Lamp Brightness Control 54254 Electric Fan 54255 Radio Music Burglar Alarm 55256 Light Dimmer 55257 Motion Detector 56258 Fan Modulator 56259 Oscillator 0.5 - 30Hz 57260 Sound Pulse Oscillator 57261 Motion Detector (II) 57262 Motor Rotation 58263 Motor Delay Fan 58264 Motor Delay Fan (II) 58265 High Pitch Bell 59266 Steamboat Whistle 59267 Steamship 59268 Steamship Horn 59269 Noise-Activated Burglar Alarm 60270 Motor-Activated Burglar Alarm 60271 Light-Activated Burglar Alarm 60

Project # Description Page #272 Photoresistor Control 61273 Microphone Control 61274 Pressure Alarm 62275 Power Microphone 62276 LED Fan Rotation Indicator 63277 Space War Sounds with LED 63278 Sound Mixer 64279 Sound Mixer Fan Driver 64280 Electric Fan Stopped by Light 65281 Motor & Lamp 65282 Start-Stop Delay 66283 Mail Notifying System 66284 Mail Notifying Electronic Bell 67285 Mail Notifying Electronic Fan 67286 Twice-Amplified Oscillator 67287 Quick Flicking LED 67288 AM Radio with Transistors 68289 AM Radio (II) 68290 Music Amplifier 69291 Delayed Action Lamp 69292 Delayed Action Fan 69293 Police Siren Amplifier 70294 Lasting Doorbell 70295 Lasting Clicking 70296 Leaky Capacitor 71297 Transistor Fading Siren 71298 Fading Doorbell 71299 Blowing Space War Sounds 72300 Adjustable Time Delay Lamp 72301 Adjustable Time Delay Fan 72302 Adjustable Time Delay Lamp (II) 73303 Adjustable Time Delay Fan (II) 73304 Watch Light 73305 Delayed Bedside Fan 73

Project Listings

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Project #102OBJECTIVE: To show the increase in voltage when batteries are

When you close the slide switch (S1), current flows from the batteriesthrough the slide switch (S1), the 100Ω resistor (R1), the LED (D1),through the LED (D2), and back to the second group of batteries (B1).Notice how both LEDs are lit. The voltage is high enough to turn onboth LEDs when the batteries are connected in series. If only one setof batteries is used, the LEDs will not light up.

Some devices use only one 1.5 volt battery, but they make hundredsof volts electronically from this small source. A flash camera is anexample of this.

Batteries in Series

Project #103OBJECTIVE: To show how batteries in parallel are used to

Build the circuit shown on the left by placing all the parts with a black1 next to them on the board first (including the 1-snap wire at base gridlocation C6). Then, assemble the parts marked with a 2. Finally, placethe slide switch (S1) on top as shown. Leave the switch in the offposition.

The light should be on and the brightness of the lamp will depend onthe quality of the batteries in the holder on the left. Put weak batteriesin the left holder and strong batteries in the right holder. Now turn onthe switch. The lamp will get brighter as the fresh batteries take overand supply the current to the light.

Batteries are placed in parallel when the voltage is high enough butthe circuit needs more current than one group of batteries can supply.Think of each battery as a storage tank that supplies water. If you puttwo in parallel, you can get more water (current), but the pressure(voltage) stays the same.

Batteries in Parallel

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Project #104Spacey Fan

OBJECTIVE: To build a fanwith space war sounds that is

Place the fan onto the motor.Space war sounds are heard iflight shines on the photoresistorOR if you press the press switch(S2), the fan may start to spin,but will only get to high speed ifyou do BOTH. Try variouscombinations of shining light andholding down the press switch.

Project #106

The alarm will sound, as long as light is present. Slowly cover thephotoresistor (RP), and the volume goes down. If you turn off thelights, the alarm will stop. The amount of light changes the resistanceof the photoresistor (less light means more resistance). Thephotoresistor and transistor (Q2) act like a dimmer switch, adjustingthe voltage applied to the alarm.

This type of circuit is used in alarm systems to detect light. If anintruder turned on a light or hit the sensor with a flashlight beam, thealarm would trigger and probably force the intruder to leave.

Light-controlled Alarm

Project #105Two-Transistor Light Alarm

This light alarm circuit uses two(2) transistors and both sets ofbatteries. Build the circuit withthe jumper connected as shown,and turn it on. Nothing happens.Break the jumper connectionand the light turns on. You couldreplace the jumper with a longerwire and run it across a doorwayto signal an alarm whensomeone enters.

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Project #107

OBJECTIVE: To show how light is used to control a street lamp.

Press the press switch (S2) on and set the adjustable resistor (RV) sothe lamp just lights. Slowly cover the photoresistor (RP) and the lampbrightens. If you place more light at the photoresistor the light dims.

This is an automatic street lamp that you can turn on by a certaindarkness and turn off by a certain brightness. This type of circuit isinstalled on many outside lights and forces them to turn off and saveelectricity. They also come on when needed for safety.

AutomaticStreet Lamp

Project #108Voice-controlled Rays of LightOBJECTIVE: To show how light is stimulated by sound.

Turn the slide switch(S1) on. There will beonly a weak lightemitting from the greenLED. By blowing onthe mic (X1) or puttingit near a radio or TVset, the green LED willemit light, and itsbrightness changes asthe loudness changes.

Project #109Blowing Off the Electric LightOBJECTIVE: To show how light is stimulated by sound.

Install the parts. Thelamp (L1) will be on. Itwill be off as long asyou blow on the mic(X1). Speaking loudinto the mic willchange the brightnessof the lamp.

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Project #110

OBJECTIVE: To show how resistor values change the frequencyof an oscillator.

Turn on the slide switch (S1), the speaker (SP) will sound and the LED(D2) will light. Adjust the resistor (RV) to make different tones. In anoscillator circuit, changing the values of resistors or capacitors canvary the output tone or pitch.

Adjustable ToneGenerator

OBJECTIVE: To show how resistor values change the frequencyof an oscillator.

Project #112Electronic Cicada

OBJECTIVE: To show how capacitors in parallel change thefrequency of an oscillator.

Use the circuit from Project #110 shown above, replace thephotoresistor (RP) back to the 100kΩ (R5) resistor. Place the 0.02µF(C1) on top of the whistle chip (WC). Place the slide switch (S1) on andadjust the resistor (RV). The circuit produces the sound of the cicadainsect. By placing the 0.02µF on top of the whistle chip, the circuitoscillates at a lower frequency. Notice that the LED flashes also at thesame frequency.

It is possible to pick resistors and capacitors that will make the pitchhigher than humans can hear. Many animals, however, can hear thesetones. For example, a parakeet can hear tones up to 50,000 cycles persecond, but a human can only hear to 20,000.

Use the circuit from Project #110 shown above. Replace the 100kΩ(R5) with the photoresistor (RP). Turn on the slide switch (S1). Thespeaker (SP) will sound and the LED (D2) will light. Move your hand upand down over the photoresistor (RP) and the frequency changes.Decreasing the light on the photoresistor increases the resistance andcauses the circuit to oscillate at a lower frequency. Notice that the LEDflashes also at the same frequency as the sound.

By using your finger, see if you can vary the sounds enough to make thiscircuit sound like an organ playing.

Project #111Photosensitive

Electronic Organ

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OBJECTIVE: To build a police siren with light.

Turn on the slide switch (S1). A police siren is heard and the lamplights.

Project #114More Light &

SoundsOBJECTIVE: To show avariation of the circuit inProject #113.

Modify the last circuit byconnecting points X & Y. Thecircuit works the same way butnow it sounds like a machine gun.

OBJECTIVE: To show avariation of the circuit inProject #113.

Project #116More Light &Sounds (III)


Project #117More Light &Sounds (IV)


Project #113 Light & Sounds

Project #115More Light &Sounds (II)

Now remove the connectionbetween X & Y and then make aconnection between T & U. Now itsounds like a fire engine.

Now remove the connectionbetween T & U and then make aconnection between U & Z. Nowit sounds like an ambulance.

Now remove the connectionsbetween U & Z and between V &W, then make a connectionbetween T & U. Now it soundslike a water faucet.

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Project #118OBJECTIVE: To show how to make electricity in one direction.

When building the circuit, be sure to position the motor with thepositive (+) side snapped to the 470µF capacitor (C5). Turn on theslide switch (S1), nothing will happen. It is a motor speed detector,and the motor isn't moving. Watch the LED (D2) and give the motor agood spin CLOCKWISE with your fingers (don't use the fan blade); youshould see a flash of light. The faster you spin the motor, the brighterthe flash will be. As a game, see who can make the brightest flash.

Now try spinning the motor in the opposite direction (counter-clockwise) and see how bright the flash is — it won't flash at allbecause the electricity it produces, flows in the wrong direction andwon't activate the diode. Flip the motor around (positive (+) sidesnapped to the 3-snap wire) and try again. Now the diode lights onlyif you spin the motor counter-clockwise.

Motor Speed Detector

Project #119OBJECTIVE: To show how a generator works.

Turn on the slide switch (S1), nothing will happen. Turn the motorslowly with your fingers (don’t use the fan blade), you will hear aclicking that sounds like an old-time manual typewriter keystrokes.Spin the motor faster and the clicking speeds up accordingly.

This circuit works the same if you spin the motor in either direction(unlike the Motor Speed Detector project).

By spinning the motor with your fingers, the physical effort you exert isconverted into electricity. In electric power plants, steam is used tospin large motors like this, and the electricity produced is used to runeverything in your town.

Old-Style Typewriter

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Project #120OBJECTIVE: To build a circuit that produces multiple spacewar sounds.

Set the slide switch (S1) to the OFF position. Press the press switch(S2) down and a space sound will be played. If you hold the pressswitch down the sound repeats. Press the press switch again and adifferent sound is played. Keep pressing the press switch to hear allthe different sounds.

Next, set the slide switch (S1) to ON position. One of the sounds willbe played continuously. Turn the switch off and then back on. Adifferent sound is played. Keep pressing the press switch to hear allthe different combinations of sounds.

The space war integrated circuit has “logic” built into its circuitry thatallows it to switch between many different sounds.

Space War Sounds

Project #121

OBJECTIVE: To change the sounds of a multiple space war withlight.

Modify the preceding circuit to look like the one shown on the left.

