Fun Projects for the Experimenter

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llr tln hoilmomtl rurProlcGB withAmerican, Duringmorethan20 years,the author,as a collaborator haspublished a large magazines*, electronics andLatinAmerican European circuitsusingcommonparts. of practical assortment in thisvolume,mostof whichyou areincluded Nowmanyof thoseprojects rangefromfuntypesthroughpractical Theprojects canbuildin oneevening. types.Of course,thereareotherdevicesthatcan be typesto amusement aboutcircuitsor components. usedto teachyousomething for intended featureofthesesprojects aretheldeasto Explore, Animportant practical projects research. in scienceor to usein lookingfor students Wecanconsider thisbookas a sourcebookof theeasiestandfun-to-make createdandpublished bytheauthorduringthese of projects of thehundreds years. last But,as the projectsare in a widerangeof types,we shouldseparatethe or intotwogroups: theoneswhowantto improve experimenters electronics interest,suchas computers, expandsomeotherareaof theirelectronics audio,securityandevengames;andthe oneswho radio,instrumentation, circuitsanddevicesor wantnew aboutelectronic wantto learnsomething ideasto usein scienceprojects. acceshereincanbestand-alone asindividual described Mostoftheprojects possible they be so that can the have been designed wherever circuits sories; gangedwithoneor moreotherprojects. manyprojects of audio Forexample, outor high-power canbegangedwithaudioamplifiers etfectsor generators putstages. thatcanbemadein withfewlow-cost components Alltheprojects aresimple, oneevening of work. we addedcodesafter Tomakeit easyforthe readerto choosethe projects the whomtheyareintended: thekindof experimenterfor eachtitleto indicate "E' "P" project practical (Practical) The code built for use. indicates a code to (Experimental) forthe experimenter indicates thatthe projectis intended teachsomething aboutcircuitsor devlces.

trolrcc Of course,you can also find projectswith both codes(E and P)whichcan dther be mountedto teachsomethingorknd be usedfor a practicalend. The presentations of the projectsare practical.Electronicscomponentsare listedwith eachcircuitdiagram.But secondarypartssuchas sockets,chassis, enclosures,miscellaneous hardwareand so on, are not specified,since the readeris free to choosethesenon-criticalitemsaccordingto his preferencesand demands. The mannerin whichthe circuitswork and can be modifiedis explainedin practicaltermsso the readercan acquiresomeknowledgeof practicalelectronicsas he progressesthroughthe book. Althoughmanyof the projectswe enjoyedconstructing as theyaredescribed here,youmaythinkof possiblemodifications. Wejust recommend thatyougo aheadand modifythe circuitsto yourpersonalends.Thereis a wide latitude in circuitmodifications and mostof themwill be of valueto the experimenter whowantsto see howthingswork,eventhougheachproject'sprimaryintent is forthe builderwhodesiresa functionalitemof equipmentas the resultof his work. As the bookincludeseasy-to-build projects,the authorhopesit will helpyou to learnmanyof the fundamentals of electronicsin an easyandfun way,and, you're if a student,providea sourcefor schoolprojects.

NewtonC. Braga

. Mini-Projects is thetitleof a columnpublished bytheauthorduringseveral yearsin a BrazilianElectronics MagazinenamedEletr6nicaTotal (TotalElectronics).

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(E/P) MlcRo-PowERLEDFLASHER A simpleLEDflashercan be builtwitha TLC7555Timerusedas a lowdeteranddriveto an LED.lC1runsin a lowfrequency frequency oscillator 0.1and5 Hzbut is intherangebetween minedbyR?R3andC1.Frequency youcanalterit bychanging canrangefrom1 to 10uF. Cl.Thiscapacitor where inapplications byR2/R3ratioandis important Dutycycleisdetermined youneedreduction Figure1 showsfixedresisof energyconsumed.Though potentiometers you if you prefer.The can usetrimmer torsfor R2 and R3, anddutycycle potentiometers, thefrequency arehandyforaltering ofcourse, of theoscillator. WithpowersuppliesbeRl valuesdependuponthe powersupplyvoltage. 6 and9 tween5 and6 volts,R1is 470ohms.Withpowersuppliesbetween power 9 and intherangebetween supplies volts,Rl is 560or680ohms.With circuitdrainsonly250uAfroma 6-volt 12volts,Rl mustbe 1,000ohms.The powersupply. At LEDFlasher. fortheMicro-Power diagram Figurel showstheschematic theheartof thecircuitis lOl, a 555timer. the Microdiagramas a guidewhenassembling Usethe partsplacement placement, as chasterminal strip using a Flasher. Components PowerLED sis,is shownin Figure2. suchas the LED components, of polarized Takespecialcarewithpositions capacitor. andelectrolytic putthe correctly, Afteryouaresurethatyouhavewiredallthecomponents TheLEDshouldflash. in thebatteryholder. batteries

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LEDFlasher PartsList - Micro-Power lC1

- TLC7555CMOSIntegratedOircuit- Timer

LEDI - Commonred,greenor yellowLED D1

- 1N914generalpurposesilicondiode

Rl

- 560 ohm, 114W,5% resistor

R2

- 1,000,000 ohm, 114W,5%resistor

Rg

- 4,700ohm, 114W,5%resistor

C1

- 4,7 uF,6IM/DC electrolytic capacitor

C2

- 10 UF,12 W\/DCelectrolytic capacitor

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- 6 to 12VAA cells,9V batteryor powersupply

ldeasto Explore learnmoreaboutthe circuitand devices: o AlterR2andR3 (minimumvaluesare 1,000ohmsforboth)andsee howthe flashingratechanges.Of course,if youwant,youcan replace trimmerpotentiometers. R2 and R3 with 1,000,000-ohm o Explainhowthe astable555 worksin this circuit. o AlterC1 in a rangebetween1 and 100uF andobserveflashingrate alteration.Explainwhathappens. o Whatis duty-cycle?

FroFGtltlmPomrlMmficr Scienceexperiments withthe clrcuit: o LED ls a monochromatic lightsource.Youcan performsome experimentsin opticsusingthiskindof lightsource.Chromaticfilterscan be usedin someexperiments involvingLEDs.TrytouseLEDsof different colors(red,yellow,greenand,if possible,blue). . Lightflashes,as the onesproducedby this circuit,can be usedin hypnoticexperiments. o The circuitcan be used to indicateoperationof otherelectronic devices.Wiredto the powersupplyof a monitoreddevice,the blinker LEDwillindicateits operation. Remember thatthetheoryin thisbookis specifically relatedto the associated projects.This experiments and bookis designedas an introduction, notas an in-depthtreatmentof electronics.lf you are interestedin findingout more aboutthe subjectstouchedon in this book,severaltextscan be foundfor furtherreading.

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FLIP-FLOP(E) SET-RESET WiththispQectwe canshowhowtwoNANDgatesof a 7400lC (TTLIntegratedGircuit) canbe wiredto performas an R-Sflip-flop. pulsesto be thatneedsnegative-going flip-flop Thiscircuitisa pulse-triggered a Thiscircuitoperatesas follows:as we see,it haltwg_outngls; triggered. (LED2).When outputcalledO andaninverted nolmdoutputcalledO (LED1) theyare because vice-versa will be 0 and oneoutputis 1theothernecessarily complementary. as shownin ThecircuithasalsotwoinputsnamedS (SET)andR (RESET) wherethetriggersignalsareapplied. diagram, theschematic R inputiswiredto Q outputandS inputiswiredto Ooutput,forminga closedloopforthedigitalsignals. triggerpulseis appliedto S inputtheoutputQ swingi Whena negative-going to the 1 staie.As thistutputis wiredto R input,the 1 statecausesoutputQ tofallto a 0 level.ButQ outputis alsowiredto S inputcausinga feedbackthat To makesitsoutputremainat 1 alsoatterthetriggerpulsehasdisappeared. negaa apply we should states, theoutput again,changing triggertheflip-flop p!-going pulseto R input.This pulsecausestheoutputto goto 1, andasthis outputis wiredto R input,thetriggerpulsealsocausestheoutputQ to goto 0level. Azeroin thisoutputgoesto R input,andalsoafterthetriggerpulsedisappearstheoutputsremainin theirstates. Seethatthe circuithastwo stablestates,andwe onlycan changethese pulsesappliedto its inputs. stateswithsetor reset(S or R) negative-going wiringa flip-flopandcanbe constructed Ourprojectis a manually-triggered switchto the R-Sinputsas shownin Figure1. twoLEDs.LED1glowswitha 1 at Q outputand Logicstatesareindicateqby LED2glowswitha 1 at d outPut.

Ffd0crzsH-i$fff,llHrr Thecircuitmustbe powered powersupplyas it usesa by a S-voltregulated TTLlC.Currentrequirements rangetypically from5 to 15 mA. placement Components ona smallprinted-circuit boardisshownin Figure2. Experiments likethiscanalsobeperformed onwhatelectronics experimenterscall"breadboards". Theseareboardson whichthe partsof experiments canbe temporarily assembled. By usingbreadboards it is notnecessary to

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Frndrctrffithe halmffil "solderlessboards" This is why theyare alsocalled solderthe components. The circuitcan be usedto teachmuchaboutflip-flops,usedin computersas countersand in memoriesand manyotherapplications. Observation:In digitalelectronicsan electricalsignalis eitherhigh or low. Thesetwo statesale usedto representbinarybits 1 and0. Sincedigitallogic lOs operatefrom a single-endedpowersupply,a high state representsa a voltagenear 0V' voltagenearthe supplyvoltageanda lowstaterepresents

FUP-FIoP PanrsLsr - SET-RESET fC1

- 74OOTTL IntegratedGircuit

LEDs

- Red,greenor yellowcommonLEDs

R1,R2

- 330 ohm, 114W,5Y"resistors

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- SPDT toggleswitch

ldeasto ExPlore Tolearnmoreaboutthecircuitanddevices: countercircuit.Mountother flip-flopis a fundamental o Thecommon unitslikethisand usethemto explainhowcountersandmemories circuits.Eachflip-flopcanstorea bit. workin computer andhowthey betweenR-SandJ-Kflip-flops . Findtheditferences areusedin logiccircuits. usingthiscircuit: andprojects Scienceexperiments anduse (reed)switchor a microswitch o Replace 51 bya-magnetic lt candetectand memoryin experiments. thiscircuitas a one-event processis whena Switchin an lure,alarm,or mechanical memorize closedfora moment. -

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(P) MIN|-METRONOME metronome whichyoucanbuildintoa small Hereis a dandytwo-transistor plasticcase.Youcan usean old nonworking radioto housethis transistor gadget.In mostcaseyou can merelyremovethe maincircuitrybut retain speakerand someparts,suchas the on-otfvolumecontrolpotentiometer, just the following batteryholder.lf youhavedonethis,youhave eliminated items:SPKR,51,and81. withtwoorfourAAcellsanddrainsabout10mA. Thecircuitcanbepowered potenByadjusting stbrtqclacking. As soonas 31 is closed,themetronorfle "beat'or youwishto set. frequency of clacking tiometerP1youfindthe yourmetronome youhaveonlyto synchronize witha commercial Tocalibrate, typeor anyknownsource. At theheart fortheMini-Metronome. diagram Figurel showstheschematic which amplifier, direct-coupled of thecircuitareQ1 andQ2,as a two-stage pulses. generate intervalled to the circuit allows usinga terminalstrip of themetronome, Figure2showsa mechanicalview "chassis" forthesmallcomponents. as suchas Gl, C2 andthe transistor, components, Positionof the polarized in themounting. shouldbe observed

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PartsList - Mini Metronome Q1

- 8C548 NPNtransistor

Q2

- 8C558 PNPtransistor

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- SPST toggleor slideswitch

81

- 3V or 6V - two or four AA cells

SPKR- 4 or I ohm,2 to 4-inchloudspeaker P1 -

1,000,000ohm Potentiometer

Rl

- 10,000ohm, 1l4W,5olo resistor

PA

- 1,000ohm, 114W,5%resistor

C1

- 10 pf, 6 VVVDCelectrolytic capacitor

C2

- 10 Uf, 6 WVDC electrolyticcapacitor

ldeasto ExPlore To learnmoreaboutthe circuitanddevicesor to get betterperformance: in the rangebetween1 and 10 pF. o ReplaceG1 by anycapacitor whatwillhappento thebeatrate.Explainit' Observe andpower Q2withaTlP32ona smallheatsink o Replace transistor haveextrapowerfor thecircuitfroma 9V or 12Vpowersupply.You'll andcanuseit in largerplaces. metronome yourexperimental o . RemovePl andtouchwithyourfingersthe pointswhereit was Canyouexplainwhatis goingon? wiied.Willthecircuitoperate? -

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Prtlm8 thl-ilrtrrnrm Scienceexperiments andditferent usesforthecircuit: o Themetronome canbe usedin gymnastic exercises or in running to findthecorrectrhythm. Themetronome canbe housedin a small plasticbox,powered bycellsandeasilycarriedwiththerunner. o Biological experiments withsoundscanbe madewiththisdevice; experiments in animalconditioning, forexample.

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PENDULUMALARM (E/P) thisalarm,enabling sensortriggers thatswingsthependulum Anymovement a relay. homesandotherplaces Thecircuitcanbeusedto protectcars,largeobjects, Thisdevicecanalsobe asthesensorcanbe usedto detectanymovement. at theendof thesection. as suggested experiments, usedforscientific suchas sirens,horns,lamps, soundsystems, Therelaycandrivepowerful etc.Thecircuitcan be poweredby a l2-voltbattery(whenusedin cars,for drainisverylow(about100uA)whenthe Current ora powersupply. instance) batterylife. extending relayis deenergized, Alarmis shownin Figurel.Thecircuit circultofthePendulum Theschematic the whichenergizes Rectifier), hasas its heartan SCR(SiliconControlled relaywhenthe sensordetectsanymovement. usinga terminalstripas chassis, viewof thecircuitmounting, A mechanical is shownin Figure2. Youcan to the powersupplyvoltage. Relaycoilvoltageis chosenaccording or,forheavyloads,a usea miniDPDT1AMiniRelay(RadioShack275'249) relays are ratedlo 12 10AminiSPDTrelay(RadioShack275-248).These is about320 ohms).As VDCand drainonly38 mA (theircoil resistance typescanbe used,youshouldtakecarewithterminallayout. equivalent wiredbetween switch(Push-On) Resetcanbemadewitha momentary-typ6 theSCRanodeandcatode,or by usingtheon-otfswitch. suchas the SCRanddiode,shouldbe components, of polarized Positions occurswhen ::t::r":tairs areatsosivenin Fisurc2.Noricethatoperation any barewiretouchesthe ringduring movement. thevertical(orhorizontal)

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m'lrfrctstrhrhuffim PartsList - PendulumAlarm Rectifier Silicon Gontrolled SCR -TlC106or equivalent D1

- 1N914or equivalent general-purpose silicondiode

K1

- 12Vrelay(seetext)

S1

- SPSTslideor toggleswitch

Rl

- 22,OOO resistor ohm,114W,5%

R2

- 10,000ohm,114W,5% resistor

X1

- Pendulum sensor(seetext)

ldeasto Explore Tolearnmoreaboutcircuitanddevices: lamp.Doesthe o Replacerelaywitha 12Yx 200mAincandescent circuitwork? if therelayis o Explain whatDl is doinginthiscircuit.ls it necessary lamp? replaced byan incandescent o Explainhowan SCRworks usesforthiscircuit: andditferent Scienceprojects o ReplaceX1 by a reedswitchto get an alarmtriggeredby a magor otherkindof X1bf a microswitch neticsensor.You canalsoreplace switch. momentary o In biological the alarmcan be usedto detectsmall experiments in animaltrapsor cages. movements

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Frfhct | ?oildumllrrm o ReplacingXl by two metalwiresenablesthe circuitto be triggered by water.Waterleveldetectorscan be madeusingthis kindof sensor, and it can be usedin manyexperiments and practicalapplications. o lnstalledin yourcar,thiscircuitcanbe usedas an alarm,drivingthe hornor a siren. o By replacingX1 witha largemetalplate,the circuitcan be usedto detectwind.Air flowcan movethe plateso thatthe barewiretouching the loopcausesthe alarmto trigger.

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(P) RF PRESELECTOR MEDIUM-WAVE is poorinthemediumAMreceivers of mostmoderately-priced Thesensivity alsodropsotfsharplywithintheupperpart waveband.worseyet,selectivity to images,noiseand highlysusceptible or tn" band,makingine receiv-er heterodYnes. annoying can'tmakeupforthese Eventhebestantennaanda goodboosteramplifier in a commonreceive/sfrontend.But,usingan RFpreselector deficiencies willgiveyou antennainputterminals andthereceiver's b;trd; theantenna quality. in the reception realincrease input antenna withthereceive/s impedance theantenna Thiscircuitmatches of thetunedstation' thefrequency according Preselector' diagramof the Medium-wave Figure I showsschematic viewof the circuit,whichcan be housedin a Figure2 showsan exploded smallplasticbox. ferrite wire,woundon a 5/16-inch Ll is formedbyturnsof No.28enameled The form.Tapsaremadeeach15 or 20 turnsandits numberis notcritical' numberof taPscanbe altered. preselector' Attachyourantennaand groundto the inputterminalsof the thebest.posiand,bychoosing Tuneto thedesiredstationonyourreceiver, bestsignal' the find CV clipon theitrip anObyadjusting tionof thealligator antennawilldependuponthestationyouwantto tune'A ranTherequired throughthe A{ band' domlengthof wiie will giveiairlygoodperformance for best ts ano150feetarerecommended withlengthsb-etween Antennas performance.

