sc-300 rev-b 11-7-02 - snap circuits · creating your own circuits after building the circuits...

SNAP CIRCUITSTM

Projects 102-305

Instruction Manual

REV-B Revised 2002

ADDITIONAL PARTS LIST (Colors and styles may vary) Symbols and Numbers

-1-

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

3 1-Snap Wire 6SC30001 1 10µF Capacitor 6SC30032



1 4-Snap Wire 6SC30004 1 1kΩ Resistor 6SC30041

1 7-Snap Wire 6SC30007 1 5.1kΩ Resistor 6SC30042

1Battery Holder - uses2 1.5V type AA (not Included) 6SC30019 1 10kΩ Resistor 6SC30043

1 Antenna Coil 6SC30025 1 100kΩ Resistor 6SC30044

1Green Light EmittingDiode (LED) 6SC30026 1

High FrequencyIntegrated Circuit 6SC30045

16V Lamp Socket6V Bulb (6.2V, 0.5A)Type 425 or similar

6SC300276SC30027B 1 PNP Transistor 6SC30051

1 Microphone 6SC30028 1 NPN Transistor 6SC30052

1Power AmplifierIntegrated Circuit 6SC30029 1 Adjustable Resistor 6SC30053

1 0.02µF Capacitor 6SC30030 1 Variable Capacitor 6SC30054

1 0.1µF Capacitor 6SC30031

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

The Electronic Snap Circuit Kit has 204 projects. They are simple to build andunderstand.

The snap circuit kit uses building blocks with snaps to build the differentelectrical and electronic circuits in the projects. Each block has a function:there are switch blocks, lamp blocks, battery blocks, different length wireblocks, etc. These blocks are in different colors and have numbers on themso that you can easily identify them. The circuit you will build is shown in colorand numbers, identifying the blocks that you will use and snap together toform 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 wire lengths.This one has the number , , , , , or on it depending on thelength of the wire connection required.

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

To build each circuit, you will have two (2) power source blocks markedthat need two (2) “AA” batteries each (not included with the snap circuit kit).

A large clear plastic base grid is included with this kit to help keep the circuitblock together. You will see evenly spaced posts that the different blocks snapinto. You do not need this base to build your circuits, but it does help inkeeping your circuit 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 in black. This tellsyou 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 bulb comes packaged separate from its socket. Install the bulb inthe lamp socket whenever that part is used. Do the same for the 6V bulband socket .

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

Some circuits use the jumper wires to make unusual connections. Just clipthem to the metal snaps or as indicated.

Note: While building the projects, be careful not to accidentally make a directconnection across the battery holder (a “short circuit”), as this will damageand/or quickly drain the batteries.

Creating Your Own CircuitsAfter building the circuits given in this booklet, you may wish to experiment onyour own. Use the projects in this booklet as a guide, as many importantdesign concepts are introduced throughout them. Every circuit will include apower source (the batteries), a resistance (which might be a resistor, lamp,motor, integrated circuit, etc.), and wiring paths between them and back. Youmust be careful not to create "short circuits" (very low-resistance paths acrossthe batteries) as this will damage components and/or quickly drain yourbatteries. Only connect the ICs using configurations given in the projects,incorrectly doing so may damage them. Elenco™ Electronics is notresponsible for parts damaged due to incorrect wiring.

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 connectedin series or in parallel does not matter — what matters is how combinationsof these sub-circuits are arranged together.

You are encouraged to tell us about new circuits you create. Upon review, wewill post them with your name, age, and hometown in a special section on ourwebsite.

TroubleshootingMost circuit problems are due to incorrect assembly, always double-check thatyour circuit exactly matches the drawing for it. Be sure that parts withpositive/negative markings are positioned as per the drawing. Sometimes thelight bulbs come loose, tighten them as needed. Try replacing the batteries.

-2-

HOW TO USE IT

S1

OFF ON

B1

2 3 4 5 6 7

L1L2

M1

-3-

Project # Description Page #102 Batteries in Series 5103 Batteries in Parallel 5104 Spacey Fan 6105 Two-Transistor Light Alarm 6106 Light-Controlled Alarm 6107 Automatic Street Lamp 7108 Voice-Controlled Rays of Light 7109 Blowing Off the Electric Light 7110 Adjustable Tone Generator 8111 Photosensitive Electronic Organ 8112 Electronic Cicada 8113 Light & Sounds 9114 More Light & Sounds 9115 More Light & Sounds (II) 9116 More Light & Sounds (III) 9117 More Light & Sounds (IV) 9118 Motor Speed Detector 10119 Old-Style Typewriter 10120 Space War Sounds 11121 Space War Sounds Controlled by Light 11122 Space War Radio 12123 The Lie Detector 12124 NPN Amplifier 13125 PNP Amplifier 13126 Sucking Fan 14127 Blowing Fan 14128 PNP Collector 14129 PNP Emitter 14130 NPN Collector 15131 NPN Emitter 15132 NPN Collector - Motor 15133 NPN Emitter - Motor 15134 Buzzing in the Dark 16135 Touch Buzzer 16