The space war IC (U3) will play a sound continuously. Block the lightfrom the photoresistor (RP) with your hand. The sound will stop.Remove your hand and a different sound is played. Wave your handover the photoresistor to hear all the different sounds.

Press the press switch down and now two space war sounds areplayed. If you hold the press switch down the sound repeats. Pressthe press switch again and a different sound is played. Keep pressingthe press switch to hear all the different combinations of sounds.

Space War SoundsControlled By Light

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Project #122OBJECTIVE: To transmit Space War sounds to a AM radio.

Place the circuit next to an AM radio. Tune the radio so no stations areheard and turn on the slide switch (S1). You should hear the space warsounds on the radio. The red LED should also be lit. Adjust thevariable capacitor (CV) for the loudest signal.

You have just performed the experiment that took Marconi (whoinvented the radio) a lifetime to invent. The technology of radiotransmission has expanded to the point that we take it for granted.There was a time, however, when news was only spread by word ofmouth.

Space War Radio

Project #123OBJECTIVE: To show how sweat makes a better conductor.

Turn on the slide switch (S1) and place your finger across point A andB. The speaker will output a tone and the LED will flash at the samefrequency. Your finger acts as a conductor connecting points A and B.When a person is lying, one thing the body starts to do is sweat. Thesweat makes the finger a better conductor by reducing its resistance.

As the resistance drops, the frequency of the tone increases. Lightlywet your finger and place it across the two points again. Both theoutput tone and LED flashing frequency increase. Now change thewetness of your finger by drying it and see how it affects the circuit.This is the same principle used in lie detectors that are soldcommercially.

The Lie Detector

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Project #124OBJECTIVE: To compare transistor circuits.

There are three connection points on an NPN transistor, called base(marked B), emitter (marked E), and collector (marked C). When asmall electric current flows from the base to the emitter, a larger(amplified) current will flow from the collector to the emitter. Build thecircuit and slowly move up the adjustable resistor control. When theLED becomes bright, the lamp will also turn on and will be muchbrighter.

NPN Amplifier

Project #125OBJECTIVE: To compare transistor circuits.

The PNP transistor is similar to the NPN transistor in Project #166except that the electric currents flow in the opposite directions. Whena small electric current flows from the emitter to the base, a larger(amplified) current will flow from the emitter to the collector. Build thecircuit and slowly move up the adjustable resistor control. When theLED becomes bright, the lamp will also turn on and will be muchbrighter.

PNP Amplifier

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Project #126 Sucking FanOBJECTIVE: To adjust the speed of a fan.

Project #128 PNP CollectorOBJECTIVE: Todemonstrate adjusting thegain of a transistor circuit.

OBJECTIVE: To build a fan thatwon’t come off.

Modify the circuit from Project #126by reversing the position of the motor(so the positive (+) side is towards thePNP (Q1). Turn it on, and set theadjustable resistor for the fan speedyou like best. Set it for full speed andsee if the fan flies off - it won’t! Thefan is blowing air upward now! Tryholding a piece of paper just abovethe fan to prove this.

Project #127Blowing Fan

Project #129 PNP EmitterOBJECTIVE: To comparetransistor circuits.

Compare this circuit to thatin Project #128. Themaximum lamp brightnessis less here because thelamp resistance reduces theemitter-base current, whichcontacts the emitter-collector current (as perProject #128). The point onthe PNP that the lamp isnow connected to (grid pointC4) is called the emitter.

Build the circuit, and be sure to orient the motor withthe positive (+) side down as shown. Turn it on, and setthe adjustable resistor for the fan speed you like best.If you set the speed too fast then the fan may fly off themotor. Due to the shape of the fan blades and thedirection the motor spins, air is sucked into the fan andtowards the motor. Try holding a piece of paper justabove the fan to prove this. If this suction is strongenough then it can lift the fan blades, just like in ahelicopter.

The fan will not move on most settings of the resistor,because the resistance is too high to overcome frictionin the motor. If the fan does not move at any resistorsetting, then replace your batteries.

Build the circuit and varythe lamp brightness withthe adjustable resistor, itwill be off for most of theresistor’s range. The pointon the PNP that the lamp isconnected to (point E4 onthe base grid) is called thecollector, hence the namefor this project.

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Project #130NPN Collector

OBJECTIVE: To comparetransistor circuits.

Project #131NPN Emitter

Compare this circuit to that inProject #128, it is the NPNtransistor version and works thesame way. Which circuit makesthe lamp brighter? (They areabout the same because bothtransistors are made from thesame materials).


Compare this circuit to that inProject #129. It is the NPNtransistor version and works thesame way. The same principlesapply here as in Projects #128-#130, so you should expect it tobe less bright than #130 but asbright as #129.

Project #132NPN Collector - Motor


Project #133NPN Emitter - Motor

This is the same circuit as inProject #130, except that it hasthe motor (M1) instead of thelamp. Place the motor with thepositive (+) side touching theNPN and put the fan on it.

The fan will not move on mostsettings of the resistor, becausethe resistance is too high toovercome friction in the motor. Ifthe fan does not move at anyresistor setting, then replace yourbatteries.


This is the same circuit as inProject #131, except that it hasthe motor (M1) instead of thelamp. Place the motor with thepositive (+) side down and putthe fan on it. Compare the fanspeed to that in Project #132.Just as the lamp was dimmer inthe emitter configuration, themotor is not as fast now.

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Project #134

OBJECTIVE: To make a circuit that

Buzzing inthe Dark

Project #136High FrequencyTouch Buzzer

OBJECTIVE: To build a high frequency

Replace the speaker (SP) with the 6V Lamp(L2). Now touching your fingers between B1and D1 creates a quieter but more pleasantbuzzing sound.

Project #137High FrequencyWater Buzzer

OBJECTIVE: To build a high frequency

Now connect two (2) jumpers to points B1 andD1 (that you were touching with your fingers)and place the loose ends into a cup of water.The sound will not be much different now,because your body is mostly water and so thecircuit resistance has not changed much.

Project #138 Mosquito

OBJECTIVE: To make a buzz like a

Place the photoresistor (RP) into the circuit inProject #137 across where you wereconnecting the jumpers (points B1 and D1 onthe grid, and as shown in Project #134). Nowthe buzz sounds like a mosquito.

Project #135 Touch Buzzer

OBJECTIVE: To build a human buzzer

Remove the photoresistor (RP) from thecircuit in Project #134 and instead touch yourfingers across where it used to be (points B1and D1 on the grid) to hear a cute buzzingsound.The circuit works because of the resistance inyour body. If you put back the photoresistorand partially cover it, you should be able tomake the same resistance your body did, andget the same sound.

This circuit makes a high-frequencyscreaming sound when light shines onthe photoresistor, and makes a buzzingsound when you shield the photoresistor.

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Project #139

Project #141Very LoudDoorbell

OBJECTIVE: To build a veryloud highly sensitive voice-activated doorbell.

Replace the antenna coil (A1)with the speaker (SP), the soundis much louder now.

OBJECTIVE: To build a press-activated doorbell.

Project #143 Darkness

AnnouncerOBJECTIVE: To play musicwhen it gets dark.

OBJECTIVE: To detect whensomeone spins the motor.

Project #142 Doorbell

with Button

Replace the microphone (X1)with the press switch (S2) andwait until the music stops. Nowyou have to press the slide switch(S1) to activate the music, justlike the doorbell on your house.

Replace the press switch (S2)with the photoresistor (RP) andwait until the sound stops. If youcover the photoresistor now themusic will play once, signalingthat it has gotten dark. If thespeaker (SP) is too loud then youmay replace it with the antennacoil (A1).

Replace the photoresistor (RP)with the motor (M1), oriented ineither direction. Now spinning themotor will re-activate the music.

Project #144 Musical

Motion Detector

OBJECTIVE: To build a loudhighly sensitive voice-activateddoorbell.

Replace the 6V lamp (L2) withthe antenna coil (A1), the soundis louder now.

Project #140 Louder

DoorbellOBJECTIVE: To build ahighly sensitive voice-activateddoorbell.

Build the circuit and wait until thesound stops. Clap or talk loud afew feet away and the musicplays again. The microphone(X1) is used here because it isvery sensitive.

HighSensitivity

Voice Doorbell

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Project #145 Radio MusicAlarm

Project #147Night Music

RadioOBJECTIVE: To build a dark-controlled radio transmitter.

Put the 100kΩ resistor back in asbefore and instead connect thephotoresistor between X & Y (youalso need a 1-snap and a 2-snapwire to do this). Now your radioplays music when it is dark.

OBJECTIVE: To build a dark-

Project #149 Radio Gun

AlarmOBJECTIVE: To build a radio OBJECTIVE: To build a light-

Project #148 Night Gun

Radio

Replace the music IC (U1) withthe alarm IC (U2). Now yourradio plays the sound of amachine gun when it is dark.

Remove the photoresistor. Nowconnect a jumper wire between X& Y on the drawing.If you remove the jumper now,the machine gun sound will playon the radio indicating your alarmwire has been triggered.

Remove the jumper wire.Replace the 100kΩ resistor (R5)with the photoresistor (RP). Nowyour AM radio will play themachine gun sound as long asthere is light in the room.

Project #150 Daylight Gun

Radio

OBJECTIVE: To build a light-

Project #146 Daylight

Music Radio

Remove the jumper wire.Replace the 100kΩ resistor (R5)with the photoresistor (RP). Nowyour AM radio will play music aslong as there is light in the room.

You need an AM radio for this project. Build thecircuit on the left and turn on the switch. Placeit next to your AM radio and tune the radiofrequency to where no other station istransmitting. Then, tune the adjustablecapacitor (CV) until your music sounds best onthe radio. Now connect a jumper wire betweenX and Y on the drawing, the music stops.

If you remove the jumper now, the music willplay indicating your alarm wire has beentriggered. You could use a longer wire and wrapit around a bike, and use it as a burglar alarm!

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Project #151 Blow Off a Space War

Project #152Series Lamps

Turn on the slideswitch (S1) and bothlamps will light. If oneof the bulbs is brokenthen neither will be on,because the lamps arein series. An exampleof this is the strings ofsmall Christmas lights;if one bulb is damagedthen the entire stringdoes not work.

