Copyright © by Elenco® Electronics, Inc. All rights reserved. No part of this book shall be reproduced by 753120any means; electronic, photocopying, or otherwise without written permission from the publisher. Patents: 7,144,255; 7,273,377; & other patents pending

Project 47

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1. Most circuit problems are due to incorrect assembly, alwaysdouble-check that your circuit exactly matches the drawing for it.

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

3. Be sure that all connections are securely snapped.4. Try replacing the batteries.5. If the flexible sheet in the sound energy demo container is

damaged, replace it with a spare (if one was included), or usehousehold plastic wrap.

6. If the echo IC (U28) stops working, turn the circuit off and onto reset it.

ELENCO® is not responsible for parts damaged due to incorrect wiring.

Basic Troubleshooting

Note: If you suspect you have damaged parts, you can follow theAdvanced Troubleshooting procedure on pages 16 and 17 to determinewhich ones need replacing.

Basic Troubleshooting 1Parts List 2, 3How to Use Snap Circuits® 4About Your Snap Circuits® SOUND Parts 5-7Introduction to Electricity 8Sound in Our World 9-14

DO’s and DON’Ts of Building Circuits 15Advanced Troubleshooting 16, 17Project Listings 18, 19Projects 1 - 188 20-85Other Snap Circuits® Projects 86

WARNING: SHOCK HAZARD - Never connect SnapCircuits® to the electrical outlets in your home in any way!

Table of Contents

WARNING: Always check your wiringbefore turning on a circuit. Never leavea circuit unattended while the batteriesare installed. Never connect additionalbatteries or any other power sources toyour circuits. Discard any cracked orbroken parts.

Adult Supervision: Because children’sabilities vary so much, even with agegroups, adults should exercisediscretion as to which experiments aresuitable and safe (the instructionsshould enable supervising adults toestablish the experiment’s suitability for

the child). Make sure your child readsand follows all of the relevantinstructions and safety procedures, andkeeps them at hand for reference.

This product is intended for use byadults and children who have attainedsufficient maturity to read and followdirections and warnings.

Never modify your parts, as doing somay disable important safety features inthem, and could put your child at risk ofinjury.

WARNING: CHOKING HAZARD -Small parts. Not for children under 3 years.!

Conforms to all applicableU.S. government

requirements.

• Use only 1.5V “AA” type, alkaline batteries(not included).

• Insert batteries with correct polarity.• Non-rechargeable batteries should not be

recharged. Rechargeable batteries shouldonly be charged under adult supervision, andshould not be recharged while in the product.

• Do not mix old and new batteries.• Do not connect batteries or battery holders

in parallel.

• Do not mix alkaline, standard (carbon-zinc), or rechargeable (nickel-cadmium)batteries.

• Remove batteries when they are used up.• Do not short circuit the battery terminals.• Never throw batteries in a fire or attempt to

open its outer casing.• Batteries are harmful if swallowed, so keep

away from small children.

Batteries:!WARNING: Some projects are intended for use withheadphones (not included in this set). Headphonesperformance varies, so you should use caution.Permanent hearing loss may result from long-termexposure to sound at high volumes. Start with aslow a volume as possible, then carefully increase toa comfortable level. Ringing or discomfort in theears may indicate that the sound levels are too high;immediately discontinue using the headphones withthis product and consult a physician.

!

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

Parts List (Colors and styles may vary) Symbols and Numbers (page 1)

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

r 1Base Grid(11.0” x 7.7”) 6SCBG

r 10.1mF Capacitor 6SCC2

r 3 1-Snap Wire 6SC01 r 1

470mF Capacitor 6SCC5

r 7 2-Snap Wire 6SC02 r 1

1mF Capacitor 6SCC7

r 3 3-Snap Wire 6SC03 r 1 Color Light Emitting

Diode (LED) 6SCD8

r 1 4-Snap Wire 6SC04 r 1

Egg LED Attachment 6SCEGG

r 1 5-Snap Wire 6SC05 r 1

Jumper Wire (black) 6SCJ1

r 1 6-Snap Wire 6SC06 r 1

Jumper Wire (red) 6SCJ2

r 2Battery Holder - usestwo (2) 1.5V type “AA”(not included)

6SCB1 r 1

Audio Jack 6SCJA

You may order additional / replacement parts at our website: www.snapcircuits.net

5

4

3

2

1

C2

C7

C5

6

B1 JA

D8

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

Parts List (Colors and styles may vary) Symbols and Numbers (page 2)

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

r 1 NPN Transistor 6SCQ2 r 1Tube for SoundEnergy DemoContainer

6SCSEDCT

r 1 100W Resistor 6SCR1 r 1Flexible Sheet for SoundEnergy Demo Container(may include spare)

6SCSEDCF

r 1 5.1kW Resistor 6SCR3 r 1 Speaker 6SCSP2

r 1 Adjustable Resistor 6SCRV r 1 Keyboard 6SCU26

r 1 500kW AdjustableResistor

6SCRV3 r 1 Voice Changer 6SCU27

r 1 Photoresistor 6SCRP r 1 Echo IC 6SCU28

r 2 Slide Switch 6SCS1 r 1 Microphone 6SCX1

r 1 Press Switch 6SCS2 r 1 Stereo Cable 9TLSCST

r 1Base for SoundEnergy DemoContainer

6SCSEDCB

You may order additional / replacement parts at our website: www.snapcircuits.net

U27

SP2

U28

S1

S2

U26

RP

Q2

RV

R3

R1

RV3

X1

How to Use Snap Circuits®

Snap Circuits® uses building blocks with snapsto build the different electrical and electroniccircuits in the projects. Each block has afunction: there are switch blocks, light blocks,battery blocks, different length wire blocks, etc.These blocks are different colors and havenumbers on them so that you can easilyidentify them. The blocks you will be using areshown as color symbols with level numbersnext to them, allowing you to easily snap themtogether to form a circuit.

For Example:This is the switch block, which is green and hasthe marking on it. The part symbols in thisbooklet may not exactly match the appearanceof the actual parts, but will clearly identify them.

This is a wire block, which is blue and comesin different wire lengths.This one has the number , , , ,or on it depending on the length of the wireconnection required.

There is also a 1-snap wire that is used as aspacer or for interconnection between differentlayers.

You need a power source to build each circuit.This is labeled and requires two (2) 1.5V“AA” batteries (not included).

A large clear plastic base grid is included withthis kit to help keep the circuit blocks properlyspaced. You will see evenly spaced posts thatthe different blocks snap into. The base hasrows labeled A-G and columns labeled 1-10.

Next to each part in every circuit drawing is asmall number in black. This tells you whichlevel the component is placed at. Place allparts on level 1 first, then all of the parts onlevel 2, then all of the parts on level 3, etc.

Some circuits use the jumper wires to makeunusual connections. Just clip them to themetal snaps or as indicated.

This set contains an egg LED attachment,which can be mounted on the color LED (D8)to enhance its light effects.

This set contains a sound energydemonstration container, which will sometimesbe placed over the speaker. Its use isexplained in project 13.

To assemble it, lay the tube and flexible sheetover the base, and then push the tube into thebase, as shown. Do not disassemble it exceptto repair it. This set may include a spare for theflexible sheet, and household plastic wrap alsoworks.

S2

2 3 4 56

B1

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Egg LED attachmentmounted to D8Egg

Note: While building the projects, be careful notto accidentally make a direct connection acrossthe battery holder (a “short circuit”), as this maydamage and/or quickly drain the batteries.

Sound Energy DemonstrationContainer Assembly

(Adult supervision recommended)

Flexiblesheet

Base

Tube

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About Your Snap Circuits® SOUND Parts(Part designs are subject to change withoutnotice).

BASE GRID

The blue snap wiresare wires used toconnect components.They are used to

transport electricity and donot affect circuit performance.

They come in different lengths toallow orderly arrangement of connections

on the base grid.

The red and blackjumper wires makeflexible connections fortimes when using the snap wireswould be difficult. They also areused to make connections off the base grid.

Wires transport electricity just like pipes are usedto transport water. The colorful plastic coatingprotects them and prevents electricity fromgetting in or out.

BATTERY HOLDER

The base grid is a platform for mounting partsand wires. It functions like the printed circuitboards used in most electronic products, or likehow the walls are used for mounting the electricalwiring in your home.

SNAP WIRES & JUMPER WIRES

The batteries (B1) produce an electrical voltageusing a chemical reaction. This “voltage” can bethought of as electrical pressure, pushingelectricity through a circuit just like a pumppushes water through pipes. This voltage ismuch lower and much safer than that used inyour house wiring. Using more batteriesincreases the “pressure”, therefore, moreelectricity flows.

Battery Holder (B1)

SLIDE & PRESS SWITCHESThe slide & press switches (S1 & S2) connect(pressed or “ON”) or disconnect (not pressed or“OFF”) the wires in a circuit. When ON they have noeffect on circuit performance. Switches turn onelectricity just like a faucet turns on water from a pipe.

Slide & PressSwitches(S1 & S2)

RESISTORSResistors “resist” the flow of electricity and areused to control or limit the current in a circuit.Snap Circuits® SOUND includes 100W (R1) and5.1kW (R3) resistors (“k” symbolizes 1,000, soR3 is really 5,100W). Materials like metal havevery low resistance (<1W), while materials likepaper, plastic, and air have near-infiniteresistance. Increasing circuit resistance reducesthe flow of electricity.

Resistors (R1 & R3)

Adjustable Resistor (RV)

The adjustableresistor (RV) is a50kW resistor butwith a center tapthat can be adjustedbetween 200W and50kW.

The 500kW adjustable resistor (RV3) is a500kW resistor that can be adjusted between200W and 500kW.

500kW Adjustable Resistor (RV3)

About Your Snap Circuits® SOUND PartsLED

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The speaker (SP) converts electricity into soundby making mechanical vibrations. Thesevibrations create variations in air pressure, whichtravel across the room. You “hear” sound whenyour ears feel these air pressure variations.

SPEAKER

Speaker (SP2)

Color LED(D8)

The color LED (D8) is a light emitting diode, andmay be thought of as a special one-way lightbulb. In the “forward” direction, (indicated by the“arrow” in the symbol) electricity flows if thevoltage exceeds a turn-on threshold (about 1.5Vfor red, about 2.0V for green, and about 3.0V forblue); brightness then increases. The color LEDcontains red, green, and blue LEDs, with a micro-circuit controlling then. A high current will burnout an LED, so the current must be limited byother components in the circuit. LED’s blockelectricity in the “reverse” direction.

CAPACITORThe 0.1mF, 1mF, and 470mF capacitors (C2, C7,& C5) can store electrical pressure (voltage) forperiods of time. This storage ability allows themto block stable voltage signals and passchanging ones. Capacitors are used for filteringand delay circuits.

Microphone (X1)

The microphone (X1) is actually a resistor thatchanges in value when changes in air pressure(sounds) apply pressure to its surface.

MICROPHONE

The photoresistor (RP) is a light-sensitiveresistor, its value changes from nearly infinite intotal darkness to about 1000W when a bright lightshines on it.

Photoresistor (RP)

Capacitors (C2, C5, & C7)

TRANSISTORS

ELECTRONIC MODULES

The NPN transistor (Q2) is a component thatuses a small electric current to control a largecurrent, and is used in switching, amplifier, andbuffering applications. Transistors are easy tominiaturize, and are the main building blocks ofintegrated circuits including the microprocessorand memory circuits in computers.

The keyboard (U26) contains resistors,capacitors, switches, and an integrated circuit. Itcan produce two adjustable audio tones at thesame time. The tones approximate musicalnotes, and may not be exact. The tone of thegreen keys can be adjusted with the tune knobor using external resistors and capacitors. Aschematic for it is available atwww.snapcircuits.net/faq.

Connections:(+) - power from batteriesRES - resistor freq adjustCAP - capacitor freq adjustOUT - output connection (–) - power return to batteries

See projects 1, 6, & 25 for example of proper connections.

NPN Transistor (Q2)

Keyboard (U26)

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About Your Snap Circuits® SOUND Parts

Audio Jack (JA)

OTHER PARTS The stereo cable is used to connect theaudio jack (JA) to your music device orexternal speaker.

The audio jack (JA) is a connectormounted on snaps, and is used forinterfacing your music device or externalspeaker to Snap Circuits®.

The egg LED attachment can be usedwith the color LED (D8) to enhance thelight effects.

Egg

The sound energy demonstrationcontainer is used to show that soundwaves have energy, and can movethings around. See project 13.

Connections:(+) - power from batteriesSPD - speed adjustSP+ - speaker (+)SP– - speaker (–) MIC+ - microphone (+)MIC– - microphone (–)REC - recordPLY - play(–) - power return to batteries

See project 7 for example ofproper connections.

The voice changer (U27) contains resistors, capacitors,and an integrated circuit that are needed to record andplay back sound at different speeds. A schematic for it isavailable at www.snapcircuits.net/faq.

Connections:(+) - power from batteriesG+ - gain controlG– - gain controlADJ - echo adjustINP - input connectionOUT - output connection(–) - power return tobatteries

See projects 10 & 41 forexamples of properconnections.

The echo IC (U28) contains resistors, capacitors, andintegrated circuits that are needed to add echo effects toa sound. A schematic for it is available atwww.snapcircuits.net/faq.

Introduction to ElectricityWhat is electricity? Nobody really knows. We only know how to produce it,understand its properties, and how to control it. Electricity is the movement of sub-atomic charged particles (called electrons) through a material due to electricalpressure across the material, such as from a battery.

Power sources, such as batteries, push electricity through a circuit, like a pumppushes water through pipes. Wires carry electricity, like pipes carry water. Deviceslike LEDs, motors, and speakers use the energy in electricity to do things. Switchesand transistors control the flow of electricity like valves and faucets control water.Resistors limit the flow of electricity.

The electrical pressure exerted by a battery or other power source is calledvoltage and is measured in volts (V). Notice the “+” and “–” signs on the battery;these indicate which direction the battery will “pump” the electricity.

The electric current is a measure of how fast electricity is flowing in a wire, justas the water current describes how fast water is flowing in a pipe. It is expressedin amperes (A) or milliamps (mA, 1/1,000 of an ampere).

The “power” of electricity is a measure of how fast energy is moving through awire. It is a combination of the voltage and current (Power = Voltage x Current). Itis expressed in watts (W).

The resistance of a component or circuit represents how much it resists theelectrical pressure (voltage) and limits the flow of electric current. The relationshipis Voltage = Current x Resistance. When the resistance increases, less currentflows. Resistance is measured in ohms (W), or kilo ohms (kW, 1,000 ohms).

Nearly all of the electricity used in our world is produced at enormous generatorsdriven by steam or water pressure. Wires are used to efficiently transport thisenergy to homes and businesses where it is used. Motors convert the electricityback into mechanical form to drive machinery and appliances. The most importantaspect of electricity in our society is that it allows energy to be easily transportedover distances.

Note that “distances” includes not just large distances but also tiny distances. Tryto imagine a plumbing structure of the same complexity as the circuitry inside aportable radio - it would have to be large because we can’t make water pipes sosmall. Electricity allows complex designs to be made very small.

There are two ways of arranging parts in a circuit, in series orin parallel. Here are examples:

Placing components in series increases the resistance; highestvalue dominates. Placing components in parallel decreases theresistance; lower value dominates.

The parts within these series and parallel sub-circuits may bearranged in different ways without changing what the circuitdoes. Large circuits are made of combinations of smaller seriesand parallel circuits.

Series Circuit

Parallel Circuit

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Sound in Our WorldSound is a variation in air pressure created bya mechanical vibration. See projects 13 & 51for a demonstration of this. These air pressurevariations travel across the room like waves,so we call them sound waves. You “hear”sound when your ears feel these air pressurevariations, and convert them to nerve pulsesthat your brain interprets. Eventually theenergy of a sound wave is absorbed, andbecomes heat.

Sound waves can also be thought of as wavesof temporary compression that travel throughmaterials. Notice that at a loud concert you cansometimes feel the pressure waves, inaddition to hearing them. Sound waves cantravel through liquids and solids but theirspeed may change and their energy may bereduced, depending on the characteristics ofthe material. Sound waves can only travelthrough a compressible material, and socannot travel through a vacuum. Outer spaceis silent, because there is no air or othermaterial for sound waves to travel through.

The “hearing” part of your ear is inside yourskull; the flaps you see are just funnels tocollect the sound and pass it along to youreardrum inside. When you were young yourbrain learned to interpret the difference in theinformation collected from your two ears, anduse it to know which direction a sound camefrom. If one of your ears is clogged, then it isdifficult to determine a sound’s direction.

You can compare sound waves from yourvoice to waves in a pond. When you speak,the movements in your mouth create soundwaves just as tossing a rock into the pondcreates water waves. Sound waves travelthrough air as water waves travel across thepond. If someone is nearby, then their ears willfeel the air pressure variations caused by your

sound waves just as a small boat at the otherside of the pond will feel the water waves.

If the mechanical vibration causing the soundwave occurs at a constant rate, then the soundwave will repeat itself at the same rate; werefer to this as the frequency of the soundwave. Nearly all sound waves have theirenergy spread unevenly across a range offrequencies. When you say a word, you createa sound wave with energy at variousfrequencies, just as tossing a handful ofvarious-sized rocks into the pond will create acomplicated water wave pattern.

Frequency measures how many timessomething occurs per second, expressed inunits called hertz (Hz). The metric prefixes canbe used, so 1,000 repetitions per second is 1kilohertz (kHz) and 1,000,000 repetitions persecond is 1 megahertz (MHz). The range offrequencies that can be heard by the humanear is approximately 20 to 20,000 Hz and isreferred to as the audio range.

Just as there are sound waves caused bymechanical vibrations, there are also electricalwaves caused by electrical variations. Just assound waves travel through air, electricalwaves travel through wires. A microphonesenses pressure variations from sound wavesand creates electrical waves at the samefrequencies. A speaker converts electricity into

sound, by using the energy in electrical wavesto create mechanical vibrations (sound waves)at the same frequencies.

How does the speaker make sound? Anelectric current flowing through a wire has avery, very tiny magnetic field. Inside thespeaker is a coil of wire and a magnet. The coilof wire concentrates the magnetic field fromthe flowing electric current, enough to makethe magnet move slightly, like a vibration. Themagnet’s vibration creates the air pressurevariations that travel to your ears.