Project # Description Page #136 High Frequency Touch Buzzer 16137 High Frequency Water Buzzer 16138 Mosquito 16139 High Sensitivity Voice Doorbell 17140 Louder Doorbell 17141 Very Loud Doorbell 17142 Doorbell with Button 17143 Darkness Announcer 17144 Musical Motion Detector 17145 Radio Music Alarm 18146 Daylight Music Radio 18147 Night Music Radio 18148 Night Gun Radio 18149 Radio Gun Alarm 18150 Daylight Gun Radio 18151 Blow Off a Space War 19152 Series Lamps 19153 Parallel Lamps 19154 Fire Fan Symphony 20155 Fire Fan Symphony (II) 20156 Fan Symphony 20157 Fan Symphony (II) 20158 Police Car Symphony 21159 Police Car Symphony (II) 21160 Ambulance Symphony 21161 Ambulance Symphony (II) 21162 Static Symphony 22163 Static Symphony (II) 22164 High-Power Symphony 22165 High-Power Symphony (II) 22166 Water Detector 23167 Salt Water Detector 23168 NPN Light Control 24169 NPN Dark Control 24

Project # Description Page #170 PNP Light Control 24171 PNP Dark Control 24172 Red & Green 25173 Current Limiters 25174 Current Equalizing 25175 Battery Polarity Tester 25176 Blow Off a Doorbell 26177 Blow Off a Candle 26178 Blow On a Doorbell 26179 Blow On a Candle 26180 Screaming Fan 27181 Whining Fan 27182 Light Whining 27183 More Light Whining 27184 Motor Than Won’t Start 27185 Whiner 28186 Lower Pitch Whiner 28187 Hummer 28188 Adjustable Metronome 28189 Quiet Flasher 28190 Hissing Foghorn 29191 Hissing & Clicking 29192 Video Game Engine Sound 29193 Light Alarm 30194 Brighter Light Alarm 30195 Lazy Fan 30196 Laser Light 30197 Water Alarm 31198 Drawing Resistors 31199 Pitch 32200 Pitch (II) 32201 Pitch (III) 32202 Flooding Alarm 32203 Make Your Own Battery 33

PROJECT LISTINGS

-4-

PROJECT LISTINGSProject # Description Page #

204 Make Your Own Battery (II) 33205 Make Your Own Battery (III) 33206 Tone Generator 34207 Tone Generator (II) 34208 Tone Generator (III) 34209 Tone Generator (IV) 34210 More Tone Generator 35211 More Tone Generator (II) 35212 More Tone Generator (III) 35213 Music Radio Station 36214 Alarm Radio Station 36215 Saved Electricity 36216 Motor & Lamp by Sound 37217 Fading Siren 37218 Fast Fade Siren 37219 Laser Gun with Limited Shots 38220 Symphony of Sounds 38221 Symphony of Sounds (II) 38222 Transistor Amplifiers 39223 Pressure Meter 39224 Resistance Meter 39225 Auto-Off Night-Light 40226 Discharging Caps 40227 Changing Delay Time 40228 Morse Code Generator 41229 LED Code Teacher 41230 Ghost Shriek Machine 41231 LED & Speaker 41232 Dog Whistle 41233 Electronic Golf Game 42234 Enhanced Quiet Zone Game 43235 Capacitor Charge & Discharge 43236 Sound Wave Magic 44237 Space War Amplifier 44

Project # Description Page #238 Trombone 45239 Race Car Engine 45240 Power Amp 46241 Electronic Kazoo 46242 AM Radio 47243 Fire Engine Symphony 48244 Fire Engine Symphony (II) 48245 Vibration or Sound Indicator 48246 Two-Finger Touch Lamp 49247 One-Finger Touch Lamp 49248 Space Battle 50249 Space Battle (II) 50250 Multi-Speed Light Fan 50251 Light & Finger Light 50252 Storing Electricity 51253 Lamp Brightness Control 51254 Electric Fan 51255 Radio Music Burglar Alarm 52256 Light Dimmer 52257 Motion Detector 53258 Fan Modulator 53259 Oscillator 0.5 - 30Hz 54260 Sound Pulse Oscillator 54261 Motion Detector (II) 54262 Motor Rotation 55263 Motor Delay Fan 55264 Motor Delay Fan (II) 55265 High Pitch Bell 56266 Steamboat Whistle 56267 Steamship 56268 Steamship Horn 56269 Noise-Activated Burglar Alarm 57270 Motor-Activated Burglar Alarm 57271 Light-Activated Burglar Alarm 57