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RF Preselector PartsList - Medium-Wave L1

- Medium-Wave Coil - see text

CV

- 365 pF miniaturevariablecapacitor

X1

- Alligatorclip - 2-positionbarrierstriP

ldeasto ExPlore Tolearnmoreaboutthecircuitanddevices: inthiscircuit. of a goodgroundconnection o Explain theimportance "impedance"? of Whatis the meaning o Usea newcoilwith20 turnsandtapsevery3 turnsto tuneshortwavestations. o Makea seoondcoil(20turns)on the sameferriterodto plugthe antennaandground.

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LURE (P) FISHING ELECTRONIC to attract thesoundof wetbugsmillingaboutthesurface Thiscircuitimitates fish. curious in a frequency operating The circuitis basicallya Hartleyaudiooscillator byanAAcell,it canhousedina clean 200and2,006Hertz.Powered between onthe emptypeanutbutterjarwiththe buzzercircuitrymountedupside-down .ofti.Vou mustbe carefullnotto drillin sucha wayasto allowwaterto leak tnrougnthecap.siliconrubbercanbe usedto closeanywaterleak' 1,000Hz'but approximately CapacitorClwouldgivea resonantfrequencyof in theaudiorange' p1 wouldgivea wid6variation in signaltonegenerated it to connecting asa transducer, earphone Youcanalsousea low-impedance the secondcoil(output)of thetransformer' thecap,throwS1ON,putthecoverbackon,anddrop unscrew Tooperate, 20 thefishlureintothewaterintnevicinityof whereyouwillbefishing'Allow tone' adiustP1to a newsignal minutesbeforereelingthemin.lf necessary, diagral for the FishLure.observethatthe Figure I showsthe schematic is notusedin thiscircuit. coilof thesmallaudiotransformer se-condary FishingLure,usinga terminalstripas detailsof the Electronic construction is not chassis,is shownin Figute 2. The exactlocationsof components critical. withcentertransformer Any500:8or 1,000:8transistor T1 isalsonotcritical. tappedprimarycanbe used.we canalsosuggestthatanysmalltransistor with' canbe experimented transformer

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- 8C548 general-purpose NPNsilicontransistor

T1 P1

- 500:8or 1,000:8transistor transformer (RadioShack2TS-1380 is suitablefor thistask) - 100,000ohm trimmerpotentiometer

R1

- 1,000ohm,114W,5% resistor

C1

- 0.01uF metalfilmor ceramiccapacitor

S1

- SPSTtoggleor slideswitch

BZ

- Piezoelectric transduceror crystalearphone (RadioShack273-073 or equivalent) - 1.5V AA cell

81

ldeasto Explore To learnmoreaboutthe circuit: o ReplaceBZbya low-impedance tweeteror smallloudspeaker connectedto the transformersecondarycoil. o ChangeC1 valuesin the rangebetween0.001and0.22 uF.Observewhat hapenswith tone pitch.A higher-value capacitorgivesa lowertone. o The circuitalso operatesfrom a 3V or 6V powersupplywithout makinganychanges.

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Plolocl6 HGGtorlcHrillululc Scienceand ditferentusesfor the device: o Youcanmakeseveralexperiments in animalconditioning, including the onesthat livein the water.Tryto alterthe RC network(P1,R1 and Cl) to get tonesof ditferentpitch.Tryto usediodes,smalltransformer coils and other passivecomponentsin this experiment.Soundslike thoseproducedbysongbirdscanbe generatedwitha fewcomponents arrangedin the correctway.Can you discoverhow to do it? o Removethe piezoelectric transducerandwireelectrodesin itsplace. The devicecan be useas a nervstimulator. Experiments withanimals and plantscan be made.What physiological functionsare atfected? Can circadianrhytmsor internalbiologicalclocksbe atfectedby continuousexposureto sounds? o Electrodesplacedintowaterand wiredin placeof the transducer will producea currentfield.Youcan pedorminteresting scientificwork relatinghowfishandotherWaterbeingsreactto the currentfield.Can the currentfieldsaffectphysiological functions?lf you experiment with plants,selecta fast growinghouseplant.

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AM RECEIVER(RE) FREE-POWER "extracted" This projectusesa strangewayto get lts power.lt usespower Witha reasonably transistor. fromthe tunedstationto giveto the amplifier produces a strong type of detector this envelope, strongappliedmodulation output. demodulated thecloseryouareto a strongstation,the morecurrentyourradio Naturally, willbeableto supply. possible to delivera strongsignalto youmustdoeverything Forbestresults, good antennaandground,the lata Werecommend detector. thetransistor groundcomposed beingmadeto a waterpipeor solidexternal ter preferably forensuring of a pipedrivenat least5 feetintomoistearth.Thisis important pickup. signal maximum I thelongertheantenna(upto about100 lf youhaveplentyof spaceavailable, feet),thebetterthe results. ObAM receiver. diagramof the Free-Power Figure I showsthe schematic thatworksas a transistor servethatthe heartof the circuitis a germanium andaudioamplifier. detector placement on a terminalstripusedas a chassisis shownin Gomponents boardthatcanbe Figurc2.Theterminalstripcanbefixedonan experiment materials. and tools usingsomecommon constructed canfindgermasuchasGE-2or2N107.You transistor, Ql is anygermanium Nonworking radioreceivers. AMtransistor inoldnonworking niumtransistors (ferrite andthe loopstick AM radioscan alsosupplythe variablecapacitor rod). earphones Low-impedance crystaltype. mustbea high-impedance Earphone don'tfunctionin thiscircuit.

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PartsList - Free-PowerAM Receiver Q1

- seetext - NPNor PNPgermanium transistor

XTAL - CrystalearPhone L1

- seetext - LooPstick

CV

- 365pFvariablecapacitor- seetext

Rl

- 12,000 resistor ohm,114W,57"

C1

- 1 uF,25WVDCelectrolytic capacitor

ldeasto ExPlore Tolearnmoreaboutthecircuit: o ReplaceLl by 15turnsof No.28 wire,woundon a ferriterod,to stations. tuneshort'wave R1andC1 diodeandremoving o Byreplacing Ql witha germanium thisradiointoa simplecrystalset' you'litransform 4,7}Oand47,000ohmsto getbetter o AlterR1in a rangebetween used' on thetransistor performance, depending witha silicontype,suchasthe8C548'What o Replace thetransistor withsensivitY? willhaPPen uses: thecircuitand,uncommon scienceprojectinvolving lf you andtellaboutradiohistory. o Explainhowcrystalsetsfunction in moreradiohistoryseveraltextscanbe foundin the areinterested publiclibrarY. tryto findinformao lf youwantto learnmoreaboutradioreceivers, types' andsuper-hereterodyne tionaboutheterodyne -

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FLASHER(E,P) DUAL-LED witha 4093CMOSlG,to producea oscillator, Thiscircuitusesa one-gate flasherin two LEDsor a bi-colorLED.The circuitcan be 50%duty-cycle powered bya 3 to 12-voltpowersupplyandis usefulin severalexperiments canuseit as partof alarms,warningsystems, applications.You andpractical here' as wewilldescribe games,toys,andsomescientific experiments, to the R2andR3valuesdependuponthe powersupplyvoltage,according table: following Power Supply

R2, R3

3 Volts

220 ohms

5 Volts

330 ohms

6 Volts

470 ohms

9 Volts

820 ohms

12Volts

1,000ohms

outputstagedrivingincandesFormoreoutputyoucanusea transistorized to observelightetfectson animalsandplantscan centlamps.Experiments withthiscircuit. beconducted flashrate.Flashratecan be adiustedby P1,butCl Pl andC1 determine to the application alsocanbe alteredin a largerangeof values,according youintendforthedevice. Flasheris shownin Figure1.Onegate fortheDual-Led diagram Schematic andtheothertwoareusedas inverters. of a 4093lC is usedas oscillator placement on a PC boardis shownin Figure2.Youcanalso Components circuit. boardto mountit as an experimental or solderless usea breadboard pieces,suchas LEDs,eletrolytics andlC,shouldbe Position ofthepolarized observed. tf

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PartsList- Dual-LedFlasher lC1

- 40938CMOSintegrated circuit

LED1 - bi-coloror redand greencommonLEDs (RadioShack276-012l resistor ohm,114W,5% R1 - 100,000 R2,3 - resistoraccordingto powersupplyvoltage- see text P1

- 1,000,000 ohm potentiometer

C1

- 1 uF,25 WVDCelectrolytic capacitor

ldeasto Explore To learnmoreaboutthe circuitand devices: o ReplaceC1 with capacitorsin the rangebetween1 and 47 uF. Observehow highervaluesalterthe flashrate. No changein the o InfraredLEDscanbe usedin someexperiments. originalcircuitis necessary. Scienceanddifferentusesfor the circuit: o RemoveP1 and R1 and wireat this ponta touchsensoror elecdevice trodes.Youcan controlthe flashrateby touch.A bio-feedback can be madethis waY. o By wiringthe lC"spin 1 to an externalcircuit,the flashercan be controlledby a logiclevel.CMOScircuitscan be usedto controlthe flasher.

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flashratecanbeadjusted to makean hypnotic or relaxingLtfect. Combinethiswitha touchsensorandyouhavean uncommon bio-feedbackdevice.You canalsousethiscircuitto makeexperiments incircadianrhythmsor internalbiological clocks,determining howtheycan bealteredbylightpulses. Various theorieshavebeenproposed about thissubject. . Psychiatrists are usingphototherapy to helpsomepatients. can youfindsomeapplication forthecircuitin thisfield? . Pl alsocanbe replaced byresistive transducers, suchas LDRsor NTCs,to givea light-or temperature-dependent flash-rate circuit.Experiments canbe madewithconductivity of materials by connecting pl withtheprobesin thiscase. probesin serieswithR1.Replace

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6V X 1A POWERSUPPLY(P) youwillneed In orderto performexperiments andprojectsinvolvingelectricity a sourceof voltage.Voltagerequirements for commonprojects,suchas the onesin thisbook,dependupontheirapplications, and typicallyrangefroma few milliamperes to one or two amperes. lnsteadof usinga batteryyou can use a circuitcalleda powersupply. The powersupplywe showherecan be usedto provide6V x 1A regulated outputto the experimental and practicalcircuitsdescribedin this book.The outputvoltageis fixedby the lC. Figure l showsthe schematicdiagramfor this powersupply.lOl is a voltage regufator, #7806. The "06"indicatesthat it is a 6-voltregulator. Figure2 showsthe componentslayout,usinga terminalstripas chassis. The completeprojectcan be assembledin a smallplasticbox.The integrated circuitshouldbe mountedon a heatsink. Youcan alsoadd an LEDin series with a 470 ohm resistor,wiredin the outputof the circuitto indicatethat it is on. Externalcircuitscan be connectedto the powersupplywith alligatorclips. Positionof the polarizedpieces,suchas diodes,the lC, and electrolyticcapacitors,mustbe observed. Thetransformer isn'ta criticalpartof this project.Typeswitha secondarycoil rangingfrom7.5 to 12 voltsand currentsbetween500 mA and 14 can be used.

5f

trolrctg 8ur ll Pil0tsuillr

c2

D2 1N4002 T1 12 + 'l2Y 1A

c1

tl_

100pFT I

I =

lou

1000pF

Figure I

2 Fiaure t

55

mFrtmctrtrtrHilffi PartsList - 6-VoltPowerSupply lOl

- 7806positive three-terminal regulator

T1

- Transformer: primary117VAC; seconda x 1A ry 12+12Y

D1,2 - 50Vx 1A- 1N4002 or equivalent siliconrectifier diodes C1

- 1,000uF,25WVDCelectrolytic capacitor

C2

- 10uF,12WVDCelectrolytic capacitor

S1

- SPSTswitch

ldeasto Explore Tolearnmoreaboutthecircuitor altertheperformance: o ReplacelC1bya 7805,7809or 7812if youwanta 5V 9Vor 12V powersupply.Youmayalso haveto changethe transformer with a 117:15+1 5V usinga7812. .

Explainhowthecircuitworks.

o Whatis theditference betweenan ACanda DCcurrent? Scienceanduncommon applications: o Thispowersupplycanbe usedin chemical experiments, suchas the onesthatinvolvecurrentflowthroughsubstances. Experiments involving electrolysis andelectroplating aretwothatcanbesuggested. potentiometer (100ohms,5 watts)shouldbe A variablewound-wire wiredinserieswiththepowersupplyoutputto limitcurrent flowthrough theload.You canalsousetheLightDimmerdescribed inthisbookfor thistask.

!a

Plrflct g 0ur lt Pilil $utilr by this lampscan be supported o 6V 200 mA smallincandescent with work to light sources powersupply. lamps are excellent These microscopes. physics, mechaninvolving o Smallmotorsandlampsinexperiments power powered with advansupply from this be robotics can icsand tages.Youdon'thaveto spenda lotof moneyon cellsor batteries. o Allcircuitsdescribed inthisbookwhichrequirea 6Vsupplycanbe powered bythispowersupply. poweradapterforyoui6V o Thecircuitcanbe usedas an excellent etc. suchas smallradios,calculators, equipment, plantgrowth.Seinvolving o 6V lampscanbe usedin experiments box or cardboard lecta fastgrowinghouseplantanduse.adarkroom in an experiment be used filters can with Lamps colored to coverthem. growthanddevelopment. involving o Circadian rhythmscan alsobe studiedusinganimalsor plants. on at nightandotfat day.Whatphysiological Lampscanbe powered couldbe atfected? functions

5t

mFilncNsfffirHrufinrm

rNsEcTREPELLENT (P) Somecontinuous soundscanrepelinsects(andalsoattract). Thefrequency andintensitydependsuponthe application andtypeof insectandcan be foundthroughexperimentation. Thecircuitshownheregenerates a continuous soundthatcan be usedto repel(orattract)sometypesof insects, or in scientific experiments involving animals. Ourinsectrepellent canbe powered by9Vbatteries, twoM cellsor fourAA cells,andits lowcurrentrequirements will extendthe lifeof thosecellsor batteries. FigureI showstheschematic diagramof the lnsectRepellent. Theheartof thecircuitis a 7555lC,a CMOStimerwiredasanaudiooscillator anddriving piezoelectric a transducer. placement Thecomponents printed-circuit ona homemade boardis shownin Figure2. Exactplacement is notthatcritical. Allthecomponents andthepowersupplycanbehoused ina smallplasticbox. Transducer BZis a crystalearpiece or a piezoelectric transducer, suchasthe RadioShack273-073. pieces,suchas c2 andthe powersupply,mustbe Position of the polarized carefully observed. Usingthe insectrepellent is veryeasy.Youonlyneedto adjustthe trimmer potentiometer P1to producea soundwiththesamepitchas the insectyou intendto repel.Experimentation shouldbemadeuntilyoufindthebestsound to repela specificinsect.

60

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R2 4K7

cl

0.047p.F

Figure 1

Figure2

01

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PartsList - InsectRepellent

R1

- TLC7555 CMOSintegrated-circuit timer - Crystalor piezoelectric transducer RadioShack273-073 or equivalent - 10,000ohm,114W,5% resistor

R2

- 4,700ohm,114W,5% resistor

P1

- 100,000ohmtrimmerpotentiometer

c1

- 0.047uF metalfilmor ceramiccapacitor

c2

- 10uF,12WVDCelectrolytic capacitor

S1

- SPSTslideor tdggleswitch

B1

- 3V (2 AA cells),6V (4 M cells),9V (battery)

c1 BZ

ldeasto Explore Tolearnmoreaboutthecircuitor getbetterperformance: . Powerful outputcanbeobtained witha transistorized outputstage as shownin Figure3.Thepowertransistor shouldbe mounted on a heatsink.The transducer isa low-impedance loudspeaker r:anging from 4 to 8 ohms. o Experiments withultrasound cahbe madewiththiscircuit:reduce Cl to 1200pFandusea piezoelectric tweeterastransducer. Remove thesmalltransformer usedin thesetweeters andplugthetransducer directlyto thecircuitoutput.outputsin frequencies as highas40,000 Hzcanbe produced bythiscircuit. o Explainhowsoundscan be produced by electronic transducers suchas theoneusedin thisproject.

?nhd l0 InrstirDdhnt o Whatareultrasounds? applications: andditferent Science a Of course,you can testthe realetfectsof this deviceon several canbeconducted biological experiment An attractive kindsof insects. basedon thiscircuit. o Etfectsof soundson plantgrowthor development can be conalterthecircaductedusingthiscircuit.Cansounds(qrultrasounds) of plantsandinsects? dianrhythms o Thecontinuous toneproduced bythiscircuitcanbeusedinalarms by Miceandothersmallanimalsare repelled or warningsystems. powerful ultrasounds. o Replace a light-dependent circuitnowbecomes R2byanLDR.The withlightandsoundscannowbe conducted Experiments oscillator. usingthedevice.