Your speaker can only create sound from aCHANGING electrical signal, for unchangingelectrical signals it acts like a 32 ohm resistor.(An unchanging signal does not cause themagnet in the speaker to move, so no soundwaves are created). Electrical variations athigh frequencies (referred to as radiofrequencies) cannot be heard by your ears, butcan be used to create electromagnetic radiowaves, which travel through air and are usedfor many forms of communication. In AM andFM radio, voice or music is superimposed onradio waves, allowing it to be transmitted overgreat distances, to later be decoded andlistened to.

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Sound and water waves

Speakersound waves

Sound in Our WorldIn stereo, sound is produced on severalspeakers (or earphones) with varyingfrequencies/loudness on each. This gives theimpression that the sound is coming fromdifferent directions, and is more pleasing tolisten to. Mono sound is the same on allspeakers, and is easier to produce. Note thata “stereo speaker” can be several speakers(possibly of different sizes) in one package.Your Snap Circuits® speaker (SP2) is a monospeaker. Surround sound is a technique forplacing several speakers (with differentsounds from each) around the listener, tocreate a more interesting listening experience.

The loudness of sound waves is a measure ofthe pressure level, and is expressed indecibels (dB, a logarithmic scale). Long-termexposure to loud sounds can lead to hearingloss. Here are some examples of sound levels:

Sound waves travel very fast, but sometimesyou can perceive the effects of their speed.Ever notice how sometimes you see lightningbefore you hear the thunder? The reason isbecause light travels at about 186,000 milesper second, while sound travels at only about1,100 feet per second in air. Sound can travelthrough liquids and solids, but with increasedspeed (the speed depends on the material’scompressibility and density). Sound travels 4.3times faster in water than in air; this differencein speed confuses our ears, making it difficultto perceive the direction of sound whileunderwater.

A sonic boom is a shock wave that occurswhen an object travels through air atsupersonic speeds (faster than the speed ofsound). These sonic shock waves are similarto how the bow of a boat produces waves inthe water. Sonic shock waves can carry a lotof sound energy and can be very unpleasantto hear, like an explosion. Aircraft can fly atsupersonic speeds, and the sonic boomproduced is so unpleasant that aircraft arerarely permitted to fly at supersonic speedsover populated areas.

Sound waves can reflect off walls and goaround corners, though their energy may bereduced depending on the angle and theroughness of the surface. Sometimes soundwaves can be channeled to focus in a certaindirection. As an example, get a long tube, likethe ones for wrapping paper. Use one of theprojects that make a continuous tone, such asprojects 6 or 92. Hold one end of the tube nextto the speaker (use the yellow side with thegrating) and the other end near your ear, thenremove the tube and compare the soundvolume at the same distance from the speaker.The long tube should make the soundreaching your ear louder, because soundwaves reflect off the tube walls and stayconcentrated, instead of spreading out acrossthe room.

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Sound Source LevelThreshold of pain 130dBChain saw 110dBNormal conversation 50dBCalm breathing 10dBHearing threshold 0dB

Surround sound

Sonic boom

It’s hard to perceivesound directionunderwater.

Placing a long tube next tothe speaker keeps its soundwaves together longer.

Sound waves

Long tube

Speaker

Sound in Our WorldSome of a sound wave’s energy can reflect offwalls or objects and come back to you.Normally you don’t notice these reflectionswhen you are speaking because not all of theenergy is reflected, and the delay is so shortthat your ears can’t distinguish it from theoriginal sound, but sometimes (such as in avery large open room) you can hear them -these are echoes! You hear an echo when alot of the energy of your voice is reflected backto you after a noticeable delay. The delay timeis the distance (to the reflection point andback) divided by the speed of sound. Mostpeople cannot distinguish reflected soundwaves with delays of less than 1/15 of asecond, and perceive them as being part ofthe original sound. Echoes can be simulatedelectronically by replaying a recorded soundwith a small delay and at reduced volume. Seeproject 10 and others for examples.

In project 10, if your speaker is too close toyour microphone then the echo sound can bepicked up by the microphone and echoedagain and again until you can’t hear anythingelse. The same thing can occur in telephonesystems, and these systems sometimes haveecho-cancelling circuitry to prevent problems(especially in overseas calls, where thetransmission delay times may be longer).

Engineers developing sensitive audioequipment need to make very accurate soundmeasurements. They need rooms that aresealed from outside sounds, and need tominimize the measured signal’s reflections offthe walls/ceiling/floor. Specialized rooms havebeen designed for this, called anechoicchambers. These chambers are virtuallysoundproof and have specially shapedmaterials (usually made of foam) on the wallsto absorb sound waves without producing anyechoes. These chambers simulate a quiet,open space, allowing the engineers toaccurately measure the equipment beingtested.

Everything has a natural frequency, itsresonance frequency, at which it will vibratemore easily. When sound waves strike anobject at its natural frequency, the object canabsorb and store significantly more energyfrom the sound waves, as vibration. To helpunderstand this concept, think of a playgroundswing, which tends to always swing back andforth at the same rate. If you push the swing atthe ideal moment, it will absorb energy fromyou and swing higher. You don’t need to pushthe swing very hard to make it go high, you just

need to keep adding energy at the rightmoment. In project 13 (Sound EnergyDemonstration), the frequency is tuned to thespeaker’s natural frequency, making it vibratenoticeably.

Resonance is an important consideration inthe design of musical instruments, and also inconstruction. If high winds blow on a tallbuilding or a bridge at the structure’s resonantfrequency, vibrations can slowly increase untilthe structure is torn apart and collapses.

A cone can help you project your voice. A conekeeps the sound waves (air pressurevariations) together longer, so they don’tspread out so quickly. Long ago, people whohad trouble hearing used an ear trumpet,which helps collect sound waves. A personwould speak into the wide end of the eartrumpet, and the trumpet makes the soundlouder at the listening person’s ear. Electronichearing aids have replaced ear trumpets.Doctors use a stethoscope to hear insidepatient’s bodies. A stethoscope uses a cone-like structure to collect sound waves; thenpasses them into the doctor’s ear.

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Sound waves reflecting off a wall

Anechoic chamber

Small pushes at the rightmoment will make the swinggo higher.

Sound in Our WorldElectronically we amplify sound by convertingthe sound waves into an electrical signal,amplify the electrical signal, and then convertthat back to sound waves.

There are many other applications for soundwaves. Here are some examples:

In SONAR (short for SOund Navigation AndRanging), sound waves are sent out underwaterat various frequencies and the echoes aremeasured; the distance to any objects can bedetermined using the time for the echoes toarrive, and the speed of sound. SONAR is usedfor navigating around underwater obstacles andfor detecting other ships, especially submarines.SONAR is also used by the fishing industry tohelp find and harvest fish. Sound waves canalso be used to determine the depth of an oilwell. RADAR (RAdio Detection And Ranging) issimilar to SONAR but uses radio waves insteadof sound waves.

Ultrasound waves are above 20 kHz, beyondthe range of human hearing. Bats useultrasound waves to effectively “see” in thedark. Ultrasound waves are also used inmedical imaging, to create pictures of musclesand organs in the human body. Ultrasoundwaves are sometimes used in cleaning itemslike jewelry.

Ultrasonic welding is used in industry to bondmaterials (usually plastics) together using highfrequency sound waves. The energy of thesound waves is concentrated at the points tobe bonded, and basically melts the material atthe contact points. This can create a strongbond, without using glue or nails. Ultrasonicwelding has been used to bond the bottoms ofSnap Circuits® parts in the past, and might stillbe used for the speaker (SP2) andmicrophone (X1).

Earthquakes are compression waves, similarto sound waves but with enormous power.Using triangulation from several measurementpoints, and knowing how fast these waves cantravel across the earth’s surface, scientists candetermine where the earthquake began (calledthe epicenter).

MusicThe subject of music is one where the worldsof art and science come together.Unfortunately, the artistic/musician field workswith qualities that depend on our feelings andso are difficult to express using numbers whilescience/engineering works with the opposite -clearly defined, measurable qualities. As aresult, some of the terms used may seemconfusing at first, but you will get used to them.

Music is when vibrations (creating soundwaves) occur in an orderly and controlledmanner forming a pattern with their energyconcentrated at specific frequencies, usuallypleasant to listen to. Noise is when thevibrations occur in an irregular manner withtheir energy spread across a wide range offrequencies, usually annoying to hear (staticon a radio is a good example). Notice howsome people refer to music that they don’t likeas noise. In electrical systems, noise isundesired interference that can obscure thesignal of interest.

Another way to think of this is that the ear triesto estimate the next sounds it will hear. Musicwith a beat, a rhythm, and familiar instrumentscan be thought of as very predictable, so wefind it pleasant to listen to. Notice also that wealways prefer familiar songs to music that weare hearing for the first time. Sudden, loud,unpredictable sounds (such as gunfire, a glassbreaking, or an alarm clock) are very

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Cone

Ear Trumpet Stethoscope

Horn

Anvil or jig

Plasticparts

Phase 1 Phase 2 Phase 3Pressure is appliedby the horn.

The horn vibratesthe plastic partsvery quickly.

The plastic partsmelt together fromthe friction created.

SONAR

Ultrasonic welding

Ultrasound photo of a heart (echocardiogram)

Sound in Our Worldunnerving and unpleasant. Most electronicspeech processing systems being developeduse some form of speech prediction filters.

Take a piece of string or rope roughly 4 feetlong and tie one end of it to a chair or otherpiece of furniture. Swing the other end up anddown so that you have a cyclic pattern, asshown:

Now swing it three times as fast (three timesthe frequency), to produce this pattern:

Now try to swing it five times as fast (five timesthe frequency), to produce this pattern:

Since the later patterns are frequencymultiples of the first, we refer to them asovertones (the music term) or harmonics (theelectronics term) and the original pattern iscalled the fundamental. If you could combineall three of the above patterns onto the stringthen you would get a pattern, which looks likethis:

This combined pattern (a single fundamentalwith overtones) is called a tone (and a puretone is a single fundamental with noovertones). Notice that each pattern is moredifficult to produce than the one before it, withthe combined pattern being quite complicated.And also notice that the more complicatedpatterns are much more interesting andpleasing to look at than the simpler ones. Wellthe same thing applies to sound waves.Complex patterns that have many overtonesfor each fundamental are more pleasant tolisten to than simple patterns. If manyovertones were combined together, the resultswould approximate a square wave shape.

All traditional music instruments use thisprinciple, with the instrument shapes andmaterials perfected through the years toproduce many overtones for each fundamentalchord or key that is played by the user. Grandpianos sound better than upright pianos sincetheir larger shape enables them to producemore overtones, especially at lowerfrequencies. Concert halls sound better thansmall rooms because they are designed forbest overtone performance and to takeadvantage of the fact that sound waves canreflect off walls to produce different overtone

relationships between both of your ears. Thesame thing applies to stereo sound. You mayhave heard the term acoustics; this is thescience of designing rooms for best soundeffects.

A commonly used musical scale (whichmeasures pitch) will now be introduced. Thisscale is called the equal temperament scale,expressed in hertz. You might think of this asa conversion table between the artistic andscientific worlds since it expresses pitch interms of frequency. Each overtone (overtone0 being the fundamental) is divided into 12semitones: C, C# (“C-flat”), D, D#, E, F, F#, G,G#, A, A#, and B. The semitones increase bythe ratio 12:2, or 1.05946. Musical notes(tones) are the measure of pitch and areexpressed using both the semitone and theovertone, such as A3, G#4, D6, A#1, and E2.

(frequency in hertz and rounded off)

-13-

Overtone C C# D D# E F0 16.4 17.3 18.4 19.4 20.6 21.81 32.7 34.6 36.7 38.9 41.2 45.72 65.4 69.3 73.4 77.8 82.4 87.33 130 139 147 156 165 1754 262 278 294 311 330 3495 523 554 587 622 659 6986 1047 1109 1174 1245 1319 13977 2093 2217 2344 2489 2637 27948 4186 4435 4698 4978 5274 55889 8372 8870 9397 9956 10548 11175

Overtone F# G G# A A# B0 23.1 24.5 26.0 27.5 29.1 30.91 46.2 49.0 51.9 55.0 58.3 61.72 92.5 98.0 104 110 117 1233 185 196 208 220 233 2474 370 392 415 440 466 4945 740 784 831 880 932 9886 1480 1568 1661 1760 1865 19767 2960 3136 3322 3520 3729 39518 5920 6271 6645 7040 7459 79029 11840 12542 13290 14080 14917 15804

Sound in Our WorldOn your U26 keyboard, the blue keysapproximate the 5th overtone notes, and thegreen keys approximate the 6th overtonenotes; actual frequency may vary from themusical scale. The tone of the green keys canbe adjusted with the tune knob, allowing themto be in tune with the blue keys, or out of tunewith them. The tone of the green keys mayalso be adjusted using external resistors andcapacitors, which can change the frequencyrange dramatically (and even beyond thehearing range of your ears), and can create anoptical theremin. Your keyboard can play oneblue note and one green note at the sametime; if you press two keys of the same colorat the same time, only the higher note will beplayed. Projects 1-4 and 25-27 demonstratethe capabilities of the U26 keyboard.

On most instruments, when you play a notethe sound produced is initially loud and thendecreases with time. On your U26 keyboard,a note ends when you release the key, unlessyou connected external resistors to produce acontinuous tone. More complex electronicinstruments can simulate more notes at thesame time, have more advanced techniquesfor producing overtones, and continue to playthe note with decreasing loudness after thekey has been released.

The musical world’s equivalent to frequencyis pitch. The higher the frequency, the higherthe pitch of the sound. Frequencies above2,000 Hz can be considered to provide trebletone. Frequencies about 300 Hz and belowprovide bass tone.

Up to now, the musical measures of pitch andloudness have been discussed. But manymusical sounds have the same pitch andloudness and yet sound very different. For

example, the sound of a guitar compared tothat of a piano for the same musical note. Thedifference is a quality known as timbre. Timbredescribes how a sound is perceived, itsroughness. Scientifically it is due to differencesin the levels of the various overtones, and socannot be expressed using a single number.

Now consider the following two tones, whichdiffer slightly in frequency:

If they are played at the same time then theirsound waves would be added together toproduce:

Notice that the combined wave has a regularpattern of where the two tones add togetherand where they cancel each other out. This isthe effect that produces the beat you hear inmusic. Two tones (that are close in frequencyand have similar amplitude for theirfundamental and for each of their overtones)will beat at the rate of their frequencydifference. Rhythm is the pattern of regularbeat that a song has.

Now observe this tone:

The frequency is slowly increasing anddecreasing in a regular pattern. This is anexample of vibrato. If the frequency ischanging slowly then it will sound like a varyingpitch; a fast vibrato (several times a second)produces an interesting sound effect. Thealarm IC (U2, included in Snap Circuits®

models SC-100, 300, 500, or 750) producessounds using the vibrato effect.

Tempo is a musical term, which simplydescribes how quickly a song is played.

-14-

DO’s and DON’Ts of Building CircuitsAfter building the circuits given in this booklet, you may wish to experiment on your own.Use the projects in this booklet as a guide, as many important design concepts areintroduced throughout them. Every circuit will include a power source (the batteries), aresistance (which might be a resistor, capacitor, speaker, integrated circuit, etc.), and wiringpaths between them and back. You must be careful not to create “short circuits” (very low-resistance paths across the batteries, see examples at right) as this will damagecomponents and/or quickly drain your batteries. Only connect the keyboard (U26), voicechanger (U27), and echo IC (U28) using configurations given in the projects, incorrectlydoing so may damage them. ELENCO® is not responsible for parts damaged due toincorrect wiring.

Here are some important guidelines:ALWAYS USE EYE PROTECTION WHEN EXPERIMENTING ON YOUR OWN.ALWAYS include at least one component that will limit the current through a circuit, such

as the speaker, capacitors, ICs (which must be connected properly),microphone, or resistors.

ALWAYS use LEDs, transistors, and switches in conjunction with other components thatwill limit the current through them. Failure to do so will create a short circuitand/or damage those parts.

ALWAYS connect capacitors so that the “+” side gets the higher voltage.ALWAYS disconnect your batteries immediately and check your wiring if something

appears to be getting hot.ALWAYS check your wiring before turning on a circuit.ALWAYS connect the keyboard (U26), voice changer (U27), and echo IC (U28) using

configurations given in the projects or as per the connection description onpages 6 and 7.

NEVER connect to an electrical outlet in your home in any way.NEVER leave a circuit unattended when it is turned on.NEVER use headphones at high sound levels.

For all of the projects given in this book, the parts may be arranged in different ways withoutchanging the circuit. For example, the order of parts connected in series or in parallel doesnot matter — what matters is how combinations of these sub-circuits are arranged together.

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

This is also aSHORT CIRCUIT.

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

NEVERDO!

NEVERDO!

NEVERDO!

Examples of SHORT CIRCUITS - NEVER DO THESE!!!

Warning to Snap Circuits® owners: Do not connectadditional voltage sources from other sets, or youmay damage your parts. Contact Elenco® if you havequestions or need guidance.

You are encouraged to tell us about new programs and circuits youcreate. If they are unique, we will post them with your name and stateon our website at:

www.snapcircuits.net/learning_center/kids_creationSend your suggestions to ELENCO®: elenco@elenco.com.

ELENCO® provides a circuit designer so that you can make your ownSnap Circuits® drawings. This Microsoft® Word document can bedownloaded from:

www.snapcircuits.net/learning_center/kids_creationor through the www.snapcircuits.net website.

WARNING: SHOCK HAZARD - Never connect Snap Circuits®

to the electrical outlets in your home in any way!

!!

!NEVER

DO!

!

!

!

-15-

Advanced Troubleshooting (Adult supervision recommended)

ELENCO® is not responsible for partsdamaged due to incorrect wiring.

If you suspect you have damaged parts,you can follow this procedure tosystematically determine which onesneed replacing:

(Note: Some of these tests connect an LEDdirectly across the batteries without anothercomponent to limit the current. Normally thismight damage the LED, however Snap Circuits®

LEDs have internal resistors added to protectthem from incorrect wiring, and will not bedamaged.)

1. Color LED (D8), speaker (SP2), andbattery holder (B1): Place batteries inholder. Place the color LED directly acrossthe battery holder (LED + to battery +), itshould light and be changing colors. “Tap”the speaker across the battery holdercontacts; you should hear static as ittouches. If neither works, then replaceyour batteries and repeat. If still bad, thenthe battery holder is damaged. Test bothbattery holders.

2. Red & black jumper wires: Use thismini-circuit to test each jumper wire; theLED should light.

3. Snap wires: Use this mini-circuit to testeach of the snap wires, one at a time. TheLED should light.

4. Slide switch (S1) and Press switch (S2):Use this mini-circuit; if the LED doesn’tlight then the slide switch is bad. Replacethe slide switch with the press switch totest it.