Project #153Parallel Lamps

Build the circuit and turn it on,you hear a space war. Since it isloud and annoying, try to shut itoff by blowing into themicrophone (X1). Blowing hardinto the microphone stops thesound, and then it starts again.

Turn on the slideswitch (S1) and bothlamps will light. If oneof the bulbs is brokenthen the other will stillbe on, because thelamps are in parallel.An example of this ismost of the lights inyour house; if a bulb isbroken on one lampthen the other lampsare not affected.

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Project #154 Fire Fan SymphonyOBJECTIVE: To combine soundsfrom the music, alarm, and space warintegrated circuits.

OBJECTIVE:See Project #156.

The preceding circuit may be tooloud, so replace the speaker (SP)with the whistle chip (WC).

Project #157 Fan

Symphony (II)


Project #155Fire Fan

Symphony (II)

Project #156 Fan SymphonyOBJECTIVE: To combine soundsfrom the music, alarm, and space warintegrated circuits.

Modify the circuit from Project #154to match the circuit shown on the left.The only differences are theconnections around the alarm IC. Itworks the same way.


Build the circuit shown and add thejumper to complete it. Note that inone place two (2) single snaps arestacked on top of each other. Also,note that there is a 2-snap wire onlayer 2 that does not connect with a4-snap wire that runs over it on layer4 (both touch the music IC). Turn iton and press the press switch (S2)several times and wave your handover the photoresistor (RP) to hearthe full spectrum of sounds that thiscircuit can create. Have fun!

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Project #158 Police Car SymphonyOBJECTIVE: To combine sounds

OBJECTIVE:


Project #161 Ambulance

Symphony (II)

OBJECTIVE:

Project #159Police Car

Symphony (II)

Project #160 Ambulance SymphonyOBJECTIVE: To combine soundsfrom the music, alarm, and space war

Modify the circuit from Project 158 tomatch the circuit shown on the left.The only differences are theconnections around the alarm IC. Itworks the same way.


Build the circuit shown and add the two (2)jumper wires to complete it. Note that in oneplace two (2) single snaps are stacked ontop of each other. Turn it on and press thepress switch (S2) several times and waveyour hand over the photoresistor (RP) tohear the full spectrum of sounds that thiscircuit can create. Have fun! Do you know why the antenna (A1) is usedin this circuit? It is being used as just a 3-snap wire, because it acts like an ordinarywire in low frequency circuits such as this.Without it, you don't have enough parts tobuild this complex circuit.

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Project #162 Static SymphonyOBJECTIVE: To combine soundsfrom the integrated circuits.


Project #163Static

Symphony (II)

Project #164 Capacitors in Series


Do you know why the antenna(A1) is used in this circuit? It isbeing used as just a 3-snap wire,because it acts like an ordinarywire in low frequency circuitssuch as this. Without it you don’thave enough parts to build thiscomplex circuit.

Build the circuit shown and add thejumper wire to complete it. Note thatin one place 2 single snaps arestacked on top of each other. Turn iton and press the press switch severaltimes and wave your hand over thephotoresistor (RP) to hear the fullspectrum of sounds that this circuitcan create. Have fun!

Project #165 Capacitors in ParallelOBJECTIVE: To compare types of circuits.

Turn on the slide switch (S1), then press and release the press switch (S2). The LED (D1)becomes bright when the 470µF capacitor charges up with the press switch on, then the LEDslowly gets dim after you release the press switch.

Now turn off the slide switch. Repeat the test with the slide swtich off; you’ll notice the LED goesout much faster after you release the press switch. The much smaller 100µF capacitor (C4) isnow in series with the 470µF and so reduces the total capacitance (electrical storage capacity),and they discharge much faster. (Note that this is opposite to how resistors in series work).

Turn off the slide switch (S1), then press and release the press switch (S2). The LED (D1)becomes bright when the 100µF capacitor charges up with the press switch on, then the LEDslowly gets dim after you release the press switch.

Now turn on the slide switch and repeat the test; you’ll notice the LED goes out much slowerafter you release the press switch. The much larger 470µF capacitor (C5) is now in parallelwith the 100µF and so increases the total capacitance (electrical storage capacity), and theydischarge much slower. (Note that this is opposite to how resistors in parallel work.)

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Project #166OBJECTIVE: To show how water conducts electricity.

Build the circuit at left and connect the two jumpers to it, but leave theloose ends of the jumpers lying on the table initially. Turn on the switch- the LED (D1) will be dark because the air separating the jumpers hasvery high resistance. Touch the loose jumper ends to each other andthe LED will be bright, because with a direct connection there is noresistance separating the jumpers.

Now take the loose ends of the jumpers and place them in a cup ofwater, without letting them touch each other. The LED should be dimlylit, indicating you have detected water!

For this experiment, your LED brightness may vary depending uponyour local water supply. Pure water (like distilled water) has very highresistance, but drinking water has impurities mixed in that increaseelectrical conduction.

Water Detector

Project #167OBJECTIVE: To show how adding salt to water changes water’selectrical characteristics.

Place the jumpers in a cup of water as in the preceding project; theLED (D1) should be dimly lit. Slowly add salt to the water and see howthe LED brightness changes, mix it a little so it dissolves. It will slowlybecome very bright as you add more salt. You can use this bright LEDcondition as a saltwater detector! You can then reduce the LEDbrightness by adding more water to dilute the salt.

Take another cup of water and try adding other household substanceslike sugar to see if they increase the LED brightness as the salt did.

Saltwater Detector

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Project #168NPN Light Control


Project #169NPN Dark Control

Put on the switch, thebrightness of the LED dependson how much light shines on thephotoresistor. The resistancedrops as more light shines,allowing more current to theNPN.


Put on the switch, thebrightness of the LED dependson how LITTLE light shines onthe photoresistor. Theresistance drops as more lightshines, diverting current awayfrom the NPN.

Project #170PNP Light Control


Project #171PNP Dark Control

Put on the switch, thebrightness of the LED dependson how much light shines on thephotoresistor. The resistancedrops as more light shines,allowing more current throughthe PNP. This is similar to theNPN circuit above.


Put on the switch, thebrightness of the LED dependson how LITTLE light shines onthe photoresistor. Theresistance drops as more lightshines, so more current gets tothe 100kΩ resistor from thephotoresistor path and less fromthe PNP-diode path. This issimilar to the NPN circuit above.

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Project #172Red & Green Control

OBJECTIVE: To demonstratehow the adjustable resistorworks.

Project #173Current Controllers

Turn on the circuit using the slideswitch (S1) and/or the pressswitch (S2) and move theadjustable resistor’s (RV) controllever around to adjust thebrightness of the LEDs (D1 andD2). When the adjustable resistoris set to one side, that side willhave low resistance and its LEDwill be bright (assuming theswitch on that side is ON) whilethe other LED will be dim or OFF.

OBJECTIVE: To comparetypes of circuits.

Build the circuit and turn on the slideswitch (S1), the LED (D1) will be lit.To increase the LED brightness, turnon the press switch (S2). Todecrease the LED brightness, turnoff the slide switch.

With the slide switch on, the 5.1Kresistor (R3) controls the current.Turning on the press switch placesthe 1K resistor (R2) in parallel with itto decrease the total circuitresistance. Turning off the slideswitch places the 10K resistor (R4) inseries with R2/R3 to increase thetotal resistance.

Project #174Current Equalizing

OBJECTIVE: To comparetypes of circuits.

Project #175Battery Polarity Tester

Put on the switch and the twoLEDs will have the samebrightness. When connected inseries, all components will haveequal electric current throughthem.

OBJECTIVE: To test thepolarity of a battery.

Use this circuit to check thepolarity of a battery. Connectyour battery to X & Y on thedrawing using the jumper cables(your 3V battery pack (B1) canalso be snapped on directlyinstead). If the positive (+) sideof your battery is connected toX, then the red LED will be on, ifthe negative (–) side isconnected to X then the greendiode will be on.

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Project #176 Blow Off a DoorbellOBJECTIVE: To turn off a circuit

OBJECTIVE: To turn on a

Replace the speaker (SP) withthe 6V lamp (L2). Blowing intothe microphone turns on thelight, and then it goes off again.

Project #179Blow On a

Candle

OBJECTIVE: To turn off a

Project #177Blow Off a

Candle

Project #178 Blow On a DoorbellOBJECTIVE: To turn on a circuit

Build the circuit and turn it on, musicplays for a few moments and thenstops. Blow into the microphone (X1)and it plays; it plays as long as youkeep blowing.

Replace the speaker (SP) withthe 6V lamp (L2). Blowing hardinto the microphone turns off thelight briefly.

Build the circuit and turn it on, musicplays. Since it is loud and annoying,try to shut it off by blowing into themicrophone (X1). Blowing hard intothe microphone stops the music, andthen it starts again.

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Project #180OBJECTIVE: To have an adjustable

Screaming Fan

Project #182Light Whining

Replace the 3-snap wire at the upper-left ofthe circuit (points A1 & A3 on the base grid)with the photoresistor (RP), and wave yourhand over it. The whining sound has changeda little and can now be controlled by light.

Project #183More Light

Whining

Replace the 0.02µF capacitor (C1) with the0.1µF capacitor (C2). The sounds are lowerin frequency and you can't make the fan spinnow.

Project #184 Motor ThatWont Start

Replace the 0.1µF capacitor (C2) with the10µF capacitor (C3), put the positive (+) sidetowards the left). It now makes clickingsounds and the fan moves only in smallbursts, like a motor that won’t start.

Project #181 Whining Fan

Replace the 0.1µF capacitor (C2) with the0.02µF capacitor (C1). The sounds are now ahigh-pitch whine and the motor starts a littlesooner.

Build the circuit on the left. Note that the0.1µF capacitor (C2) is specially mountedabove the NPN transistor (Q2); its leftside is on level 4 while the right side is onlevel 3. Turn on the switch and move thesetting on the adjustable resistor acrossits range. You hear screaming soundsand the fan spins.

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Project #185OBJECTIVE: To build a circuit thatmakes a loud whine.

Whiner

Project #187Hummer

OBJECTIVE: To show how addingcapacitance reduces frequency.

Now place the 0.1µF capacitor (C2) abovethe whistle chip (WC) and vary the adjustableresistor again. The frequency (or pitch) of thewhine has been reduced by the greateradded capacitance and it sounds more like ahum now.

Project #188AdjustableMetronome

OBJECTIVE: To build an adjustableelectronic metronome.