6 to 12V

Figure3

08

HnPnlmts||]mHlo|lmeml

(E/P) GENERATOR ULTRASONIC upto Dogs,mice,batsandotheranimalscanhearsoundswithfrequencies Hz.Thereareseveralkindsof insectsthatcanalsohearor reactto 4O,O0O sound thesesounds.The circuitwe proposehereproducesa continuous abovethe humanlimit,or a rangebetween18,000 in frequencies emission andcan be usedin and40,000Hz.Thesesoundsare calledultrasounds applications. andpractical severalexperimental in herecanbeusedto scaredogsandotheranimals, Thedevicewedescribe applications. andmanyotherinteresting experiments, biological outputpower piezoelectric hasits maximum transducer Therecommended between700 and 3,000Hz, but it alsowill operateat higherfrequencies emittinglesspower. powersupplyis fourM cellsor a 9-voltbattery. Therecommended 18,000and40,000Hz,butyoucan approximately Ourprojectrunsbetween C1,in a rangebetween470pFand0.001 easilyalterthisrangebychanging by C1. canbe setby P1in the rangedetermined uF. Frequency upto 500kHz. in frequencies thatthe40938lC willoscillate Remember usingthe fourgatesof a Generator, circuitof the Ultrasonic Thecomplete circuit,is shownin Figute 1. 40938integrated placement boardis shownin Figurc2. on a printed-circuit Components willbe Thecircuitcanbe housedin a smallplasticboxandthe transducer fixedin thefrontpanel. Takecarewiththe positionof the polarizedparts,suchas the transistor, andpowersupply. capacitor electrolytic on a heatsink' operation, Q1 shouldbe mounted Forcontinuous coil witha secondary is nota criticalpart.Anytransformer Thetransformer from100to 500mAcanbe usedin thisproject. ranging -

00

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Figure I

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PartsList - UltrasonicGenerator circuit lC1 - 40938CMOSIntegrated

Tl

- 8D135medium-power NPNsilicontransistor - Piezoelectric transducer RadioShack273-090or equivalent - Transformer: primary117VAC;secondary 6Vx100mA

R1

- 10,000 resistor ohm,114W,5%

R2

- 1,000ohm,114W,5% resistor

Pl

- 100,000 ohmtrimmerpotentiometer

C1

- 4,700pF ceramicor metalfilmcapacitor

C2

- 100uF,12\M/DCelectrolytic capacitor

S1

- SPSTtoggleor slideswitch

81

- 6V or 9V - AA cellsor battery- seetext

Ql BZ

ldeasto Explore Tolearnmoreaboutthecircuitor to getbetterperformance: o Youcanreplacethepiezoelectric transducer bya commontweeter. T1 andBZandplacethetweeterbetween51 andQl's colRemove power? lector.Canyoumeasurethe generated ultrasound . Thecircuitcanalsogenerate soundin theaudiblerange.Replace in therangebetween 0.02and0.1uF. Cl bya capacitor o Explain transultrasounds andhowtheyareproduced byelectronic ducers.

0l

P'rhct tt Uhffuh8emn0r o Whatis a piezoelectric material? Scienceandditferent applications: o Severalexperiments canbe madeusingultrasounds. Youcanexperiment withdogconditioning. youcancalla dog Usingthisoscillator usingan inaudible sound!(inaudible to humans) o Ghoose a capacitor between 0.01and0.047uFto produce sounds bothin the audiorangeandultrasound range.Youcan nowconduct experiments to determine the exactupper-limit frequencyheardby humans.You alsocanconductexperiments withanimals. lt willbe importantto havea frequency counteron handto do thiswork. o ReplaceBZbyelectrodes. Thecircuitwillgenerate a high-voltage outputthatcanbeusedin nervestimulation. Usea 10,000ohmpotentiometer to adjustoutputvoltageat thispoint.Pulsescanreachpeaks as highas 400volts. o To get pulses(fornervestimulation you and otherexperiments) onlyhaveto replace C1witha 1 uFcapacitor andP1witha 1,000,000 ohmpotentiometer. Pulsesin the raterangebetween 0.1persecond per to 10 secondcanbe generated withthischange. o Thiscircuitcanalsobeusedasa fluorescent lampinverter. A commonfluorescent lamp(4 to 20 wafts)in placeof the transducer will glow,evenonethatis weakenoughto notfunctionon theAC power line.

00

Hr PnhG[slorl[c milmmt

DC LAMPDIMMER(E,P) Thiscircuitcanbe usedto controltheamountof currentin an incandescent lamp andalsoa DC motor.lf youchangethe amountof currentthrougha And if youchangethe amountof current lampyou changeits brightness. througha DCmotoryouchangeitsspeed.lnputvoltagecanrangefrom6 to 12 voltsandcurrentdrainin the outputis up to 2A.Youcan alsousethis it intoa circuitin the outputof a 6V or 12Vfixedpowersupply,converting variable 0 to 6 voltor 0 to 12voltsupply. Thecircuitcan be shouldbe mountedon a heatsink. Thepowertransistor fixedon the withthetransistor housedina smallplasticboxandtheheatsink outside. of a car'spanellampsandin Thecircuitcanbe usedto controlbrightness to controlDCmotorspeedalonga widerangeof values.Also,sevrobotics usingthis currentflowcontrolcan be performed involving eralexperiments circuit. current Thecircuitactsas a variableresistoror rheostatwiththe principal pothe through flowing control current andthe flowingthroughthetransistor is onlya fewmilliamperes. Currentthroughthepotentiometer tentiometer. diagramof the DC dimmeris shownin Figurc t. Ql is an The schematic usedin thisproject. component andtheprincipal NPNpowertransistor doesnot showon layoutis shownin Figure2. Thetransistor Components the heatsink,however. current canbe used,buttakecarewiththe maximum transistors Equivalent theycan control.Typessuchas TlP31andTlP41can be usedto control in Rl valuemustbe Also,a furthermodification lampsup to 2 amperes. value,thatcurrentis madeto ensurethat,whenP1is set nearits minimum flowingthroughthelamP. as areused,takecarewiththeirterminalpositions, transistors lf equivalent theycanbe ditferent. AD

Prrfoct12 DG hmr Iilmmu

F1 5A

Q1 2N3055

+12V IN

oul I:

Figure I

Figure2

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Hr]||Fc0tffimDculmffir PartsList - DCLampDimmer Q1

- 2N3055 SiliconNPNpowertransistor

P1

- 4,700ohm potentiometer

R1

- 470ohm,2W,.5"/"resistor

F1

- 5A fuse

:

ldeasto Explore Tolearnmoreaboutthecircuitor to getbetterperformance: o Youcan usea PNPpowertransistor, inverting inputpolarization. ExplainwhythiscircuitcanonlycontrolDCcurrents. o A Darlington transistor canbe usedto reducecurrentflowthrough potentiometer. Replace P1witha 100,000 ohmcommonpotentithe ometerand Rl witha 10,000ohm,1/4wattresistorwhenusinga powertransistor. TlPl10canbe usedin thiscase. Darlington o Whatis a rheostat? applications: Scienceanduncommon o Youcan usethiscircuitto controlbrightness light of microscope A 6V lampcanbe usedfor thattaskandthiscircuitwillbe sources. wiredbetweenthe lampand a 6V powersupply.The 6V regulated powersupplydescribed in thisbookis idealforthisapplication. o Experiments in electrolysis canbe current-flow andelectroplating controlled by usingthiscircuit. a Thiscircuitcan be usedto controlsmallmotorsin roboticsor in physics experiments.

tl

ffi|m n mllmDllmmei o The amountof currentin currentfieldscan be controlledby using this circuitand a DC powersupply.Experimentsinvolvingelectrotropismcan be attempted. Try to put plantswithina coil to observethe influenceof the magneticfield on theirgrowthand development. Rememberthat there is a magneticfield arounda coil of wire that is carryinga current. Figure3 showshowthis experimentcan be arranged. The coil is formedby 10 to 50 turnsof commonNo.1I to 22wirearounda cardboardboxor woodform.An ammeterin serieswiththe coilcircuitcan be usedto controlthe amountof currentusedin the experiment. Rememberthat too much currentwill causethe coil and the transistorto overheat.lt is a good ideato add a lampin serieswith the coil circuit.The lampwill add resistanceto the coil circuit,reducingcurrentflow to a safe level.

Figure 3 t5

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(E) AUDrOOSCILLATOR audiblesignalsin the oscillator can generate Thislow-power experimental loudspeaker or a low-ima small 2,000 Hz, driving 100 and rangebetween by2 twoor fourAAcellsor a pedance Thecircuitcanbe powered earphone. forthiscircuitdependupon Currentrequirements fixed6 voltpowersupply. impedance and rangetypithe powersupplyvoltageandthe loudspeaker callyfrom10to 300mA. frequency andcan be set withina P1 adjuststhe operating Potentiometer ohmscan be used, up to 1,000,000 largerangeof values.Potentiometers rangelowerlimitto about10Hz. thefrequency changing for 0.01andO.22uFaresuitable andvaluesbetween C1canalsobealtered, in thelowerpart frequencies LargeC1valueswillproduce experimentation. of therange. Thecircuitcan be usedas partof alarms,games,toysandto learnmore oscillators. abouttransistorized Q1 andQ2 diagramof the Audio-Oscillator. FigureI showsthe schematic amplifier andRl/Cl is theclosedloopthattakesthe forma directed-coupled signalbackfromtheoutputto theinput. , . usinga terminalstripaschasthelayoutofthecomponents, Figure2shows andpowersupplycanbe housedin a smallplastic sis.All the components box. homemade-type switch,butyoucanalsouseanSPST Thekeyis atelegraph if you A keyis recommended operation. toggleor slideswitchforcontinuous pracor in demonstrations Morse sender asa Code wantto usetheoscillator tice.Youcanwirethe pointsA and B to the contactsof a relayto usethe circuitas partof an alarm.

tt

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cl 0.047pF

B1 3TO6V

Figure I

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:

PartsList - AudioOscillator Q1

- 8C548generalpurposeNPNtransistor

Q2

- 8C558generalpurposePNPtransistor

SPKR- 4 or 8 ohmsmallloudspeaker K

- Telegraphic key- Seetext

81

- 3 to 6 volts- twoor fourAAcells

Ri

- 10,000 ohm,114w,5% resistor

R2

- 1,000ohm,114W,5% resistor

Cl

- 0.047uF metalfilmor ceramiccapacitor

ldeasto Explore Tolearnmoreaboutthecircuitor to getbetterperformance: o ChangeC1fora capacitor in therangebetween 0.01and0.22uF. Thefrequency rangeof the produced tonewillbe altered. With0.01 uF or lowervaluesfor Cl, the circuitwillproduceultrasounds. Usea tweeteror a piezoelectric transducer in thiscase. . Replace Q1witha TlP32orTlP42andpoqerthecircuitwitha 12 getmuchmorepowerin theoutput. voltsupply.You'll .

Explainwhyoscillators needa closedloopto the signalto work.

Scienceprojects andotherapplications: o Experiments in acoustics canbemadewiththisdevice. Thecircuit canproduceanytonebetween10and20,000Hz,andevenhigher.

tt

1

I l

I

;nlrcr l3 |latr Iscffia.] o A telegraph stationcanbe simulated withthiscircuit. Youcanfind MorseCodein anybookabouttelegraphy. o Byreplacing K witha reedswichwiredto pointsA andB,thecircuit willoperateas an alarm. o Experiments involving conductivity of materials canbe madewith probesplugged to pointsA andB. o Connectresistive transducers as LDRsandNTCsat pointsA and B to geta light-dependent or temperature-dependent oscillator. a Usingtwo metalrodsas sensors, the circuitcan be useas a lie detectoror bio-feedback device.ReplaceCl witha 0.22or 0.47uF pulsesat the speaker. capacitor andadjustPl to getseparated The pulseratewillbealteredwhentheskinconductivity oftheinterrogated personchanges whilein a stateof straindueto a lieor stress. o A 117V+V x 250mAtransformer canreplaceSPKRto produce pulses high-voltage in nervestimulation Thegenerated experiments. pulsescanreachvoltages as highas 400Vpp. o Experiments in animalphysiology canbeconducted usingsounds projects. or highvoltageas described in other Growthof plantssubmittedto high-power soundsor high-voltage fieldscan be observed usingthiscircuitwithpractical experiments. o ACfieldscanbegenerated byreplacing thespeaker witha 2O-turn coil.Theplantsor animalscanbe positioned withinthecoil'selectric field.Seethesameexperiment usingthe DCDimmerforcoilandexperiment details.

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AUDIOSWTTCH(E/P) Thisaudiocontrolled relayhasa largenumberof applications andis interestingto theexperimenter whowishesto explore theworkinguniverse of relays andaudioor soundcontrolled circuits. Anaudiosignalintheamplitude rangebetween 1Vppand5 Vpptriggersthe pointsA andB. relay,powering on thedevice,wiredbetween Relayvalueis determined bypowersupplyvoltage. Fora 12voltpowersupplyyoumustusea 12voltrelay.Gurrent draindepends uponthepowersupplyvoltageandalsotherelayused.Usinga12Yx 38 mA(RadioShack275248'1relay, thecurrentdrainis lowenoughto allowtheuseof common cellsin the powersupply. 0.01and1.0uF,anddetermines thesensitivity of the Cl canrangebetween at lowfrequencircuitin theaudiorange.Largevaluesgivemoresensitivity cies. inputandneedsa strongaudiosignalto Thiscircuithasa high-impedance operate. FigureI showstheschematic diagram oftheAudioSwitch. thatthe Observe heartof thecircuitis a commongeneral-purpose NPNtransistor thatactsas a DCamplifier. forthisproject. Thecomponents ln Figure2we showlayoutof components canbesoldered ona terminal stripusedaschassis.The terminal stripcanbe flxedon a woodenboard. Position of thepolarized components, suchasthediodes,powersupplyand capacitor C2,mustbe observed. To usethisaudiorelayyou haveto wirepontsA andB to the outputof an powerrequiredis 5 watts)andadjustthevolume (minimum audioamplifier controlfor bestoperation. A smalltransistor therelaywith outputtransformer shouldbeusedto operate low-impedance signals, suchastheonesfromtheoutputof audioamplifiers.

I

I

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D2 1N914

(.)sEE

TEXT

D1 R1 1N914 ,t0K

B1 6OR9V

Figure I

Figure2 05

:

I

mrilffi||rrhsll|mmr Figure3 showshowto usethistransformer. R,dependsontheoutputpowerof theamplifier andis givenbelow:

I

OutputPower 0 to 1 watt 1 to 10watts

47 ohms,1/4watt

10to 25 watts

100ohms,'ll4watI

25 to 50 watts

220ohms,ll2watt

PartsList - Audio Switch

t0

Q1

- 8C548general-purpose NPNsilicontransistor

D1

- 1N914general-purpose silicondiode

D2

- 1N4002siliconrectifierdiode

Kl

- 6V or 12V relay- see text

R1

- 10,000ohm,1/4W,5%resistor

Cl

- metalfilm or ceramiccapacitor- see text

C2

- 100 uF,12 WVDCelectrolytic capacitor

81

- 6V or 12Vcells,powersupplyor battery

;TrM lf rilm$nilH

ldeasto Explore Tolearnmoreaboutthecircuitanddevicesor to getbetterperformance: o ReplaceQl witha Darlington (suchas a BCS17)and transistor resistorR1 with100,000 ohms.Thecircuitwillincrease in sensitivity. o ExplainhowC1functions in thiscircuit. Scienceanddifferent applications: o Connect thecircuitto anaudioamplifier output,witha mioophone pluggedto theamplifier input.You'll havea sound-operated switch. o Thiscircuitwitha microphone andan audioamplifier canbe used to closea trapwith soundactivationor to activatea recordingwith sounds. Youcan alsouse it to photograph an explosion or the crashof an produced objectbytriggering a flashwiththe sound. o The audiooutputof a multimedia systemin a computercan be usedto controlexternal deviceswiththiscircuit.

R;

FRoM AM P L T F T E R ourPUT

l-----+x

IIF 3lE ''l |

ro

AUDlos\ L._--_-{'Y

8: 1000

o

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i

I I I

(P) 6 VOLTSFROM12V BATTERTES Withthisadapteryoucan power6 volt(upto 1A)devices,suchas recorders, CD players,calculators,radios,batterychargers,etc.,fromyourcar battery. The currentadapteris pluggedinto the vehiclelightersocketand is small enoughto be housedin a very compactplasticbox. Only four componentsare used.The lC determinesthe outputvoltageand shouldbe mountedon a heatsink.Capacitorsare polarizedcomponents, so you mustobservetheirpositionwhenmounting.The fuseis veryimportantin orderto protectthe deviceand car wiringagainstshorts. Outputvariesaccordingto the deviceyou are applyingpowerto. DC extension cableswith plugsto fit the deviceto be poweredshouldbe used.Take care with the outputpoles.Checkif your devicehas a positiveor negative polein the centralterminal. The schematicdiagramof the 12Vto 6V x 1Aconverteris shownin Figure 1. The principalcomponentis lC1, a 6V voltageregulatorthat operateswith inputvoltagesrangingfrom I to 35 volts. Componentslayoutis shownin Figure 2. Allthe componentscan easilybe housedin a plasticbox. The integratedcircuitcan be changedto alterthe outputvoltage.You can use a 7809for 9V x 1A outputor a 7805for 5V x 1A output. It is very importantthat no partsof the componentsusedin this circuittouch one another.The lC has short-circuit and thermalprotection.