Project # Description Page #272 Optocoupler with LED 58273 Optocoupler with Speaker 58274 Pressure Alarm 59275 Power Microphone 59276 LED Fan Rotation Indicator 60277 Space War Sounds with LED 60278 Sound Mixer 61279 Sound Mixer Fan Driver 61280 Electric Fan Stopped by Light 62281 Motor & Lamp 62282 Start-Stop Delay 63283 Mail Notifying System 63284 Mail Notifying Electronic Bell 64285 Mail Notifying Electronic Fan 64286 Twice-Amplified Oscillator 64287 Quick Flicking LED 64288 AM Radio with Transistors 65289 AM Radio (II) 65290 Music Amplifier 66291 Delayed Action Lamp 66292 Delayed Action Fan 66293 Police Siren Amplifier 67294 Lasting Doorbell 67295 Lasting Clicking 67296 Leaky Capacitor 68297 Transistor Fading Siren 68298 Fading Doorbell 68299 Blowing Space War Sounds 69300 Adjustable Time Delay Lamp 69301 Adjustable Time Delay Fan 69302 Adjustable Time Delay Lamp (II) 70303 Adjustable Time Delay Fan (II) 70304 Watch Light 70305 Delayed Bedside Fan 70

-5-

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

When you close the slide switch (S1), current flows from the batteriesthrough the slide switch (S1), the 1kΩ 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

Build the circuit shown on the left by placing all of the parts with a black1 next to them on the board first. Then, assemble the parts marked witha 2 (including the 1-snap wire at base grid location C5). Finally, place a2-snap wire at grid location C4, leaving the other end of it unconnected asshown.

The light should be on and the brightness of the lamp will depend on thequality of the batteries in the holder on the left. Put weak batteries in theleft holder and strong batteries in the right holder. Snap in the loose endof the 2-snap wire to grid point C5. Now the lamp will get brighter as thefresh batteries take over and supply the current to the light.

Batteries are placed in parallel when the voltage is adequate but the loadneeds more current than one group of batteries can supply. Think of eachbattery as a storage tank that supplies water. If you put two in parallel, youcan get more water (current), but the pressure (voltage) stays the same.

Batteries in Parallel

-6-

Project #104 Spacey FanOBJECTIVE: To build a fan with space war sounds that

Place the fan onto the motor.Space war sounds are heard iflight shines on thephotosensitive resistor OR if youpress the press switch (S2), thefan may start to spin, but will onlyget to high speed if you doBOTH. Try various combinationsof shining light and holding downthe press switch.

Project #106OBJECTIVE: To show how light is used to turn an

The alarm will sound, as long as light is present. Slowly cover thephotosensitive resistor (RP), and the volume goes down. If you turnoff the lights, the alarm will stop. The amount of light changes theresistance of the photosensitive resistor (less light means moreresistance). The photosensitive resistor and transistor (Q2) act like adimmer switch, adjusting the 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.

-7-

Project #107OBJECTIVE: To show how light is used to control a

Press the press switch (S2) on and set the adjustable resistor (RV) sothe lamp just lights. Slowly cover the photosensitive resistor (RP) andthe lamp brightens. If you place more light at the photosensitiveresistor 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.

Automatic Street Lamp

Project #108Voice-Controlled Rays of Light

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 Light

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.

-8-

Project #110OBJECTIVE: To show how resistor values change the

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 Tone Generator

OBJECTIVE: To show how resistor values change the

Project #112Electronic Cicada

OBJECTIVE: To show how capacitors in parallel

Use the circuit from Project 110 shown above, replace thephotosensitive resistor (RP) back to the 100kΩ (R5) resistor. Place the0.02µF (C1) on top of the whistle chip (WC). Place the slide switch (S1)on and adjust the resistor (RV). The circuit produces the sound of thecicada insect. By placing the 0.02µF on top of the whistle chip, thecircuit oscillates at a lower frequency. Notice that the LED flashes alsoat the same 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 photosensitive resistor (RP). Turn on the slide switch (S1). Thespeaker (SP) will sound and the LED (D2) will light. Move your hand upand down over the photosensitive resistor (RP) and the frequencychanges. Decreasing the light on the photosensitive resistor increasesthe resistance and causes the circuit to oscillate at a lower frequency.Notice that the LED flashes 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

-9-

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

Project #114More Light &

SoundsOBJECTIVE: To show avariation of the circuit in

Modify the last circuit byconnecting points X and Y. Thecircuit works the same way butnow it sounds like a machinegun.

OBJECTIVE: To show avariation of the circuit in

Project #116More Light &Sounds (III)


Project #117More Light &Sounds (IV)


Project #113 Light & Sounds

Project #115 More Light &Sounds (II)

Now remove the connectionbetween X and Y and then makea connection between T and U.Now it sounds like a fire engine.