5. 100W (R1) and 5.1kW (R3) resistors, andmicrophone (X1): Use this mini-circuit;the LED will be bright if the R1 resistor isgood. Next use the 5.1kW resistor in placeof the 100W resistor; the LED should bemuch dimmer but still light. Next, replace5.1kW resistor with the microphone (“+” toright); the LED should flicker dimly but stilllight.

6. 500kW adjustable resistor (RV3) andPhotoresistor (RP): Use the mini-circuitfrom test 5 but replace the 100W resistorwith RV3. Turning RV3’s knob all the wayto the left (counter-clockwise) should makethe color LED bright and most othersettings should make the LED dim or off;otherwise RV3 is bad. Next, replace RV3with the photoresistor, and shine a brightlight on it. Waving your hand over thephototransistor (changing the light thatshines on it) should change the brightnessof the color LED; otherwise thephotoresistor is bad.

7. Adjustable resistor (RV): Build project98. Move the resistor control lever to bothsides. The color LED (D8) should be brightif the lever is to the far left or far right, anddim if the lever is in the middle.

8. NPN transistor (Q2): Build the mini-circuit shown here. The color LED (D8)should only be on if the press switch (S2)is pressed. If otherwise, then Q2 isdamaged.

-16-

1

Advanced Troubleshooting (Adult supervision recommended)9. Keyboard (U26): Build project 92, but

omit the 0.1mF capacitor (C2) and the5.1kW resistor (R3). You should hear atone when you press any key. Turning theTUNE knob while pressing any green keyshould change the tone slightly. Now addR3 to the circuit, and you should hear acontinuous tone. If any of this does notwork then the keyboard is damaged.

10. 0.1mF (C2), 1mF (C7), and 470mF (C5)capacitors: Build project 92; removingC2 from it should change the tone, or C2is damaged. Next, replace C2 with C7; thepitch of the tone should be lower now, orC7 is damaged. Next, replace C7 with C5;you should hear a click every few seconds,or C5 is damaged.

11. Voice changer (U27): Build project 7.Follow the project’s instructions to confirmthat you can make a recording and play itback at different speeds.

12. Echo IC (U28): Build the circuit shown atright, turn it on, and set the knob on the500kW adjustable resistor (RV3) to theright. Press any keys on the keyboard; youshould hear tones with echo, and be ableto adjust echo level using the lever on theadjustable resistor (RV). Removing the1mF capacitor (C7) should reduce thevolume a little. Sometimes an echo ICproblem can be fixed by turning the circuitoff and back on to reset it.

12. Audio Jack (JA) and stereo cable: Ifyou have headphones, use them to testthe audio jack using project 14. If you havea music device, use it to test the audio jackusing project 66. Use project 66 to testyour stereo cable.

13. Sound energy demonstration container:If the flexible sheet is damaged,disassemble the container and replace theflexible sheet; this set may have includeda spare for it, or you can use householdplastic wrap.

ELENCO®

150 Carpenter AvenueWheeling, IL 60090 U.S.A.

Phone: (847) 541-3800Fax: (847) 520-0085

e-mail: help@elenco.comWebsite: www.elenco.com

You may order additional / replacementparts at: www.snapcircuits.net

-17-

Project # Description Page # 1 Electronic Keyboard 20 2 Aligning the Keyboard 20 3 Be a Musician 21 4 Be a Musician (II) 21 5 Optical Theremin 22 6 Keyboard Slider 22 7 Voice Changer 23 8 Voice Changer & Light 23 9 Color Light 23 10 Echo 24 11 Echo with Headphones 24 12 Louder Echo with Headphones 24 13 Sound Energy Demonstration 25,26 14 Keyboard in Stereo 27 15 Optical Theremin in Stereo 27 16 Light & Sound 28 17 See Saw 28 18 Light, Sound, & Motion 29 19 Brighter Light, Sound, & Motion 29 20 Keyboard with Voice Changer 30 21 Optical Keyboard with Voice Changer 30 22 Keyboard Voice Changer & Light 30 23 Voice Changer with Echo 31 24 Sound Controlled Light 31 25 Low Pitch Keyboard 32 26 Lower Pitch Keyboard 32 27 Very Low Pitch Keyboard 32 28 Echo Speed Changer 32 29 Keyboard Echo 33 30 Lower Pitch Keyboard Echo 33 31 Optical Keyboard Echo 33

Project # Description Page # 32 Low Pitch Optical Keyboard Echo 33 33 Keyboard Echo with Stereo Effects 34 34 Optical Echo in Stereo 35 35 Color Short Light 35 36 Keyboard with Optical Theremin 36 37 Keyboard with Optical Theremin (II) 36 38 Adjustable Dual Range Keyboard 36 39 Adjustable Dual Range Keyboard (II) 36 40 Adjustable Dual Range Keyboard (III) 36 41 Your Music with Echo 37 42 Your Music with Echo and Light 37 43 Your Music Speed Changer 38 44 Your Music Speed Changer (II) 38 45 Your Music Speed Changer (III) 38 46 Sound On Light 38 47 Super Optical Keyboard Echo 39 48 Softer Optical Keyboard Echo 39 49 Reflection Detector 39 50 Super Optical Keyboard Echo for Headphones 40 51 Sound is Air Pressure 41 52 Sound is Air Pressure - Keyboard 41 53 Brightness Adjuster 42 54 Brightness Limiters 42 55 Big Brightness Adjuster 42 56 Photo Brightness Adjuster 43 57 Amplified Photo Brightness Adjuster 43 58 Amplified Big Brightness Adjuster 43 59 Cup & String Communication 44 60 Audio Amplifier 45 61 Low Power Audio Amplifier 45 62 Audio Amplifier with L/R Control 45

Project # Description Page # 63 Your Music without Echo 46 64 Low Power Your Music without Echo 46 65 Adjustable Music without Echo 46 66 L/R Music Amplifier 47 67 Another Transistor Amplifier 47 68 Microphone Resistance - LED 48 69 Microphone Resistance - Audio 48 70 Time Light 49 71 Time Light (II) 49 72 Easier Adjust Time Light 49 73 Small Adjust Time Light 49 74 Day Light 50 75 Lower Day Light 50 76 Dark Light 50 77 Blow Noise 50 78 Listen to the Light Change 51 79 Adjustable Listen to the Light Change 51 80 Bright or Loud? 51 81 LED Keyboard Control 52 82 LED Keyboard Control (II) 52 83 Photo LED Keyboard Control 52 84 Adjustable LED Keyboard Control 52 85 Capacitor Keyboard Control 53 86 Capacitor Keyboard Control (II) 53 87 Voice & Keyboard Echo 53 88 LED Voice & Keyboard Echo 54 89 Photo LED Keyboard Echo 54 90 Photo LED Keyboard 54 91 Audio Dark Light 54 92 Oscillator 55 93 Oscillator (II) 55

Project Listings

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Project # Description Page # 94 Oscillator (III) 55 95 Oscillator (IV) 55 96 Oscillator (V) 55 97 Oscillator (VI) 55 98 Left Right Bright Light 55 99 Adjustable Oscillator 56 100 Adjustable Oscillator (II) 56 101 Adjustable Oscillator (III) 56 102 Adjustable Oscillator (IV) 56 103 Water Detector 56 104 Clicker 57 105 Clicker with Echo 57 106 3V Audio Amplifier 58 107 Mini Music Player 58 108 Voice Echo with Light 58 109 Color Sound 59 110 Color Sound (II) 59 111 Color Sound (III) 59 112 Backwards Color Sound 59 113 White Light 60 114 Red to White 60 115 Alarm 60 116 Super Voice Echo with Light 61 117 Press Echo 61 118 Photo Echo 61 119 Loud Press Photo Echo 61 120 Knob Echo 61 121 Echo Light Headphone 62 122 Echo Light Headphone Variants 62 123 Press Echo Light 62 124 Photo Echo Light 62 125 Another Voice Echo Light 63

Project # Description Page # 126 Daylight Voice Echo 63 127 Dark Voice Echo 64 128 Dark Echo Light 64 129 Dark Echo Variants 64 130 Day Echo Light 65 131 Day Echo Variants 65 132 Photo Light Timer 65 133 Adjustable Photo Light Timer 65 134 Tone Stoppers 66 135 Tone Stoppers (II) 66 136 Tone Stoppers (III) 66 137 Tone Stoppers (IV) 66 138 Tone Stoppers (V) 67 139 Alarm Light 67 140 Voice Changer with Headphones 67 141 Day Keyboard 68 142 Night Keyboard 68 143 Color Keyboard 69 144 Color Keyboard (II) 69 145 Color Keyboard (III) 69 146 Color Keyboard (IV) 69 147 Color Keyboard (V) 70 148 Color Keyboard (VI) 70 149 Adjustable Voice Changer & Light 70 150 Adjustable Voice Changer & Light (II) 70 151 Play Fast 71 152 Red First 71 153 Adjustable Timer Tone 72 154 Photo Timer Tone 72 155 Delay Lamp 72 156 Adjustable Delay Lamp 72 157 Water Alarm 73

Project # Description Page # 158 Continuity Tester 73 159 High Low Light 73 160 Flicker Clicker 74 161 Fast Flicker Clicker 74 162 Slow Flicker Clicker 74 163 Timer Tone 74 164 Little Battery 75 165 Tiny Battery 75 166 Little Battery Beep 75 167 Capacitors in Series 76 168 Capacitors in Series (II) 76 169 Capacitors in Series (III) 76 170 More Capacitors in Series 76 171 Capacitors in Parallel 77 172 Capacitors in Parallel (II) 77 173 Capacitors in Parallel (III) 77 174 More Capacitors in Parallel 77 175 Resistors in Series 78 176 Resistors in Parallel 78 177 Lots of Resistors in Series 79 178 Lots of Resistors in Parallel 79 179 Be a Loud Musician 80 180 Be a Loud Musician (II) 80 181 Morse Code 81 182 Transistor Audio Amplifier 82 183 Transistor Audio Amplifier (II) 82 184 Make Your Own Parts 83 185 Color Touch Light 83 186 Test Your Hearing 84 187 See the Sound 84 188 See the Spectrum 85

Project Listings

-19-

Project 1 Electronic Keyboard

Placement LevelNumbers

Snappy says the green keyshave approximately doublethe pitch (frequency) of theblue keys. When the blueand green keys have beenaligned using the TUNEknob, then they have(almost) exactly double thepitch, and sound goodtogether because they are inharmony.

Placement LevelNumbers

(1-snap wire is placedunder the speaker)

Project 2 Aligning the KeyboardUse the preceding circuit. Press one of the greenkeys and turn the TUNE knob on the keyboard toadjust the pitch of the tone. The TUNE knob willnot affect the blue keys.

Now turn the TUNE knob while pressing the blueC key and the green C key at the same time.Slowly turn the knob across its entire range, andsee how the sound varies. At most TUNE knobpositions you will notice separate tones from theblue and green keys, but there will be a knobposition where the blue and green tones blendtogether and seem like a single musical note - thisis the best TUNE setting to play songs with. Theblue and green keys are now aligned together.

Snap Circuits® uses electronic blocks that snap ontoa clear plastic grid to build different circuits. Theseblocks have different colors and numbers on themso that you can easily identify them.

Build the circuit shown on the left by placing all theparts with a black 1 next to them on the board first.Then, assemble parts marked with a 2. Then,assemble the part marked with a 3. Note that the 1-snap wire is placed beneath the speaker (SP).Install two (2) “AA” batteries (not included) into eachof the battery holders (B1) if you have not done soalready.

Turn on the slide switch (S1), and press any of thekeys on the keyboard (U26) to hear tones. Twotones may be played at the same time, one tonefrom the blue keys and one tone from the greenkeys. If you press two keys of the same color thenthe higher pitch one will be played.

-20-

To play a song, just press the key corresponding with the letter shown. Ifthere is a “–” after a letter, press the key longer than usual.

Mary Had a Little Lamb E  D C D E E E– D D D– E G G–Ma-ry had a lit-tle lamb, Lit-tle lamb, lit- tle lamb. E D C D E E E E D D E D C–––Ma-ry had a lit-tle lamb, Whose fleece was white as snow.

Row, Row, Row Your Boat C– C– C D E– E D E F G–––Row, row, row your boat, Gen-tly down the stream.C C C G G G E E E C C C G F E D C–––Mer-ri-ly, mer-ri-ly, mer-ri-ly, mer-ri-ly, Life is but a dream.

The Farmer in the Dell––G C C C C C–– D E  E E E

The far-mer in the dell, The far-mer in theE–– G– G A G E C  D E E D D C––dell, Heigh-ho the der-ry-oh, the far-mer in the dell.

Muffin Man D G G A B C G  F# E A A  G F# D D Do you know the muf-fin man, The muf-fin man, the muf- fin man?D G G A  B  G  G G  A  A  D D G–– Do you know the muf-fin man Who lives on Dru-ry Lane?

Twinkle, Twinkle, Little StarC C  G G A A G F F E E D D  C–

Twin-kle, twin-kle, lit-tle star, How I won-der what you are.G G F F E E D– G G F F E E D– Up a-bove the world so high, Like a dia-mond in the sky.C C  G G A A G F F E E D D  C––

Twin-kle, twin-kle, lit-tle star, How I won-der what you are.

Rain, Rain, Go AwayG E G G E G G  E A G G  E Rain, rain, go a-way. Come a-gain some o-ther day.F F D D D F F D G F E D E C C– We want to go out- side and play. Rain, rain, go a-way.

For He’s a Jolly Good Fellow––C E E E D E F E E D D D C D 

For he’s a jol-ly good fel-low, For he’s a jol-ly goodE C  D E E E D E F– A  A G G G F D C––fel-low, For he’s a jol-ly good fel-low, Which no-bo-dy can de- ny.

Ring Around the RosyG G  E A G E F G G E A G ERing a-round the ro-sy, A poc-ket full of pos-ies, F D F D F G G C–Ash-es, ash-es, We all fall down!

Mystery song (see if you recognize it)C C D C F E–C C D C G F–C C C A F F EA# A# A F G F–

Project 3 Be a Musician

Project 4 Be a Musician (II)Use the preceding circuit and songs, but press both the blue and green keysfor each note, at the same time. Try this with the blue and green keys aligned(as per project 2), but also try them at different TUNE knob settings (so thekeys are out of alignment.

-21-

Some songs havebeen modified to makethem easier to play onyour keyboard.

Project 5 Optical Theremin

A theremin is an electronic musical instrument whereyou change the sound by moving your hands aroundnear it (without touching it); using the tiny changesyour hands have on the electromagnetic field of anantenna. This circuit is an optical theremin becauseinstead you adjust the sound by changing the amountof light reaching a photosensor (the photoresistor).

Project 6 Keyboard Slider

Modify the preceding circuit to match this one. Turn on both slideswitches (S1), and move the lever on the adjustable resistor (RV)around to change the sound. At some settings there may not be anysound.

You can play the keyboard (U26) keys while changing the sound withthe adjustable resistor, to get a combination of sound effects. Turn offthe left slide switch to disable the adjustable resistor sound effects.

Build the circuit as shown. Turn on both slide switches (S1), and moveyour hand over the photoresistor (RP). You can adjust the sound justby moving your hand around. See what range of sounds you canproduce, then change the amount of light in the room, and see howsound the range of sounds has changed. There may not be any soundif there is too much or too little light on the photoresistor.

You can play the keyboard (U26) keys while adjusting the sound usingthe photoresistor, to get a combination of sound effects. Turn off the leftslide switch to disable the photoresistor sound effects.

-22-

Project 7 Voice Changer

Placement LevelNumbers

+

Project 9 Color Light

+

LEDs (Light Emitting Diodes)convert electrical energy into light;the color of the light emitteddepends on the characteristics ofthe material used in them.

The color LED actually containsseparate red, green, and bluelights, with a micro-circuitcontrolling them.

Project 8Voice Changer & Light Build the circuit as shown. Turn on the slide switch

(S1), and enjoy the light show from the color LED(D8). For best effects, place the egg LED attachmenton the color LED, and dim the room lights.

Use the preceding circuit, but replace the3-snap wire that is next to the speaker(SP2) with the color LED (D8, “+” to theleft). Now when you press S2 to play therecording, the sound will not be as sound,but the color LED will be flashing.

Build the circuit shown on the left by placing all the parts with a black1 next to them on the board first. Then, assemble parts marked witha 2. Then, assemble the part marked with a 3. Install two (2) “AA”batteries (not included) into each of the battery holders (B1) if youhave not done so already. Be sure to install the microphone (X1)with its “+” side positioned as shown.

Set the 500kW adjustable resistor (RV3) to mid-range, turn OFF theleft slide switch (S1), and then turn on the right slide switch. Nowturn on the left slide switch, you hear a beep signaling that you maybegin recording. Talk into the microphone until you hear a beep(signaling that recording time is over), then turn off the left slideswitch to exit recording mode. Push the press switch (S2) to playback the recording, and turn the knob on RV3 to change theplayback speed. You can play your recording faster or slower bychanging the setting on RV3.

Recording time is 6 seconds at normal speed, but this can bechanged depending on the setting of RV3 when you are making therecording.

Egg LEDAttachment

-23-

Build the circuit as shown, and connect your ownheadphones (not included in this set) to the audiojack (JA). Turn on the bottom slide switch (S1).Talk into the microphone, and listen the echo on yourheadphones. Set the 500kW adjustable resistor (RV3)for most comfortable sound level (turn to the left forhigher volume, most of RV3’s range will be very lowvolume), then adjust the amount of echo using thelever on the adjustable resistor (RV); move the leverup for more echo or down for less echo. Try this atdifferent RV settings, because the effects are veryinteresting with both high and low echo amounts. Alsotry it while saying different words/sounds.Turn on the top slide switch to make the soundlouder, or turn it off to make the sound softer.

Project 10 Echo

Project 11 Echo with Headphones Project 12Louder Echo

withHeadphones

Headphones (not included)

WARNING: Headphones performancevaries, so use caution. Start with low volume,and then carefully increase to a comfortablelevel. Permanent hearing loss may result fromlong-term exposure to sound at high volumes.

!

Turning on the top slide switchadds the 0.1mF capacitor (C2)to the circuit, which increasesthe amplification in the echoIC. With headphones, thesound can be made louderbecause the microhone doesnot pick it up easily.

Build the circuit as shown, and place it in a quietroom. Connect the speaker (SP2) using the red &black jumper wires, and then hold it away from themicrophone (X1). Turn on the slide switch (S1). Talkinto the microphone, and listen the echo on thespeaker. Adjust the amount of echo using the leveron the adjustable resistor (RV); move the lever upfor more echo or down for less echo. Try this atdifferent RV settings, because the effects are veryinteresting with both high and low echo amounts.Also try it while saying different words/sounds.