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Figure 1

Figure2 gl

m?nmffimsu||nomcr PartsList - 6 VoltsFrom12VBatteries lC1

- 7806Integratedcircuit

C1

- 1,000uF,16 WVDCelectrolytic capacitor

C2

- 100 uF,12WVDCelectrolytic capacitor

Fl

- 2A fuse

ldeasto Explore Tolearnmoreaboutthedeviceor to getbetterperformance: o Replace theintegrated circuit(lOl) witha 7805or 7809to getoutputvoltagesof 5Vand9V. o Explaintheditference between thislinearvoltageregulator anda powersupplies. switch-mode regulator usedin computer o Thiscircuitcanalsobeusedin nonregulated powersupplies to get a regulated x 1A 6V output. o lt'spossible powersupplyby replacing to geta negative regulated the7806witha 7906lC.Doa searchforinformation aboutthischange in theproject. Scienceprojects anduncommon uses: a Youcan usethis downconverter to powerfourAA cell-powered circuitsfroma 12Vbatteryin scienceexperiments. o 6V lampsusedas lightsourcefor microscopes can be powered fromthe car batteryusingthisdownconverter. Fieldwork usinga microscope canbe conducted usingthiscircuit.

t2

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(E) TRANSMITTER oNE-COMPONENT by thosewithno patiencefor Hereis a projectthatshouldbe constructed wireis usedto builda complete building. Onlyonecomponent electronics lesstransmitter! lt is a CW(conradiosignals. wayto generate Ofcourse,thisis thesimplest and is powerfulenoughto plunkdowna signal tlnuouswave)transmitter on the550kHzto 7 MHzband. anywhere uponpowersupplyvoltageandis inthe Thefundamental frequency depends reaching 100kHzand1 MHz,buttherearestrongharmonics rangebetween upto 7 MHz. Asyoucan diagram ofthissimpletramsmitter. Figure/ showstheschematic a 4049CMOSlC thatis formedby six see,we haveonlyonecomponent: areused. ln thisprojectonlyfiveinverters inverters. fromAAcellsor batteryandcurrentdrainis verylow. Thecircuitis powered projectyoucan placethe lC on a universal solderless As an experimental board.Theantennais a singlewire2 to 5 feetlong. A commonAM (mediumwaveor shortwave)receiveris placednearthe upto somefeetaway. A signalcanbetunedin fromdistances transmitter. showninFigure2. Therearetwowaysto tunethetransmitter, wechangethepower isvoltage-dependent, Inthefirstcase,asthefrequency Usea 12voltpowersupplyandadjustthevoltagein the lC supplyvoltage. in thefeedback capacitor withP1.Inthesecondcase,we includea variable loopto alterthefrequency.

Transmitter PartsList - One-Component lC

- 4069or 4049CMOSintegratedcircuit(onlythis!) (Anda powersupply,of course)

30

PnftGtl0 FGmnmil

Tnmillt0l

l*

lC1= 4O49B

1 oe

Figure I

Figure2 -

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n;||FdFilDgnntr l&as to Erplore Tolearnmoreaboutthe circuitanddwice: o Explainhowradiosignalsaregenerated andWhywedon'tneeda tunedcircuit. o Whyshouldan evennumberof gatesbe usedin thiscircuit?Will an oddnumberwork? o Whycanyoutuneinthesignalson morethanonepointof thedial? Scienceprojects: o Sendtelegraphsignalsthrougrh a wallusingthiscircuitastransmitter andan AM radioas receiver. o Explainhowcomputercircuitscangonerateradiosignals(noise), usingthiscircuitas an example.

It

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WIRELESSFMTRANSMITTER(E/P) Thesecircuitshavealwaysbeenpopularfor bothutilityandentertainment purposes. TheFMtransmitter described hereis builtwithfewcomponents tosavespace powered andcost.Thecircuithasonlyonetransistor is and bytwoorfourAA cells. The broadcasting frequency of the unit,in the rangebetween88 and 108 MHz(FMband),is determined by Ll andthevariable capacitor CV (a 2Oor L1consists 30 pFtrimmercapacitor). of fourturnsof No.22wire,woundin a singleclose-spaced layeron a 112-inch form.Thecoilis centertappedwhere it is wiredto theantenna terminal. Anypieceof stitfwirewillserveas theantennaandwillgivegoodcoverage. Forbetteroperation, antennalengthshouldbe between 5 and15inches. Tryoutyourunit at anyconvenient deadspotonthetheFMband.AdjustCV to thebestsignal.Thesignalscanbetunedin distances upto 150feet. A schematic diagramof the FMtransmitter is shownin Figure1.Onlyone transistor as usedas a high-frequency oscillator. AnysmallRFNPNtransistor canbe usedforthetask. placement Components on a printed-circuit boardis shownin Figure2.Capacitorsare criticalcomponents and shouldbe the typesindicatedin the partslist.Don'tusemetalfilmcapacitors insteadof the ceramiccapacitors whicharecalledfor in thepartslist. Youcanalsousea terminalstripas chassisas shownin Figure3,butkeep allthecomponent terminals andwiringshortto avoidinstability. Thecircuitcanbehousedin d smallplasticboxalongwiththepowersupply. Avoidtheuseof metalboxesto housethecircuit. pieces,suchas the electretmicroTakecarewithpositionof the polarized phone,electrolytic capacitor andpowersupply.

r02

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Q1 \ 8F494 R4 47

Figure 1

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PartsList - WirelessFMTransmitter Q1

- 8F494RF silicontransistor

MIC - two-terminal electretmicrophone L1

- coil - see text

CV

- trimmercapacitor(20 to 50 pF)

R1,3 - 4,00ohm,114W,5% resistor R2

- 10,000ohm, 114W,5% resistor

R4

- 47 ohm,1l4W,5%resistor

C1

- 10 uF,6 WVDCelectrolytic capacitor

C2

- 0.01 uF ceramiccapacitor

Cg

- 4.7 pF ceramiccapacitor

C4

- 0.1 uF ceramiccapacitor

S1

- SPSTslideor toggleswitch

81

- 3V or 6V - two or fourAA cells

A

- antenna- see text

ldeasto Explore To learnmoreaboutthe circuitor to get betterperformance: o ReplacetransistorQ1 with a2N2218and powerthe circuitfrom a 9V battery.The signalswillbe tunedin fromdistancesup to 1,500feet. o The circuitcan be usedas a "bug"to hearsecretconversations.

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Figure 3 Placethe circuitinsidea falsebook on a deskto pick up conversations. o Explainhowthe transmitterworks. o Whatare radiowavesor electromagnetic waves? o What is FrequencyModulation(FM) and AmplitudeModulation (AM)?Explainthe ditferences.

IunPlolects folu|elrrcr|memcl Scienceprojectsusingthistransmitter: o The transmittercan be usedto pickup remotesounds.Youcan fix it in animalpensor jailsto monitorthemremotely. o The mikecan be placedin the focusof a parabolicreflectorto concentrate sounds.Birdsandotheranimalsintheforestor otherplaces can be heardusingthissystem,as suggestedin Figure4. An interestingstudycan be madeinvolving localsongbirds. o Youcan usethis transmitterfor an experimental broadcastin your schoof.However,don't use long antennas becauseFCC rules are severeregarding strong illegal radio emissions in the FM band.

Figure 4 100

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HIGH-POWER (E) AUDIOOSCTLLATOR Thishigh-power produces versionof anaudiooscillator a strongaudible tone usinga piezoelectric transducer. All fourgatesexistingin the 4093lC are usedin thisprojectto drivethetransducer witha goodaudiosignal. The circuitcan be usedin alarms,toys,as a standalone projectto teach aboutoscillators specifically, or in experiments usingcontinuous soundsin thefrequency rangebetween 100and10,000Hz. piezoelectric The recommended transducer emitsmaximumoutputpower 700and3,000Hz,butit willalsooperatein otherfrequencies between with lesspower. Powersupplyvoltagerangeis between 5 and12volts.Currentrequirements dependuponthepowersupplyvoltage,rangingfrom10to 50 mAtypically. Pl adjuststhe tonefrequency. Cl can be alteredwithina largerangeof valuesas indicated in theschematic diagram, shownin Figurel. placement Components on a printed-circuit boardis shownin Figurc2.You canalsomountthecircuitusinga solderless boardforexperimental applications. Allthecomponents (ifusedaspowersupply) andthebatteries canbehoused in a smallplasticbox. BZ canbe replaced witha commonpiezoelectric tweeter. But,in thiscase, youshouldopenthetweeterandremove thesmalltransformer frominsideit. Thentheoutputof thecircuitshouldbeconnected directlyto thesmallpiezoelectrictransducer.

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P1

- 40938CMOSintegrated circuit - Piezoelectric transducer (RadioShack273-090 or equivalent) - 100,000 ohmpotentiometer

Rl

- 10,000 ohm,114W,5% resistor

C1

- 1200pFto 0.047uFceramicor metalfilmcapacitor

lOl BZ

ldeasto Explore Tolearnmoreaboutcomponents anddevices: o Thiscircuitcanalsoproducesoundin the ultrasound band.Using a 1,200pF capacitor for C1,the rangewill reachan upperlimitof about100,000 Hz. o Explainhowa push-pull outputstageoperates. Scienceanduncommon applications: o Thiscircuitcanbe usedfor animalconditioning or in experiments involving sounds. o Byreplacing Pl withsensors, suchas LDRs(LightDependent Resistors)or NTCs(Negative-Temperature Coefficientresistors),tone frequency willbe light-dependent or temperature-dependent. -

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o By replacing Pl withtouchsensorsor electrodes, wecanusethe circuitas lie detectoror bio-feedback The soundpitchwill devices. dependuponskinresistance.

PnfccrlE lllti-'lrdlilllr0sd[ru o The circuitcan also be usedas a fish attractoror in experiments BZwithwiresimmersed involving wateranimalsandsounds.Replacing works into waterwill generateelectriccurrentfieldsfor experimental involvingthe influenceof thesefieldson fish or otherbeings. o Someanimals,suchas miceandrats,arescaredoff by ultrasounds. to determinethe frequencies The circuitcan be usedin experiments that are moreetfectivefor this task. Seeotherprojectsinvolvingsoundsfor newideasto explore.

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TIMER(E/P) Smallhomeappliances andcircuitscanbeturnedonattera timedelayrangingfromsecondsto minutesusingthissimpletimer. Schoolandhobbyist experiments canbetime-controlled by usingthiscircuit. Theunithasa constant-current sourceto chargecl. Cl andPl adjustthe timerange.You canalterC1withina rangeof 100and1000uFto change the timerange.

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Usinga 1 ampererelayyoucancontrolACloadsupto 100wattswiredto the 117VACpowerline. Tooperatethe unit,connectthe loadto the relaycontacts(pointsA andB, usedas a switch)andadjustP1to the desiredtimedelay.Press52 do dischargeCl completely . ThencloseSl to start.Aftertheadjusted timedelay, therelaywillclose,andtheloadwillbe powered ON. Conversely, byusingtheNC(Normally Closed)contacts of therelayyoucan turna deviceOFFaftertheadjusted time. Tousetheunitagainyoumustpress52 to discharge C1 beforestarting. FigureI showsthe schematic diagramof the tlmer.Observethe ditferent components usedin thisproject: (UJT)andan SCR a unijunction transistor (SiliconControlled Rectifier). An mechanical viewis shownin Figure! usinga terminalstripas chassis. All thecomponents andpowersupplycanbe housedin a smallplasticbox. Takecarewith'positions of criticalcomponents, suchas the UJI, SCR,diodesanddlectrolytic capacitors. Therelaydependsuponthepowersupplyvoltageandvoltagedropthrough the SCR.Thisdropis about2 volts,so youneedto use6 to 7.S-volt relays witha 9-voltpowersupply. TheSCRneedn'tbe mounted on a heatsink, as thecurrentdrainis low.

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Figure2 thatcurrent to powerthistimer.Remember UseAA cellsor a transformer drainis lowonlywhenthe relayis notenergized.

IunEofccts for[n trnel|mcmcr PartsList-Timer Q1

- 8C548NPNgeneral-purpose silicontransistor

Q2

- 2N2646unijunction transistor

SCR - TlC106siliconcontrolled rectifier D1,2 - 1N4002silicondiodes R1

- 47,OOO ohm,1/4W,5%resistor

R2

- Lz}ohm,1/4W,5%resistor

R3

- 100ohm,1/4W,5% resistor

P1

- 100,000ohm potentiometer

C1,2 - 100 uF,12WVDCelectrolytic capacitors K1

- Relay- see text

51

- SPSTslideor toggleswitch

S2

- NormallyOpenmomentary switch

81

- 9V - six AA cells

ldeasto Explore To learnmuchaboutcircuitand devicesor to get betterperformance: a Explainhow a constant-current sourceoperates. o Explainhowa UJTand SCRoperate. o AlterC1 to get highertimedelays.Tryvaluesup to 1,000uF.

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?rutctlg fhtr projects usesforthisdevice: anduncommon Science o All experiments thatneedtime-delay controlcanusethisdevice, as longas thetimedelayneededfallsin the rangeof thistimer(betweena fewsecondsand minutes). Usea commonwatchas refer. enceto makea scaleforthe potentiometer. a Thecircuitcanbe usedto activate witha experiments dangerous to reachsafedistance. theexperimenter safetime-delay allowing o Trapscan be armedaftera time-delay, can so the experimenter avoidthetraphimself. o Chemical processes usingthistimer.Anyaudio canbe controlled in thisbookcanbe useas warningcircuitwhen described oscillator wiredto therelayoutput.

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(E/P) MrcRoAMRADIO ThismicroAMradiowilltunestrongstationsinthefrequency rangebetween 530and1,600kHz. Thecircuitusesonlyonetransistor as the amplifier andwitha transformer poor Asthecircuitisvery drivesa smallloudspeaker. inamplification, it needs Theantennashouldbe from15to 50 feetlongforbest a longwireantenna. results. A goodgroundconnection is alsoimportant. Of course,thisis a smallinexpensive transistor radiowithlowlistening volume,particularly on a weakstation.lf the stationis too weak,replacethe SPKRbya low-impedance earphone. Thepowersupplyis formedbytwoor fourAA cellsandcurrentdrainis very low,extending theirlife.Thecircuitdrainsonlyfewmicroamperes. L1 is a tappedloopstick, connected to variablecapacitor CV. Theseitems canoftenbe foundin non-working transistor radios,as wellas the speaker andtransformer. FigureI showsthe schematic diagramforthisproject.DiodeDl actsas a T1 is a commontransistoroutput detectorand Q1 as an audioamplifier. transformer. ln Figure2 we showthe components layout.All the components can be housedina smallplasticbox.A terminal stripis usedaschassisinanexperimentalversion. (1,000:8) T1 is a transistor transformer andthe SPKRis a miniature type. But,if youhavean unworking AMradioyoucangetthesepartswithoutspendinganymoney. To use,closeSl andtuneto the desiredstationby adjusting CV.Youcan gain. adjustR1forthebestresultsaccording to yourtransistor

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PartsList - MicroAM Radio Q1

- 8C548general-purpose NPNtransistor

D1

- 1N34general-purpose germanium dlode

L1

- loopstick- seetext

CV

- 365pFvariable capacitor

T1

- Transistor 1,000:8 transformer

speaker SPKR- I ohmsx 2 in.miniature R1

- 2,200,000 resistor ohm,114W,5%

Cl

- 0.1uFceramicor metalfilmcapacitor

Sl

- SPSTtoggleor slldeswitch

81

- 3 or 6V - twoor fourAAcells

ldeasto Explore Tolearnmoreaboutthecircuitor to getbetterperformance: o Replace andfind transistor, suchasa BC517, Ql witha Darlington and a bettervaluefor R1.Valuesin the rangebetween2,200,000 10,000,000 ohmscanbe used. o Replace L1by20turnsof No.28wireona ferriterodandtrytuning Position oftheL1tap stations. Usea longwireasantenna. short-wave get to best selectivity and sensibility. mustbe carefully studied o Experiment witha crystalearpiece intheplaceofT1 andSPKR.A 10,000ohmresistor shouldbewiredin parallelwiththeearpiece.