Now remove the connectionbetween T and U and then makea connection between U and Z.Now it sounds like an ambulance.

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

-10-

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

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 #119

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

-11-

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

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 #121OBJECTIVE: To change the sounds of a multiple space

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 photosensitive resistor (RP) with your hand. The sound willstop. Remove your hand and a different sound is played. Wave yourhand over the photosensitive resistor 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 Sounds Controlled By Light

-12-

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

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

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

-13-

Project #124

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 #125

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

-14-

Project #126 Sucking Fan

Project #128 PNP CollectorOBJECTIVE: Todemonstrate adjustingthe gain of a transistor

OBJECTIVE: To build a fan

Modify the circuit from Project 126 byreversing the position of the motor (sothe 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 #127 Blowing Fan

Project #129 PNP EmitterOBJECTIVE:To compare

Compare this circuit tothat in Project 128. Themaximum lampbrightness is less herebecause the lampresistance reduces theemitter-base current,which contacts theemitter-collector current(as per Project 25). Thepoint on the PNP thatthe lamp is nowconnected 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 all settings of the resistor,because the resistance is too high to overcome frictionin the motor.

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.

-15-

Project #130NPN Collector

OBJECTIVE: To compare

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.


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.

-16-

Project #134

OBJECTIVE: To make a circuit

Buzzing inthe Dark

Project #136High FrequencyTouch Buzzer

OBJECTIVE: To build a high

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

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 #138Mosquito

OBJECTIVE: To make a buzz like a

Place the photosensitive resistor (RP) into thecircuit in Project 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

Remove the photosensitive resistor (RP) fromthe circuit in Project 134 and instead touchyour fingers across where it used to be(points B1 and D1 on the grid) to hear a cutebuzzing sound.The circuit works because of the resistance inyour body. If you put back the photosensitiveresistor and partially cover it, you should beable to make the same resistance your bodydid, and get the same sound.

This circuit makes a high-frequencyscreaming sound when light shines onthe photosensitive resistor, and makes abuzzing sound when you shield thephotosensitive resistor.

-17-

Project #139

Project #141Very LoudDoorbell

OBJECTIVE: To build avery loud highly sensitive

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

OBJECTIVE: To build a

Project #143Darkness

AnnouncerOBJECTIVE: To play OBJECTIVE: To detect

when someone spins the

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 photosensitive resistor(RP) and wait until the soundstops. If you cover thephotosensitive resistor 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 photosensitiveresistor (RP) with the motor (M1),oriented in either direction. Nowspinning the motor will re-activatethe music.

Project #144Musical

Motion Detector

OBJECTIVE: To build aloud highly sensitive voice-

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

Project #140Louder

DoorbellOBJECTIVE: To build ahighly sensitive voice-

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

-18-

Project #145 Radio MusicAlarm

OBJECTIVE: To build a radio music

Project #147Night Music

RadioOBJECTIVE: To build adark-controlled radio

Put the 100kΩ resistor back in asbefore and instead connect thephotosensitive resistor betweenX and Y (you also need a 1-snapand a 2-snap wire to do this).Now your radio plays music whenit is dark.

OBJECTIVE: To build adark-controlled radio

Project #149Radio Gun

AlarmOBJECTIVE: To build a OBJECTIVE: To build a

light-controlled radio

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 photosensitiveresistor. Now connect a jumperwire between X and Y on thedrawing.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 photosensitive resistor(RP). Now your AM radio willplay the machine gun sound aslong as there is light in the room.

Project #150Daylight Gun

Radio

OBJECTIVE: To build alight-controlled radio

Project #146 Daylight

Music Radio

Remove the jumper wire.Replace the 100kΩ resistor (R5)with the photosensitive resistor(RP). Now your AM radio willplay music as long as there islight 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!

-19-

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.

-20-

Project #154 Fire Fan SymphonyOBJECTIVE: To combinesounds from the music, alarm,

OBJECTIVE:

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

Project #157Fan

Symphony (II)

OBJECTIVE:

Project #155Fire Fan

Symphony (II)

Project #156 Fan SymphonyOBJECTIVE: To combinesounds from the music, alarm,

Modify the circuit from Project 154 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 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 photosensitive resistor (RP)to hear the full spectrum of soundsthat this circuit can create. Have fun!

-21-

Project #158 Police Car SymphonyOBJECTIVE: To combinesounds from the integrated

OBJECTIVE:


Project #161Ambulance

Symphony (II)

OBJECTIVE:

Project #159Police Car

Symphony (II)

Project #160 Ambulance SymphonyOBJECTIVE: To combinesounds from the music, alarm,

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 photosensitive resistor(RP) to hear the full spectrum of sounds thatthis circuit 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.