Note: you must hold the speaker away from themicrophone or the circuit may self-oscillate due tofeedback. You also need a quiet room, with lowbackground noise.

Use the preceding circuit,but replace the 0.1mFcapacitor (C2) with the 1mFcapacitor (C7). The sound islouder now when both slideswitches (S1) are on.

If you hold your headphonesnext to the microphone (X1),you may hear a whiningsound, because theheadphones sound might bepicked up by themicrophone and be echoedagain and again and again.

If the speaker is too close to themicrophone, then the speaker’s soundwill be picked up by the microphone andbe echoed again and again and again,until you can’t hear anything else. Thesame thing can happen if the room is toonoisy, or if you talk too loud.

-24-

Project 13 Sound Energy Demonstration

Pour salt, glitter, or small foam/candyballs (not included) into the container,but do not cover the bottom.

Assemble the Sound energy demonstration container (as per page 4, orshown on next page) if you have not done so already. Build the circuit asshown. Turn off the left slide switch (S1) and turn on the right slide switch.Lay the speaker (SP2) down on the unused 3-snap and 6-snap wires (toelevate it slightly off the table); be sure it is lying flat, and place the soundenergy demonstration container over it. Pour some salt, glitter, small foamor candy balls of 0.1 inch diameter or less (not included) or similar into thecontainer, but not enough to cover the bottom.

Press the keys on the keyboard to make sound. For some keys thesalt/glitter/balls will vibrate and bounce or dance around in the container,find the key that gives the best effects. Most keys will create little or novibration. For the best key, adjust the TUNE knob on the keyboard for besteffects.

Now turn on the left slide switch and move the lever on the adjustableresistor (RV) around. At some positions the salt/glitter/balls will vibrate andbounce or dance around in the container; find the setting that gives thebest effects. Press some keyboard keys to add more sound effects.

Experiment with different materials in the container and see which givethe most impressive results. Our engineers found that nonpareils (rounddecorative candy sprinkles) of up to 0.1” work best.

Try lifting the container a little higher above the speaker with your hands,and see how much this affects the bounce height; see where you get thebest effects. Try it at best key or RV setting, and at other keys/settings.Also, placing the speaker directly on the table (without the 3-snap and 6-snap under it) should reduce the vibration a little, but you can try it to seethe difference.

Try removing the 0.1mF capacitor (C2), and see how the sounds andbounce effects change. Next, remove the sound energy demonstrationcontainer from the speaker and instead lay your hand on it for the bestsetting, you can feel the speaker vibrate.

Don’t eat anything you placed into the sound energy demonstrationcontainer.

The bouncing salt/glitter/balls showthat sound hasenergy! Typically theE keys and the keysnear them give thebest effects, but yourresults may vary.

Lay the speaker on the extra 3-snapand 6-snap wires, to elevate it. Besure speaker lays flat.

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Tube

Flexible sheet

Container base

Speaker

Sound Energy DemonstrationContainer Assembly

(Adult supervision recommended)

Pour salt, glitter, or smallfoam/candy balls into thecontainer, but do not coverthe bottom.

Lay the speaker on the extra 3-snap and 6-snapwires, to elevate it. Be sure speaker lays flat.

Part B: Optical VersionModify the circuit to be this one, which has thephotoresistor (RP) instead of the adjustableresistor (RV).

Turn on both slide switches and wave your handover the photoresistor (RP), to change how muchlight shines into it. The sound changes as yourhand adjusts the light. At some hand positions thesalt/glitter/balls will vibrate and bounce or dancearound in the container; find the hand position thatgives the best effects. Press some keyboard keysto combine their sounds with the photoresistorsound. Try moving to an area with more or lesslight, and wave your hand over the photoresistoragain.

Don’t eat anything you placed into the soundenergy demonstration container.

How does this work? There is a small range offrequency at which the sound waves resonatewith the mechanical constructioncharacteristics of the speaker, and cause thespeaker to vibrate noticeably. The speaker’svibration creates changes in air pressure. Thesound energy demonstration container coversthe speaker and traps the air pressurechanges, which then push/pull the flexiblesheet up/down quickly, making thesalt/glitter/balls bounce. Raising the speakerand container by placing them on the snapwires (or holding them) makes the vibrationsmore noticeable, because otherwise the tablecan dampen the vibrations.

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This project requires stereo headphones or a stereo speaker; neither is includedwith this set, but this set does include a stereo cable to facilitate connection toyour stereo speaker.

Build the circuit as shown. Connect your own headphones or stereo speaker tothe audio jack (JA). Turn on the slide switch (S1).

Press keys on the keyboard (U26) and listen to the sound on your headphonesor stereo speaker. Set the 500kW adjustable resistor (RV3) for most comfortablesound level (turn to the left for higher volume, most of RV3’s range will be verylow volume), and then move the lever on the adjustable resistor (RV) to varythe amplitude to each ear.

Project 14 Keyboard in Stereo

Project 15 Optical Theremin in Stereo

Headphones orStereo Speaker(not included)

In stereo, sound is produced on severalspeakers with varying amplitude on each.This gives the impression that the soundis coming from different directions.

WARNING: Headphones performance varies, so use caution. Start withlow volume, then carefully increase to a comfortable level. Permanenthearing loss may result from long-term exposure to sound at high volumes.!

Use the preceding circuit, but modify it by adding the photoresistor (RP) andthe parts next to it.

Press keys on the keyboard (U26) and wave your hand over thephotoresistor (to adjust the amount of light shining on it) while listening tothe sound on your headphones or stereo speaker. Set the 500kW adjustableresistor (RV3) for most comfortable sound level (turn to the left for highervolume, most of RV3’s range will be very low volume), and move the leveron the adjustable resistor (RV) to vary the amplitude to each ear. There maynot be any sound if there is too much or too little light on the photoresistor.

Close your eyes and have a friend vary the light to the photoresistor andmoving the lever on the adjustable resistor. See if you get an impression ofthe sound changing direction.

WARNING: Headphonesperformance varies, so usecaution. Start with low volume,then carefully increase to acomfortable level. Permanenthearing loss may result fromlong-term exposure to soundat high volumes.

!

Headphones orStereo Speaker(not included)

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Project 16 Light & Sound

Project 17 See Saw

Build the circuit as shown; note that a 2-snap wire is placed directlyunder the speaker (SP2). Turn off the left slide switch (S1) and turn onthe right slide switch. Press keys on the keyboard (U26) to make soundon the speaker (SP2) and light on the color LED (D8). If you hold a keydown then the color LED will change colors.

Now turn on the left slide switch. If there is light on the photoresistor(RP), or if you press keys on the keyboard, then there will be soundfrom the speaker and light from the color LED. Wave your hand overthe photoresistor to change the sound, or turn off left S1 to disablephotoresistor control. Holding a key down will also make the color LEDchange colors.

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Turn on the slide switch (S1), and move the lever on the adjustableresistor (RV) around. The pitch of the sound will be lowest with the leverin the middle position, and higher with it set to the left or right.

You can replace the 5.1kW resistor (R3) with the 100W resistor (R1) or500kW adjustable resistor (RV3), but there may be no sound at somesettings.

Project 18 Light, Sound, & Motion

Use the preceding circuit, but replace the 470mF capacitor(C5) with the 1mF capacitor (C7). The color LED (D8) isbrighter now, but may not be changing colors.

Let’s add motion to the preceding circuit. Modify the circuit to match thisone. Turn off the left slide switch (S1) and turn on the right slide switch.Lay the speaker (SP2) down on unused 2-snap and 6-snap wires (toelevate it slightly off the table), be sure it is laying flat, and place the soundenergy demonstration container over it (the container should have beenassembled as per instructions on page 4). Pour some salt, glitter, smallfoam or candy balls of 0.1 inch diameter or less (not included) or similarinto the container, but not enough to cover the bottom.Press the keys on the keyboard to make sound and light the color LED(D8). For some keys the salt/glitter/balls will vibrate and bounce or dancearound in the container, find the key that gives the best effects. Most keyswill create little or no vibration. For the best key, adjust the TUNE knob onthe keyboard for best effects. The color LED will not be very bright.Now turn on the left slide switch and wave your hand over the photoresistor(RP), to change how much light shines into it. The sound changes as yourhand adjusts the light, and the color LED will light if there is bright light onthe photoresistor. At some hand positions the salt/glitter/balls will vibrate

and bounce or dance around in the container; find the hand position thatgives the best effects. Press some keyboard keys to combine their soundswith the photoresistor sound. Try moving to an area with more or less light,and wave your hand over the photoresistor again.Experiment with different materials in the container and see which givethe most impressive results. Our engineers found that 0.1” round nonpareils (decorative candy sprinkles) work best.Try lifting the container a little higher above the speaker with your hands,and see how much this affects the bounce height; see where you get thebest effects. Try it at best key or RV setting, and at other keys/settings.Also, placing the speaker directly on the table (without the 3-snap and 6-snap under it) should reduce the vibration a little, but you can try it to seethe difference.Add the 0.1mF capacitor (C2) over the keyboard (U26) at base gridlocations D4-F4 (on level 3) and see how the circuit changed, especiallywhen pressing the green keys.

Project 19Brighter Light, Sound, & Motion

Lay the speaker on theextra 3-snap and 6-snapwires, to elevate it. Besure speaker lays flat.

Place the sound energydemonstration container overthe speaker. Pour salt, glitter,or small foam/candy balls (notincluded) into the container,but do not cover the bottom.

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Project 20 Keyboard with Voice Changer

Project 21 Optical Keyboardwith Voice Changer

Project 22

This circuit is similar to the preceding one, but adds opticalcontrol. Modify the preceding circuit by adding thephotoresistor (RP) and the parts next to it.

When making your recording, wave your hand over thephotoresistor to change the sound recorded, in addition topressing keys. The photoresistor may have no effect if there istoo much or too little light on it, so adjust the light on it ifnecessary.

Use either of the preceding circuits,but replace the 3-snap wire that is nextto the speaker (SP2) with the colorLED (D8, “+” to the left). Now whenyou press S2 to play the recording, thesound will not be as sound, but thecolor LED will be flashing.

Set the 500kW adjustable resistor (RV3) to mid-range, turn OFFthe left slide switch (S1), and then turn on the right slide switch.Now turn on the left slide switch, you hear a beep signaling thatyou are recording. Press keys on the keyboard (U26) until youhear a beep (signaling that recording time is over), then turn offthe left slide switch to exit recording mode. Push the pressswitch (S2) to play back the recording, and turn the knob onRV3 to change the playback speed. You can play yourrecording faster or slower by changing the setting on RV3.

The keyboard overhangs the base grid, so be sure theconnections to it stay secure as you are pressing keys.

Recording time is 6 seconds at normal speed, but this can bechanged depending on the setting of RV3 when you are makingthe recording. You won’t hear the notes when you are pressingthe keys during recording; you only hear them during playback.

Keyboard VoiceChanger & Light

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Project 24 Sound Controlled Light

If the adjustable resistor’s lever is set toolow then the color LED will never turnon; if it is set too high then the color LEDwill never turn off.

+

+

Project 23 Voice Changer with Echo

Build the circuit as shown. Turn on the switch (S1) and set the lever onthe adjustable resistor (RV) so the color LED (D8) is just off. Talk loud intothe microphone (X1) or clap loudly near it to activate the color LED. Try along loud “ahhhhhhhh” directly into the microphone; this can make thecolor LED change patterns.

The color LED may not be very bright, so this circuit works best in a dimlylit room.

Build the circuit as shown; note that the microphone (X1) is covering a2-snap wire, and that the 5.1kW resistor (R3) is a tight fit over theadjustable resistor (RV) but does fit. Set the 500kW adjustable resistor(RV3) to mid-range, set the adjustable resistor (RV) lever towards R3,turn OFF the left slide switch (S1), and then turn on the right slideswitch.

Now turn on the left slide switch, you hear a beep signaling that youare recording. Talk into the microphone (X1) until you hear a beep(signaling that recording time is over), then turn off the left slide switchto exit recording mode. Now move the lever on RV to set the echo level,turn the knob on RV3 to change the playback speed, and push thepress switch (S2) to play back the recording. You can play yourrecording faster or slower by changing the setting on RV3, and withmore or less echo by changing the setting on RV.

Recording time is 6 seconds at normal speed, but this can be changeddepending on the setting of RV3 when you are making the recording.RV should be set for no echo when making a recording.

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Project 25 Low Pitch Keyboard Project 26Lower Pitch Keyboard

Project 28Echo Speed Changer

Set the 500kW adjustable resistor (RV3) to mid-range, turn OFF the leftslide switch (S1), and then turn on the right slide switch. Set the echolevel using adjustable resistor (RV). Now turn on the left slide switch, youhear a beep signaling that you are recording. Talk into the microphone(X1) until you hear a beep (signaling that recording time is over), thenturn off the left slide switch to exit recording mode. Push the press switch(S2) to play back the recording, and turn the knob on RV3 to change theplayback speed. You can play your recording faster or slower bychanging the setting on RV3, and with more or less echo by changingthe setting on RV.

Recording time is 6 seconds at normal speed, but this can be changeddepending on the setting of RV3 when you are making the recording.C2 is only used to support RV, so is only connected on one side.

Use the preceding circuit, but replacethe 1mF capacitor (C7) with the 470mFcapacitor (C5, “+” on left). Press one ofthe green keys and hold it down; all youshould hear is a click every few seconds.

Use the preceding circuit, but replace the0.1mF capacitor (C2) with the 1mFcapacitor (C7). The pitch of the green keysis much lower now. See how the blue andgreen keys sound when pressed together.

Build the circuit as shown. Turnoff the left slide switch and turn onthe right slide switch (S1), andpress some of the green keys.Now turn on the left slide switchto add the 0.1mF capacitor (C2) tothe circuit, and press some greenkeys again. The pitch (frequency)of the sound is lower now. Theblue keys will not be affected.

Compare the sound for blue andgreen keys at the same place onthe keyboard (such as C to C, F#to F#, or B to B). Turn the TUNEknob to align a pair of blue/greentogether, or to take them out ofalignment. Experiment to seesome interesting effects.

Adding the 0.1mF capacitor lowers the frequency(pitch) of the sound produced by the green keys,and makes them similar to the blue keys.

Project 27Very Low Pitch Keyboard

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Project 29 Keyboard Echo Project 30Lower Pitch

Keyboard Echo

Project 31 Optical Keyboard Echo Project 32Low Pitch

OpticalKeyboard Echo

Use the precedingcircuit, but add the0.1mF capacitor(C2) or the 1mFcapacitor (C7)across the “CAP”and “(-)” snaps onthe keyboard usinga 1-snap wire. Thepitch of the greenkeys is lower now.

Build the circuit as shown,and turn on the slide switch(S1). Press keys on thekeyboard (U26) and hearthe sound with echo on thespeaker (SP2). RV adjuststhe amount of echo, andRV3 adjusts the volume. Trythis at different RV settings,because the effects arevery interesting with bothhigh and low echo amounts.

Build the circuit as shown,and turn on both slideswitches (S1). Press keys onthe keyboard (U26) or shinelight into the photoresistor(RP) to hear sound with echoon the speaker (SP2). RVadjusts the amount of echo,and RV3 adjusts the volume.Wave your hand over thephotoresistor to adjust thepitch of the “optical” sound.Try this at different RVsettings, because the effectsare very interesting with bothhigh and low echo amounts.There may not be any soundif there is too much or toolittle light on the photo-resistor.

Use the precedingcircuit, but add the0.1mF capacitor(C2) or the 1mFcapacitor (C7)across the “CAP”and “(-)” snaps onthe keyboard. Thepitch of the greenkeys is lower now.

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In this project you will listen to the keyboard sound both withand without echo, at the same time (in stereo). This projectrequires stereo headphones or a stereo speaker; neither isincluded with this set, but this set does include a stereocable to help connect to your stereo speaker.

Build the circuit as shown; note that the 5.1kW resistor (R3)is a tight fit over the adjustable resistor (RV) but does fit.Connect your own headphones or stereo speaker to theaudio jack (JA). Turn on the slide switch (S1).

Press keys on the keyboard (U26), and listen to the soundon your headphones or stereo speaker. One ear (or side ofthe speaker) hears the keyboard directly, set RV3 for mostcomfortable sound level (turn to the left for higher volume,most of RV3’s range will be very low volume). The other ear(or side of the speaker) hears the sound with echo; adjustthe amount of echo using the lever on the adjustable resistor(RV). Try this at different RV settings, because the effectsare very interesting with both high and low echo amounts.

If the echo sound is not loud enough then add the 1mFcapacitor (C7) next the echo IC (U28) as shown here:

For best effects, try to set RV3 so that the sound level isabout equal on both sides of the headphones/speaker.

Headphones or StereoSpeaker (not included)

WARNING: Headphones performance varies, so use caution. Start withlow volume, then carefully increase to a comfortable level. Permanenthearing loss may result from long-term exposure to sound at high volumes.

!

Project 33

The 100W and 5.1kW resistors (R1 &R3) make the keyboard signal smaller,otherwise it would be distorted by theamplifier in the echo IC.

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Keyboard Echo withStereo Effects

Headphones or StereoSpeaker (not included)

The 0.1mF capacitor (C2) isbeing used as a spacer (a1-snap wire) to supportother components.

WARNING: Headphones performance varies, so use caution. Start withlow volume, then carefully increase to a comfortable level. Permanenthearing loss may result from long-term exposure to sound at high volumes.

!

The project is similar to the preceding one, but adds opticalcontrol using the photoresistor (RP). Rebuild the precedingcircuit to match this one. Follow the preceding circuit’sinstructions, except also turn on the slide switch next to thephotoresistor, and then wave your hand over thephotoresistor to change the sound.

The keyboard overhangs the base grid, so be sure theconnections to it stay secure as you are pressing keys.

In the preceding circuit you could add the 1mF capacitor (C7)to make the echo sound louder, but do not have enoughparts to add it to this circuit.

Build the circuit, turn on the slide switch (S1),and push the press switch (S2). The color LED(D8) is on for a while and then shuts off.Turning S1 off and back on will not get the lightback on. Push S2 to get the light back on. Ifdesired, place the egg attachment on the colorLED.

RV is used as a fixed resistor (50kW); somoving its control lever will have no effect.