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Fnllcr 20 ffilrilmlh operate. receivers o Explainhowcrystalsetsor direct-detection o Definetheterm"selectivitt''. o Whatis a galena-crystal? Scienceprojects: howantiqueradioreo This receivercan be usedto demonstrate as lt canbepresented whenradiowasfirstinvented. ceiversoperated "modern galena in a demonstration. receiver of a crystalor version" a AM exhibitcan be madewiththisset,the free-power An interesting (described in thisbook),anda crystalset. receiver a The circuitcan alsobe usedas an RF "snitfe/',detectingradio band. circuitsintheAMorshort-wave byexperimental signalsproduced get a sensitive ReplaceLl witha 1,000uHchokeandremoveC1to RFsnitfer.

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TOUCHSWITCH(E) bya simpletouchwith lampsandmotorscanbecontrolled Smallappliances, by Pl fora circuit.LoadsareONduringthetimeadiusted thisexperimental byusingtheNC(normally to morethan10minutes.conversely, fewseconds time. aftertheadjusted youcanalsoturnotf an appliance closed)contacts be placedfar Thesensoris formedbytwosmallmetalplates,andshouldn't at thesamemomentThemetalplatesarefinger-touched fromthecircuit. on depending froma 6- or 12-voltpowersupply, Thecircuitcanbe powered proiect' to this with powersupplies therelayused.Donotusetransformeless powersuppliesare not shorts.Transformerless avoidshocksor dangerous shockhazard. a dangerous fromtheAc-powerlineandrepresent isolated bycurrentupto 50 mA' K1is a relaywith6- or 12-voltcoilandis energized Withrelaysin this rangeyoucan powerthe touchswitchfromAA cells(6 volts)or smallPowersuPPlies. Switchis showntn Figurcl.The circuitusesa 555 of theTouch A schematic P1' byadjusting lC timeras itsheart,andtimedelayis determined printed-circuit board,is shownin usinga smallhomemade circuitmounting, diaFigure2.lf you:dliketo etchyourownboardusethispartsplacement gramas guide. ln Figure3weshowthesensorthatcanbemadewithtwosmallmetalplates belong.A maximum orwoodbase.Wiresto thesensorshouldn't ona-plastic to avoiderraticoperation. lenghtof 10feetis recommended and capacitors suchastheelectrolytic components, Pos16nof the polarized A and B. Reto terminals Loadis connected diodes,shouldbe observed. memberthatthe relayactsas a switch. to avoiddangerpowersupplies Don'tpowerthiscircuitfromtransformerless ousshocksandshorts. use a controlcanbe addedto thiscircuitin a simplemanner. A sensitivity forthistask. ohmpotentiometer 1,000,000 -

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Hr Frdrctslolho Dndmomcl PartsList -Touch Switch lC1

- 555 integratedcircuit,timer

NPNtransistors Q1,2 - 8C548general-purpose D1

- 1N914silicondiode

Kl

- relay- see text

Rl

- 100,000ohm, 114W,5% resistor

R2

- 47,OOO resistor ohm,114W,5%

R3

- 10,000ohm,114W,5% resistor

R4

- 1,000ohm,1l4W,5olo resistor

P1

- 1,000,000 resistor ohm,114W,5%

C1

- 10 to 470 uF,12 WVDCelectrolytic capacitor- see text

C2

- 100 uF,16 WVDCelectrolytic capacitor

S1

- SPSTtoggleor slideswitch

81

- 6 or 12V- M cells,batteryor powersupply

ldeasto Explore or to learnmoreaboutthecircuit: Togetmoreperformance tranbyreplacing Ql witha Darlington o Sensitivity canbeincreased sistor,suchas a BC517. pointsY andX youcanuse o Byconnecting a reedswitchbetween thiscircuitdo detectmovement.Fixa smallmagneton the pieceto acton the reedswitch. rtl lu!

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'3 Figure 3 Scienceanduncommon applications: . Thiscircuitcanbe usedto closea trap.Thetouchsensorwilldetectwhentheanimalentersthetrap. o Projectsthatneeda wayto detectmovements, switching anyload, made with this kind like microswitches, canbe circuit.Several ofsensors, pendulum sensorsor anyothermomentary-type switchcanbe used inthiscircuit. pointsA andB.Alsoconnecta 100,000 o Connect an LDRbetween poleofthepowersupX andthenegative ohmpotentiometer between ply.You'llhavea light-operated relayor remotecontrol. A flashof light produced lightercanclosethe relay, by a lanternor evena cigarette powering theload.Thecircuitcanbe usedto detectflashesof lightin FixtheLDRintoa telescope scienceexperiments. andyoucandetect meteorfallings. a Experiments involving thunderstorms at nightcan be conducted Thefirstflashof lightning automatically usingthiscircuit. canbe used to powerONtheequipment.

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SIMPLEFLUORESCENT (E/P) LAMPTNVERTER tube(from7 to 4Owatts)froma 6Thiscircuitwilllighta commonfluorescent or 12-voltpowersupply,suchas ni-cadcells,D cells,car batteryor other source,withoutneedof a chokeor starter.Eventhe oldtubeswhichno longer functionat all on AC powerlineswilllightwhenusedforthispurpose.(Some of them,though,maybe too weakto lightwhenthe circuitis poweredfrom6 beforehand.) or 12 volts.Youshouldexperiment light,in trailers,signaling, etc. Youcan usethe deviceas an emergency By poweringthe fluorescentlampwith a transformerpowersupplyyou inavoidingdangerousshocksor shorts. creasesafetyfactorof an experiment, Currentdrain,typicallyrangingfrom 100to 800 mA,dependson the characteristicsof the lampused,the powersupplyvoltage,and the transformer. to the drainedcurrent.Experiments should The lampwillbrightenaccording be done with some ditferenttransformersand oscillatorfrequenciesto get out of the circuit. betterperformance High oscillatordrivinga transformer. Basicaly,the circuitis a low-frequency light. to'lighta fluorescent voltageis obtainedfromthe transformer The trimmerpotentiometer allowsfrequencyadjustmentto get betterperformance. Schematicdiagramof the FluorescentLampInverteris displayedinFigure oscillatorwith a pairof 1.As you see,the circuitconsistsof a low-frequency transistors. complementary Componentslayout,usinga terminalstripas chassis,is shownin Figure2, placement is not critical. Components Transistor Q2 shouldbe mountedon a largeheatsink.Tlis a 6V x 450 mA or secondarycoil) trans12Y x 450 mA transformer.lf a CT (center-tapped wires. formeris you shoulduse onlytwo of the threesecondary's

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IunPnf0cFful[o H$lmilu from300to 800mA currents withsecondary withtransformers Experiments 9 and15Vcanbe madeto getbetterperformance. betweeen andvoltages lampis poweredwithhighvoltagesthatcan be Warning:Thefluorescent connecandwhenhandling Takecareof the wires'insulations dangerous. tionsto thedevice.

PartsList - SimpleFluorescentLampInverter Q1

- 8C548- generalpurposeNPNsilicontransistor

Q2

-T,P42- PNPpowertransistor

T1

- Transformer: 117VAC;6V x 450 mA or 12Yx 450 mA

Xl

- Fluorescent lamp- see text

P1

- 470,000ohms- trimmerpotentiometer

R1

- 10,000ohms,1/4-watt,5% - resistor

R2

- resistor - 1,000ohms,114-watl,5%

C1

- 0.047uF - metalfilm caPacitor

ldeasto Explore Tolearnmoreaboutthecircultor to getbetterperformance: o Tryto usea ferritetransformer in placeof T1.Thecircuitperformancewillincrease. o Explain workinthiskindof circuitandwhytranshowtransformers formersdo notworkin DCcircuits. applications: anduncommon Scienceprojects lampandyou'llhave o Replace Xl byansmallultravioletfluorescent

Prolcct22 SlMcHurlr$mtlrmtlflmcl materials Manymaterials, including a mineralor fluorescent searcher. percentage glow theoneswitha high of calcium, will whenilluminated Manyexperiments by ultraviolet. and demonstrations can be made plantsandfluorescent involving minerals, materials . o An interesting withplantsis to studytheetfectof ultraexperiment plants'growth violetradiation onditferent orgermination. lrradiate severalbatchesof variousseeds,suchas tomato,been,squash,etc., reaching withUV andthenplant.Because of increasing UVradiation theearthdueto depletion oftheozonelayer,theetfectofthisradiation plant lifeis of concernto us all. on o Compareetfectsof ditferentlightwavelengths to seedgermination.Thewavelenghts rangefrom200to of incoming solarradiation (nm). 3,000nanometers UV radiationis between380and400 nm. batchesto Selectseedsfromcommonplantsandexposeditferrent wlththediferent UVand/orcommonlight(redto blue).Whathappens Youalsocanconductthe experiment not seedsduringgermination? onlywithseeds,butplantsandinsects. o Highvoltagepresentin the 117Vtransformer coilcanbe usedin Pleaseadda 10,000ohmpotentiomnervestimulation experiments. eter to controlthe appliedvoltageif the circuitis intendedto be used haspeaksashighas400V! voltagein thetransformer onhumans!The o Fluorescent lightcanalsobeuseinexperiments withinsects. Some lnsect kindsof insectsareattracted by light(visibleandultraviolet!). trapscanbe constructed usingthiscircuitas base. o Fishandotheranimalscanbeattracted light.A cirbyfluorescent powered forfieldwork. cuit bycellsor batteryis important o Alternate methods offarmpestcontrolcanuselight,visibleaswell partof thespectrum. lnsecttrapscanbe as radiation in theultraviolet inverters. withfluorescent lamp Forfurtherinformation: constructed Alliance for Sustainable Agriculture Thelnternational 1701University Avenue SE (612)331-1099 Minneapolis, MN55414 tft

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TOUCHON/TOUCHOFF RELAY (P) toolsand AO-powered appliances, suchas lamps,smallhomeappliances, otheritems,can be controlledby yourfingertipsusingthis circuit.Also,test can be controlled by thiscircuit.You canturnon equipment andexperiments any load by first touchingtime sensorX1, then turn it otf by touchingXl again.Thereis no shockhazard,as the controlcircuitis completelyisolated fromthe AC powerline. The controlcircuitis poweredfrom four or eightAA cells,or, if you prefer,a powersupplyrangingfrom 6 lo 12 voltsaccordingto the relaycoil. powersuppliesbecausetheyare not isolatedfrom Don'tusetransformerless the AC powerlineand can causesevereshocksand shorts. The schematicdiagramof theTouchOnffouchOff Relayis givenin Figure 1. producing The circuitusestwo lOs.The 555 timerworksas a monostable, one controlpulsewhenthe sensoris touched.The 4013 is a flip-flopthat controlsthe relayby a transistor. placementon a homemadeprinted-circuit boardis as shownin Components Figure2. Componentlayoutshouldbe alteredif the relayusedin the project is an equivalentof the type indicatedin partslist. Relaycoil voltageis determinedby the powersupplyvoltageand the load Youcan use a mini 1A DPDT(RadioShack275-2491 currentrequirement. 12V,280ohm,43 mA,andwireit as shownin thefigure,or useanothertype of relay,dependingon the loadrequirements. A 10A SPDT mini-relay(RadioShack 275-278)is suitablefor heavyduty appliances. As a simplerule,you can use a 6- or 12-voltrelaywith coil currentsranging from 10 to 100mA andcontactsup to 10A,accordingto the taskyou havein mind. Positionsof the polarizedcomponents, suchas the diode,electrolytic capacitors and transistor,shouldbe observed.

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Sensorarethe Sameas the'TouchSwitch"pQect describedin this book. Don't use metallicbox to housethe device,as there are parts connected directlyto the AC powerline.Be sure that thereare no powerline contacts withthe lowvoltagecircuitto avoidshocksand dangerousshorts. The loadis connectedas shownin Figure 3, to be ON whenthe relaycoil is Youcan also use the normallyclosedcontactsto turn otf a load energized. whenthe relaycoil is energized. are highwhenthe relaycoil is enerRememberthat currentrequirements That is gizedand lowwhenthe transistorQ2 is otf (relaycoil nonenergized). an importantfactorto considerif you are usingbatteriesto powerthe unit.

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ErleG[20 Iffi mtltrEl0rr.trr plugthe Afteryouaresurethatyouhavewiredallpartsofthecircuitcorrectly, powercordintothewallsocket. Youcannowtestthecircuit. Theload a loadto theoutput(relaycontacts) andtouchthesensor. Connect powered shouldbe ONif all is OK.

PartsList -Touch On/TouchOff Relay lC1

- 555 Integratedcircuit- timer

lC2

- 40138CMOSintegratedcircuit- dualflip-flop

NPNsilicontransistors Q1,2 - 8C548General-purpose D1

- 1N914General-purpose silicondiode

K1

- Relay- see text

R1,2, 5

- 100,000ohm,114W,5% resistors

R3,4 - 47,OOO resistors ohm,114W,57o RO

- 1,000ohm,114W,5% resistor

Cl

- 1 uF,25 WVDCelectrolytic capacitor

C2

- 0.1 uF ceramicor metalfilm capacitor

Cg

- 4.7 uF,12 WVDCelectrolytic capacitor

C4

- 100 uF,16 WVDCelectrolytic capacitor

S1

- SPSTtoggleor slideswitch

81

- 6 or 12V (accordingto relay)- see text

X1,2 - sensor- seetext

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ldeasto ExPlore Tolearnmoreaboutthe circuitor to get betterperformance: can be obtainedby replacingQl with a o Betterperformance suchas a 8C517. transistor, Darlington placedbetween thebaseof Q1and o A 100,000 ohmpotentiometer adjustment thenegativepoleof thepowersupplywillgivea sensitivity forthecircuit. as usedin thiscircuit,works,andthefunco Explainhowa flip-flop, tionof theC3/R5networkin thisproject.Explainwhythecurrentflowingthroughthefingerswhenthesensoris toucheddoesn'tcauseany shockhazard. youcanpoweroN theloadwhen o Depending upontheapplication, is possible (toreducepowerconsumption).That relayis notenergized usingthe normallyclosedcontactsof the relay.

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PililiGr2E lffim/rdclffirffiu uses: anduncommon Scienceprojects . By connecting a reedswitchbetweenpointsX1 andX2 you can itemsinexperiments of mechanical usethecircuitto detectmovement to actontheswitch. item moving projects. on the Justatfixa magnet or withthiscircuitbyusing o Experiments canbeconducted withanimals X1 andX2. between connected transducers appropriate o An LDRcan be usedto controlthe circuitwitha flashof light.A onor otf. lighteletc.,canbeusedto turnappliances lantern, cigarette

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(E) GALVANOMETER EXPERIMENTAL galvanometer describedhere can detectcurrentsas low The experimental operates and uses unusualparts.This galvanometer as few microamperes other several galvanometers foundin multimetersand as commoncommercial analoginstruments. that thereis a magOne purposeof this experimentcan be to demonstrate (Oersted Experiment). electricity neticfieldarounda coilthatthat is carrying an electriccurrentflowThe operatingprincipleis verysimpleto understand: ing acrossa coil (or a wire)producesa magneticfield.The fieldcan act on a mobilemagneticmetalpiece,suchas a compasspointeror a blade,as shown in the figuresherein.The compassor blademovementindicatesthe presenceof a current. galvanometer, Figure I showsthe two basicversionsof the experimental usinga commoncompassand usinga blade.ls very importantto observe the correctpathfor the currentflow in the coil.The coil shouldbe wiredexactlyas shownin the figure. The resistorcan ln Figure 2 we havea circuitto operatethe galvanometer. moresensitive resistor, the higher the The ohms. 100 to 100,000 rangefrom Experimentto find the highestresistorvaluethat can is the galvanometer. causethe pointerto move. The coil is madewith 50 to 200 turnsof No.28 to 32 wire on a paperform. The higherthe numberof turns,the sensitivity. Numberof turnsdetermines galvanometer. moresensitiveis the can be detectedwith a carefully Gurrentsas low as a few microamperes madeprototype.

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- coil- seetext

X1

- Compassor blade- seetext

ldeasto Explore Toget betterperformance or to learnmoreaboutthecircuit: o Experiment withseveralcoilswithdifferent numbers of turnsand comparesensitivity. Scienceprojects: o Demonstrate howOersteddiscovered fieldarounda the magnetic wire that is carryingelectricityand how moderngalvanometers are constructed. o Wherecangalvanometers canbe used?Whatarevoltmeters and ammeters? o Determine by connecting it in thesensitivity of yourgalvanometer (DCmA or uA scale)and a 100,000ohm serieswitha multimeter potentiometer.