Now place the 10µF capacitor (C3, plus sideon right) above the whistle chip (WC) andvary the adjustable resistor again. There is nohum now but instead there is a click and aflash of light repeating about once a second,like the “beat” of a sound. It is like ametronome, which is used to keep time for therhythm of a song.

Project #189 Quiet Flasher

OBJECTIVE: To make a blinkingflashlight.

Leave the 10µF capacitor connected butreplace the speaker (SP) with the 6V Lamp.

Project #186 Lower Pitch

WhinerOBJECTIVE: To show how addingcapacitance reduces frequency.

Place the 0.02µF capacitor (C1) above thewhistle chip (WC) and vary the adjustableresistance again. The frequency (or pitch) ofthe whine has been reduced by the addedcapacitance and it sounds more like musicnow.

Build the circuit, turn it on, and move thesetting on the adjustable resistor. Itmakes a loud, annoying whine sound.The green LED (D2) appears to be on,but it is actually flashing at a very fastrate.

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Project #190OBJECTIVE: To build a transistor oscillator that can make afoghorn sound.

Hissing Foghorn

Project #191Hissing & Clicking

OBJECTIVE: To build an adjustable clicking oscillator.

Modify the circuit in Project 190 by replacingthe 100kΩ resistor (R5) with the photoresistor(RP).Move the adjustable resistor setting until youhear hissing sounds, and then shield thephotoresistor while doing so and you hearclicking sounds.

OBJECTIVE: To build a human oscillator.

Build the circuit on the left andmove the adjustable resistorsetting. Sometimes it will make afoghorn sound, sometimes it willmake a hissing sound, andsometimes it will make no soundat all.

Project #192Video Game

Engine Sound

Remove the photoresistor (RP) from thecircuit in Project 191 and instead touch yourfingers between the contacts at points A4 andB2 on the base grid while moving theadjustable resistor. You hear a clicking thatsounds like the engine sound in auto-racingvideo games.

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Project #193 Light AlarmOBJECTIVE: To build a transistor lightalarm.

OBJECTIVE: To build a simple laser.

Replace the Motor (M1) with the 6VLamp (L2). Now pressing the pressswitch (S2) creates a blast of light like alaser.

Project #196 Laser Light

OBJECTIVE: To build a brightertransistor light alarm.

Project #195 Lazy FanOBJECTIVE: To build a fan that doesn’twork well.

Press the press switch (S2) and the fan will beon for a few turns. Wait a few moments andpress again, and the fan will make a few moreturns.

Modify the circuit in Project #193 byreplacing the LED (D1) with the 2.5Vlamp (L1) and replacing the 5.1kΩresistor with the 100Ω resistor (R1). Itworks the same way but is brighter now.

Build the circuit with the jumper connected asshown, and turn it on. Nothing happens. Breakthe jumper connection and the light turns on.You could replace the jumper with a longer wireand run it across a doorway to signal an alarmwhen someone enters.

Project #194Brighter

Light Alarm

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Project #197OBJECTIVE: To sound an alarm when water is

Build the circuit at left and connect the two (2) jumpersto it, place the loose ends of the jumpers into an emptycup (without them touching each other). Press thepress switch (S2) - nothing happens. Add some waterto the cup and an alarm will sound. Add salt to the waterand the tone changes.

You can also test different liquids and see what tonethey produce.

Water Alarm

Project #198 Drawing ResistorsOBJECTIVE: To make your own resistors.

Use the circuit from Project 197, but make the following changes:Replace the press switch (S2) with the slide switch (S1); Replaceresistor (R5) with the variable resistor (RV); Remove the 1-snap and 3-snap at points A3 & A5, and place jumper wires at these points; Place a3-snap at points E1 & E3; and you don’t need the cup of water. Thereis one more part that you need and you are going to draw it. Take apencil (No. 2 lead is best but other types will also work). SHARPEN IT,and fill in the shape below. You will get better results if you place a hard,flat surface directly beneath this page while you are drawing. Presshard (but don’t rip the paper), and fill in the shape several times to besure you have a thick, even layer of pencil lead.

Turn on the switch and take the loose ends of the jumpers, press themto the shape and move them around over the drawing. The tone of thesound should have a higher pitch if the ends are farther apart in theshape. If you don’t hear any sound then move the ends closer togetherand move over the drawing, add another layer of pencil lead, or put adrop of water on the jumper ends to get better contact.

Now you can draw your own shapes and see what kinds of sounds youcan make!

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Project 201Pitch (III)


Project #202OBJECTIVE: To sound an alarm when water is detected.

Flooding Alarm

Project #199 PitchOBJECTIVE: To show howto change the pitch of asound.

Project 200Pitch (II)


Remove the 0.1uF capacitor andreplace the 100kΩ resistor (R5)wth the photoresistor (RP).Wave your hand up and downover the photoresistor to changethe sound. Changing the light onthe photoresistor changes thecircuit resistance just like varyingthe adjustable resistance does.Note: If you have the adjustableresistor set to the right and lightshining on the photoresistor,then you may not get any soundbecause the total resistance istoo low for the circuit to operate.

Build the circuit on the left, turnit on, and vary the adjustableresistor (RV). The frequency orpitch of the sound is changed.Pitch is the musical profession’sword for frequency. If you’vehad music lessons, you mayremember the music scaleusing chords such as A3, F5,and D2 to express the pitch of asound. Electronics prefers theterm frequency, as in when youadjust the frequency on yourradio.

Build the circuit at left and connect the two (2) jumpers to it, place theloose ends of the jumpers into an empty cup (without them touchingeach other). Turn on the switch - nothing happens. This circuit isdesigned to detect water and there is none in the cup. Add somewater to the cup - an alarm sounds!

You can use longer jumper wires and hang them near your basementfloor or next to your sump pump to give a warning if your basement isbeing flooded. Note that if the loose jumper ends accidentally touchthen you will have a false alarm.

Since we’ve seen we canadjust the frequency byvarying the resistance in theadjustable resistor, are thereother ways to changefrequency? You can alsochange frequency bychanging the capacitance ofthe circuit. Place the 0.1µFcapacitor (C2) on top of the0.02µF capacitor (C1); noticehow the sound has changed.

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Project #203

OBJECTIVE: To demonstrate how batteries can store electricity.

Build the circuit, then connect points Y & Z (use a 2-snap wire) for amoment. Nothing appears to happen, but you just filled up the 470µFcapacitor with electricity. Now disconnect Y & Z and instead touch aconnection between X & Y. The green light emitting diode will be lit andthen go out after a few seconds as the electricity you stored in it isdischarged through the diode and resistor.

Notice that a capacitor is not very efficient at storing electricity -compare how long the 470µF kept the LED lit for with how yourbatteries run all of your projects! That is because a capacitor storeselectrical energy while a battery stores chemical energy.

Make Your OwnBattery

OBJECTIVE: To demonstrate how batteries can store electricity. OBJECTIVE: To demonstrate how batteries can store electricity.

Now replace the 1kΩ resistor (R2) with the 100Ω resistor (R1) and try it.The LED gets brighter but goes out faster because less resistanceallows the stored electricity to dissipate faster.

In the preceding circuit, replace the 470µF capacitor (C5) with the100µF capacitor (C3) and repeat the test. You see that the LED goesout faster, because the 100µF capacitor does not store as muchelectricity as the 470µF.

Project #204Make Your Own

Battery (II)

Project #205Make Your Own

Battery (III)

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Project #206OBJECTIVE: To build a high-frequency oscillator.

Tone Generator

Project #207Tone

Generator (II)OBJECTIVE: To lower the frequency of atone by increasing circuit capacitance.

Place the 0.02µF capacitor (C1) on top of thewhistle chip (WC) in the preceding circuit, youhear a middle-frequency sound. Why? Thewhistle chip is used here as a capacitor andby placing the 0.02µF on top (in parallel) wehave increased the capacitance, and doing solowers the frequency.

Project #208Tone

Generator (III)OBJECTIVE: To lower the frequency of atone by increasing circuit capacitance.

Next, replace the 0.02µF capacitor and thewhistle chip with the larger 0.1µF capacitor(C2). You now hear a low frequency sound,due to yet more capacitance.

Project #209 Tone

Generator (IV)OBJECTIVE: To lower the frequency of atone by increasing circuit capacitance.

Now replace the 0.1µF with the much larger10µF capacitor (C3), (orient with the positive(+) side towards the left); the circuit just clicksabout once a second. There isn’t a constanttone anymore due to other transistorproperties. You need a different type of circuitto create very low frequency tones.

Build the circuit and turn it on, you hear ahigh-frequency sound.

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Project #210OBJECTIVE: To build a middle-frequency oscillator.

Build the circuit, as the name suggests this circuit is similar to that inproject #206. Turn it on, you hear a middle-frequency sound.

More Tone Generator

OBJECTIVE: To raise the frequency of a tone by decreasingcircuit resistance.

OBJECTIVE: To raise the frequency of a tone by decreasingcircuit resistance.

Next, replace the 1kΩ resistor (R2) with the 100Ω resistor (R1). You nowhear a very high frequency sound, due to even less resistance.

Now place the 1kΩ resistor (R2) on top of the 10kΩ resistor (R4), younow hear a high-frequency sound. By placing the 1kΩ resistor on top ofthe 10kΩ (in parallel), we have decreased the resistance, and doing soraises the frequency.

Project #211More Tone

Generator (II)

Project #212More Tone

Generator (III)

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Project #213 Music Radio StationOBJECTIVE: To create music andtransmit it to a radio.

OBJECTIVE: To create musicand transmit it to a radio.

Project #214Alarm Radio

Station

Project #215 Standard Transistor CircuitOBJECTIVE: To save some electricity for later use.

Turn on the slide switch (S1) and move the adjustableresistor (RV) control lever across its range. When the leveris all the way down the LED (D1) will be off, as you movethe lever up it will come on and reach full brightness.

This circuit is considered the standard transistorconfiguration for amplifiers. The adjustable resistor controlwill normally be set so that the LED is at half brightness,since this minimizes distortion of the signal being amplified.

Replace the music IC (U1) withthe alarm IC (U2), and then youwill hear a machine gun sound onthe radio. You may need to re-tune the adjustable capacitor.