-22-

Project #162 Static SymphonyOBJECTIVE: To combinesounds from the integrated

OBJECTIVE: See Project

The preceding circuit may be tooloud, so replace the speaker (SP)with the whistle chip (WC). Insome cases, the fan may now belouder than the sound, sodisconnect the jumper from F3 toG3 if desired.

Project #165High-Power

Symphony (II)

OBJECTIVE: See Project

Project #163Static

Symphony (II)

Project #164 High-Power SymphonyOBJECTIVE: To combinesounds from the music, alarm,

Build the circuit shown and place thefan on the motor. Be sure to use the6V lamp, not the 2.5V one. 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 photosensitive resistor (RP)to hear the full spectrum of soundsthat this circuit can create. Have fun!


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 thephotosensitive resistor (RP) to hearthe full spectrum of sounds that thiscircuit can create. Have fun!

-23-

Project #166

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

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 salt-water 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.

Salt-Water Detector

-24-

Project #168NPN Light Control


Project #169NPN Dark Control

Put on the switch, thebrightness of the LED dependson how much light shines on thephotosensitive resistor. Theresistance drops as more lightshines, allowing more current tothe NPN.


Put on the switch, thebrightness of the LED dependson how LITTLE light shines onthe photosensitive resistor. 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 thephotosensitive resistor. Theresistance drops as more lightshines, allowing more currentthrough the PNP. This is similarto the NPN circuit above.


Put on the switch, thebrightness of the LED dependson how LITTLE light shines onthe photosensitive resistor. Theresistance drops as more lightshines, so more current gets tothe 100kΩ resistor from thephotosensitive resistor path andless from the PNP-diode path.This is similar to the NPN circuitabove.

-25-

Project #172Red & Green


Project #173Current Limiters

Put on the switch and bothLEDs will be on and equallybright. This is because thediodes are in parallel, and theelectric current divides equallybetween them.


Put on the switch and notice thedifference in brightnessbetween the two LEDs, thiscomes from the difference oftheir in-series resistance. Thesmaller the resistance, thestronger the electric current thatis allowed to pass through. Thisis how resistance limits thecurrent.

Project #174Current Equalizing


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 the

Use this circuit to check thepolarity of a battery. Connectyour battery to X and 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.

-26-

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

OBJECTIVE: To turn on a

Replace the speaker (SP) withthe LED (D1), with the positive(+) side on top. Blowing into themicrophone turns on the light,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

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 light emitting diode (D1), withthe positive (+) side on top.Blowing hard into themicrophone stops the turns offthe light briefly, and then it comeson again.

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.

-27-

Project #180OBJECTIVE: To have anadjustable resistance control a

Screaming Fan

Project #182Light Whining

OBJECTIVE: To make different

Replace the 3-snap wire at the upper-left ofthe circuit (points A1 and A3 on the base grid)with the photosensitive resistor (RP), andwave your hand over it. The whining soundhas changed a little and can now becontrolled by light.

Project #183More Light

WhiningOBJECTIVE: To make different

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 #184Motor ThatWon’t 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 above the NPN(Q2). Turn on the switch and move thesetting on the adjustable resistor acrossits range. You hear screaming soundsand the fan spins.

-28-

Project #185OBJECTIVE: To build a circuit

Whiner

Project #187Hummer

OBJECTIVE: To show how adding

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

Now place the 10µF capacitor (C3, in eitherorientation) 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 #189Quiet Flasher

OBJECTIVE: To make a blinking

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

Project #186 Lower Pitch

WhinerOBJECTIVE: To show how adding

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 be on, but itis actually flashing at a very fast rate.

-29-

Project #190OBJECTIVE: To build a transistor oscillator that can

Hissing Foghorn

Project #191Hissing & Clicking

Modify the circuit in Project 190 by replacingthe 100kΩ resistor (R5) with thephotosensitive resistor (RP).Move the adjustable resistor setting until youhear hissing sounds, and then shield thephotosensitive resistor while doing so andyou hear clicking sounds.

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 photosensitive resistor (RP) fromthe circuit in Project 191 and instead touchyour fingers between the contacts at pointsA4 and B2 on the base grid while moving theadjustable resistor. You hear a clicking thatsounds like the engine sound in auto-racingvideo games.

-30-

Project #193 Light AlarmOBJECTIVE: To build a

OBJECTIVE: To build a simple

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

Project #196Laser Light


Project #195 Lazy FanOBJECTIVE: To build a fan

Press the press switch (S2) and thefan will be on for a few turns. Wait afew moments and press again, andthe fan will make a few more turns.

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 jumperconnected as shown, and turn it on.Nothing happens. Break the jumperconnection and the light turns on.You could replace the jumper with alonger wire and run it across adoorway to signal an alarm whensomeone enters.

Project #194Brighter

Light Alarm

-31-

Project #197OBJECTIVE: To sound an alarm whenwater is detected, tone will vary with salt

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 sound will sound. Add salt tothe water and the tone changes.