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ALARM (E/P) OVER-TEMPERATURE when transducer beepsbya piezoelectric intermittent Thiscircuitwillproduce in this circuit use preadjusted You can value. risesovera the temperature silicondiodebutan NTC is a common etc.TheSensor greenhouses, heaters, canalsobe usedif youchangesomecomponents'values. positions of R1andPl withDl willcausethedeviceto operate Exchanging alarm. as an under-temperature lGla (pins1,2and3) bytwooscillators. signalis generated Theintermittent lOlc (pins8, 9 and10) lCl b andlOlc (oscillators). thatcontrols is aninverter ratefor the the modulation thatprovides oscillator is a very-low-frequency frequency its 4) has (pins5,6 and Thesecondoscillator secondoscillator. audiotonecanbealteredbyadjustbyR2andC1.Theproduced determined ingbothC1andR2withina largerangeof values. Forportableusea small9Powercomesfroma 3- to lS-voltpowersupply" Currentdrainis verylow,about0.5mAwhen voltbatteryis recommended. thetoneis otf.Whenthetoneis on,currentdrainrisesto about5 mA. Alarmis shownin Figurc 1. lOl, a of the Over-Temperature A schematic and twoas butfer'inverters. as oscillators 40ggB,hastwogatesoperating printed-circuit boardis shownin placement on a homemade Components PCboard. usinga single-sided Figure2.Youcanmadeyourprototype diodeD1(usedas sensor), especially components, of thepolarized Position placed fromthedeviceby using far Thissensorcanbe shouldbe observed. or waterfalling commonwiring.Youmusttakesomecareto avoidhumidity atfectthealarmoperation. ontothesensor,whichwillcauseadversely or a or equivalent) (RadioShack27g-O7g transducer BZ is a piezoelectric crystalearpiece. to getsoundat the deis adjustedby P1.Setthispotentiometer Operation you can replacethe To get a morepreciseadiustment siiedtemperature. potentiometer. by a multi-turn commontrimmerpotentiometer

ltf

Pfrfrcl25 M-Iomnnurulhm vcc

+3Vto +15V

P1 10M R1 100K

Figure 1

0V +Vcc

+

Figure2 yourfingersto seehowit works:whenthetemperaGetthesensorbetween turerisessomedegreesthecircuitwillproducea serieof beeps.lsolatethe willstop. sensor,andaftersomesecondssoundemission

ftnPniloctsfi$e mdlffibl

Alarm PartsList - Over-Temperature lC1 - 4093CMOSintegrated circuit

R1

- 1N914or 1N4148 purpose general silicondiode - Piezoelectric transducer or crystalearphone (RadioShack273-073 or equivalent) - 100,000 resistor ohm,1l4W,5olo

R2

- 33,000ohm,114W,5% resistor

R3

- 2,200,000 resistor ohm,114W,5%

Pl

- 10,000,000 ohmtrimmerpotentiomer

Cl

- 0.047uF metalfilmor ceramiccapacitor

C2

- 0.47uF metalfilmor ceramiccapacitor

Cg

- 100uF,16WVDCelectrolytic capacitor

D1 BZ

ldeasto Explore To learnmoreaboutthecircuitor to getbetterperformance: o AlterbothR2 andC1 to changetonepitchor bothR3 andG2to rate. altermodulation o Replace Dl witha 10,000 to 100,000 ohmNTC,Rl witha2,200 to 1,000,000 ohmpotentiometer, ohmresistor, andP1witha 100,000 get new kind of sensor. to a o Tryto adda power{ul suchas outputaudiostageusinga transistor, projects in thisbookfor Seeother a 8D135anda smallloudspeaker. suggestions abouttheconfiguration.

r50

; j I I !

Pnfocfl 25 ow-lcmrunnnilnm Scienceprojectsand otherapplications: o Chemicalprocessesthat involveheatchangescan be controlled usingthis alarm.The sensorshouldbe protectedagainstmoisture and waterin experiments involvingliquids. o ReplaceD1 by an LDRor photodiode. The circuitwill operateas a lightalarmor darkalarm,dependingupon sensorposition. Withan LDRit wouldbe betterto replaceP1 witha 1,000,000ohm potentiometer and R1 with a 10,000ohm resistor.Lensesplacedin frontof the LDRor phototransistor can be usedto increasesensitivity. o The circuitcan alsooperateas a water-level alarmby usinga twowire sensorto replaceDl. The sensoris madewith two barewires. The wires are separatedby a distanceof about2 or 3 inches.The watercompletesthe circuitwhilethe wiresare immersed.Whenthe waterlevelfallsbelowthe wires,the circuitis openedandthe alarmis triggered. . o Temperature in greenhouses, animalpens,incubatorsand aquariums can be monitoredusingthis device.And if workingwith an LDR involvinglightcan be conducted. as the sensor,experiments

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TESTER(P) GAPACTTOR capacitors andothertypes Thiscircuitcanbeusedto testmetalfilmceramic in a rangeof valuesbetween470pFto 10 uF. of capacitors a tonedetermined thatproduces Thedeviceis formedbyanaudio-oscillator to thecircuit.The undertest.Probesconnectthecapacitor bythecapacitor A falling capacitors. toneis higherforlower-value frequency of theproduced a badcapacitor. toneindicates willproin the rangebetween1 and10 uF,the oscillator Testingcapacitors audiopulses,workinglikea metronome. duceseparated bytwoor fourAA cells,andcurrentdrainis verylow. Thecircuitis powered thevalueof according to setan audibletoneat thespeaker, P1 is adjusted beingtested. thecapacitor values.Twocapacitors Youcan alsousethisdeviceto comparecapacitor withthesamevaluewillgivethesametone. Testeris shownin Figute 1.The diagramof the Capacitor Theschematic workingas a directtransistors circuithasas its hearttwo complementary unis provided byresistorR1andthecapacitor Feedback coupledamplifier. dertest. placement on a terminalstripis shownin Figure2. Usethis Gomponents partsplacement the terminalstripandwhen as a guidewhenassembling thecircuitintoa box. housing to avoidinstability. shouldbe shortas possible components Termination and capacitor suchas theelectrolytic components, Position of thepolarized undertest Thecapacitor powersupply, whenmounting. shouldbe observed clipsas shownin Figure2. is placedin thecircuitbytwoalligator Thecircuitcanbe housedin a smallplasticbox.

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P1 1M

.-l Q2 BC558

R2 4K7

Q1

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I

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81 ._ 3/6V T

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:tCAPACITOR UNDER TEST

S1 \

R1 1K

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Figure I

Figure2 til

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j

PartsList - GapacitorTester Q1

- 8C548general-purpose NPNtransistor

Q2

- 8C558general-purpose PNPtransistor

R1

- 1,000ohm,114W,5% resistor

R2

- 4,700ohm,114W,5% resistor

P1

- 1,000,000 resistor ohm,114W,5%

Cl

- 100uF,6 WVDCelectrolytic capacitor

Cx

- capacitor in test

S1

- SPSTtoggleor slideswitch

81

-3orOV-2or4M-cells

SPKR- 4 to 8 ohms- 2to4 in.loudspeaker

ldeasto Explore To get betterperformance or to learnmoreaboutthe clrcuit: o ReplaceP1 with 10,000,000 ohmsto testcapacitorsunder470pF. Don'ttouchthe alligatorclipsor probeswhentestingsmallcapacitors bellow1,000pF. o Explainhowcapacitorsfunctionin this circuit.Whatis feedback?

It2

Frohc|28 Grrrcllrlffi uses: anduncommon Scienceprojects o Mountanexperimentalcapacitor foilandpaperas usingaluminum thevalue Testthecapacitor dielectric. usingthisdeviceandcompare withknowncapacitors. o Experiments involving transducers can be conducted capacitive (A/D) withthiscircuit.Thecircuitcanbe usedas an analog-to-digital quan(ananalog Thesecircuitscanconvertcapacitances converter. quantity). (a With appropriate converinto frequencies digital an tity) counterto measure to usea frequency sionscaleit will be possible capacitances.

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(VP) TESTER coNTrNUrrY suchas diodes,resiscomponents Thiscircuitcanbe usedto testelectronic lamps, fuses, switches, loudspeakers andmanyothtors,coils,transformers, undertestis indicated byan LED. ers.Thestateof thecomponent themisvery between orwhentheresistance Whentheprobesareseparated is low (more is When the resistance the LED otf. than 1,000,000 ohms) high (thetransistor is in a conduction state)theLEDis on. Current froma 6- or 9-voltsupply(AAcellsor battery). Thecircuitis powered drainis lessthan10 mAwiththe LEDon.R2valuedependson the power Fora 9V supplywe recommend 820or 1,000ohmsfor R2. supplyvoltage. Testeris givenin Figure1.TwotranA schematic diagramof theContinuity pair.Theconfiguration reducesthe current sistorarewiredas a Darlington probesto microampere values. flowbetween placement on a terminalstrip,usedas chassis,is shownin Components of thetransistors andLED. to observepositions Figure2. lt is veryimportant clipsto Housethe devicein a smallplasticboxanduseprobesor alligator undertest. connectthecomponents

PartsList - ContinuityTester PNPsilicontransistors Ql, 2 - 8C558general-purpose LED - Commonred,greenor yellowLED R1

- 100,000 resistor ohm,114W,5%

R2

- 470ohm,114W,5% resistor- seetext

S1

- SPSTslideor toggleswitch

81

- 6Vor 9V (fourAAcellsor battery)

PPl,2 - Redandblackprobes r80

l

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Figure I

Figure2 t0t

IunfrofoctsffimHEaffirSl ldeasto Explore Togetbetterperformance or to learnmoreaboutcircuitanddevices: o InvertpowersupplypolesandLEDposition anduseNPNtransistors.Willthecircuitoperateas theoriginalversion? A transistor such asthe8C548canbeusedinthisexperiment.You canalsoreplace the LEDandR1witha 6-voltx 50 mAsmallincandescent lamp. o Determine the highestresistance thatcanbe connected between probesthatcausesthe LEDto illuminate. Scienceprojects: o Conductability of chemical substiances canbedetected or demonstratedwiththiscircuit.Usetwobarewiresas probes. o By replacing youcanuse theLEDwitha 0-200uAmicroammeter thiscircuitas a liedetector. Smallchangesin skinresistance canbe detectedin thisway.Skinresistance alterswithstressor bythe straln causedby an interrogation session. o Experiments withplantscan be conductedinvolvingalterationin placedon theirleafs. An interestthe resistance between electrodes ing studyaboutthis subjectis foundin the book The SecretLifeof Plants byPeterTompkins andChristopher Bird.Theauthors associate phenomena plants in electrical to a rudimentary nervoussystem.

IB

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LEDBARGRAPH(E/P) Thiscircuitdrivesten LEDsin response to an analogvoltageappliedto its inputandcan be usedto providea visualindication of the instantaneous powerbeingdeveloped by an audioamplifier. lt canalsobe usedto provide visualindication of variable eventsin scienceexperiments. Youcanextendtheprojectby usingtwochipsandyou'llbe ableto continuouslymonitor theaudiooutputpowerof bothchannels ofyourstereosystem. Thecircuitcanbe usedwithamplifiers rangingfrom0.1to 100watts. In somecasesyoushouldusea smalltransformer, wiredas in Figurc1,to isolatethe inputandmatchimpedances. Thisls necessary whentheamplifierhasa low-output impedance. Resistor R, is chosenaccording to theoutputpowerof theamplifier. ValuesaregiveninTable1.

Table1 Amplifier OutputPower

Rx

-

0.1 to 1 watt 1 to 5 watts

10 ohms, ll2watl

5 to 20 watts

22 ohms,1 watt

20 to 50 watts

47 ohms,1 watt

50 to 100 watts

100ohms,2watts

A schematic diagramof the LEDbargraph is showninFigure2.Thecircuit usesan LM3914lC to drivethe LEDs,converting voltagesintooneof ten outputs. Thecomponents areplacedon a printed-circuit boardas shownin Figure3. lf youd liketo buildyourcircuitthesameway,youcanetchyourownboard usingthesolderandcomponent-side templates shownin thisfigure.

l

j

I

F!|ffi 2t llDlrlrruh I

(-)SEETABLE

8:1000o TRANSF'RMER

Figure I +6112Y

18

't7

16

15

14

13

12

11 . 10

tcl 1M3914 5 D1 R1 1N914 10K

Figure2 fn

HmHdcctslrrilcHpilmmu

Figure 3 P2 adjuststhe dynamicrangein whichthe circuitoperates.P1 adjustssensiYoucansetthevalueto a fixedpointby tivityanddependson the application. usinga trimmerpotentiometer. Audiocomesfrom the loudspeaker outputof the amplifier.Any smalltranscoil can be used. formerwith a high-impedance coil and a low-impedance Any smalltransformerwith a 117VAC primary,secondaryratedfrom 5 to 12.6volts,and currentratingsbetween100and 500 mA can be used. Positionof the polarizedcornponents, suchas LEDs,diode,and electrolytic capacitor,shouldbe observed. Bass responseis providedby C1.Youcan alter this componentwithinthe rangegivenin the schematicdiagramto achievebestperformance. Rememberthatthe highestappliedvoltageto the inputshouldn'texceedthe powersupplyvoltage.

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PartsList - LEDBargraph lC1

- LM3914Integrated circuit(National)

LEDs - Commonred,yellowor green D1

- 1N914or 1N4148generalpurposesilicondiode

Rl

- 10,000ohm, 114W,5% resistol

R2

- 470ohm,114W,5% resistor

P1

- 10,000ohm potentiometer

P2

- 4,700ohmtrimmerpotentiometer

C1

- 1 to 10 uF,12 WVDCelectrolytic capacitor- see text

ldeasto Explore To learnmoreaboutthe circuitor to get betterperformance: o Determinethe voltagelevelthat turns on each LED usinga DC powersupplypluggedto the inputof the device. . By wiringprobesat the positivepowersupplyline and the input meter. you can usethis circuitas a digitalresistanceor conductance SciencepQects: o Thiscircuitcan replacethe commonmultimetertoindicatevoltage The visualetfectis better. variationsin experiments. o lt can alsobe usedin the outputof a lb detectoror bio-feedback. o Conectan LDRbetweenthe inputand (+)for a digitalphotometer. wire an NTCbetween(+) and the input. Fora digitalthermometer o Thiscircuitcan also replacethe LEDand resistorin the Continuity can be performed. withadvantages, Testerandthe sameexperiments, fl5

forllc Hrulnrnmr IunPl0f0cts

LTQUTDS SHAKER (P/E) A toy'ssmall DC motorcan be usedto mounta liquidsshaker.The shaker can be used in chemicalexperimentsto mix substancesquicklyand efficiently. The circuitis poweredfrom the powersupplyline (to avoidthe expenseof batteries),but thereis no shockhazardbecausean isolationtransformeris used.Of course,for fieldworkyou can also poweryour mixerfrom common AA cells. DC The transformeris chosenaccordingto the motorvoltage.A four-AA-cell (a motorrequiresa 6+6voltx 500 mA transformer 6-voltcentertappedtransformer).A two-AA-cellDC motorrequiresa 3V x 500 mA transformer. Securethe motorinto a smallcylindricalplasticbox.Use a longshaftto attach a smallplasticscrewpropeller. Figure l showsthe schematicdiagramof the electronicpart of the circuit:a powersupply.The diodesare common50V x 1A siliconrectifiers,and C1 is not critical.C1 shouldbe in the rangebetween100and 1,000uF. Figure 2 showsa mechanicalview,usinga smallterminalstripas chassis. The fuse is importantto avoidseveretroublesif shortsoccur. resistorand can be alteredaccordingto the motor. Rl is a current-limiting with for betterperVafuesbetween4.7 and 100ohmscan be experimented formance. capacitor, Positionof the polarizedparts,suchas the diodesand electrolytic shouldbe observed.Rememberthat the motorrotatescloclcriseor not accordingto the voltagepolarization.

tt8

PnFrt 20 lhffiSmilor D1 1N4002

F1 6+6V 500mA

Figure l

Figure2 il att

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PartsList - LiquidsShaker D1,2 - 1N4002silicondiodes T1

- Transformer: 117 VAC:6+6Vx 500 mA - see text

S1

- SPSTslideor toggleswitch

F1

- 500 mA fuse

C1

- 220uF,16 WVDCelectrolytic capacitor

R1

- 15 ohm,2W,SYo resistor

M

- smallDC motor(3 to 6 volt)

ldeasto Explore Tolearnmoreaboutcircuitanddevicesor to getbetterperformance: to the DGmotor according o AlterR1to achievebetterperformance 4.7and'l00ohms. used.Tryvaluesbetween in thisbookto geta speed o Usethe DC LampDimmerdescribed R1if thedimmeris used. controlforthe motor.Remove thecircuit. geta regulated outputfrom o Usethe6VDCconverterto uses: anduncommon Scienceprojects experiments, o Thispowersupplycan be usedin electro-chemical andelectroplating. suchas electrolysis witha fanblade.Experiment. o Replace thescrewpropeller in watercurrents involving o Thedevicecanbe usedin experiments suchas aquariums. smallplaces, of a smallDC movement o Otherapplications thatrequirecontrolled motorcanusethiscircuit. rft

tunEobcrsbr thcEoedmcrFl

(P) STGNALTRACER methodforservicSignaltracingbymeansof a signaltracerotfersa valuable whena Thismethodis oftenemployed equipment. inga varietyof electronic AMandFMreceivdead,butrathermalfunctioning. circuitis notcompletely TV sets,etc.,canbe servicedusing multimedia amplifiers, ers,CD players, thissimplesignaltracer.

I l

transistor direct-coupled The circuitwe showhereconsistsof a two-stage Whentheprobeis usedin theRFmode Thecircuithastwoinputs. amplifier. thedetectordiodeis insertedintothecircuit.Whenthe probeis usedin the audiomodethe signalis applieddirectlyto the baseof the firsttransistor

(o1).