Project 34 Optical Echo in Stereo

1

Project 35 Color Short Light

The light is on while the 470mF capacitor(C5) is charging, and shuts off when thecapacitor gets fully charged. Pressing S2discharges the capacitor. The charge-uptime is set by the capacitor’s value andresistors R3 and RV.

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Project 36 Keyboard with Optical Theremin Project 37Keyboard with

OpticalTheremin (II)

Project 39Adjustable Dual

Range Keyboard (II)

Project 40Adjustable Dual

Range Keyboard (III)Use the preceding circuit, but replace the1mF capacitor (C7) with the 470mFcapacitor (C5, “+” on left). You will hear aclick at regular intervals. The intervaldepends on the RV setting, it could beseveral per second or many seconds apart.

Build the circuit as shown andturn on the slide switch (S1).Press keys on the keyboard(U26) and move the lever on theadjustable resistor (RV) tochange the sound. Push thepress switch (S2) to change thepitch of the green keys. Theremay not be any sound at somesettings on RV.

Use the preceding circuit, but replacethe 0.1mF capacitor (C2) with the 1mFcapacitor (C7). The pitch of the greenkeys is lower when S2 is pressed.

Use the preceding circuit, butreplace the 1mF capacitor (C7) withthe 0.1mF capacitor (C2). The pitchof the green keys is higher whenS2 is pressed.

Build the circuit as shown andturn on the slide switch (S1).Press keys on the keyboard(U26), wave your hand over thephotoresistor (RP) to adjust theamount of light shining on it, andlisten to the sound. Push thepress switch (S2) to change thepitch of the green keys. Theremay not be any sound if there istoo much or too little light on thephotoresistor.

Project 38 Adjustable Dual Range Keyboard

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Project 41 Your Music with Echo

MP3 player

Project 42 Your Music with Echo and Light

MP3 player

This circuit is similar to the preceding one, exceptit adds light and has lower sound volume. Build thecircuit, and turn on the slide switch (S1). Connecta music device (not included) to the audio jack (JA)as shown, and start music on it. Set the knob onthe 500kW adjustable resistor (RV3) all the way tothe left (for loudest sound).

Set the volume control on your music device for acomfortable sound level, and adjust the amount ofecho using the lever on the adjustable resistor(RV). Try this at different RV settings. The colorLED (D8) will light when the sound is loud enough.

Try with different music, or with the touch-tones onyour cell phone.

Build the circuit, and turn on the slide switch (S1). Connecta music device (not included, but this set does include acable to connect it) to the audio jack (JA) as shown, andstart music on it.

Set the volume control on your music device for acomfortable sound level, and adjust the amount of echousing the lever on the adjustable resistor (RV); move thelever up for more echo or down for less echo. Try this atdifferent RV settings, because the effects are veryinteresting with both high and low echo amounts.

Try with different music, or with the touch-tones on your cellphone.

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Use the circuit from project 43,but replace the 100W resistor(R1) with the color LED (D8, “+”to the left). Now when you pressS2 to play the recording, thecolor LED will be flashing.

Project 43 Your Music Speed Changer

MP3 player

Project 44Your Music

Speed Changer(II)

Project 46 Sound On LightProject 45 Your Music

Speed Changer(III)

Build the circuit as shown. Set the 500kW adjustable resistor(RV3) to mid-range, turn OFF the left slide switch (S1), and thenturn on the right slide switch. Connect a music device (notincluded) to the audio jack (JA) as shown, and start music on it.

Now turn on the left slide switch, you hear a beep signaling thatrecording has started. Wait until you hear a beep (signaling thatrecording time is over), then turn off the left slide switch to exitrecording mode. Push the press switch (S2) to play back therecording, and turn the knob on RV3 to change the playbackspeed. You can play your recording faster or slower by changingthe setting on RV3. Try with different music, or with the touch-tones on your cell phone.

To adjust the volume, adjust it on your music device beforerecording, or see the next project.

Recording time is 6 seconds at normal speed, but this can bechanged depending on the setting of RV3 when you are makingthe recording.

Use the preceding circuit, butreplace the 100W resistor (R1)with a 3-snap wire to make thesound louder, or with the 5.1kWresistor (R3) to make the soundquieter.

Build the circuit as shownand turn on the slide switch(S1). Set the lever on theadjustable resistor (RV) sothe color LED (D8) justshuts off. Talk loudly into themicrophone (X1), blow on it,or clap near it to make theLED flicker on.

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Project 47 Super Optical Keyboard Echo

Project 48Softer Optical

KeyboardEcho

This circuit is shown on the SnapCircuits® Sound box cover; usethat picture to help in building it.

Use the preceding circuit, but remove the1mF capacitor (C7) from the circuit, orswap it with the 0.1mF capacitor (C2), orreplace it with the 470mF capacitor (C5).The sound volume is different now.

Build the circuit as shown. Turn off the left slide switch (S1), andturn on the right slide switch. Press some of the keyboard keysand listen to the echo. Move the lever on the adjustable resistor(RV) to change the amount of echo (up is maximum echo, downis no echo). Try this at different RV settings, because the effectsare very interesting with both high and low echo amounts. Thecolor LED (D8) will light when any green key is pressed, but willnot be very bright.

Now turn on the left slide switch to add the photoresistor (RP) tothe circuit. Wave your hand over the photoresistor to change thesound. Try it with different levels of light shining on thephotoresistor, and at different RV settings.

Project 49 Reflection Detector

Build the circuit and turn theslide switch (S1). Take itinto a dimly lit room, so thatthe color LED (D8) isflashing but there is nosound.

Now hold a mirror directlyover the color LED andphotoresistor (RP). Whenthe mirror reflects the LED’slight into the photoresistor,a tone will be produced,signaling that a reflectionwas detected. The tone willchange as the LED flashes.

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Project 50 Super OpticalKeyboard Echo for

Headphones

Headphones or StereoSpeaker (not included)

WARNING: Headphones performance varies, so use caution. Start withlow volume, then carefully increase to a comfortable level. Permanenthearing loss may result from long-term exposure to sound at high volumes.

!

Build the circuit as shown. This project requires stereoheadphones or a stereo speaker (neither is included).Turn off the left slide switch (S1), and turn on the right slideswitch. Press some of the keyboard keys and listen to theecho. Set the 500kW adjustable resistor (RV3) for mostcomfortable sound level (turn to the left for higher volume,most of RV3’s range will be very low volume). Move thelever on the adjustable resistor (RV) to change the amountof echo (up is maximum echo, down is no echo). Try thisat different RV settings, because the effects are veryinteresting with both high and low echo amounts. Thecolor LED (D8) will light when any green key is pressed,but will not be very bright.

Now turn on the left slide switch to add the photoresistor(RP) to the circuit. Wave your hand over the photoresistorto change the sound. Try it with different levels of lightshining on the photoresistor, and at different RV settings.

Note that the “R” snap on the audio jack is not snappedor connected, so there will not be any sound from the “R”side of your headphones/speaker.

You can replace the 0.1mF capacitor (C2) with the 1mFcapacitor (C7) to lower the pitch of the green keys.

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Sound is a variation in air pressure created by a mechanicalvibration. For a demonstration of this, take a stereo speaker inyour home (the larger the better), lay it on the floor, and startsome music.

1. Place your hand on yourstereo speaker and turn upthe volume. Do you feel thespeaker vibrate?

2. Now place a piece of paperon the speaker; if the sound isloud enough, you will see thepaper vibrate.

3. Take a balloon (not included) and holdit on the speaker. You should feel itvibrating with the sound.

4. Get your parents’ permission for this part,because it could get messy. Place thesound energy demonstration container(which should have been assembled asper instructions on page 4) on the centerof the speaker. Pour some salt, glitter,small foam or candy balls (0.1 inchdiameter or less) or similar into thecontainer, but not enough to cover thebottom. Slowly increase the musicvolume. When the music is at certainfrequencies, the salt/glitter/balls willbounce around in the container.

Stereo Speaker (not included)

If you have a stereo speaker (not included), thenyou can also do the preceding demonstrationusing the sounds from your keyboard (U26). Buildthe circuit as shown, and connect your stereospeaker to it. Start with the left slide switch (S1)turned off and the right switch turned on. Presskeys to find the one that gives the best effects withthe 3 experiments in the preceding project, thenturn the tune knob on the keyboard to see if youcan make the effects even better.

Now turn on the left slide switch to add thephotoresistor (RP) to the circuit. Move your handover the photoresistor to adjust how much lightshines into it, to change the sound to give the besteffects for the 3 experiments in the preceding project.

Project 51 Sound is Air Pressure

Project 52 Sound is Air Pressure -Keyboard

Your Snap Circuits®speaker (SP2) is notpowerful enough touse for this, unlessusing the soundenergy demonstrationcontainer as done inproject 13.

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Project 53 Brightness Adjuster

Project 54 BrightnessLimiters

Resistors are used to control or limit the flow of electricity in a circuit.Higher resistor values reduce the flow of electricity in a circuit.

In this circuit, the adjustable resistor is used to adjust the LED brightness,to limit the current so the batteries last longer, and to protect the LEDfrom being damaged by the batteries.

What is Resistance? Take your hands and rub them together very fast.Your hands should feel warm. The friction between your hands convertsyour effort into heat. Resistance is the electrical friction between anelectric current and the material it is flowing through.

The adjustable resistor can be set for as low as 200W, or as high as50,000W (50kW).

Project 55

Vary the brightness of the colorLED (D8) using the 500kWadjustable resistor (RV3).

Use the preceding circuit, butreplace the 3-snap with one of theyellow resistors in this set (R1 orR3). Observe how each changesthe LED brightness at differentsettings for the adjustable resistor.

Build the circuit and turn on the slide switch (S1). Move the lever on theadjustable resistor (RV) to vary the brightness of the light from the colorLED (D8). If desired, you may place the egg LED attachment on theLED.

Big BrightnessAdjuster

The 500kW adjustable resistor(RV3) can be set for as low as200W, or as high as 500,000W(500kW), so the color LED willonly light on a small portion ofRV3’s range.

The R1 resistor (100W) will havelittle effect, because the adjustableresistor (RV) will always dominateit. Resistor R3 (5.1kW) willdominate when RV is set for lowvalues, but have little effect whenRV is set at high values.

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Photo BrightnessAdjuster

Project 56

Amplified PhotoBrightnessAdjuster

Project 57Amplified Big

Brightness Adjuster

Project 58

Vary the brightnessof the color LED(D8) by varying theamount of lightshining on thephotoresistor (RP).

Vary the brightness of the color LED(D8) by varying the amount of lightshining on the photoresistor (RP). Noticethat you have to cover the photoresistorto make the color LED dim.

Some materials, such as Cadmium Sulfide, change theirresistance when light shines on them. Electronic parts madewith these light-sensitive materials are called photoresistors.Their resistance decreases as the light becomes brighter.

The resistance of your Snap Circuits® photoresistor changesfrom nearly infinite in total darkness to about 1kW when brightlight shines directly on it. Note that a black plastic casepartially shields the Cadmium Sulfide part.

Photoresistors are used in applications such as streetlamps,which come on as it gets dark due to night or a severe storm.

In the preceding circuit the photoresistordirectly controlled the current through thecolor LED. In this circuit the currentthrough the photoresistor is amplified bythe NPN transistor (Q2), so the light onthe photoresistor must get very darkbefore the color LED brightness isreduced.

Vary the brightness of thecolor LED (D8) using the500kW adjustable resistor(RV3). The brightnesswon’t change a lot; youmay need to view it in adark room to notice thedifference. Placing the eggattachment on the colorLED may help to notice thebrightness difference.

Compare this circuit to project 55 (BigBrightness Adjuster). In project 55 thecolor LED was dark for most of RV3’srange. In this circuit the NPN transistor(Q2) amplifies the current throughRV3, so the color LED is bright formost of RV3’s range.

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Project 59 Cup & String CommunicationHow it works: When you talk into the cup, the cupbottom vibrates back and forth from your soundwaves. The vibrations travel through the string bypulling the string back and forth, and then makethe bottom of the second cup vibrate just like thefirst cup did, producing sound waves that thelistener can hear. If the string is tight, the receivedsound waves will be just like the ones sent, andthe listener hears what the talker said.

Telephones work the same way, except thatelectric current replaces the string. In radio, thechanging current from a microphone is used toencode electromagnetic waves sent through theair, then decoded in a listening receiver.

Cups

String

Pencil

Tiny hole Knot

String threadedthrough cup bottom

Taut string

Sound, radio signals, and light all travel through air like waves travel throughwater. To help you understand how they are like waves, you can make a cup& string telephone. This common trick requires some household materials (notincluded with this kit): two large plastic or paper cups, some non-stretchablethread or kite string, and a sharp pencil. Adult supervision is recommended.

Take the cups and punch a tiny hole in the center of the bottom of each witha sharp pencil (or something similar). Take a piece of string (use between 25and 100 feet) and thread each end through each hole. Either knot or tape thestring so it cannot go back through the hole when the string is stretched. Nowwith two people, have each one take one of the cups and spread apart untilthe string is tight. The key is to make the string tight, so it’s best to keep thestring in a straight line. Now if one of you talks into one of the cups while theother listens, the second person should be able to hear what the first personsays.

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Project 60

MP3 player

Project 61Low Power

AudioAmplifier

Project 62 Audio Amplifier with L/R Control

Build the circuit, and turnon the slide switch (S1).Connect a music device(not included) to the audiojack (JA) as shown, andstart music on it. Set thevolume using the lever onthe adjustable resistor(RV). This is a simpleamplifier, so the soundmay not be very loud.

Use the preceding circuit, but replace oneof the battery holders (B1) with a 3-snapwire. The circuit works the same but is notas loud now.

Build the circuit, and connect the 2-snap wire between theB1 battery holders last. Connect a music device (notincluded) to the audio jack (JA) as shown, and start musicon it. Turn on both of the slide switches (S1), and set thevolume using the lever on the adjustable resistor (RV). Thisis a simple amplifier, so the sound may not be very loud.

Turn off either of the slide switches to shut off the left orright outputs of your music device. If the left and rightoutputs of your music signal are the same, then turning offone switch will reduce the volume a little.

When finished, remove the 2-snap wire between thebattery holders to turn off the circuit.

Audio Amplifier

MP3 player

This circuit does not have anon/off switch, because the slideswitches are being used tocontrol the music device outputs.

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Project 63 Your Music without Echo

MP3 player

Project 64Low PowerYour Music

withoutEcho

Here we are using theamplifier inside the echoIC (U28), without addingany echo effects to themusic.

Project 65 Adjustable Music without Echo

MP3 player

Modify the project 63 circuit to include avolume control, the adjustable resistor(RV). It works the same way, but adjust thevolume using the lever on RV.

Build the circuit, and turnon the slide switch (S1).Connect a music device(not included, but this setdoes include a cable toconnect it) to the audiojack (JA) as shown, andstart music on it.

Set the volume control onyour music device for acomfortable sound level. Use the preceding circuit, but

remove the 1mF capacitor(C7) from the circuit, orreplace it with the 0.1mFcapacitor (C2). The volume isnot as loud now.

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Project 66 L/R Music Amplifier

MP3 player The left and right outputs ofyour music device are intendedto control separate speakers,but are combined herebecause you only have oneSnap Circuits® speaker.

This circuit is similar toproject 58 (Amplified BigBrightness Adjuster), butthe color LED will not bequite as bright. In this circuitboth the controlling current(through RV3) andcontrolled current (throughR1) also flow through thecolor LED, reducing theamplification.

Vary the brightness of the color LED (D8) using the 500kW adjustableresistor (RV3).

Build the circuit, and turn on the slide switch (S1).Connect a music device (not included) to the audiojack (JA) as shown, and start music on it. Use thelever on the adjustable resistor (RV) to adjust thevolume for the left and right outputs of your musicdevice; both won’t be loud at the same time.

Project 67 Another Transistor Amplifier

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Build the circuit, and turn on the slide switch (S1).The resistance of the 5.1kW resistor (R3) andmicrophone (X1) determine the pitch (frequency)of the tone.

Push the press switch (S2) to bypass themicrophone, and the tone changes.

Build the circuit, and turn on the slide switch (S1).The color LED (D8) is dimly lit, because theresistance of the microphone (X1) keeps thecurrent low.

Push the press switch (S2) to bypass themicrophone, and the LED gets bright.

You can also try replacing the microphone withthe 5.1kW resistor (R3), to see how theirresistances compare.

Project 69 MicrophoneResistance - Audio

Project 68 MicrophoneResistance - LED

The microphone changes resistance whenexposed to changes in air pressure, such asfrom sound waves or blowing on it. Talkinginto the microphone or blowing on it willchange the LED brightness, but probably notenough for you to notice the difference.

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Project 70 Time Light Project 71Time Light (II)

The 470mF capacitor (C5)can store electricity. Thistimer circuit works by slowlycharging up C5; the colorLED goes out when C5 getsfull. If you replace C5 with C2or C7, the LED will go outalmost immediately becausethese values can’t storenearly as much electricity.

Use the preceding circuit, but replace theadjustable resistor (RV) with the 5.1kW resistor(R3). The circuit works the same way, but thecolor LED can only light over a small part ofRV3’s range, and it gets dim faster.

Build the circuit, and turn on the slideswitch (S1). Push the press switch (S2)and set the 500kW adjustable resistor(RV3) so the color LED (D8) just comeson, then release the press switch. Thecolor LED will be bright for a while andslowly get dim and go out. Push the pressswitch again to reset the color LED’s timer.

You can change RV3’s setting to keep thecolor LED on much longer. The adjustableresistor (RV) is used here as a fixedresistor (of 50kW), so moving its lever willhave no effect.

Use the preceding circuit, but replace theadjustable resistor (RV) with the 5.1kW resistor(R3). The circuit works the same way, but thecolor LED gets dim faster.

Project 72 Easier AdjustTime Light

Build the circuit, and turn on the slideswitch (S1) Push and release the pressswitch (S2). Set the 500kW adjustableresistor (RV3) so the color LED (D8) is onand bright, then wait for it to get dim andgo out. Push the press switch again toreset the color LED’s timer. The brighterthe color LED starts, the faster it gets dim.

The adjustable resistor (RV) is used hereas a fixed resistor (of 50kW), so moving itslever will have no effect.

Project 73Small Adjust Time Light

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Project 74 Day Light Project 75 Lower Day Light

Build the circuit, and turn on theslide switch (S1). Set the knob onthe 500kW adjustable resistor(RV3) all the way to the right. If theroom light is bright then the colorLED (D8) should be off. Cover thephotoresistor (RP) or take thecircuit into a dark room, and thecolor LED should turn on.