You need an AM radio for this project.Build the circuit shown on the left andturn on the switch. Place it next toyour AM radio and tune the radiofrequency to where no other station istransmitting.

Then, tune the adjustable capacitor(CV) until your music sounds best onthe radio.

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Project #217 Fading SirenOBJECTIVE: To produce sound ofa siren driving away into thedistance.

OBJECTIVE: To producesound of a siren driving awayinto the distance.

Replace the 470µF capacitor(C5) with the 100µF capacitor(C4), the siren fades faster.

Press the switch (S2), the integratedcircuit should make the sound of anup-down siren that gets weaker withtime. The fading is produced by thecharging of the 470µF capacitor (C5),After it is charged the current stopsand the sound is very weak.

To repeat this effect you must releasethe press switch (S2), remove thecapacitor (C5), and discharge it byplacing it across the snaps on thebottom bar marked A & B. Then,replace the capacitor (C5) and pressthe switch again.

Project #218Fast Fade

Siren

Project #216

OBJECTIVE: To control a motor using light.

Turn the switch on, the motor spins and the lamp lights. As you moveyour hand over the photoresistor, the motor slows. Now place fingeronto the photoresistor to block the light. The motor slows down. In afew seconds, the motor speeds up again.

Motor & Lampby Sound

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Project #219 Laser Gun withLimited Shots

OBJECTIVE: To build the circuit used in a toy laser gun withflashing laser light and trigger and limited amount of shots.

Project #220 Symphony of SoundsOBJECTIVE: To combine soundsfrom the music, alarm, and space warintegrated circuits.



Can you guess why the jumper isused in this circuit? It is beingused as just a 3-snap wirebecause without it you don’t haveenough parts to build thiscomplex circuit.

Build the circuit shown and add thejumper to complete it. Note that intwo places two (2) single snaps arestacked on top of each other. Also,note that there is a 2-snap wire onlayer 2 that does not connect with a4-snap wire that runs over it on layer4 (both touch the music IC). Turn iton and press the press switch (S2)several times and wave your handover the photoresistor (RP) to hearthe full symphony of sounds that thiscircuit can create. Have fun!

When you close the press switch (S2), the integrated circuit shouldstart sounding a very loud laser gun sound. The red LED will flashsimulating a burst of laser light. You can shoot long repeating laserburst, or short zaps by tapping the trigger switch. But be careful, thisgun will run out of energy and you will have to wait for the energy pack(C5) to recharge. This type of gun is more like a real life laser gunbecause power would run out after a few shots due to energy drain. Ina real laser, the energy pack would have to be replaced. Here you onlyhave to wait a few seconds for recharge.

Project #221Symphony ofSounds (II)

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Project #222OBJECTIVE: To learn about the most important component inelectronics.

Transistor Amplifiers

OBJECTIVE: To show how electronic amplifiers can detect skinpressure on two contacts.

OBJECTIVE: To show how electronic amplifiers can detectdifferent values of resistance.

Use the circuit from Project 222 shown above.

When you placed your fingers across the two snaps marked X & Y younoticed the LED came on in Project 222. Repeat this process, but thistime press very lightly on the two snaps marked X & Y. Notice how thebrightness of the LED is dependent on the amount of pressure you use.Pressing hard makes the LED bright while pressing very gently makesit dim or even flash. This is due to what technicians call contactresistance. Even switches made to turn your lights on and off havesome resistance in them. When large currents flow this resistance, willdrop the voltage and produce the undesirable side effect of heat.

Project #223Pressure Meter

Project #224Resistance Meter

When you place one or more fingers across the two snaps marked X& Y you will notice the light comes on. The two transistors are beingused to amplify the very tiny current going through your body to turnon the LED. Transistors are actually electrical current amplifiers. ThePNP transistor has the arrow pointing into the transistor body. TheNPN transistor has the arrow pointing out of the transistor body. ThePNP amplifies the current from your fingers first, then the NPNamplifies it more to turn on the LED.

Use the circuit from Project 222 shown above

When you placed your fingers across the two snaps marked X & Y younoticed the LED came on in Project 222. In this project, you will placedifferent resistors across R & Z and see how bright the LED glows. Donot snap them in; just press them up against the snaps labeled R & Z inthe diagram above.First, place the 100kΩ resistor across the R & Z snaps and note thebrightness of the LED. Next, press the 5.1kΩ resistor across R & Z.Notice how the LED gets brighter when the resistance is less. This isbecause the NPN amplifier gets more current at its input when theresistance is lower. The PNP amplifier is not used in this test.

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Project #225OBJECTIVE: To learn about one device that is used to delayactions in electronics.

Auto-Off Night-Light

OBJECTIVE: To show how capacitor delays can be repeated bydischarging the capacitor.

OBJECTIVE: To show how the size of the capacitor effects thedelay time.

Use the circuit from Project #225 shown above.

When you first turned on the slide switch (S1) in Project 225, the LEDcame on and very slowly got dimmer and dimmer. When you turned theslide switch (S1) off and back on after the light went out, it did NOTcome on again. The 470µF capacitor (C5) was charged and everythingstopped. This time turn the slide switch (S1) off. Then press the pressswitch (S2) for a moment to discharge the 470µF capacitor. Now whenyou turn the slide switch (S1) back on the delay repeats. Shorting acapacitor with a low resistance will allow the charges on the capacitor toleave through the resistance. In this case, the low resistance was thepress switch.

Project #226Discharging Caps

Project #227Changing Delay Time

When you turn on the slide switch (S1) the first time the light will comeon and very slowly get dimmer and dimmer. If you turn the slide switch(S1) off and back on after the light goes out it will NOT come on again.The 470µF capacitor (C5) has charged up and the NPN transistoramplifier (Q2) can get no current at its input to turn it on.

This circuit would make a good night-light. It would allow you to getinto bed, and then it would go out. No further current is taken from thebattery so it will not drain the batteries even if left on all night.

Use the circuit from Project #225 shown above.

Change the 470µF capacitor (C5) to the 100µF capacitor (C4). Makesure the capacitor (C4) is fully discharged by pressing the press switch(S2) before closing the on-off slide switch (S1). When slide switch (S1)is closed, notice how much quicker the LED goes out. Since 100µF isapproximately 5 times smaller than 470µF, the light will go out 5 timesfaster. The bigger the capacitor the longer the delay.

In electronics, capacitors are used in every piece of equipment to delaysignal or tune circuits to a desired frequency.

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Project #228 Morse Code GeneratorOBJECTIVE: To make a Morse code generator and learn togenerate code.

Project #229LED CodeTeacher

OBJECTIVE: A method oflearning the Morse code without

Use the circuit from Project 228shown above. Replace thespeaker with a 100Ω resistor (R1)so you can practice generatingthe Morse code without the loudspeaker. Have someone transmitcode and watch the LED. Tellthem the letter or number aftereach is generated. When youhave learned code, replace thespeaker.

OBJECTIVE: To make a ghostlike special effect from the Morse

Project #231 LED &

SpeakerOBJECTIVE: To improveMorse code skills and visual

OBJECTIVE: To make anoscillator that only a dog can

Project #230 Ghost Shriek

Machine

Use the circuit from Project 228shown above, but change the 1kΩresistor (R2) to a 10kΩ resistor(R4), and .1µF capacitor (C2) tothe variable capacitor (CV). Whileholding the press switch (S2)down adjust both the variableresistor (RV) and the variablecapacitor (CV) for a ghost likesound. At certain settings, soundmay stop or get very faint.

Use the circuit from Project 228shown above. Try and find aperson that already knows theMorse code to send you amessage with both sound andLED flashing. Try in a dark roomfirst so LED is easier to see.Morse code is still used by manyamateur radio operators to sendmessages around the world.

Use the circuit from project 228shown above, but change the 1kΩresistor (R2) to the 100Ω resistor(R1). While holding down the pressswitch (S2), move the slider on theadjustable resistor (RV) around.When the slider is near the 100Ωresistor you won't hear any sound,but the circuit is still working. Thisoscillator circuit is making soundwaves at a frequency too high foryour ears to hear. But your dog mayhear it, because dogs can hearhigher frequencies than people can.

Project #232 Dog Whistle

When you press down on the press switch (S2) you will here a tone.By pressing and releasing the press switch you can generate long andshort tones called Morse code. For International code, a short tone isrepresented by a “+”, and a long tone by a “–”. See the chart belowfor letter or number followed by code.

A + –B – + + +C – + – +D – + +E +F + + – +

G – – +H + + + +I + +J + – – –K – + –L + – + +

M – –N – +O – – –P + – – +Q – – + –R + – +

S + + +T –U + + –V + + + –W + – –X – + + –

Y – + – –Z – – + +1 + – – – –2 + + – – –3 + + + – –4 + + + + –

5 + + + + +6 – + + + +7 – – + + +8 – – – + +9 – – – – +0 – – – – –

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Project #233 Mind Reading GameOBJECTIVE: To make an electronic game of mind reading.

Build the circuit shown on the left. It usestwo (2) 2-snap wires as shorting bars.

Setup: Player 1 sets up by placing oneshorting bar under the paper on row A, B, C,or D. Player 2 must NOT know where theshorting bar is located under the paper.

The object is for Player 2 to guess thelocation by placing his shorting bar atpositions W, X, Y, or Z. In the drawing on theleft, Player 1 set up at position "D". If Player2 places his shorting bar across "Z" on thefirst try, then he guessed correctly andmarks a 1 on the score card sheet underthat round number. If it takes three tries,then he gets a three.Player 2 then sets the A, B, C, D side andPlayer 1 tries his luck. Each player recordshis score for each round. When all 18rounds have been played, the player withthe lowest score wins. Additional playerscan play. Use the score card below todetermine the winner.

Round # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Total

Player 1 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _____

Player 2 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _____

Player 3 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _____

Player 4 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _____

Shorting Bar forA, B, C, or D.

Paper Sheet tohide position ofshorting bar.

Shorting Bar forW, X, Y, or Z.

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Project #234OBJECTIVE: Make and play the electronic game of "QuietZone".

Use the circuit from Project 233, but place three (3) 2-snap wires(“shorting bars”) under paper as shown on left.

Setup: Player 1 sets the "Quiet Zone" by placing three (3) shortingbars under the paper on row A, B, C, or D, leaving only one open.Player 2 must NOT know where the shorting bars are located underthe paper.