As the circuithas a low-poweroutput,a gaincontrolis not used. The circuitis poweredfromtwo M cells,and currentdrainis onlyfew milliamperes.Sincethe circuitdrawssuch low current,long batterylife can be expected. Figure I showsthe schematicdiagramof the signaltracer.R1 determines the gain of the amplifierstageand can be alteredto get betterperformance dependingon the transistorsused. Figure2 showsthe signaltracermountedon a terminalstrip,whichis used one is an NPNandthe otheris a as a chassis.liakecarewiththe transistors; you will not work. the with the other circuit PNP.lf switchone This projectcan be housedin a smallplasticbox.The sizeof the plasticbox is determinedby the speakersize.Positionof the polarizedpiecesshouldbe observed.

Itf

I

i .l

I

Ftdcct80 $llmllnecr

RF

Dl 1N34

1

A+Fl B+

AUDIO

I C 2 +

C1 0.1pF

100pF

SPKR 4l8A Cr-

(coMMoN)

Figure I

Figure2

1t[

l

milnFGtslorhsulmmt PartsList - SignalTracer Ql

- 8C548general-purpose NPNsilicontransistor

Q2

- 8C558general-purpose PNPsilicontransistor

D1

- anygermanium - 1N34or equivalent transistor

R1

- 1,500,000 resistor ohm,114W,5%

C1

- 0.1uFceramic or metalfilmcapacitor

C2

- 100uF,6 WVDCelectrolytic capacitor

SPKR- 4/8 ohms- 2 or 4 in.smallloudspeaker S1

- SPSTslideor toggleswitch

81

- 3V - twoAAcells

ldeasto ExPlore Tolearnmoreaboutthecircuitor to getbetterperformance: o Explainhowsignaltracersareusedforservicework. o ChangeRl valueto achievebetterperformance. o Usethetracerin a smallAM radioto studyitsoperation. earphoneto get a poro Replacethe speakerby a low-impedance plastic box. tableunitthatcanbe housedin a verysmall Scienceprojects: in experiments o Thetracercanbe usedto detectsignalsproduced in thisbook. currentfields,as described involving with audioamplifier o The tracercan be usedas an experimental pickupsor microphones. suchas piezoelectric transducers -

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oNE-EVENTREGISTER(P/E) Thisis a one-bitmemorythatcan be usedto storea simplebit of information, or closed-trapdetector,or a touchsensor. suchas a remotepower-failure The circuitoperatesas follows:When the resistancebetweenthe alligator poweringON the LED. clipsfalls,the SCRis triggered, The SCR and LED stay in the ON stateevenafterthe appliedpulseto the the event. inputis gone.So the device"memorizes" or a touch The sensorcan be a magneticswitch(reedswitch),a microswitch, switch.A simpletouchswitchis a metalplatewiredto G2.To get bestsensitivity,G1 needsa goodground.Youcan alsouse as sensortwo metalplates that are touchedat the sametimeto triggerthe circuitON. The circuitis poweredby fourAA cellsandcurrentdrainis verylowwhenthe LEDis off.Whenthe LEDis on, currentdrainis lessthan10 mA. To resetthe deviceyou only haveto toggleS1. Anotherway to resetthe circuitis to wire a momentaryswitchbetweenthe anodeand cathodeof the SCR.Sensorscan be wiredto the devicewith longunshieldedwires. Theschematicof the One-Eventis shownin Figure l.ThoughR2and R3 are if you prefer.A shownas fixed,you can use a 1,000,000ohm potentiometer fromthe register. sensitivityadjustmentwill get betterperformance Figure 2 showsthe One-eventRegister,on terminalstrip mounting.As it is an experimentalcircuityou can also use a solderlessboardto installthe components. The circuitcan easilybe housedinto a smallplasticbox.Observethe posisuchas the LED,SCRand powersuptionsof all the polarizedcomponents,

plv. if TlC106is used.OtherSCRs,suchas the ResistorR3 is onlynecessary R3. require don't MCRl06andCl06,

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i

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i

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R3 47KO(")

Figure I

Figure2 t0l

folt[e trrcilmentcl IunPloiects

Register PartsList- One-Event Rectifier SCR - TlC106or MCR106SiliconControlled LEDs - Red,yellowor greencommon R1

- 470ohm,114W,5% resistor

R2

- 100,000 resistor ohm,114W,5%

R3

- 47,000ohm,1/4W,5%resistor- seetext

S1

- SPSTslideor toggleswitch

81

-6V-fourAAcells

clips G1,2 - Alligator

ldeasto Explore or to learnmoreaboutthe circuit: Toget betterperformance o Youcan replaceR1 and the LEDwith a buzzeror audiooscillator to get an alarm.But, rememberthattherea voltagedropof about2 voltswhencurrentflowsthroughthe SCR.Thisvoltagedropcan be compensatedby addingtwo or threevolts to the powersupply.For voltagefor the instance,if you use a 6-voltrelay,the recommended volts. powersupplyis 8 or 9 on the o As currentdrainis verylowwhenthe LEDis off,depending intendeduse,51 can be removed. .

192

Explainhowthe SCRoperatesin thiscircuit.

FrFcr 8l holnillrffr Scienceanduncommon applications:

.

o Youcanconnectan LDRbetween Gl andG2fora light-operated memory one-event or alarm.A singleshortpulseof lightcantrigger thecircuit. o Usethiscircuitto knowwhensomeonetouchesan objectwhen you leaveit unattended. Youcanalsoknowif someoneenteredyour roomwhenyouwereout. a By usingtwo barewireas sensors,youhavea water-level alarm. TheLEDwillglowwhenthewatertouchesthetwobarewiresat the sametime.

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(E) NO|SEGENERATOR is to producenoisein the AM radio Thepurposeof thissimpleexperiment band.Thecircuitcanbe usedto showhowbrushmotorsandgeneralappliin radio, in the radioband,interfering anceswithmotorscangenerate.noise radio services. TV,and communication noiseis tooweakto causeany Thecircuitis verysimpleandthe produced problem (FCCrulesaboutnoiseandradiointerference are to radioreceivers. willinterfere Thenoiseproduced bythisexperiment onlyin receivers severe.) justa fewteetaway. Theschematic diagramof thedeviceis shownin Figure1.Theheartof the rapid key,producing circuitis a smallDC motorthatworksas a automatic variation in thecurrentflow. is shownin viewofthecircuit,usinga terminal stripaschassis, A mechanical including thepowersupply,canbe fixedon a Figure2. Allthecomponents, plasticboard. toy can be usedin this AnysmallDC motorobtainedfroma nonworking project. Thepowersupplydependsuponthemotorused. fromanynonworking AM radio. CVandL1canbeobtained Youcan get morepowerfor the RF noiseby wiringa pieceof wireto the butlimitthiswireto nolongerthan6 feet.Ll is formed antenna(A)terminal, No. wirewoundon a ferriterod(diameter andlengthare 100 turns of 28 by notcritical). ona deadpoint Byadjusting CV youcantryto tunethesignalto bestronger of theAM radioband.

100

l

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(.)ser rEXT B1 3/6V

cl L1 (.)

Figure I

Figure2 t0,

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PartsList - NoiseGenerator B1

- 3 to 6V - cellsor battery- see text

T

- Keyor SPSTtoggleor slideswitch

c1

- 0.1 uF ceramicor metalplatecapacitor

CV

- 365 pF variablecapacitor

L1

- loopstick- see text

M

- 3 to 6V DC motor

ldeasto Explore To learnmoreaboutthe circuitor to get morepedormance: bandby replacing o Tryto produceRF noisein the high-frequency produce you signalsin the can coilon a ferriterod L1.Witha 3Q-turn rangebetween2 and7 MHz. .

ExplainhowRF noiseis Produced.

o Find out throughreferencebookshow Marconiand otherradio pioneersgeneratedradiowavesfromtheirtransmitters. applications: Scienceand uncommon o Youcan showhow antiqueradiotransmittersoperatedusingthis usinga keyin place circuit.Morsecodedmessagescan be transmitted o f5 1 . o Explainwhy this noisegeneratorcan be usedto transmitvoicesignals. modulated

198

fu lf,olltOilm0mil RmftJoGts -

(E) OHMMETER EXPERIMENTAL arecheapandeasyto find,anyonewhowantsa ohmmeters As commercial goodinstrument forhisownusewillnotbuildone.Butyoucanbuilda simple howit worksor studyhowthebigonesaremade. to demonstrate ohmmeter herecaneasilybemadefroma milliammedescribed Thesimpleohmmeter and demonstrations andcanbe usedin experiments, ter or microammeter, manyotherapplications. canmeasurea Andsincethisohmmeter is alsoa voltmeter. Ourohmmeter we can saythat it is, in practice,a largerangeof voltagesand resistances 0 and12volts Inthe rangebetween canbe measured Voltages multimeter. (therangeusedto poweralmostall circuitsin this book),and resistances 0 andinfinite. between willbe 5,000ohmspervolt. thesensitivity lf usinga2OOuA microammeter, of commonmultimeters. Thisvalueis typicalof severalcommercialtypes from100 valueranging witha full-scale Butyoucanuseanyotherammeter performance. best uAto 1 mA.SimplychangeRl to achieve is shownin Figure1.Notethat oftheexperimentalohmmeter Theschematic thatcaneasilybehousedina smallplasticbox. weuseonlyfourcomponents is notcritical,andyou mounting Layoutis shownin Figute2. Components canreplacethe bananajacksby probesor anyothermethodto makeexternalconnections. on the meato theexternalbananajacksdepending Probesareconnected surementyou intendto make.To measurevoltage,the red probeis conresistance, to J2.Tomeasure nectedto J1 andtheblackprobeis connected connectthe redprobeto J1 andthe blackprobeto J3. Putthe probestoscale. of zeroat the instrument getherandadjustP1to getan indication themeterscale to calibrate it is possible Byusinga seriesof knownresistors, Startfrom0 (withJl andJ2 shorted),andnotethe to readohmsdirectly. acrossJl andJ3. areconnected whenlk,2k, etc,reslstors meterreadings

202

PlUoGt 88 S0ftncmlol|ffir

Figure I

Figure2 Aftercalibrating the deviceto readohms,use a variablepowersupplyto calibrate thevoltagescale. Position of thepolarized components, suchAstheammeter andpowersupply(cells),mustbe observed.

fmH!ffifrthomilmffi

PartsList - ExperimentalOhmmeter 81

-3V-twoMcells

R1

- 10,000 resistor ohm,114W,5%

Pl

- 47,000ohm,1l4Wtrimmerpotentiometer

M1

- seetext - 0-200uAmicroammeter

l l

jacks J1-3 - banana

ldeasto Explore Tolearnmoreaboutthecircuitor to getbetterperformance: o Explainhowresistance andvoltagescalesoperateinthisohmmeter. powersup. Calibrate usinga variable thescalesof yourohmmeter plyandsomeknown-value resistors, as described above. o Calculate valuesreadin the meterand compare the resistance resultsconDoyourcalculated withthe realvaluesof usedresistors. previous firm studies? applications: anduncommon Science o Youcanusetheohmmeter to determine sensorandmediaresismultiif youdon'thavea commercial tancesin severalexperiments meter. o Bywiringa47,OOO between ohmpotentiometer Jl andJ3 youcan indicator. canbedirectly Cursorpositions usethisdeviceasa position intocurrentas indicated bythemeter.A scaleof anglescan converted to readdegreesdirectly. be arranged

2U

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NERVES(P/E) TESTYOUR Thiscircuitputsyourmanualskillsto a livelytest.Asshownin theschematic arounda wire. the circuithasa smallloopthatyoumustnavigate diagram, coursewithout Theobjectof thegameis to guidetheloopovertheweaving touching thewire. I

or quiverof the handandthe ringwillcontactthe A slightmisdjudgement (butinoffenthecircuitthatwillproducea noticeable wire,enabling weaving sive)shock! to playthe gamedependslargelyon the sizeof the loop Theskillrequired andthedegreeof twistandturnin thewire. by thenumberof timestheplayeris atfected Scoringis a matterof counting (or wins. person no touch) lowest total with the a shock!The froma D cell,asthecurrentdrainis highwhentheloop Thecircuitis powered thewire.Whennotin use,don'tleavetheringandwiretogether.This touches willcausethebatteryto rundownin a shorttime. of thedeviceis shownin Figurel.The heartof theproject A circuitdiagram pulsesup to 400 thatconverts1.5VDCintohigh-voltage is thetransformer volts. is shownin Figurc2. viewof themounting A mechanical canbe housedin a smallplasticbox.Wiresto the loop All the components whenthe andweavingwireshouldbe 2 or 3 feetlongto preventpull-outs playeris struck. the pointswherethe playertouchesandthe between the isolation Observe wire.ThetwowiresthatconnectX2 shouldbetwisted. weaving coilrangwitha 117VACprimaryandsecondary T1 is anysmalltransformer 3 and9V.Currentdraincanrangefrom100to 500mAwhenthe ingbetween wiretouchestheloop.

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- ^ n ^ Ay\^ -v u/v

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Figure2 240

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PartsList-TestYour Nerves

81

- Anytransformer witha 117VACcoiland low-voltage text see secondary -1.5V-Dcell

X1

- Loop- see text

X2

- Weavingwire - see text

T1

ldeas to Explore or to learnmoreaboutthe circuit: To get betterperformance o Explainwhythe transformer doesnot operatewith DC butthatthis projectis ableto generatehighvoltageusingthatdevice. o Whathappensif the loopis placedtogetherwiththeweavingwire? Why it is necessaryto avoidthis condition? Scienceprojects: o Changesin the projectcan be madeto generatehighvoltagefrom can be triedusingthis simple Nervestimulation cellsin experiments. circuit. o Neonor fluorescent lampswiredbetweenthe loopand wire will can be usedto flashwhenthe loopand wiretouch.Thisexperiment generated by the circuit. provethat highvoltageis

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BEEPER(E) WTRELESS produces a beepthatcanbetunedonanydead tranJmitter ThisFMwireless when pointof the FMbroadcast band.Thecircuitcanbe usedas a localizer persons. wireless alarm. it a Youalsocanuse as to objectsor attached

I

Thesignalcan be tunedon commonFM radiosin a rangeup to 150feet. versionaregivenbelow. fora far-reaching Alterations

l

beepof about1 Hz.An audiotoneis an intermittent Thecircuitproduces by R2 is determined generated by lClb (pins5, 6 and4) anditsfrequency values R2.Resistor by adjusting andC2.Youcaneasilyalterthisfrequency if you with or, 100,000 can be experimented ohms and between22,OOO R1. prefer, ohmscanreplace 100,000 ohmsin serieswith10,000 rateis per R1 andC1.Valuesarevariable.ForC1,valuesbeRepetition to testfortheidealvalueof tween0.15and1 uFcanbetried.lt is important application. depending on the intended thiscomponent, diagramof thewirelessbeeperis shownin Figure1.Three Theschematic andone signals, gatesof a 4093lGareusedto generate thelow-frequency signal. the high-frequency is usedto generated RFtransistor printed-circuit placement boardis shownin on a homemade Components inthis high-frequency stage.Capacitors iscriticalforthe Figure2. Placement stageshouldbe ceramic. a ferrite offourturnsof No.18or 20wireona1l2 in.formwithout L1consists core. 5 and10incheslong. is formedbya pieceof barewirebetween Theantenna to get betterperforto anytap on the coil.Experiment It canbe connected mance. canusefourM-cellsor Thepowersupplycurrentdrainis about10mA.You a 9V batteryto powerthetransmitter. relay of a relay.The bythecontacts alarm,51 canbereplaced Fora wireless in this application. the transmitter with interface the alarm is usedto tfl

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Anotherwayto interface an alarmwiththe transmitter is to connectrelay pointsA andB in theschematic. contacts in serieswithC3 or between See moredetalsin ldeasto Explore.

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PartsList-Wireless Beeper

fl0

lC1

- 4093CMOSIntegrated Circuit

Q1

- 8F494or equivalent NPNRF silicontransistor

L1

- coil- seetext

CV

- trimmercapacitor- 20 to 40 pF maximum

R1

- 2,200,000 ohm,114W,5% resistor

R2

- 39,000ohm,1/4W,5% resistor

R3

- 8,200ohm,114W,5% resistor

R4

- 6,800ohm,114W,57o resistor

R5

- 47 ohm,1/4W 5% resistor

C1

- 0.22uF ceramicor metalfilmcapacitor

C2

- 0.047uF ceramicor metalfilmcapacitor

Cg

- 0.01uF ceramicor metalfilmcapacitor

C4

- 4,700pF ceramiccapacitor

C5

- 4.7 pF ceramiccapacitor

CG

- 0.1 uF ceramiccapacitor

A

- antenna- see text

S1

- SPSTslideor toggleswitch

81

- 6 to 9V - fourAA cellsor 9V battery

Prdcct8[ f,hrlcsslmnr , ldeasto Explore Togetbetterperformance or to learnmoreaboutthecircuit: o Youcancontrolthe beeperoscillator by lOl, pins1 and5. Put thesepinstogether. Whenin a highlogiclevelthe circuitproduces intervalled beeps.Whenin a lowlogiclevelthecircuitstops. . Replace circuitwitha 12VpowersupQl by a2N2218.Powerthe ply.Signalscannowbetunedfromdistances upto 1,500feet.A 5- to the rangeof thetransmitter. 6-footantennawillincrease or uncommon applications: Scienceprojects . Housethiscircuitin a boxandtellsomeone to hideit.You'llfindit by usinga smallFMreceiver. o Thetransmitter canbeusedto trackanimalsbyfixingit ona collar. o Youalsocanusethetransmitter to monitorremotesensorsin experiments. The circuitscan powerON the transmiter or triggerthe oscillator as indicated above.