Build the circuit, and turn on the slide switch (S1). Blow into themicrophone (X1), and hear it on the speaker (SP2).

This circuit is like thepreceding one, butcan be used indarker rooms. Buildthe circuit, and turnon the slide switch(S1). Set the leveron the adjustableresistor (RV) so thecolor LED (D8) justgets bright. Nowwhen you block thelight to the photo-resistor (RP), thecolor LED will turnoff.

Build the circuit, andturn on the slideswitch (S1). Set thelever on theadjustable resistor(RV) so the colorLED (D8) just getsbright. Now whenyou block the light tothe photoresistor(RP), the color LEDwill turn off. If thecolor LED cannot beturned on or off atany RV setting, thenchange your roomlighting.

Project 76 Dark Light Project 77 Blow Noise

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Listen to theLight Change

Project 78

The color LED actuallycontains separate red, green,and blue lights, with amicrocircuit controlling them.Each time the LED changescolors, the voltage across itchanges. Each time thevoltage changes, you hear a“click” from the speaker.

Project 79Adjustable Listen to

the Light Change

Project 80Bright or Loud?

Turn on the slide switch (S1). The colorLED (D8) changes colors in a repeatingpattern, and you hear a clicking soundfrom the speaker (SP2).

Turn on the slide switch (S1). Set thelever on the adjustable resistor (RV) fordifferent brightness levels on the colorLED (D8). The color LED is bright on amore limited range of RV settings thanin the preceding project, and thespeaker (SP2) is not nearly as loud.

Now push the press switch (S2); theLED is dimmer but the sound is louder.

Turn on the slide switch (S1). Setthe lever on the adjustable resistor(RV) for different brightness levelson the color LED (D8). You alsohear a clicking sound from thespeaker (SP2).

The transistor (Q2) amplifies theLED current, to make the speaker(SP2) sound louder.

When S2 is off the transistor(Q2) has little effect, and thecircuit is similar to project46. With S2 pressed, thetransistor acts as anamplifier, increasing thecurrent through the speaker.The LED current is lower inthis arrangement.

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Project 81 LED Keyboard Control Project 82LED

KeyboardControl (II)

Project 83Photo LEDKeyboardControl

Use the project 81 circuit, but replacethe 5.1kW resistor (R3) with thephotoresistor (RP). Wave your handover the photoresistor or adjust theroom lighting to vary the amount oflight shining on the photoresistor, andlisten to the sounds. You can alsopress keys on the keyboard (U26) toadd more sounds.

Build the circuit, and turn on the slideswitch (S1). You hear a sound patternthat is synchronized with the color LED(D8) flashing. You can press keys on thekeyboard (U26) to change the sound.

Use the preceding circuit, butremove the 5.1kW resistor(R3). Now there is only soundwhen you press keys on thekeyboard, and the sounds forsome keys are different.

Modify the project 81 circuit to matchthis one. Turn on the slide switch (S1)and move the lever on the adjustableresistor (RV) to vary the sounds. Youcan also press keys on the keyboard(U26) to add more sounds.

Project 84 AdjustableLED Keyboard

Control

The color LED turns off briefly when itchanges colors. Here the color LEDcontrols the keyboard through thetransistor (Q2), so when the color LEDturns off, the keyboard sound is alsoturned off. This produces the soundeffects you hear.

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Build the circuit as shown. Place the circuit ina quiet room. Connect the speaker (SP2)using the red & black jumper wires, then holdit away from the microphone (X1). Turn on theslide switch (S1). Talk into the microphone orpress keys on the keyboard (U26), and listenthe echo on the speaker. Adjust the volumeusing the knob on RV3. Adjust the amount ofecho using the lever on RV; move the lever upfor more echo or down for less echo. Try thisat different RV settings, because the effectsare very interesting with both high and lowecho amounts.

Note: You must hold the speaker away fromthe microphone or the circuit may self-oscillatedue to feedback. You also need a quiet room,with low background noise.

Project 85 Capacitor Keyboard Control Project 86CapacitorKeyboard

Control (II)

Adding the capacitor changesthe range of tones producedby the keyboard.

Project 87 Voice & Keyboard Echo

Build the circuit, and turn bothslide switches (S1). You heara sound pattern that issynchronized with the colorLED (D8) flashing. Move thelever on the adjustableresistor (RV) to change thesound produced. You can alsopress keys on the keyboard(U26) to change the sound.

Use the preceding circuit, but replacethe 1mF capacitor (C7) with the 0.1mFcapacitor (C2). The sounds aredifferent now.

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Build the circuit as shown. Place the circuit in a quietroom. Connect the speaker (SP2) using the red & blackjumper wires, then hold it away from the microphone.Turn on the slide switch (S1). Talk into the microphoneor press keys on the keyboard (U26), and listen theecho on the speaker. Adjust the amount of echo usingthe lever on the adjustable resistor (RV); move thelever up for more echo or down for less echo. Try thisat different RV settings, because the effects are veryinteresting with both high and low echo amounts.

The color LED (D8) lights when keys arepressed but will be dim. It is easier to seein a dimly lit room.

Note: You must hold the speaker awayfrom the microphone or the circuit may self-oscillate due to feedback. You also need aquiet room, with low background noise.

Project 88 LED Voice Keyboard Echo

Project 89Photo LEDKeyboard

Echo

Project 90Photo LEDKeyboard

Project 91 Audio Dark Light

Use the preceding circuit, butremove the adjustable resistor (RV)from the circuit. Press keys on thekeyboard (U26), and vary the light tothe photoresistor (RP) to adjust thevolume. There won’t be any echoeffects now.

Use the preceding circuit, butreplace the microphone (X1) with thephotoresistor (RP). As you arepressing keys on the keyboard(U26), vary the amount of lightshining into the photoresistor tochange the sound. Try it usingdifferent settings on the adjustableresistor (RV).

Build the circuit, andturn on the slideswitch (S1). Set theknob on the 500kWadjustable resistor(RV3) to the rightuntil the color LED(D8) is off. Coverthe photoresistor(RP) or take thecircuit into a darkroom, and the colorLED should turn on,and you hearclicking from thespeaker (SP2). Theclicking will not bevery loud.

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Project 92 Oscillator

This circuit is an oscillator, because itproduces a repetitive electrical signal on itsown. You hear it as sound waves from thespeaker. The signal is produced by a circuitinside the keyboard module, but may becontrolled using your Snap Circuits®resistors and capacitors, and the keys onthe keyboard. The keys are actuallyconnecting different resistors inside thekeyboard, similar to the 5.1kW resistor (R3).

Project 93Oscillator (II)

Project 94Oscillator (III)

Project 95Oscillator (IV)

Project 96Oscillator (V)

Use the preceding circuit, butreplace the 1mF capacitor (C7) withthe 0.1mF capacitor (C2). Do youhear anything? The circuit isproducing a high frequency tone,which may be too high for your earsto hear, especially if you are older.

Now remove the 0.1mF capacitorfrom the circuit. This makes thetone even higher frequency, andyou probably won’t hear anythingnow. Dogs have better highfrequency hearing, so maybe yourdog can hear it.

Use the preceding circuit, but replacethe 5.1kW resistor (R3) with the 100Wresistor (R1). The frequency of thesound is higher now, and you hearseveral clicks a second.

Use the preceding circuit, but replacethe 470mF capacitor (C5) with the 1mFcapacitor (C7). The frequency of thesound is much higher now, and you heara continuous tone.

Use the preceding circuit, but replacethe 1mF capacitor (C7) with the 470mFcapacitor (C5). The frequency of thesound is now so low that you just heara click every few seconds.

Use the preceding circuit, but replacethe 0.1mF capacitor (C2) with the 1mFcapacitor (C7). The frequency (pitch)of the sound is lower now.

Build the circuit, and turn the slide switch(S1). You hear a tone. You can also presskeys on the keyboard (U26) to change thesound.

Project 98 Left Right Bright Light

Turn on the slide switch(S1) and move thelever on the adjustableresistor (RV) around.The color LED (D8) isbright if the lever is tothe far left or far right,and dim if the lever is inthe middle.

Project 97Oscillator (VI)

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Project 99 Adjustable Oscillator Project 100AdjustableOscillator

(II)

Project 101AdjustableOscillator

(III)

Project 102AdjustableOscillator

(IV)

Project 103 Water Detector

Use the preceding circuit, butremove the 470mF capacitor(C5) from the circuit. See therange of sounds that thiscircuit can produce.

Use the preceding circuit, butreplace the 1mF capacitor (C7)with the 470mF capacitor (C5).You can hear a clicking soundfor a small part of RV3’sadjustment range.

Use the preceding circuit, butreplace the 0.1mF capacitor(C2) with the 1mF capacitor(C7). The frequency (pitch) ofthe sound is lower now.

Build the circuit, and turn the slide switch(S1). Turn the knob on the 500kWadjustable resistor (RV3) to see the rangeof sounds that can be produced; there willonly be sound for a small part of RV3’srange. You can also press keys on thekeyboard (U26) to change the sound.

Build the circuit, andinitially leave the looseends of the red &black jumper wiresunconnected. Turn onthe slide switch (S1);nothing happens. Nowplace the loose endsof the red & blackjumper wires into acup of water, withouttheir snaps touchingeach other. The colorLED (D8) should beon now, indicating thatyou have detectedwater!

RV’s 500kW adjustmentrange is wide, and theoscillator circuit insidethe keyboard (U26)won’t function over RV’sfull range. At somesettings the circuit mayfunction, but produce toohigh of frequency foryour ears to hear.

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Project 104 Clicker

The color LED turns off briefly whenit changes colors. What you hear inthe speaker is the change in currentas the LED turns on or off.

Build the circuit, and turn the slide switch (S1). The color LED (D8) isflashing, and you hear a clicking sound.

Modify the preceding circuit to be this one, which adds echo effects.Turn on the slide switch (S1) and push the press switch (S2) to see thecolor LED (D8) flashing and hear a clicking sound. When you releasethe press switch, the color LED shuts off but you hear echo effects. Usethe lever on the adjustable resistor (RV) to set the echo level.

Project 105 Clicker with Echo

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Project 106 3V Audio Amplifier

MP3 player

Build the circuit as shown, and place it in a quiet room.Connect the speaker (SP2) using the red & black jumperwires, then hold it away from the microphone (X1). Turn onthe slide switch (S1). Talk into the microphone, and listen theecho on the speaker, and see it on the color LED (D8). Adjustthe amount of echo using the lever on the adjustable resistor(RV); move the lever up for more echo or down for less echo.Try this at different RV settings. You may need to talk louddirectly into the microphone to make the color LED bright.

Note: You must hold the speaker away from the microphoneor the circuit may self-oscillate due to feedback. You alsoneed a quiet room, with low background noise.

Build the circuit, and turn on theslide switch (S1). Connect amusic device (not included) to theaudio jack (JA) as shown, andstart music on it. Turn the knobon the 500kW adjustable resistor(RV3) to adjust the volume.

Project 107 Mini Music Player

To demonstrate how much the transistor wasamplifying the sound, connect the speakerdirectly to the audio jack, as shown here, andstart music on your music device. If you don’thear anything then hold the speaker next toyour ear, or set the volume control on yourmusic device higher.

MP3 player

Project 108 Voice Echo with Light

The transistor (Q2) amplifies thecurrent from your music device, tomake the sound louder. Theresistors (R1 & RV3) andcapacitors (C5 & C7) conditionthe signal to minimize distortion.

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Use the preceding circuit, but add the 0.1mFcapacitor (C2) over the keyboard (U26)using a 1-snap wire, as shown. Press a blueand a green key at the same time, whileturning the TUNE knob.Watch the colors on the colorLED (D8), and listen to thesound. Normally the color LED doesn’t work

when you connect it backwards, but inthis circuit it does. The changingvoltage produced by the keyboardactually goes both ways (positive andnegative), so here the color LED willwork in either direction.

Project 112Backwards Color

SoundUse any of the 3 preceding circuits, but reverse thedirection of the color LED (D8). The circuit works thesame, but the sound may not be as loud and the LEDmay not be as bright.

Use the preceding circuit, but use the 1mFcapacitor (C7) instead of the 0.1mF capacitor(C2). Press a blue and a green key at thesame time, while turning the TUNE knob.Watch the colors on the color LED (D8), andlisten to the sound.

Next, replace the 1mF capacitor (C7) insteadof the 470mF capacitor (C5). Press one ofthe green keys and hold it down. Every fewseconds, the color LED flashes and you heara click from the speaker.

Build the circuit and turn the slide switch(S1). Press any key on the keyboard(U26), but just one key at a time. Thecolor LED (D8) lights (mostly red), andyou hear a tone from the speaker (SP2).

Now press one blue key and one greenkey at the same time, to produce 2tones on the speaker. Watch the colorLED (D8) closely; you should see moregreen and blue color than before. Tryviewing it in a dimly lit room.

Now turn the TUNE knob while pressingthe blue C key and the green C key atthe same time. Slowly turn the knobacross its entire range, and see how theLED color changes.

The spectrum of LED color heredepends on your batteries. With strongbatteries you will see more green andblue. With weak batteries you will mostlysee red.

Project 109 Color SoundNormally the color LED changes colors, but hereit doesn’t, why? The U26 keyboard produces achanging voltage, intended to produce sound onthe speaker. The color LED is designed for usewith a stable voltage (like the batteries); whenused with the changing voltage from thekeyboard, it gets confused and blurs its pattern.

Red is the easiest color for the color LED toproduce, and blue is the hardest. So when thevoltage to it is weak, the more difficult colors getdim first.

The keyboard produces separate tones for theblue and green keys, which are played togetherat the speaker. The two tones are also controlthe color LED. When the tones combine, it iseasier for the color LED to produce green andblue color.

Project 111Color Sound (III)

Project 110Color Sound (II)

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The color LED actually contains separate red, green,and blue LED controlled by a microcircuit. It is designedfor use with a stable voltage (like the batteries); whenused with the keyboard output (a changing voltageintended to produce sound on the speaker), it getsconfused and blurs its pattern. The result appears whitebecause mixing equal amounts of red, green, and bluelight makes white light.

Project 114 Red to White

RV3 controls the voltageto the color LED, throughtransistor Q2. When thevoltage is low, the colorLED only produces red,since that is the easiestcolor for it to produce. Asthe voltage increases,green light is added, thenblue.

Build the circuit and turn the slide switch (S1). Press any key on thekeyboard (U26), but just one key at a time. The color LED appearswhite, and isn’t changing colors like it normally does. If you look closelyat the color LED you can see separate red, green, and blue lights on it,which combine to produce white. This is best seen in a dark room. Youcan also view it with the egg attachment on the color LED, which helpsto blend the LED colors together.

Use the preceding circuit, but replace the 5.1kW resistor (R3) withthe 500kW adjustable resistor (RV3). Press any key on the keyboard(U26), but just one key at a time. Slowly turn the knob on RV3 fromright to left across its range while watching the color LED (D8)closely. Notice how first red gets bright, then green too, then alsoblue. This is best seen in a dark room. You can also try it with theegg attachment on the color LED.

Build the circuit with the black jumper wire connected as shown, and turn it on.Nothing happens. Disconnect the jumper wire and an alarm sounds.

Project 113 White Light

Project 115 Alarm

You could replacethe jumper wire witha longer wire andrun it across adoorway to signal analarm when some-one enters.

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Project 120 Knob Echo

Project 116 Super Voice Echo with Light Project 117Press Echo

Project 118Photo Echo Build the circuit as shown,

turn on the slide switch (S1),and turn the knob on the500kW adjustable resistor(RV3). You hear clicking in thespeaker (SP2), and the colorLED (D8) flashes. Adjust theamount of echo using thelever on the adjustableresistor (RV). Try this atdifferent RV settings.

If you remove the speaker(SP2) from the circuit then thecolor LED (D8) will be a littlebrighter, because the echo IC(U28) isn’t trying to control thespeaker at the same time.

Use the preceding circuit, butreplace the microphone (X1)with the press switch (S2).Set RV3 to max volume (turnit to the left). Press S2 to seelight on the color LED (D8),and hear a clicking soundfrom the speaker (SP2).

Build the circuit as shown, and turn onthe slide switch (S1). Talk into themicrophone, and listen the echo on thespeaker, and see it on the color LED(D8). Set the sound volume using theknob on the 500kW adjustable resistor(RV3). Adjust the amount of echo usingthe lever on the adjustable resistor(RV).

Note: There will only be sound if RV3is set towards the left (most of its rangewill have no sound). Also, at the loudestRV3 setting the circuit may oscillateand make a whining sound; just set theRV3 volume a little lower to stop it.

Use the preceding circuit, but replace the pressswitch (S2) with the photoresistor (RP), Adjustthe amount of light shining on the photoresistorto change the sound and light.

Use the circuit from project 117 (with S2) or 118(with RP), but replace RV3 with a 3-snap wire. Thesound will be louder but the light will be dimmer.

Project 119 Loud PressPhoto Echo

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Project 121 Echo Light Headphone Project 122Echo Light

Headphone Variants

Headphones (not included)

WARNING: Headphones performance varies, so use caution. Start withlow volume, then carefully increase to a comfortable level. Permanenthearing loss may result from long-term exposure to sound at high volumes.

!

Project 123 Press Echo Light Project 124Photo Echo Light

+

Use the preceding circuit, butreplace the press switch with thephotoresistor (RP). Adjust theamount of light shining on thephotoresistor to change the soundand light. You may need a bigdifference in brightness to noticethe effects.

Next, replace the photoresistor withthe microphone (connect the “+”side to the echo IC (U28)). Talkloudly directly into the microphoneto flash the light and hear yourvoice on the speaker (SP2), butyour voice will be badly distorted.

Build the circuit as shown, andturn on the slide switch (S1).Push the press switch (S2) tosee light on the color LED (D8),and hear a clicking sound fromthe speaker (SP2). Adjust theamount of echo using the leveron the adjustable resistor (RV).

Use the preceding circuit, butreplace the microphone (X1) withthe press switch (S2). Press S2 tosee light on the color LED (D8),and hear a clicking sound fromyour headphones.

Next, replace the press switch with thephotoresistor (RP), Adjust the amountof light shining on the photoresistor tochange the sound and light.

You can use a stereo speaker (notincluded) instead of headphones.When using it with the microphone(X1), you may need to lower thevolume to prevent feedback intothe microphone.

Build the circuit as shown, and connect yourown headphones (not included) to the audiojack (JA). Turn on the slide switch (S1).