Both Player 1 and Player 2 are given 10 points. The object is for Player2 to guess the location of the "Quiet Zone" by placing his shorting barat positions W, X, Y, or Z. In the drawing on the left Player 1 set up the"Quiet Zone" at position "C". If Player 2 places his shorting bar across"Z" on the first try, the sounds played mean he has not found the "QuietZone" and he loses 1 point. He has 3 tries to find the zone on eachturn. Each time sounds are made he loses a point.Player 2 then sets the A, B, C, D side and Player 1 starts searching.Play continues until one player is at zero points and makes soundduring that players turn.

Enhanced Quiet Zone Game

Project #235

OBJECTIVE: To show how capacitors store and releaseelectrical charge.

Turn on the slide switch (S1) for a few seconds, then turn it off. Thegreen light emitting diode (LED, D2) is initially bright but goes dim asthe batteries charge up the capacitor (C5). The capacitor is storingelectrical charge.

Now press the key (S2) for a few seconds. The red LED (D1) is initiallybright but goes dim as the capacitor discharges itself through it.

The capacitor value (470µF) sets how much charge can be stored init, and the resistor value (1kΩ) sets how quickly that charge can bestored or released.

Capacitor Charge &Discharge

Shorting Barfor A, B, C,or D.

Paper Sheet tohide position ofshorting bar.

Shorting Bar forW, X, Y, or Z.

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Project #236OBJECTIVE: To show how sound waves travel on a papersurface.

Sound Wave Magic

Project #237

OBJECTIVE: To amplify sounds from the spacewar integrated circuit.

Build the circuit, turn on the switch, and press the pressswitch (S2) several times. You will hear loud space warsounds, since the sound from the space war integratedcircuit is amplified by the power amplifier integratedcircuit. Nearly all toys that make sound use a poweramplifier of some sort.

Space WarAmplifier

Build the circuit shown on the left and connect the speaker using thetwo (2) jumper wires. Then, lay the speaker on a flat hard surface.

Setup: Use some paper and scissors to cut out a rectangular pattern.Use the one shown below as a guide. Use colored paper if available.Fold at the points shown. Scotch tape the corners so the tray has nocracks at the corners. Place the tray over the speaker and sprinkle asmall amount of white table salt in the tray. There should be enoughsalt to cover the bottom with a little space between each salt grain.

Sound Magic: Turn on the circuit by closing slide switch (S1). Adjustthe adjustable resistor (RV) for different pitches and watch the saltparticles. Particles that bounce high are directly over the vibratingpaper and ones that do not move are in the nodes where the paper isnot vibrating. Eventually, all the salt will move to the areas that have novibration, and stay there.Change the position of the tray and the material used to create differentpatterns due to the sound. Try sugar and coffee creamer, for example,to see if they move differently due to the sound waves.

Paper Tray

Salt

Sample Cut-out Pattern

(fold)

(fold)

(fold)

(fold)

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Project #238Trombone

OBJECTIVE: To build an electronic trombone that changes pitch

When you turn on the slide switch (S1) the trombone should start playing.To change the pitch of the note, simply slide the adjustable resistor control(RV) back and forth. By turning the slide switch (S1) on and off andmoving the slider, you will be able to play a song much like a tromboneplayer makes music. The switch represents air going through thetrombone, and the RV control is the same as a trombone slider bar. Thecircuit may be silent at some positions of the resistor control.

Project #239Race Car Engine

OBJECTIVE: To show how changing frequency changes the

Use the circuit from Project 238 shown on the left, but change the 0.02µFcapacitor (C1) to a 10µF capacitor (C3). Make sure the positive (+) markon the capacitor is NOT on the resistor (R2) side when you snap it in.

When the switch is turned on, you should hear a very low frequencyoscillation. By sliding the adjustable resistor control (RV) up and down,you should be able to make the sound of a race car engine as it's motorspeeds up and slows down.

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Project #240Power Amp

OBJECTIVE: To check stability of power amplifier with open

When you turn on the slide switch (S1), the power amplifier should notoscillate. You should be able to touch point X with your finger and hearstatic. If you do not hear anything, then try touching point X with one ofthe snaps on any part. High frequency clicks or static should be comingfrom speaker indicating that the amplifier is powered on and ready toamplify signals.

The power amplifier may oscillate on its own. Do not worry, this is normalwith high gain high-powered amplifiers.

Project #241Electronic Kazoo

OBJECTIVE: To show how electronic feedback can be used tomake a musical instrument.

Use the circuit from Project #240 shown on the left.

When you place one finger on point X and a finger from your other handon the speaker (SP) snap that is not connected to the battery, whathappens? If the amplifier starts to oscillate it is due to the fact that youjust provided a feed back path to make the amplifier into an oscillator. Youmay even be able to change the pitch of the oscillation by pressing harderon the snaps.

This is the principle used to make an electronic kazoo. If you practice andlearn the amount of pressure required to make each note, you may evenbe able to play a few songs.

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Project #242

OBJECTIVE: To make a complete working AM radio.

When you close the slideswitch (S1), the integratedcircuit (U5) should amplify anddetect the AM radio waves allaround you. The variablecapacitor (VC) can be tunedto the desirable station.Varying the adjustable resistor(RV) will make the audiolouder or softer. The poweramplifier (U4) drives thespeaker (SP) to complete theAM radio project.

AM Radio

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Project #243 Fire Engine SymphonyOBJECTIVE: To combine soundsfrom the music, alarm, and space

OBJECTIVE:

Project #244Fire Engine

Symphony (II)

Project #245 Vibration or Sound IndicatorOBJECTIVE: To build a circuit that is activated by vibration or

Set the slide switch (S1) on, the war sounds start playingand the LED flashes. When all of the sounds are played,the circuit stops. Clap your hands next to the whistle chipor tap on it. Any loud sound or vibration causes the whistlechip to produce a small voltage, which activates the circuit.You can repeat a sound by holding down the press switch(S2) while it is playing.


Can you guess why the jumper isused in this circuit? It is beingused as just a 3-snap wire,because without it you don’t haveenough parts to build thiscomplex circuit.

Build the circuit shown and add thejumper to complete it. Note that intwo places two (2) single snaps arestacked on top of each other. Also,note that there is a 2-snap wire onlayer 2 that does not connect with a4-snap wire that runs over it on layer4 (both touch the music IC). Turn iton and press the press switch (S2)several times and wave your handover the photoresistor (RP) to hearthe full spectrum of sounds that thiscircuit can create. Have fun!

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Project #246OBJECTIVE: To show that your body can be used as anelectronic component.

Build the circuit on the left. You’re probably wondering how it can work,since one of the points on the NPN transistor (Q2) is unconnected. Itcan’t, but there is another component that isn’t shown. Thatcomponent is you.

Touch points X & Y with your fingers. The LED may be dimly lit. Theproblem is your fingers aren’t making good enough electrical contactwith the metal. Wet your fingers with water or saliva and touch thepoints again. The LED should be very bright now. Think of this circuitas a touch lamp since when you touch it the light emitting diode lights.You may have seen such a lamp in the store or already have one inyour home.

Two-Finger Touch Lamp

Project #247OBJECTIVE: To show you how finger touch lamps work.

The touch lamps you see in stores only need to be touched by onefinger to light, not two. So let’s see if we can improve the last circuit toonly need one finger. Build the new circuit, note that near point X thereis a 2-snap wire that is only mounted on one side, swing it so theplastic touches point X. Wet a large area of one of your fingers andtouch it to both metal contacts at point X at the same time; the LEDlights. To make it easier for one finger to touch the two contacts, touchlamps or other touch devices will have the metal contacts interweavedas shown below and will also be more sensitive so that you don’t haveto wet your finger to make good contact.

One-Finger Touch Lamp

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Project #248 Space BattleOBJECTIVE: To show how sound can turn"ON" an electronic device.

Project #250 Multi-Speed Light FanOBJECTIVE: To vary thespeed of a fan activated bylight.

OBJECTIVE: To show how lightcan turn "ON" an electronic device.

Replace the slide switch (S1) with thephotoresistor (RP). Now covering anduncovering the photoresistor willchange the sound.

Project #249 Space Battle (II)

Project #251Light & Finger Light

OBJECTIVE: To show another way the Space War IC may beused.

In the circuit at left, replace the motor (M1) with a 2.5V lamp shownbelow. Vary the brightness of the lamp by covering the photoresistorand holding down the press switch (S2) in various combinations.Notice that pressing the press switch when the photoresistor iscovered still turns on the lamp, while in Project 250, doing this wouldturn off the motor.

Build the circuit shown on the left. Activatethe circuit by flipping the switch or pressingthe press switch (S2), do both several timesand in combination. You will hear excitingsounds and see flashing lights, as if a spacebattle is raging!

Build the circuit shown onthe left, with the fan on themotor.

This circuit is activated bylight on the photoresistor,though the fan will barelyturn at all. Press the pressswitch (S2) and the fan willspin. If you hold the pressswitch down, the fan willspin faster. If you cover thephotoresistor, the fan willstop even if the pressswitch is pressed.

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Project #252 Storing ElectricityOBJECTIVE: To store electricity in a capacitor.

Project #253 Lamp Brightness ControlOBJECTIVE:To use a transistor combination tocontrol a lamp.

OBJECTIVE: To make anelectric fan using a transistorcircuit.

Use the circuit from Project 253.Replace the lamp (L2) with themotor (M1) and install the fan. Bycontrolling the adjustableresistor, the speed of the fanchanges. Now you can makeyour own speed changingelectric fan.

Here is a combination with twotransistors. This combinationincreases the amplifying power. Bychanging the resistance, the currentat the base of the transistor is alsochanged. With this amplifying abilityof the combination, there is a greaterchange of current to the lamp. Thischanges the brightness.

Turn the switch on and connect point A and B with a 2-snap wire. Thegreen LED will flash and the capacitor will be charged with electricity.The electricity is now stored in the capacitor. Disconnect point A andB. Connect point B and C and there will be a flash from the 6V lamp.

The capacitor discharges through the resistor to the base of the NPNtransistor. The positive current turns on the transistor like a switch,connecting the lamp to the negative (–) side of the batteries. The lightwill go out after the capacitor discharges, because there is no morecurrent at the base of the transistor.

Project #254Electric

Fan

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Project #255

OBJECTIVE: To build an alarm that plays music on the radio.