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

Water Alarm

Project #198

Use the circuit from Project 197, but replace the press switch (S2) with the slide switch (S1) and you don’tneed the cup of water. There is one more part that you need and you are going to draw it. Take a pencil(No. 2 lead is best but other types will also work). SHARPEN IT, and fill in the shape below. You will getbetter results if you place a hard, flat surface directly beneath this page while you are drawing. Press hard(but don’t rip the paper), and fill in the shape several times to be sure you have a thick, even layer ofpencil lead.

Turn on the switch and take the loose ends of the jumpers, press them to the shape and move them aroundover the drawing. The tone of the sound 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 together and move over the drawing, addanother layer of pencil lead, or put a drop of water on the jumper ends to get better contact.

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

Drawing Resistors

-32-

Project 201Pitch (III)

OBJECTIVE:

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

Flooding Alarm

Project #199 PitchOBJECTIVE: To showhow to change the pitch

Project 200Pitch (II)

OBJECTIVE:

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.

-33-

Project #203OBJECTIVE: To demonstrate how batteries can store

Build the circuit, then connect points Y and Z (use a 2-snap wire) for amoment. Nothing appears to happen, but you just filled up the 470µFcapacitor with electricity. Now disconnect Y and Z and instead touch aconnection between X and 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 Own Battery

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

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)

-34-

Project #206 Tone Generator

Project #207Tone

Generator (II)OBJECTIVE: To lower thefrequency of a tone by increasing

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 thefrequency of a tone by increasing

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 #209Tone

Generator (IV)OBJECTIVE: To lower thefrequency of a tone by increasing

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.

-35-

Project #210

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 OBJECTIVE: To raise the frequency of a tone by

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)

-36-

Project #213 Music Radio StationOBJECTIVE: To create music

OBJECTIVE: To createmusic and transmit it to a

Project #214Alarm Radio

Station

Project #215 Saved Electricity

Put on the switch, then connect points X and Y (use a 2-snap wire). The green LED will flash and then go out, asthe 470µF capacitor is charged with electricity. Nowdisconnect X and Y and instead make a connectionbetween Y and Z. The 6V bulb will flash as the electricitystored in the 470µF discharges through the resistor andtransistor. The capacitor was storing electricity to be usedat a later time, just like a battery does!

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

-37-

Project #217 Fading SirenOBJECTIVE: To producesound of a siren driving away

OBJECTIVE: To producesound of a siren driving

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

Turn the switch on, the motor spins and the lamp lights. As you moveyour hand over the photosensitive resistor, the motor slows. Nowplace finger onto of the photosensitive resistor to block the light. Themotor slows down. In a few seconds, the motor speeds up again.

Motor & Lamp by Sound

-38-

Project #219 Laser Gun with Limited ShotsOBJECTIVE: To build the circuit used in a toy lasergun with flashing laser light and trigger and limited

Project #220 Symphony of SoundsOBJECTIVE: To combinesounds from the music, alarm,

OBJECTIVE:


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 photosensitive resistor (RP)to hear the full symphony of soundsthat this circuit 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)

-39-

Project #222OBJECTIVE: To learn about the most important

Transistor Amplifiers

OBJECTIVE: To show how electronic amplifiers can OBJECTIVE: To show how electronic amplifiers can

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 and Y. Notice howthe brightness of the LED is dependent on the amount of pressure youuse. Pressing hard makes the LED bright while pressing very gentlymakes it 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 and Z and see how bright the LED glows.Do not snap them in; just press them up against the snaps labeled Rand Z in the 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.

-40-

Project #225OBJECTIVE: To learn about one device that is used to

Auto-Off Night-Light

OBJECTIVE: To show how capacitor delays can be OBJECTIVE: To show how the size of the capacitor


When you first turned on the slide switch (S1) in Project 225, the LEDcame on and very slowly get 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 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 (U2) 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.


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.

-41-

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

Project #229LED CodeTeacher

OBJECTIVE: A method oflearning the Morse code

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 aghost like special effect from

Project #231LED &

SpeakerOBJECTIVE: To improveMorse code skills and

OBJECTIVE: To make anoscillator that only a dog

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 (C5). 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 the100kΩ resistor (R5) to a 1kΩresistor (R2). While holdingdown the press switch (S2)slowly move the slider on theadjustable resistor (RV) towardthe 1kΩ resistor. If the frequencygoes low again, snap the 100µFcapacitor (C4) on top of the 1kΩresistor (R2) and try again.

Project #232Dog 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 – – – – –

-42-

Project #233 Mind Reading Game

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 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _____

-43-

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

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 #235OBJECTIVE: To show how capacitors store and

Turn on the slide switch (S1) for a few seconds, then turn it off. The redlight emitting diode (LED, D1) is initially bright but goes dim as thebatteries charge up the capacitor (C5). The capacitor is storingelectrical charge.