Talk into the microphone, and listen theecho on your headphones, and see it onthe color LED (D8). Set the 500kWadjustable resistor (RV3) for mostcomfortable sound level (turn to the left forhigher volume, most of RV3’s range will bevery low volume); then adjust the amountof echo using the lever on the adjustableresistor (RV). Only the left side of yourheadphones will have sound.

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+Project 126 Daylight Voice Echo

Note that there is a 4-snap wire under Q2, partially hidden. Place the circuit in a quietroom with bright light shining into the photoresistor (RP). Connect the speaker (SP2)using the red & black jumper wires, then hold it away from the microphone (X1). Turnon the slide switch (S1). If the speaker makes a whining sound that does not stop, thenyou need brighter light on the photoresistor, or the room is too noisy.

Talk into the microphone, and listen the echo on the speaker. Now block the light to thephotoresistor to turn off the circuit; slowly wave your hand over it to turn the echo on andoff. You can adjust the amount of echo using the lever on the adjustable resistor (RV).

Build the circuit as shown, and turn on the slide switch (S1). Talk into themicrophone (X1) to light the color LED (D8) and hear your voice on the speaker(SP2). Adjust the amount of echo using the lever on the adjustable resistor(RV).

Next, replace the microphone with the press switch (S2). Push the press switchto see light on the color LED, and hear a clicking sound from the speaker.

Project 125 Another Voice Echo Light

The photoresistor controls power tothe echo IC (U28), and acts as anon/off switch. If there is some light onit but not bright light, it may onlypartially turn on the echo IC, causingthe echo IC to malfunction.

Also, you must hold the speakeraway from the microphone or thecircuit may self-oscillate due tofeedback. You also need a quietroom, with low background noise.

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Project 127 Dark Voice Echo

Project 128 Project 129Dark EchoVariants

Use either of the preceding twocircuits, but replace the microphone(X1) with the press switch (S2) or500kW adjustable resistor (RV3). PressS2 or turn the knob on RV3 to changethe sound or light.

Modify the preceding circuit to match thisone; it uses the color LED (D8) instead ofthe speaker (SP2). Turn on the slide switch(S1); nothing will happen unless the room isdark. This circuit only works if there is nolight on the photoresistor (RP).

Cover the photoresistor, talk into themicrophone, and see the light flash. You canadjust the amount of echo using the leveron the adjustable resistor (RV). Shine lighton the photoresistor to shut off the circuit.

If the color LED never turns off, then youneed to block light from the photoresistorbetter.

Build the circuit as shown, and place it ina quiet room. Connect the speaker (SP2)using the red & black jumper wires, thenhold it away from the microphone (X1).Turn on the slide switch (S1); nothing willhappen unless the room is dark. Thiscircuit only works if there is no light on thephotoresistor (RP).

Cover the photoresistor, talk into themicrophone, and listen the echo on thespeaker. You can adjust the amount ofecho using the lever on the adjustableresistor (RV). Shine light on thephotoresistor to shut off the circuit.

If the speaker makes a whining sound that doesnot stop, then you need to block light from thephotoresistor better, or the room is too noisy.

The photoresistor controls power to theecho IC (U28), and acts as an on/off switch.If the photoresistor is not dark enough, itmay only partially turn on the echo IC,causing the echo IC to malfunction.

Also, you must hold the speaker away fromthe microphone or the circuit may self-oscillate due to feedback. You also need aquiet room, with low background noise.

Dark Echo Light

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Project 130 Day Echo Light Project 131Day EchoVariants

Project 132Photo Light Timer

Build the circuit, and turnon the slide switch (S1). Ifthere is light on thephotoresistor (RP) thenthe color LED (D8) will beon. Block the light to thephoto-resistor, and thecolor LED should slowlyget dimmer and dimmer.

Use the preceding circuit, but replace themicrophone (X1) with the press switch (S2)or 500kW adjustable resistor (RV3). PressS2 or turn the knob on RV3 to change thelight.

You can also replace the color LED (D8)with the speaker (SP2). When used with themicrophone, you must connect the speakerusing the red & black jumper wires and holdit away from the microphone, and also omitC7.

Build the circuit as shown, andplace it where there is bright lightshining into the photoresistor(RP). Turn on the slide switch(S1). If the color LED neverturns off, then you need brighterlight on the photoresistor.

Talk into the microphone, andsee the color LED (D8) flash.Now block the light to thephotoresistor to turn off thecircuit; slowly wave your handover it to turn the echo on and offwhile talking. You can adjust theamount of echo using the leveron the adjustable resistor (RV).

Project 133Adjustable Photo Light Timer

This circuit is similar to thepreceding one, except the colorLED (D8) stays on longer whenyou block the light to thephotoresistor (RP). Use the leveron the adjustable resistor (RV) toset how long the color LED willstay bright after the photoresistoris covered.

The 470mF capacitor (C5)stores up some electricity,and releases it when youblock the light.

The resistance of RVslows down the dis-charging of the 470mFcapacitor (C5).

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Project 135Tone Stoppers (II)

The sound is a littlelouder now becausethe larger 1mFcapacitor passesmore of the tonethan the smaller0.1mF capacitor did.

Project 136Tone Stoppers (III)

The sound is much louder now becausethe larger 470mF capacitor passesmuch more of the tone than the smaller1mF capacitor did. Now pressing S2does not increase the sound, becauseC5 is already passing all of it.

C7 will give less change onhigh frequency tones thanon low frequency tones; youshould be able to notice thedifference as you vary thetone using RV3. The smallerC2 will affect both high andlow tones a lot. The largerC5 will have little effect onboth high and low tones.

Use the circuit from project 135 (with the 1mF capacitor (C7)), butadd the 500kW adjustable resistor (RV3) as shown here. Slowlyturn RV3’s knob to vary the pitch (frequency) of the tone fromlowest to highest possible (there will only be sound for a smallpart of RV3’s range). At the same time, press S2 on and offseveral times, to see how C7 is changing on the sound.

Next, replace C7 with smaller C2 or larger C5, and compare thecapacitor’s effect as you vary the tone frequency.

Use the preceding circuit, but replacethe 1mF capacitor (C7) with the muchlarger 470mF capacitor (C5). Comparethe sound volume to the precedingcircuits. How much difference doespressing S2 make now?

Use the preceding circuit, but replacethe 0.1mF capacitor (C2) with thelarger 1mF capacitor (C7). Comparethe sound volume to the precedingcircuit.

Build the circuit and turn the slide switch (S1). Press any key on thekeyboard (U26). You hear a tone from the speaker (SP2), though it maynot be very loud.

Now push the press switch (S2) while pressing the same key. Thesound is louder now, because the press switch bypassed the 0.1mFcapacitor.

Project 134 Tone Stoppers

Capacitors can store electricity in small amounts. Thisstorage ability allows them to block stable electrical signalsand pass changing ones, making them useful in filtering anddelay circuits. Capacitors with higher values have morestorage capacity, and can pass changing signals more easily,

In this circuit the 0.1mF capacitor blocks most of the keyboardtone signal. You can hear the difference when you press S2to bypass the capacitor.

Project 137Tone Stoppers (IV)

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Project 138 Tone Stoppers (V)

Project 140 Voice Changer with Headphones

WARNING: Headphones performance varies, so use caution. Start withlow volume, then carefully increase to a comfortable level. Permanenthearing loss may result from long-term exposure to sound at high volumes.

!Headphones or Stereo Speaker (not included)

This project requires stereo headphones or a stereo speaker (neitherincluded); connect them to the audio jack (JA). Set the 500kW adjustableresistor (RV3) to mid-range. Turn on both slide switches (S1), you hear abeep signaing that you may begin recording. Talk into the microphone untilyou hear a beep (signaling that recording time is over), then turn off the leftslide switch to exit recording mode. Push the press switch (S2) to play backthe recording and flash the color LED (D8), and turn the knob on RV3 tochange the playback speed. You can play your recording faster or slower bychanging the setting on RV3.

Adjust the volume to your headphones or stereo speaker using the lever onthe adjustable resistor (RV).

Recording time is 6 seconds at normal speed, but this can be changeddepending on the setting of RV3 when you are making the recording.

In project 137, there is only sound fora small part of RV3’s range, whichcan be difficult to tune. To help,modify the circuit to add theadjustable resistor (RV) in series withRV3, as shown. Slowly adjust RVand RV3 to vary the tone from lowestto highest possible, while pressingS2 on and off, to see how thecapacitors (C7, or C2 or C5) changethe sound.

You can also replace RV3 with thephotoresistor (RP). Set RV to the left,and then adjust the tone by varyingthe light to RP, while comparing theeffects of the capacitors.

Build the circuit with the blackjumper wire connected asshown, and turn it on.Nothing happens. Disconnectthe jumper wire and the colorLED (D8) comes on,signalling an alarm.

RV is moresensitive and canbe adjusted from200W to 50kW,compared to200W to 500kWfor RV3.

Project 139 Alarm Light

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Build the circuit (note that there is a 4-snap wire under Q2, partiallyhidden) and turn the slide switch (S1). Press any key on the keyboard(U26) and set the 500kW adjustable resistor so the sound just shuts off.Now block the light to the photoresistor (RP) and press some keys toplay tones.

Build the circuit (note that there is a 4-snap wire under Q2, partiallyhidden) and turn the slide switch (S1). Press keys on the keyboard(U26). This keyboard only works during the day, so you have to havelight on the photoresistor or there won’t be any sound. If you cover thephotoresistor or place the circuit in a dark room then it won’t work. If thelight is dim then the sound may be abnormal.

Project 141 Day Keyboard

Project 142 Night Keyboard

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Build the circuit and turn the slide switch (S1). Press and hold down anygreen key on the keyboard (U26), and see what happens.

Project 143 Color Keyboard

Project 145 Color Keyboard (III)

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Project 144 Color Keyboard (II)

Modify the preceding circuit byadding the adjustable resistor(RV) as shown here. Turn theslide switch (S1). Move the leveron the adjustable resistor around;best effects are when it is to theleft. Press keys on the keyboard(U26) at the same time. You willsee some cool effects.

Build the circuit and turn the slide switch (S1). Press and hold down anygreen key on the keyboard (U26), and see what happens.

Project 146 Color Keyboard (IV)

Modify the preceding circuit byadding the 100W resistor (R1) andreplacing the 1mF capacitor (C7)with the 470mF capacitor (C5), asshown here. Turn the slide switch(S1) to see some cool effects.Press any of the blue keys formore effects. Pressing the greenkeys won’t do anything.

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Project 147 Color Keyboard (V) Project 148Color Keyboard

(VI)

Project 149 Adjustable Voice Changer & Light Project 150Adjustable

VoiceChanger &Light (II)

Use the precedingcircuit, but swap thelocations of the speaker(SP2) and color LED(D8). Now the colorLED is at full brightnessduring playback, andRV adjusts the soundvolume.

Set the 500kW adjustable resistor (RV3) to mid-range. Turn on both slide switches (S1), you heara beep signaling that you may begin recording.Talk into the microphone until you hear a beep(signaling that recording time is over), then turnoff the left slide switch to exit recording mode.Push the press switch (S2) to play back therecording, and turn the knob on RV3 to changethe playback speed. You can play your recordingfaster or slower by changing the setting on RV3.

Move the lever on the adjustable resistor (RV) tochange the brightness of the color LED (LED)during playback. Most of RV’s range will give littleor no LED brightness.

Recording time is 6 seconds at normal speed, butthis can be changed depending on the setting ofRV3 when you are making the recording.

Use the preceding circuit, but replace the1mF capacitor (C7) with the 0.1mF capacitor(C2). The sound is a little different now, andthe green keys can change it.

Turn on the slide switch (S1).Move the lever on theadjustable resistor (RV) aroundnear the left (not the middle orright). Press any of the bluekeys for more effects. Pressingthe green keys may not doanything.

Build the circuit and turn the slide switch (S1). Push the press switch(S2) and play keys on the keyboard (U26). Play fast, because thiskeyboard will only work for a few seconds! Push S2 again to restart thekeyboard and its timer.

Turn on the slide switch (S1). Set the lever onthe adjustable resistor (RV) all the way to theleft. The color LED (D8) should be on, but maybe mostly red. Slowly move the lever on RV tothe right until the LED is completely off. Noticethat the red color stays on the longest.

Now push the press switch (S2) and adjust RVagain, watching the LED colors. Blue and greencolor may also appear now, but may go dimbefore red does.

Now move S1 from the points marked C & D tothe points marked A & B. Move RV’s leveraround again, watching the LED colors andbrightness. Try pushing S2 again, but it won’tmake as much difference now.

Project 151 Play Fast

Project 152 Red FirstThe voltage needed to turn on an LEDdepends on the light color. Red needs theleast voltage, and blue needs the most.With S1 at points C & D and S2 off, thevoltage to the color LED is lowest, and maybarely be enough to turn on the red color.Pressing S2 bypasses the NPN transistor(Q2), and boosts the LED voltage a little.Shifting S1 to points A & B increases thecircuit voltage from 3V to 6V, making theLED work for a greater part of RV’s range.

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Project 153 Adjustable Timer Tone Project 154Photo Timer

ToneNote that there is a 3-snap wireunder Q2, partially hidden. Turnon both slide switches (S1) andpush the press switch (S2). Youhear a tone, which turns off aftera while. Push S2 again to restartthe keyboard and its timer. Usethe adjustable resistor (RV) to sethow long the timer keeps thesound on for, it can be set for afew seconds or very long. Youcan change the tone that plays bypressing keys on the keyboard(U26).

Turning off the left slide switchturns off the tone, but not the keysor timer.

Use the preceding circuit, but replacethe 5.1kW resistor (R3) with thephotoresistor (RP). The circuit worksthe same way, but you can vary thepitch of the tone by adjusting theamount of light on the photoresistor.

Project 156AdjustableDelay Lamp

Use the preceding circuit, but replaceadjustable resistor (RV) with the500kW adjustable resistor (RV3). Setthe knob on RV3 to different positions,press S2 to start the timer, and seehow long it takes for the color LED toturn on. Turning RV3’s knob clockwisegives longer delay, turning counterclockwise gives shorter delay.

Project 155 Delay Lamp Push and release the press switch (S2), then turn on theslide switch (S1). Nothing happens at first, but after a fewseconds the color LED (D8) turns on. Press S2 to turn off D8and reset the delay timer.

The adjustable resistor (RV) is used as a fixed resistor, andmoving its lever won’t have any effect.

This circuit works because capacitor C5can store electricity. When you turn on thecircuit, electricity flows through resistor RVinto C5. When C5 gets full, electricity startsflowing into transistor Q2, which turns onthe color LED. Pressing S2 empties C5,and resets the timer. Capacitors C2 andC7 also store electricity, but only smallamounts; if used in this circuit they wouldappear to fill up instantly.

RV3 controls how fast electricity flowsinto capacitor C5. Increasing RV3’svalue makes it take longer to chargeup C5.

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Turn on both slide switches (S1). Move the lever onthe adjustable resistor (RV) all the way to the left orright, and watch the brightness of the color LED (D8).The light should be a little brighter when RV’s lever isto the left.

Now move RV’s lever toward one side, but not all theway. There should be a larger difference between thesame positions on the left compared to the right.

Project 158Continuity

Tester

Use the preceding circuit,but instead connect theloose ends of the jumperwires to differentmaterials in your home. Ifyou hear sound, then thematerial you tested haslow resistance and is agood conductor ofelectricity.

Project 159 High Low LightThe left side of RV is connected to 6V, whilethe right side is only connected to 3V; so thecolor LED will be brighter when RV’s leveris to the left. Moving the lever toward themiddle increases the resistance in thecircuit, and the higher voltage left side willbe less affected than the right side.

Project 157 Water AlarmBuild the circuit, and initially leave the looseends of the red & black jumper wiresunconnected. Turn on the slide switch (S1);nothing happens. Now place the loose endsof the red & black jumper wires into a cup ofwater, without their snaps touching eachother. You should hear a tone now, indicatingthat you have detected water!

Don’t drink any water used here.

You could place this circuitin your basement, then it willsound an alarm if yourbasement starts to floodduring a storm.

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Project 161Fast Flicker

ClickerTurn on the slide switch(S1). Move the lever onthe adjustable resistor(RV) around to make thecolor LED (D8) flicker andmake clicking or buzzingon the speaker (SP2).Press keys on thekeyboard (U26) for morefun effects. Try pressing ablue key and a green keyat the same time, whilemoving RV’s leveraround.

Use the preceding circuit, but replace the1mF capacitor (C7) with the smaller 0.1mFcapacitor (C2). It works the same way, butthe tone has higher pitch, and the colorLED may appear to be on continuously.

Project 162Slow Flicker

ClickerUse the preceding circuit, butreplace the 1mF capacitor (C7)with the larger 470mF capacitor(C5). With RV set to the left,the LED flashes and thespeaker clicks about once asecond. As you move RV’slever toward the right, the timebetween flashes/clicksincreases and can get verylong. Also try holding down oneof the blue keys; best effectsare when RV is set toward theleft.

Turn on the slide switch (S1) andpush the press switch (S2). Youshould hear a tone; adjust its pitchusing the adjustable resistor (RV).The tone shuts off after about 10seconds. Push S2 again to re-startthe keyboard and its timer.

Some settings on RV may notproduce any sound. Press S2 andset RV to where you hear sound.

Project 160 Flicker Clicker

If the speaker is buzzingand the color LED is onbut not flashing, then thecolor LED is probablyflashing so fast that it justappears as a blur.

Project 163 Timer Tone

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Project 164 Little BatterySet the knob on the 500kW adjustable resistor (RV3) to theleft. Place the color LED (D8) across the points marked B &C (“+” to B); the LED lights as the capacitor charges. Next,place the color LED across points A & B (“+” to A) instead;now the LED lights as the capacitor discharges. Move thecolor LED back to B & C and repeat. Use the knob on RV3to vary the charge / discharge rate, but keep it close to theleft (otherwise the LED would be too dim to see).

The capacitor is storing energy like a little battery.

Project 165Tiny Battery

Use the preceding circuit, butreplace the 470mF capacitor (C5)with the smaller 1mF capacitor(C7). Set RV3 all the way to theleft. Place the color LED across B& C to charge C7, then across A& B to discharge it. The LED willonly flash for a moment, becauseC7 can’t store much electricity(C5 holds 470 times more). TheLED is easier to see in a dimly litroom.

Set the knob on the 500kW adjustableresistor (RV3) to mid-range. Place the470mF capacitor (C5) across thepoints marked B & C (“+” to C), thenSWING its “+” side around to point A(without unsnapping it from point B).Swing its “+” side between points C &A several times.