Place the circuit next to an AM radio. Tune the radio so no stations areheard. Set the slide switch (S1) on. You should hear the song play.The red LED should also be lit. Adjust the variable capacitor (CV) forthe loudest signal.

Connect a jumper wire across points A & B and the music stops. Thetransistor acts like a switch connecting power to the music IC. Positivevoltage on the base closes the switch and negative voltage opens it.Connect a string to the jumper wire and the other end of the string toa door or window. Set the switch on. If a thief comes in through thedoor or window, the string pulls the jumper off and the music plays onthe radio.

Radio MusicBurglar Alarm

Project #256OBJECTIVE: To build a light dimmer.

Press the press switch (S2) to complete the current's path flow. Youmight expect the LED to light instantly but it doesn't. The chargingcurrent flows into the capacitor (C4) first. As the capacitor charges,the charging current decreases, input current to the PNP transistor(Q1) increases. So current begins to flow to the LED and the LEDgradually brightens.

Now release the press switch. The capacitor begins to discharge,sending input current to the transistor. As the capacitor discharges,the input current reduces to zero and gradually turns off the LED andthe transistor.

Light Dimmer

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Project #257OBJECTIVE: Build a circuit that detects motion.

Set the adjustable resistor (RV) to the center position. Turn the switch onand the LED lights. Wave your hand over the photoresistor (RP) and theLED turns off and on. The resistance changes as the amount of lightstrikes the photoresistor. As the light decreases, the resistanceincreases. The increased resistance lowers the voltage at the base ofthe NPN transistor (Q2). This turns off the transistor, preventing currentflowing through the LED to the negative (–) side of the battery. Waveyour hand over photoresistor at different distances. The LED getsbrighter the farther away your hand is.

Motion Detector

Project #258OBJECTIVE: To modulate the brightness of an LED.

Using the fan outline as a guide, cut a 3" circle out of a piece of paper.Then, cut a small triangle in it as shown. Tape the circle onto the fanand then place it onto the motor. Set the adjustable resistor (RV) to thecenter position and turn the switch on. Press the press switch (S2),the fan spins and the lamp lights. As the triangle opening moves overthe photoresistor, more light strikes it. The brightness of the LEDchanges, or is modulated. As in AM or FM radio, modulation uses onesignal to modify the amplitude or frequency of another signal.

Fan Modulator

3” dia.

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Project #261OBJECTIVE: To build a motion detector that senses an objectsmovement.

Turn the switch on and move the adjustable resistor (RV) control all theway up. The brightness of the LED is at maximum. Now, move theadjustable resistor control down until the LED goes out. Set the controlup a little and the LED lights dimly.

Move your hand from side to side over the photoresistor (RP). As yourhand blocks the light, the LED goes out.

The amount of light changes the resistance of the photoresistor and thecurrent flow to the base of the NPN transistor (Q2). The transistor actslike a switch. Its base current is supplied through the photoresistor. Asthe base current changes, so does the current flow through the LED.With no base current, the LED goes out.

Motion Detector (II)

Project #259Oscillator 0.5 - 30Hz

OBJECTIVE: To build a 0.5Hz - 30Hz oscillator that will light an LED.

Set the adjustable resistor (RV) to the bottom position and then turn the switch on.The LED will start flashing at a frequency of 0.5Hz (once every two seconds).Slowly adjust the adjustable resistor and the LED flashes faster. As the frequencyincreases, the LED flashes faster. Eventually, the LED flashes so fast, it looks likeit is on all of the time.

Project #260Sound Pulse Oscillator

OBJECTIVE: To build a 0.5Hz - 30Hz oscillator and hear it on a speaker.

Use the circuit from Project #259.Connect a single snap under the speaker and then connect it across the LED (onlevel 4). Turn the switch on and now you can hear the oscillator. Adjust theadjustable resistor (RV) to hear the different frequencies. Now you can hear andsee the frequencies.

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Project #262

Place the fan onto the motor. Press the press switch (S2). The fanrotates clockwise. When you connect the positive (+) side of the batteryto the positive (+) side of the motor, it spins clockwise. Release the pressswitch and turn on the slide switch (S1). Now the fan spins the other way.The positive (+) side of the battery is connected to the negative (–) sideof the motor. The polarity on the motor determines which way it rotates.Notice that the lamp lights in both polarities. It is not effected by thepolarity changes.

Motor Rotation

Place the fan onto the motor and set the adjustable resistor control to the far right. Turn theslide switch (S1) on and then press the press switch (S2) once. The motor will spin andthen stop. Now set the resistor control to the far left and press the press switch again. Thetime the fan spins is much less now.

When the press switch is pressed, the current flows through the circuit and the fan spins.The capacitor charges up also. When the switch is released, the capacitor discharges andsupplies the current to keep the transistors on. The transistor acts like a switch connectingthe fan to the battery. When the capacitor fully discharges, the transistors turn off and themotor stops. The adjustable resistor controls how fast the capacitor discharges. The moreresistance, the longer the discharge time.

Project #264Motor Delay Fan (II)

OBJECTIVE: To change capacitance to affect time.

Use the circuit from Project #263. Connect a single snap under one side of the 470µFcapacitor (C5) and then connect it over the top of the 100µF capacitor. Turn the switch onand press the press switch (S2). Notice that the fan spins longer now. When capacitorsare in parallel, the values are added, so now you have 570µF. The time it takes to dischargethe capacitors is longer now, so the fan keeps spinning.

Project #263 Motor Delay Fan

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OBJECTIVE: To build a high pitch bell.

Build the circuit shown and press the press switch (S2). The circuitstarts to oscillate. This generates the sound of a high pitch bell.

Project #266Steamboat Whistle

OBJECTIVE: To build a steamboat whistle.

Using the circuit in Project #265, connect the 0.02µF capacitor (C1)across the whistle chip. Press the press switch (S2). The circuitnow generates the sound of a steamboat.

Project #267Steamship

OBJECTIVE: To generate thesound of a steamship.

Using the circuit in Project #265,connect the 0.1µF capacitor (C2)across the whistle chip. Press thepress switch (S2). The circuit nowgenerates the sound of a steamship.

Project #268 Light NOR GateOBJECTIVE: To build a NOR gate.

Build the circuit on the left. You will find thatthe lamp is on when neither the slide switch(S1) NOR the press switch (S2) are on. Thisis referred to as an NOR gate in electronicsand is important in computer logic.Example: If neither condition X NORcondition Y are true, then execute instruction Z.

Project #265 High Pitch Bell

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Project #269

OBJECTIVE: To build a noise activated alarm.

Noise-ActivatedBurglar Alarm

OBJECTIVE: To build a Motor Activated burglar alarm. OBJECTIVE: To build a Light Activated burglar alarm.

Use the circuit from Project #269 shown above.Replace the whistle chip with the motor. Wind a piece of string aroundthe axis of the motor so when you pull it the axes spins. Connect theother end of the string to a door or window. Set the switch on and waitfor the sound to stop. If a thief comes in through the door or window thestring pulls and axes spins. This will activate the sound.

Project #270Motor-ActivatedBurglar Alarm

Project #271Light-ActivatedBurglar Alarm

Set the switch on and wait for the sound to stop. Place the circuit intoa room you want guarded. If a thief comes into the room and makesa loud noise, the speaker will sound again.

If you find that the sound does not turn off, then vibrations created bythe speaker may be activating the whistle chip. Set the speaker on thetable near the circuit and connect it to the same locations using thejumper wires to prevent this.

Use the circuit from Project #269 shown above.Connect a photoresistor (RP) across points A and B and cover it or turnoff the lights. Set the switch on and wait for the sound to stop. At night,when the thief comes in and turns on the light, the speaker makes thesound of a machine gun.

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Project #272Photoresistor Control

OBJECTIVE: To use a photoresistor to control the brightness ofan LED.

In this circuit, the brightness of the LED depends on how much lightshines directly on the photoresistor. If the photoresistor were held nextto a flashlight or other bright light, then the LED would be very bright.

The resistance of the photoresistor decreases as more light shines onit. Photoresistors are used in applications such as streetlamps, whichcome on as it gets dark due to night or a severe storm.

Project #273Microphone Control

OBJECTIVE: To use a microphone to control the brightness of anLED.

In this circuit, blowing on the microphone changes the LED brightness.

The resistance of the microphone changes when you blow on it. Youcan replace the microphone with one of the resistors to see whatresistor value it is closest to.

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Project #274Pressure Alarm

OBJECTIVE: To build a pressure alarm circuit.

Connect two jumper wires to the whistle chip (WC) as shown. Set thecontrol of the adjustable resistor (RV) to the far left and turn on theswitch. There is no sound from the speaker and the LED is off. Tap thecenter of the whistle chip. The speaker sounds and the LED lights. Thewhistle chip has a piezocrystal between the two metal plates. The soundcauses the plates to vibrate and produce a small voltage. The voltage isamplified by the power amplifier (U4), which drive the speaker and LED.

Place a small object in the center of the whistle chip. When you removethe object the speaker and LED are activated. In alarm systems, a sirenwould sound to indicate the object has been removed.

Project #275Power Microphone

OBJECTIVE: To build a power microphone.

Use the circuit from Project #274.

Replace the whistle chip with the microphone (X1), and hold it away fromthe speaker. Set the control of the adjustable resistor (RV) to the far left.Turn the switch on and talk into the microphone. You now hear your voiceon the speaker. The sound waves from your voice vibrate themicrophone and produce a voltage. The voltage is amplified by thepower amplifier (U4) and your voice is heard on the speaker.

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Project #277

OBJECTIVE: To build a circuit that uses a programmed soundIC.

Build the circuit shown on the left, which uses the space war integratedcircuit. Set the switch on. Press the press switch (S2) and a spacewar sound plays, and the LED flashes. Release the press switch andthen press it down again. Now a different sound plays. See how manysounds are programmed into the space war sound IC (U3).You can also play the sounds by tapping or blowing on the whistle chip(WC).

Space War Soundswith LED

Project #276

OBJECTIVE: To build an LED fan rotation indicator.