Now press the key (S2) for a few seconds. The green LED (D2) isinitially bright 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

-44-

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

Sound Wave Magic

Project #237

OBJECTIVE: To amplify sounds from the

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 the two (2)jumper wires. Then, lay the speaker on a flat hard surface.

Setup: Use some paper and scissors to cut out a rectangular pattern. Usethe one shown below as a guide. Use colored paper if available. Fold at thepoints shown. Scotch tape the corners so the tray has no cracks at thecorners. Place the tray over the speaker and sprinkle a small amount of whitetable salt in the tray. There should be enough salt to cover the bottom with alittle space between each salt grain.

Sound Magic: Turn on the circuit by closing slide switch (S1). Adjust theadjustable resistor (RV) for different pitches and watch the salt particles.Particles that bounce high are directly over the vibrating paper and ones thatdo not move are in the nodes where the paper is not vibrating. Eventually, allthe salt will move to the areas that have no vibration, 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 seeif they move differently due to the sound waves.

Paper Tray

Salt

Sample Cut-out Pattern

(fold)

(fold)

(fold)

(fold)

-45-

Project #238Trombone

OBJECTIVE: To build an electronic trombone that

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 control is same as trombone slider bar. The circuitmay be silent at some positions of the resistor control.

Project #239Race Car Engine

OBJECTIVE: To show how changing frequency changes

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 turn 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.

-46-

Project #240Power Amp

OBJECTIVE: To check stability of power amplifier with

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 touch point X with one of thesnaps on any part. High frequency clicks or static should be coming fromspeaker indicating that the amplifier is powered on and ready to amplifysignals.

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

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.

-47-

Project #242

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

-48-

Project #243 Fire Engine SymphonyOBJECTIVE: To combinesounds from the music, alarm,and space war integrated

OBJECTIVE:

Project #244Fire Engine

Symphony (II)

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

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, the whistle chipproduces a small voltage and activates the circuit. You canrepeat a sound by holding down the press switch (S2) whileit 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 photosensitive resistor (RP)to hear the full spectrum of soundsthat this circuit can create. Have fun!

-49-

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

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 and 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 #247

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

-50-

Project #248 Space BattleOBJECTIVE: To show how sound

Project #250 Multi-Speed Light FanOBJECTIVE: To varythe speed of a fan

OBJECTIVE: To show howlight can turn "ON" an

Replace the slide switch (S1) with thephotosensitive resistor (RP). Nowcovering and uncovering thephotosensitive resistor will change thesound.

Project #249 Space Battle (II)

Project #251Light & Finger Light

OBJECTIVE: To show another way the Space War IC

In the circuit at left, replace the motor (M1) with a 2.5V lamp shownbelow. Vary the brightness of the lamp by covering thephotosensitive resistor and holding down the press switch (S2) invarious combinations. Notice that pressing the press switch whenthe photosensitive resistor is covered still turns on the lamp, while inProject 250, doing this would turn 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 photosensitiveresistor, though the fan willbarely turn at all. Press thepress switch (S2) and thefan will spin. If you hold thepress switch down, the fanwill spin faster. If you coverthe photosensitive resistor,the fan will stop even if thepress switch is pressed.

-51-

Project #252 Storing Electricity

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

OBJECTIVE: To make anelectric fan using a

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

-52-

Project #255OBJECTIVE: To build an alarm that plays music on

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 and B and the music stops.The transistor acts like a switch connecting power to the music IC.Positive voltage on the base closes the switch and negative voltageopens it. Connect a string to the jumper wire and the other end of thestring to a door or window. Set the switch on. If a thief comes inthrough the door or window, the string pulls the jumper off and themusic plays on the radio.

Radio Music Burglar Alarm

Project #256

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

-53-

Project #257

Set the adjustable resistor (RV) to the center position. Turn the switch onand the LED lights. Wave your hand over the photosensitive resistor(RP) and the LED turns off and on. The resistance changes as theamount of light strikes the photosensitive resistor. As the lightdecreases, the resistance increases. The increased resistance lowersthe voltage at the base of the NPN transistor (Q2). This turns off thetransistor, preventing current flowing through the LED to the negative (–)side of the battery. Wave your hand over photosensitive resistor atdifferent distances. The LED gets brighter the farther away your hand is.

Motion Detector

Project #258

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 photosensitive resistor, more light strikes it. The brightness of theLED changes, or is modulated. As in AM or FM radio, modulation usesone signal to modify the amplitude or frequency of another signal.

Fan Modulator

3” dia.

-54-

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

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 photosensitive resistor (RP).As your hand blocks the light, the LED goes out.