When the capacitor (C5) touches pointC, the color LED (D8) flashes to showthat the batteries charged up thecapacitor. When the capacitor touchespoint A, you hear beep from thespeaker (SP2) to show that the audiocircuit discharged the capacitor.

You can change the “beep” sound alittle by turning the knob on RV3.

Batteries can hold a lotmore electricity thancapacitors becausebatteries store chemicalenergy while capacitorsstore electrical energy.

Project 166 Little Battery BeepThe capacitor is storingenergy like a little battery.The “beep” you hear is thevoice changer (U27) enteringrecording mode, but youcan’t make any recordingwith this circuit. Capacitor C5can’t store enough electricityto operate the voice changercircuit, but it can power it longenough to make a beep.

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Project 168Capacitors

in Series (II)Turn on the right slide switch (S1). Pressany green key and compare the sound withthe left slide switch on or off.

With the left switch off, the 0.1mF and 1mFcapacitors (C2 & C7) are connected inseries. Turning on the left switch bypassesthe 0.1mF capacitor. Notice that having the0.1mF included has a big effect on the tone.

Use the preceding circuit,but swap the locations ofthe 0.1mF and 1mFcapacitors (C2 & C7).Press any green key andcompare the sound with theleft slide switch on or off.

The tone does notchange nearly as muchas in the precedingcircuit. When capacitorsare connected in series,the smaller valuedominates the circuit.

Use the project 167 circuit, but replace the 0.1mFcapacitor (C2) with the much larger 470mFcapacitor (C5). Press any green key and comparethe sound with the left slide switch on or off.

Now the tone is the same whether the left switchis on of off, because connecting the large 470mFin series with the small 1mF has little effect on thetotal capacitance.

Swap the locations of the 1mF and 470mFcapacitors (C7 & C5). Press any green key andcompare the sound with the left slide switch on oroff (When the switch is off, hold down the key,because you will only hear a click every fewseconds.) Now turning on the left switch has a bigeffect on the circuit, because connecting the small1mF in series with the large 470mF greatlyincreases the total capacitance.

Turn on the right slideswitch (S1). Press anygreen key andcompare the soundwhen you remove oneor two of the capacitors(C2, C5, and C7) andreplace them with a 3-snap wire. You will onlyhear a click every fewseconds if C5 is theonly one in the circuit.

Project 170 More Capacitors in SeriesProject 169Capacitors in Series (III)

Project 167 Capacitors in Series

Think of capacitors asstorage tanks for electricity.If you place a small storagetank in series with a bigone, electricity flows intoboth at the same time, butthe small one fills upquickly and stops the flow.

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Project 171 Capacitors in Parallel Project 172Capacitors inParallel (II)Turn on the right slide switch (S1). Press

any green key and compare the sound withthe left slide switch on or off.

With the left switch on, the 0.1mF and 1mFcapacitors (C2 & C7) are connected inparallel. Turning off the left switchdisconnects the 0.1mF capacitor. Notice thathaving the 0.1mF included has only a smalleffect on the tone.

Use the precedingcircuit, but swap thelocations of the 0.1mFand 1mF capacitors (C2& C7). Press any greenkey and compare thesound with the left slideswitch on or off.

The tone changesmuch more now than inthe preceding circuit.When capacitors areconnected in parallel,the larger valuedominates the circuit.

Think of capacitors asstorage tanks for electricity. Ifyou place a large storagetank in parallel with a big one,electricity flows into both atthe same time, but keepsflowing until both are full.

Use the project 171 circuit, but replace the 0.1mFcapacitor (C2) with the much larger 470mF capacitor(C5). Press any green key and compare the soundwith the left slide switch on or off. (When the switch ison, hold down the key, because you will only hear aclick every few seconds.)

Turning on the left switch has a big effect on the circuit,because connecting the large 470mF in parallel withthe small 1mF greatly increases the total capacitance.

Swap the locations of the 1mF and 470mF capacitors(C7 & C5). Press any green key and compare thesound with the left slide switch on or off. Now the toneis the same whether the left switch is on of off,because connecting the small 1mF in parallel with thelarge 470mF has little effect on the total capacitance.

Turn on the rightslide switch (S1).Press any greenkey and comparethe sound whenyou remove oneor two of thecapacitors (C2,C5, and C7). Youwill only hear aclick every fewseconds if C5 is inthe circuit.

Project 174 More Capacitors in ParallelProject 173Capacitors in Parallel (III)

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Turn on the right slide switch(S1). Set the lever on theadjustable resistor (RV) to eachside and compare the soundwith the left slide switch on or off.

With the lever up, RV is a 200Wresistor. Turning the left switchoff connects this in series withthe 5.1kW resistor (R3), andhas a small effect on the tone.

With the lever down, RV is a50kW resistor. Turning the leftswitch off connects this inseries with the 5.1kW resistor(R3), and has a big effect onthe tone.

Turn on the right slide switch (S1). Set thelever on the adjustable resistor (RV) toeach side and compare the sound with theleft slide switch on or off. If there is nosound when the lever is set all the way up,adjust it down a little until there is sound.

With the lever up, RV is a 200W resistor.Turning the left switch off connects this inparallel with the 5.1kW resistor (R3), andhas a big effect on the tone.

With the lever down, RV is a 50kW resistor.Turning the left switch off connects this inparallel with the 5.1kW resistor (R3), andhas a small effect on the tone.

Pressing any of the green keys now willchange the tone, by connecting resistorsinside the keyboard in parallel with yourR3-RV resistor network.

Project 175 Resistors in Series

Project 176 Resistors in ParallelThink of resistors asobstructions to the flow ofelectricity. When there is onlyone path for electricity andpart of it has a bigobstruction, not much willflow. When there are severalpaths for electricity and onehas a big obstruction, a lotwill flow because most willflow through theunobstructed path.

Inside the keyboard module (U26) is anoscillator circuit that produces separatetones for the blue and green keys. Thefrequency (pitch) of the tone is set usingan internal resistor-capacitor network,with each key representing a differentresistor value. The green keys can beadjusted using the tune knob.

The tone of the green keys can also bechanged using external resistors andcapacitors, which is done in many of theprojects.

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Turn on the right slide switch (S1).There are five resistors (R1, R3, RV,RV3, and RP), connected in parallel,that are controlling the current to thecolor LED (D8). See which resistorhas the most effect on the LEDbrightness, by removing them one ata time. The resistance of RV and RV3depends on their setting, so try themat different settings.

These five resistors are allconnected in parallel, so thesmallest one (R1, 100W),will have the most effect.

Turn on the slide switch (S1). There are fiveresistors (R1, R3, RV, RV3, and RP),connected in series, that are controlling thecurrent to the color LED (D8). See whichresistor has the most effect on the LEDbrightness, by replacing them with a 3-snapwire or the red/black jumper wires, one at atime. The resistance of RV and RV3 dependson their setting, so try them at differentsettings. Note that the photoresistor’s (RP’s)resistance can be very high if there isn’t brightlight shining on it.

Project 177 Lots of Resistors inSeries

Project 178 Lots of Resistors inParallel

These five resistors are allconnected in series, so thehighest value, will have themost effect.

Swapping the locations of anyparts in the circuit (withoutchanging the direction of their“+” side) will not change howthe circuit works. Try it.

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Project 179 Be a Loud Musician

Project 180Be a Loud Musician (II)

Use the preceding circuit and songs, but press both the blue andgreen keys for each note, at the same time. Try this with the blue andgreen keys aligned (as per project 2), but also try them at differentTUNE knob settings (so the keys are out of alignment.

It’s Raining, It’s Pouring:A G E A G E G G E A G E E It’s rain-ing, it’s pour-ing, Rain-y days aren’t bor-ing. We

F F D D F F D D G F E D E Clike to jump, we like to splash, Let’s hope it rains till mor-ning.

Jingle BellsE E E E E E E G C D E–

Jin-gle bells, jin-gle bells, Jin-gle all the way,

F F F F F E E E E C G F D C–Oh what fun it is to ride in a one horse o-pen sleigh.

London Bridge is Falling DownG A G F E F G D E F E F G

Lon-don Bridge is fal-ling down, Fal-ling down, fal-ling down.

G A G F E F G D– G– E C–Lon-don Bridge is fal-ling down, My fair la-dy.

If You’re happy and You Know ItC C F F F F F F E F G–If your’re hap-py and you know it, clap your hands.

C C G G G G G G F G A–If your’re hap-py and you know it, clap your hands.

A A A# A# A# A# D D A# A# A A A G F F–If you’re hap-py and you know it, And you real-ly want to show it,

A# A# G G G F E C D E F–If your’re hap-py and you know it, clap your hands.

A Tisket, A TasketE G E F G E G C E A G E E A tis-ket a tas-ket, A green and yel-low bas-ket

F F D D F F D D G F E D E C–I wrote a let-ter to my love and on the way I dropped it.

Let’s play some more songs. Build the circuit shown here (it is similarto the project 1 circuit, but louder), and turn on the slide switch (S1).

For best song quality, align the blue and green keys together: Turn theTUNE knob while pressing the blue C key and the green C key at thesame time. Slowly turn the knob across its entire range, and see howthe sound varies. At most TUNE knob positions you will noticeseparate tones from the blue and green keys, but there will be a knobposition where the blue and green tones blend together and seem likea single musical note - this is the best TUNE setting to play songs with.The blue and green keys are now aligned together.

To play a song, just press the key corresponding with the letter shown.If there is a “–” after a letter, press the key longer than usual.

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Some songs havebeen modified tomake them easierto play on yourkeyboard.

Build the circuit and turn on the right switch (S1). Pressone key in a series of long and short bursts with pausesin between, and use Morse Code to send secretmessages to your friends.

You can use the difference in pitch between keys to sendmessages to different people. For example, sendingMorse Code with the blue C key can mean that themessage is for one friend, using the green C key canmean it’s for someone else, the green B key can besomeone else. Turn on the left slide switch makes thepitch of the green keys much different, so can be used toidentify messages for additional friends.

Morse Code: The forerunner of today’s telephone systemwas the telegraph, which was widely used in the latter halfof the 19th century. It only had two states - on or off (that is,transmitting or not transmitting), and could not send therange of frequencies contained in human voices or music. Acode was developed to send information over long distancesusing this system and a sequence of dots and dashes (shortor long transmit bursts). It was named Morse Code after itsinventor. It was also used extensively in the early days ofradio communications, though it isn’t in wide use today. It issometimes referred to in Hollywood movies, especiallyWesterns. Modern fiber optics communications systemssend data across the country using similar coding systems,but at much higher speeds. Indian tribes sometimes usedsmoke signals to send messages.

MORSE CODEA . _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 _ _ . .

Period . _ . _ . _Comma _ _ . . _ _Question . . _ _ . .1 . _ _ _ _2 . . _ _ _3 . . . _ _4 . . . . _5 . . . . .6 _ . . . .7 _ _ . . .8 _ _ _ . .9 _ _ _ _ .0 _ _ _ _ _

Project 181 Morse Code

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Transistor AudioAmplifierBuild the circuit with the speaker (SP2) connectedusing the red & black jumper wires. Set theadjustable resistor (RV) to mid-range, and turn onthe slide switch (S1). Hold the speaker next to yourear and blow into the microphone (X1), or talkdirectly into it with your mouth close to it.

This circuit amplifies your voice and plays it on thespeaker. It should be easy to hear the blowing, but itmay be difficult to understand your voice, becausethere isn’t enough amplification and there will besome distortion. Also, the sound from the speakermay not be as loud as hearing your voice directly.

If you have headphones (not included),then modify the preceding circuit to matchthis one, and connect your headphones tothe audio jack (JA). Set the adjustableresistor (RV) to mid-range, and set the500kW adjustable resistor (RV3) for mostcomfortable sound level (turn to the left forhigher volume, most of RV3’s range will bevery low volume). Turn on the slide switch(S1). Blow into the microphone (X1), or talkdirectly into it with your mouth close to it.The sound may not be very loud.

Headphones (not included)

WARNING: Headphones performance varies, so use caution. Start withlow volume, then carefully increase to a comfortable level. Permanenthearing loss may result from long-term exposure to sound at high volumes.

!

Project 182

Transistor AudioAmplifier (II)

Project 183

With headphones it may beeasier to recognize thedifference between thecircuit sound and hearingyour voice directly, than ithad been with the speaker.

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Method A (easy): Spread some water on the table intopuddles of different shapes, perhaps like the onesshown here. Touch the jumper wires to points at theends of the puddles. Small, narrow puddles may notproduce any sound.

Method B (challenging): Use a SHARP pencil (No. 2 lead is best) and drawshapes, such as the ones here. Draw them on a hard, flat surface. Press hardand fill in several times until you have a thick, even layer of pencil lead. Touchthe jumper wires to points at the ends of the drawings, then move them acrossthe drawing to vary the sound. You may get better electrical contact if you wetthe metal with a few drops of water. Wash your hands when finished.

Method C (adult supervision and permission required): Use some double-sided pencils if available, or VERY CAREFULLY break a pencil in half. Touchthe jumper wires to the black core of the pencil at both ends.

Build the circuit and turn on the switch (S1). Initially set the lever on theadjustable resistor (RV) to the left, then move it later to vary the range ofsounds that can be produced. Make your parts using either the waterpuddles method (A), the drawn parts method (B), or the pencil parts method(C). Touch the metal in the jumper wires to your parts and listen to the sound.

Long, narrow shapeshave more resistancethan short, wide ones.The black core ofpencils is graphite,the same materialused in the resistors.

Next, place the loose ends of the jumperwires in a cup of water, make sure themetal parts aren’t touching each other.The water should change the sound.The pitch may depend on the amount ofwater, so see if adding more water to thecup changes the sound.

Now add salt to the water and stir todissolve it. The sound should havehigher pitch now, sincesalt water has lessresistance than plainwater.

Don’t drink any water usedhere.

Project 185Color Touch Light

Build the circuit. It doesn’t do anything,and may appear to be missingsomething. It is missing something,and that something is you.

Touch points A & B with your fingers.The color LED (D8) may be lit. If isn’t,then you are not making a goodenough electrical connection with themetal. Try pressing harder on thesnaps, or wet your fingers with wateror saliva. The LED should be on now.If it isn’t very bright, then try going intoa dimly lit room.

Make Your Own PartsProject 184

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Project 186Test Your Hearing

This project requires a smart phone with an internet connection, so youcan download a free app. Find and download a “function generator” appthat can generate sine and square signals. Visit the Snap Circuits® Soundproduct page at http://www.elenco.com/downloads/scs185/ to find a fewsuggestions.

Set the app for “Sine” function (for asingle tone), start it, and vary thefrequency across the available range.You can listen to the sound directly onyour smart phone, or use the circuit inproject 60. Set the volume control onyour smart phone (and using RV, ifyou are using project 60) so that thesound is at a comfortable level formiddle frequencies.

See what range of frequency you canhear. Notice that the sound is loud atmiddle frequencies, but low (or nosound at all) at low or high frequency.There are two reasons for this:

1. Your hearing ability depends on frequency. Most people can hearfrequencies in the range of 20 Hz to 20,000 Hz, but much better in themiddle of this range than at the low or high ends of it. As you get olderyou don’t hear higher frequencies as well, so use the same circuit tosee what range of frequency your grandparents can hear.

2. Your speaker’s ability to produce sound depends on frequency, and itmay not perform as well at low or high frequency. Speakers are onlydesigned to produce sound in the range that we can hear.

Part B: set the frequency on the function generator app to just below whatyou can hear, then change the function from “Sine” to “Square” function(for a tone with lots of overtones). You should be able to hear it now,because a signal with overtones has some energy at higher frequencies,which should be within your hearing range.

This project requires a smart phone with an internet connection, so youcan download a free app. Find and download an “oscilloscope” app thatlets your smart phone act as an oscilloscope. Visit the Snap Circuits®

Sound product page at http://www.elenco.com/downloads/scs185/ to finda few suggestions.

An oscilloscope is an instrument that engineers use to actually look atelectrical signals. Constant tones are especially interesting to look at,because they are repetitive and actually look like a wave.

Start the app and talkinto the smart phone’smicrophone, and watchyour voice on the screen.Try making a single toneat different frequencies,or whistling, or snappingyour fingers.

Next, use the one of the keyboard (U26) circuits such as projects 1 or 25-26. Make sound with the keyboard and see what it looks like.

Try an echo circuit such as project 29, and see what an echo looks like.

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Project 187See the Sound

This project requires a smart phone with an internet connection, so you candownload a free app. Find and download a “spectrum analyzer” app thatlets your smart phone view the frequency spectrum of a signal. Visit theSnap Circuits® Sound product page athttp://www.elenco.com/downloads/scs185/ to find a few suggestions.

A spectrum analyzer is an instrument that engineers use to look at thefrequency content of electrical signals, and shows which frequencies havethe most energy. A pure tone will have all its energy at a single frequency,while a tone with overtones will have the most energy at the main tone,but also have energy at multiples of the main tone. A complex sound willhave its energy spread across many frequencies.

Spectrum analyzers usually show data as a chart of energy content versusfrequency. Energy is usually shown in dB (decibels), a logarithmicmeasurement, so the strongest frequencies have much more energy thanthe weak ones shown. There is always a “noise floor” of background noise,which can make weak signals difficult to observe.

Start the app and talk into the smart phone’s microphone, and watch thefrequency content of your voice on the screen. Try making a single toneat different frequencies, or whistling.

Next, use the one of the keyboard (U26) circuits such as projects 1, 6, or 25-26.Make sound with the keyboard and see what its frequency content looks like.

See the SpectrumProject 188

Project #B1See the Sound

This circuit uses the color organ module (U22) from the SCL-175set. Build the circuit as shown, turn off the left slide switch (S1),and turn on the right slide switch. Press keys on the keyboard tomake sounds and change the light on the color organ. Turn on theleft slide switch to add optical control, and wave your hand overthe photoresistor to also change the sound and light. If desired,add one of the SCL-175 LED attachments on the color organ.

BONUS CIRCUIT FOR SNAP CIRCUITS® LIGHT OWNERS

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If you own Snap Circuits® LIGHT (Model SCL-175), thenyou may also build this circuit. Do not connect additionalvoltage sources from other sets, or you may damageyour parts. Contact Elenco® if you have any questions.

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SCS-185 SOUND Block LayoutImportant: If any parts are missing or damaged, DO NOT RETURN TO RETAILER.Call toll-free (800) 533-2441 or e-mail us at: help@elenco.com. Customer Service • 150 Carpenter Ave.Wheeling, IL 60090 U.S.A. Note: A complete parts list is on pages 2 and 3 in this manual.

Base grid (11.0” x 7.7”) overlays many parts