Place the fan onto the motor. Turn the slide switch (S1) on. The fanrotates clockwise, the green LED and the lamp light. When youconnect the positive (+) side of the battery to the positive (+) side ofthe motor, it spins clockwise. Turn the switch off and press down thepress switch (S2). Now the fan spins the other way and the red LEDand lamp light. The positive (+) side of the battery is connected to thenegative (–) side of the motor. The polarity on the motor determineswhich way it rotates. Notice that the lamp lights in both polarities.

LED Fan RotationIndicator

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Project #278OBJECTIVE: To connect two sound ICs together.

In the circuit, the outputs from the alarm and music ICs are connectedtogether. The sounds from both ICs are played at the same time.

Sound Mixer

Project #279

OBJECTIVE: To connect two sound ICs together to drive twoLEDs and a motor.

Build the circuit shown on the left. Place the fan onto the motor.

In the circuit, the alarm IC and the music IC are connected together.The sounds from both ICs can be played at the same time. Press thepress switch (S2). The music IC plays and the green LED lights. Nowset the switch on and press the press switch again. You should hearthe sounds from both ICs playing. As the alarm IC plays, it also drivesthe fan and the red LED.

Sound Mixer FanDriver

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Project #280

OBJECTIVE: To show how light can control a motor.

Turn the slide switch (S1) on and set the adjustable resistor (RV)control so the motor just starts spinning. Slowly cover thephotoresistor (RP) and the motor spins faster. By placing more lightover the photoresistor, the motor slows.

The fan will not move on most settings of the resistor, because theresistance is too high to overcome friction in the motor. If the fan doesnot move at any resistor setting, then replace your batteries.

Electric Fan Stoppedby Light

Project #281OBJECTIVE: To control large currents with a small one.

Place the fan on the motor. Turn the slide switch (S1) on and the motorspins. The transistors are like two switches connected in series. Asmall current turns on the NPN transistor, which turns on the PNPtransistor. The large current used to spin the motor now flows throughthe PNP. The combination allows a small current to control a muchlarger one.

Press the press switch (S2) and the lamp lights and slows the motor.When the lamp lights, the voltage across the motor decreases andslows it down.


Motor & Lamp

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Project #282OBJECTIVE: To start and stop a motor with light.

Place the fan on the motor. Turn the switch on, the motor startsspinning. As you move your hand over the photoresistor, the motorslows. Now place a finger on top of the photoresistor to block the light.The motor slows down. In a few seconds the motor speeds up again.


Start-Stop Delay

Project #283OBJECTIVE: To build a circuit to indicate if you have mail.

Turn the switch on. If there is light on the photoresistor the red LED willnot light. Place your finger over the resistor and now the red LEDlights. A simple mail notifying system can be made using this circuit.Install the photoresistor and the green LED inside the mailbox facingeach other. Place the red LED outside the mailbox. When there ismail, the light is blocked from the photoresistor and the red LED turnson.

Mail Notifying System

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Project #284 Mail Notifying Electronic BellOBJECTIVE: To build a circuit toindicate if you have mail by

OBJECTIVE: To build a flicking

Use the circuit from Project #286.Replace the speaker with a red LED(the + sign on top). Now you see thefrequency of the oscillator. Installdifferent values of capacitors to changethe frequency.

Project #287Quick Flicking LED

OBJECTIVE: To build a circuit toindicate if you have mail by activating

Project #286

OBJECTIVE: To build an

The tone you hear is the frequency ofthe oscillator. Install different valuesof capacitors in place of the 0.1µF(C2) to change the frequency.

Replace the speaker with the motor andfan. When there is mail, the light isblocked from the photoresistor and themotor spins.

Turn the switch on. If there is light onthe photoresistor, the speaker will notmake any sound. Place your fingerover the resistor and now the speakersounds. The sound will stay on untilyou turn off the switch. A simple mailnotifying system can be made usingthis circuit. Install the photoresistorand the green LED inside the mailboxfacing each other. When there is mail,the light is blocked from thephotoresistor and the speaker turnson.

Project #285Mail NotifyingElectronic Fan

Twice-AmplifiedOscillator

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Project #288OBJECTIVE: To build a complete, working AM radio withtransistor output.

When you close the slide switch (S1), the integrated circuit (U5) shouldamplify and detect the AM radio waves. Tune the capacitor (CV) to thedesirable station. The adjustable resistor (RV) is used as a simpleresistor since the center tap is not used. The two transistors drive thespeaker to complete the radio. The radio will not be very loud.

AM Radio with Transistors

Project #289OBJECTIVE: To build a complete, working AM radio.

When you close the slide switch (S1), the integrated circuit (U5) shoulddetect and amplify the AM radio waves. The signal is then amplifiedusing the power amplifier (U4), which drives the speaker. Tune thecapacitor (CV) to the desirable station.

AM Radio (II)

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Project #290OBJECTIVE: To amplify sounds from the music integratedcircuit.

Build the circuit and turn on the switch. You will hear loud music, sincethe sound from the music integrated circuit is amplified by the poweramplifier integrated circuit. All radios and stereos use a poweramplifier.

Music Amplifier

Project #291 Delayed Action LampOBJECTIVE: To build a lamp thatstays on for a while.

OBJECTIVE: To build a fanthat stays on for a while.

Replace the lamp (L2) with themotor (M1), positive (+) side up.Be sure to put on the fan. Turn onthe switch and press the pressswitch (S2). The fan turns onslowly but stays on for a whileafter you release the pressswitch.

Be sure to use the 6V lamp (L2) forthis circuit. Turn on the switch andpress the press switch (S2). Thelamp turns on slowly but stays on fora long while after you release thepress switch.

Project #292Delayed

Action Fan

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Project #293 Police Siren AmplifierOBJECTIVE: To amplify sounds from the music integratedcircuit.

Build the circuit and turn on the switch. You will hear a very loud siren,since the sound from the alarm integrated circuit is amplified by thepower amplifier integrated circuit. Sirens on police cars use a similarcircuit, with an IC to create the sound and a power amplifier to make itvery loud.

Project #294 Lasting DoorbellOBJECTIVE: To build a doorbellthat stays on for a while.

OBJECTIVE: To build aclicker that stays on for a while.

Place the 10µF capacitor (C3) ontop of the whistle chip (WC).Press and release the pressswitch. It makes a clicking soundthat repeats for a while.

Build the circuit at left, note that thereis a 4-snap wire on layer 1 that is notconnected to a 3-snap wire that runsover it on layer 3. Turn on the slideswitch (S1), then press and releasethe press switch (S2). There is adoorbell sound that slowly fades away.

When the press switch is pressed,the transistors are supplied withcurrent for oscillation. At the sametime, the capacitor is being charged.When the press switch is released,the capacitor discharges and keepsthe oscillation going for a while.

Project #295LastingClicking

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Project #296OBJECTIVE: To show how capacitors can leak.

Build the circuit (be sure the positive (+) side of the capacitor istowards the left) and turn on the switch. The green light emitting diode(LED, D2) will flash brightly as the capacitor (C5) charges up and thenbecomes dim but will not be off. When you turn off the switch the redLED (D1) is initially bright but goes dim as the capacitor dischargesitself through it.

Why doesn’t the green LED go off after the capacitor becomescharged? It is because current is leaking through the 470µF capacitor.The positive (+) side of the capacitor should normally be facingtowards the higher voltage side, in this circuit we have it facing awayfrom the batteries. In most circuits this doesn’t matter but in this caseit does.

Reverse the position of the capacitor (so the positive (+) side is on theright) and turn on the switch again, now the green LED becomestotally off after the capacitor gets charged up. It doesn’t leak now.

Leaky Capacitor

Project #297 Transistor Fading SirenOBJECTIVE: To build a siren thatslowly fades away.

OBJECTIVE: To build adoorbell that slowly fades away.

Replace the alarm IC (U2) withthe music IC (U1). The circuitworks the same way but now ithas a doorbell sound.

Turn on the switch, then press andrelease the press switch. You hear asiren that slowly fades away andeventually goes off. You can modifythis circuit to make machine gun orambulance sound instead like in theother projects. You can also replacethe 10µF capacitor (C3) with the100µF (C4) or 0.1µF (C2) to greatlyslow down or speed up the fading.

Project #298Fading

Doorbell

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Project #299OBJECTIVE: To change space war sounds by blowing.

Turn on the switch and you will hear explosion sounds and the lamp ison or flashing. Blow into the microphone (X1) and you can change thesound pattern.

Blowing Space War Sounds

Project #300 Adjustable Time Delay LampOBJECTIVE: To build a lamp thatstays on for a while.

OBJECTIVE: To build a fanthat stays on for a while.

Replace the lamp (L2) with themotor (M1), be sure to put on thefan. Turn on the switch and pressthe press switch (S2). The fanstays on for a while after yourelease the press switch. Youcan change the delay time withthe adjustable resistor (RV).

Be sure to use the 6V lamp (L2) forthis circuit. Turn on the switch andpress the press switch (S2). Thelamp stays on for a while after yourelease the press switch. You canchange the delay time with theadjustable resistor (RV).

Project #301AdjustableTime Delay Fan

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Project #302

OBJECTIVE: To build a lamp thatstays on for a while.

OBJECTIVE: To build a fan thatstays on for a while.

Replace the lamp (L2) with the motor(M1, positive (+) side up), be sure to puton the fan. Turn on the switch and pressthe press switch (S2). The fan stays onfor a while after you release the pressswitch. This could have a longer delayand be near your bed, to turn off afteryou fall asleep.

Project #305 Delayed

Bedside Fan

OBJECTIVE: To build a fan thatstays on for a while.

Project #304 Watch LightOBJECTIVE: To build a lamp thatstays on for a while.

Turn on the switch and press thepress switch (S2). The lamp stays onfor a few seconds after you releasethe press switch.

A miniature version of a circuit likethis might be in your wristwatch -when you press a light button on thewatch to read the time in the dark, alight comes on but automaticallyturns off after a few seconds to avoiddraining the battery.

Replace the lamp (L2) with the motor(M1), be sure to put on the fan. Turn onthe switch and press the press switch(S2). The fan stays on for a while afteryou release the press switch. You canchange the delay time with theadjustable resistor (RV).

Be sure to use the 6V lamp (L2) forthis circuit. Turn on the switch andpress the press switch (S2). Thelamp stays on for a few seconds afteryou release the press switch. Youcan change the delay time with theadjustable resistor (RV).

Project #303Adjustable TimeDelay Fan (II)

AdjustableTime DelayLamp (II)

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