The amount of light changes the resistance of the photosensitive resistorand the current flow to the base of the NPN transistor (Q2). Thetransistor acts like a switch. Its base current is supplied through thephotosensitive resistor. As the base current changes, so does thecurrent flow through the LED. With no base current, the LED goes out.

Motion Detector (II)

Project #259Oscillator 0.5 - 30Hz

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 OscillatorUse 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.

-55-

Project #262OBJECTIVE: To show how voltage polarity affects a

Place the fan onto the motor. Turn the slide switch (S1) on. The fanrotates clockwise. When you connect the positive (+) side of thebattery to the positive (+) side of the motor, it spins clockwise. Turn theswitch off and press down the key switch. Now the fan spins the otherway. The positive (+) side of the battery is connected to the negative(–) side of the motor. The polarity on the motor determines which wayit rotates. Notice that the lamp lights in both polarities. It is not effectedby the polarity 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)

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

-56-

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

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 the

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 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

-57-

Project #269 Noise-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-Activated Burglar Alarm

Project #271Light-Activated Burglar 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 photosensitive resistor (RP) across points A and B and coverit or turn off 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 speakermakes the sound of a machine gun.

-58-

Project #272Optocoupler with LEDOBJECTIVE: To build an optocoupler circuit to light an

Connect two jumper wires to the photosensitive resistor (RP) as shown.Set the adjustable resistor (RV) control to the far-left side. Turn the switchon and the red LED starts flashing. Hold the photosensitive resistor overthe red LED so it is facing it. As the red LED lights, so will the green. Thisis an example of an optocoupler/opto-isolator. An electric device thattransmits signals without an electrical connection between the lightsource (input) and the light detector (output).

Project #273Optocoupler with SpeakerOBJECTIVE: To build an optocoupler circuit to drive a

Use the circuit from Project #272.

Remove the green LED and replace the 100Ω resistor (R1) with thespeaker. Set the adjustable resistor to the far-left side. Connect twojumper wires to the photosensitive resistor (RP) as shown. Turn theswitch on and the red LED starts flashing. Hold the photosensitiveresistor over the red LED so it is facing it. Now when the red LED lights,the speaker outputs a tone.

-59-

Project #274Pressure Alarm

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

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.

-60-

Project #277OBJECTIVE: To build a circuit that uses a

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 Sounds with LED

Project #276

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 Rotation Indicator

-61-

Project #278

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 #279OBJECTIVE: To connect two sound ICs together to

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 Fan Driver

-62-

Project #280

Turn the slide switch (S1) on and set the adjustable resistor (RV)control so the motor just starts spinning. Slowly cover thephotosensitive resistor (RP) and the motor spins faster. By placingmore light over the photosensitive resistor, the motor slows.

Electric Fan Stopped by Light

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

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

-63-

Project #282

Place the fan on the motor. Turn the switch on, the motor startsspinning. As you move your hand over the photosensitive resistor, themotor slows. Now place a finger on top of the photosensitive resistorto block the light. The motor slows down. In a few seconds the motorspeeds up again.

Start-Stop Delay

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

Turn the switch on. If there is light on the photosensitive resistor thered LED will not light. Place your finger over the resistor and now thered LED lights. A simple mail notifying system can be made using thiscircuit. Install the photosensitive resistor and the green LED inside themailbox facing each other. Place the red LED outside the mailbox.When there is mail, the light is blocked from the photosensitive resistorand the red LED turns on.

Mail Notifying System

-64-

Project #284 Mail Notifying Electronic BellOBJECTIVE: To build acircuit to indicate if you have


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 circuitto indicate if you have mail by

Project #286 Twice-Amplified OscillatorOBJECTIVE: 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 photosensitive resistorand the motor spins.

Turn the switch on. If there is light onthe photosensitive resistor, thespeaker will not make any sound.Place your finger over the resistorand now the speaker sounds. Asimple mail notifying system can bemade using this circuit. Install thephotosensitive resistor and the greenLED inside the mailbox facing eachother. When there is mail, the light isblocked from the photosensitiveresistor and the speaker turns on.

Project #285Mail NotifyingElectronic Fan

-65-

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

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 #289

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)

-66-

Project #290OBJECTIVE: To amplify sounds from the music

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

OBJECTIVE: To build afan that stays on for a

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

-67-

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

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 adoorbell that stays on for a

OBJECTIVE: To build aclicker that stays on for a

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

-68-

Project #296

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

OBJECTIVE: To build adoorbell that slowly fades

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

-69-

Project #299

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


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

-70-

Project #302 Adjustable Time Delay Lamp (II)OBJECTIVE: To build a lamp


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 #305Delayed

Bedside Fan


Project #304 Watch LightOBJECTIVE: To build a lamp

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)

sc-300 rev-b 11-7-02 - snap circuits · creating your own circuits after building the circuits...

Documents