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(E/P) ELECTROSCOPE thepresence Anelectroscope is aninstrument thatcanbeusedfordetecting versionof the of an electricstaticcharge.We describeherean electronic traditional electroscopHnethatis madewithgoldfoilsplacedintoa glass jar.Thiscircuitcan alsobe usedfor "snitfing" highvoltagewithoutactually circuitry. makingcontactwithdangerous the sensor,is simplypokedintothe electric A metalring,whichconstitutes field.Thisoperation mustbedonewithcautionto avoidcontactwiththeconductorscarryingthe highvoltage. (Vande withhighvoltagegenerators Youcanusethedevicein experiments andin manyotherapplications at homeor school. Graaffaccelerator) powered fromfourM cellsor a 9V baftery. Thecircuitis portable, linesis Presence of a staticchargeor a strongfieldcreatedby high-voltage indicated byan LED. is showninFigurel.The circuit Theschematic diagram of theElectroscope gates 4093 lC work as buffers andinverters, drivingthe of a that usesfour circuitsresultsin inputof the CMOSintegrated LED.The high-impedance to detectstaticcharges. highsensivity printed-circuit boardas All the components are mountedon a homemade shownin Figure2. canbe housedinto SensorX1 is a smallbarewirelop.Thecompletedcircuit TheLEDshouldbe placedin a visible a smallplasticboxwiththe batteries. pointof thebox. Touse: A pieceof paperorplasticstroked Bringa charged sourceclosetothesensor. materialwill do.AdjustPl to getbettersensitivity.The witha rodof insulating to theelectricchargemovement. LEDwillglowaccording

220

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PartsList - Electroscope IC1

- 40938CMOSIntegrated Circuit

LED - Commonred,yellowor greenLED X1

- Sensor- seetext

P1

- 1,000,000 ohm potentiometer

R1

- 22,000,000 resistor ohm,114W,5%

R2

- 100,000 resistor ohms,114W,5%

R3

- 1,000ohms,114W,5% resistor

S1

- SPSTslideor toggleswitch

81

- 6V or 9V - fourAA cellsor 9V battery

ldeasto Explore learnmoreaboutthe circuitor to get betterperformance: candetectclouds' a Connectthe sensorto an externalantenna.You electricalchargeas theypassoverhead. .

Explainhowthe circuitworks.

couldbe performedto show o An interesting studyor experiment howstaticchargesare producedand howtheycan be detected.

222

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I

o In allthe experiments that can be conductedwith a commonelectroscope,the electronicversioncan replaceit. .

Determinethe polarityof the chargethat makesthe LEDto glow.

o Staticchargescouldhavesomeinfluenceon animalsand plants. project, An experimentto supportthisaffirmation canbeconducted.This of course,will involvesomespecialequipmentsuchas a high-voltage generator(Vande Graaffor other)and an electroscope. Selectseeds from commonplantssuchas tomatoesand beans,and exposeseveral batchesof seedsto a statichigh-voltage field.What are the effectson seed germination?ls plantgrowthalso atfectedby electric fields?

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(P) PROBE uNrvERsAL compoprobecanbe usedto testalmosteveryelectronic Thisultra-simple wires, diOdes, tranSformerS, COils, fuses,SwitcheS, reSiStorS, nent.CapaCitOrS, etc.,canbetestedwiththissimplecircuit. areusedandtheycaneasilybe housedin a small Onlythreecomponents plasticbox,performing as a portableunit. by testerwitha visualindication of a continuity Thecircuitconsistsbasically glows; probes LED if not, the LED the the an LED.lf currentcanflowbetween remainsotf. the tested Currentflowingbetweenprobesis verylowto avoidoverloading components. Probeis shownin Figure1.Asyoucan oftheUniversal diagram A schematic areusedin thisproject. components see,onlythreeelectronic can be layoutviewis shownin Figure2.The components A components housedin a smallboxandnoON-OFFsutitchis necessary. the components" ofthetwopolarized takecarewithposition Whenmounting, LEDandpowersupply. of twoM cells. Thepowersupplyconslsts asthecircuitis otfwhentheprobesare AnON-OFFswitchis notnecessary separated. bythevoltagedrop undertestis determined Currentthroughthecomponent acrossthe LED(about1.6Vfor red LEDsand 1.8Vfor yellowLEDs),and resistance of R1.

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Figure2

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PartsList - UniversalProbe LED - Commonred,greenor yellowLED R1

- 470ohm,114W,5% resistor

PP1,2 - Redand blackprobes 81

- 3V - two AA cells

ldeasto Explore Scienceprojects: o Usethis probein to find materialsthatconductor do not conduct in electricity can be electriccurrent.Severalothersimpleexperiments showhowa switchworks,or usingthisprobe:forexample, conducted how a potentiometer used as a rheostatcontrolsthe currentflow accrossan LED. o Explainhowthe LEDproducesits light. o Usethisprobeto explainhowa diodeworks.(Remember thatDC is usedin the probesand diodes,allowingthe currentto flowonlyin onedirection.) o Thiscircuitcanalsobe usedas a monochromatic sourceof lightin involving experiments optics.

228

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RELAY(E) TONE-ACTTVATED Whenthistone Thiscircuitcanbe usedto recognize a toneby itsfrequency. whichcouldsupplypowerto a is presentin a circuitthe relayis energized, selected appliance. the circuitcanbe usedas partof a toneWiredto the outputof a receiver, receiver wirelessremotecontrol.The canbe a commonFMradio modulated application. depending on theintended or an infraredreceiver, Hz.Thecircuitis Thecircuitcanbe usedwithtonesrangingup to 1O0,0OO tunedbyP1. remote Inputsof otherunitscan be wiredin parallelto get a multi-channel frequencies. controlsystem.Takecareto avoidusingharmonic The schematicdiagramof the ToneActivatedRelayis shownin Figure 1. PLL(PhaseSemiconductor TheheartofthecircuitistheLM567lC,a National Q1. LockedLoop)thatdrivesthe relaythroughtransistor printed-circuit placement boardis shownin on a homemade Components when in frequencies above is notcritical,but operating Figure2. Placement to avoidlongconnections. 50,000Hzit is important Therelayis anytypewitha 6Vcoilandcurrentratedforvaluesbetween10 and100mA. casuchas thediodeandelectrolytic Position of thepolarized components, pacitor, shouldbe observed. Touse: to pointsX andY. or audiooscillator Wirethe outputof an audiogenerator 100mVand1 V peakhaveamplitude in a rangebetween Thesignalshould AdjustP1to triggertherelay.Reducethesignalamto-peakforbestresults. plitudeandtrimP1 forthebestperformance.

292

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PartsList -Tone-ActivatedRelay lC1

- LM567Integrated Circuit(National)

Q1

- 8C558 general-purpose PNP siticontransistor

D1

- 1N914general-purpose silicondiode

P1

- 100,000ohmtrimmerpotentiometer

K1

- relay- 6V - see text

R1

- 10,000ohm,114W,5% resistor

C1,4 - 0.1 uF ceramicor metalfilmcapacitor C2

- 0.022uF ceramicor metalfilmcapacitor

C3

- 0.O47ceramicor metalfilmcapacitor

C5

- 100 uF,12WVDCelectrolytic capacitor

ldeasto Explore To get betterperformance or to learnmoreaboutthe circuit: o Explainhowa PLL (Phase-Locked Loop)works. o Whatare harmonics of a signal? uses: Scienceand uncommon o Remotesensorscan be usedto closethe relay.Usingan oscillator to producethe tone,the wiresusedcan be very long,reachingdistancesup to 5 miles.

ztl

Pnbct 88 lom{silrrtdtffiU o Youcanusea smalloscillator astransmitter andthiscircuitaspart of a receiver to activate devicesbytelephone line. o Connect theinputof thiscircuitto theoutputof an audioamplifier. Pluga microphone you to theinputoftheamplifier. Withsomepractice cancontroltherelaybywhistling. o Youcan alsousethistone-activated relayto controlappliances fromyourcomputer, usingthe multimedia audiooutput.Writea programto produce a tonewhenanicononyourWindows screenisclicked withthe mouse. o Thetonecanbeusedto turnontherelayif thecircuitis plugged to theaudiooutputof yourcomputer. Threemodesof operation arepossible: a) By adjustlng the lengthof thetonepulseyoucanturnon any appliance connected to the relayduringthistimeinterval. Theapplipulse will ance turnotfafterthe ends. b) Usinga monostable witha 555timer,forinstance, a shortpulse canturnon theappliance attera preadjusted timeinterval. c) Usingthe turn-on-and-otf circuit,described in thisbook,you'll havea bistableoperation: a clickon the icon'turnson the appliance controlled bytherelay,andthene)ftclickturnsit otf.

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(E) LIGHTCOMPARATOR Thisdevicecan be usedto comparetwo lightsourcesby theirintensities. canbe conducted usingthis.Youcancompare Severalopticalexperiments lightor compare colorsusingspecialfilters. colorsof surfaces by reflected Resisor LDRs(LightDependent ThesensorsusedareCdSphotoresistors part in the red tors)thathavepeaksensitivity of the spectrum(7350angstromsor 735nm). whichvariesaslightfallson Asthenamesuggests, theLDRhasa resistance falls.In total As thelightintensity increases, resistance itssensitive surface. by ohmsor more.llluminated resistance canbe highas 1,000,000 darkness fallsto 100ohmsor less. directsolarlight,the resistance Bridgeequilibrated by twoLDRsandan Ourcircuitis a simpleWheatstone potentiometer (Pl). ddjustable thesameamountof light,P1canbe adWhenthetwo LDRsarereceiving justedto geta nullindication (M1). ontheammeter wecancompare anothersourceof lightwith lf weuseoneLDRas reference, A newadjustment of Pl canrevealthe thisbyusingtheotherLDRassensor. thetwolightsources. difference between is shownin Figure 1. No The schematic diagramof the lightcomparator project
280

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P1 10K R2 1K

Figurc I

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Figure2

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PartsList- LightComparator Resistors) LDR1,2 - Common1cmLDRs(LightDependent or CdSphotosensors M1 - 50-0-50uA ammeter- seetext resistor R1,2 - 1,000ohm,114W,5% R3

- 4,700ohm,114W,5% resistor

P1

- 10,000ohm potentiometer

51

- SPSTtoggleor slideswitch

81

- 3 to 6V - two or fourM cells

ldeasto Explore To learnmoreaboutthe circuitor to get betterperformance: o Useothertypesof sensors,suchas phototransistors in the circuit. Whatis the ditference? .

Explainhowan LDRor CdScelloperates.

o Usea convergentlensin frontof the cellsfor moresensitivity. Scienceprojects: o Severalexperiments involvinglightsourcesin opticscan be made usingthiscircuit. o Comparethereflections frompaperusingdifferent butequal-power Whichof them lightsources,suchas incandescent and fluorescent. has the betterperformance? a lt is possibleto changethiscircuitintoa temperature comparator. Justreplacethe LDRswithNTCs.

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ELECTRONTC ORGAN(E/P) in audiowhichwouldmakea nicetoyfor experiment Thisis an interesting children. The a keyon a keyboard. a musicalnoteby pressing Thiscircuitproduces bya smallspeaker. soundis produced Theelectronic organwillplayonlyonenoteat a time,butthenumberof notes is unlimited. Ditferenttonescan be selectedby pressingditferentkeys,as in a common byC1,whichcanbealteredwithin rangeisdetermined organ.Tonal electronic 0.022uF(forhighernotes)and1 uF Valuesbetween a largerangeofvalues. (forlowernotes)canbe experimented. bellin yourhomeor to monitor Youcanalsousethiscircuitas a multi-tone sensors the keyswithditferent severalplacesat the sametime.Replacing produce when closed. tones (reedswitches, will ditferent for instance) Organis givenin Figurel.The ofthesimpleElectronic A schematic diagram are diThetransistors oscillator. circuitconsistisof a simpletwo-transistor loudspeaker. a small rect-coupledanddrive layout,usinga terminalstripas chassisis,shownin Figure2. Components Thecircuitcanbe housedin thesameboxas thekeyboard. Eachtrimmerpotentiometer ln Figure3we showthelayoutof thekeyboard. notes. is usedto adjustindividual from3 to fromAAcellsor a powersupplyranging Thecircuitcanbepowered 6 volts. boardor withsmall canalsobe madefroma printed-circuit The keyboard probe plate thecorresponding plates. is a metal touched by Wheneach metal circuitclosesanda musicaltoneis produced.

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PartsList- ElectronicOrgan Q1

- 8C548general-purpose NPNsilicontransistor

Q2

- 8C558general-purpose PNPsilicontransistor

51-4 - keyboard-see text ohmtrimmerpotentiometer P1-4 - 1,000,000 R1

- 10,000ohm,114W,5% resistor

C1

- 0.047uF ceramicor metalfilmcapacitor

C2

- 100 uF,12WVDCelectrolytic capacitor

55

- SPSTtoggleor slideswitch

81

- 3 or 6V - AA cells

SPKR- 4/8 ohm,2to 4 in.- smallloudspeaker

246

Erm $ IhcurdG&Hn ldeasto Explore To learnmoreaboutthe circuitor to get beilerpedormance: o AlterCl in the rangegivenin the textto producea differentrange of sounds. o Explainhowthe circuitworks. o Try to replaceR1 with a networkformedby small transformers, diodes,resistors,capacitorsand othercomponents. Modifications in the tonepitchcouldbe foundthis way. Scienceand uncommonapplications: o ReplaceS1,S2,etc.,withditferentkindsof switches.You can identity the closedswitchby the tone. o Useonly one potentiometer coupledto a cursor.Youcan produce musicby rapidlychangingcursorpositionand pressingthe series switch. o The samekeyboardcan be usedin otheraudiooscillators, resulting in ditferentconfigurations of electronicorgan.

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-

(E) LIGHT-ALARM EXPERIMENTAL alarmwhichuses light-activated of a simplebutetfective Thiscircuitconsists A lightfallingon the LDRturnson the SCR. onlya halfdozencomponents. Thelampwillremainonuntilthepoweris otfor 51 is usedto resetthecircuit. p1 adjustssensitivity Togetbetterperformance to theapplication. according lens. theLDRcanbe housedin an opaquetubewitha convergent sincethereis a voltagedropof A 6-voltlampcanbe usedwithoutproblems about2 voltswhenin theONstate. asyoucanreset is shownlnFigure1.51 is optional, diagram Theschematic thecircuitbyturningoffthe powersupply. strip,isshownin Figure2.Thelampcan usinga terminal layout, Components also byan LEDin serieswitha 470ohmresistoror abuzzer.You be repfac'ed it. with lamp the replacing cancontrolan audiooscillator, from50to 250mA Any6Vlampranging Thelampisn'ta criticalcomponent. canbe used. ona SCRneedn'tbemounted GdSphotoresistor.The TheLDRis a common as thecurrentis verylow. heatsink

Light'Alarm PartsList- Experimental Rectifier Controlled SCR -TlC106Silicon LDR- seetext LDR - Gommon

Xl

- 1,000,000 ohmPotentiometer - 6V incandescent lamP- seetext

Bl

- 6-9V- fourAA cells,D cells,batteryor powersupply

S1

- SPSTmomentary switch

P1

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Figure2 251

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ldeasto ExPlore To learnmoreaboutthe circuitor to get betterperformance: o ReplaceX1 witha 6V relayto controlexternalloads.Wirea 1N914 kick from diodein parallelwith the relaycoil to preventhigh-voltage or other canalsocontrolsmallaudiooscillators theSCR.You damaging devices. alarm. o Changepositionof the LDRwith P1 to get a dark-activated work' Resistors) o ExplainhowLDRs(LightDependent Willthe circuitoperateas o Replacethe LDRwitha phototransistor. you want? Scienceprojects: o This circuitcan be used to monitortraps or eventsthat involve objector animalmovements. o SeveralLDRscan be wiredin parallelto monitormorethan one alarm,when P1 switches placeat the sametime.In a dark-activated position withtheLDR,morethanoneLDRcanalsobe used.But,inthis case,you mustwirethe LDRsin series.

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(E/P) PHOTOMETER in forLDRsareassensingelements applications Someof themostcommon photography andalsoexperilightmetersfor counters, alarms,photo-relays, mentsin optics. hereis a simplelightmetermadefroman LDR(Light Theprojectdescribed anda 3V a 0-200uA microammeter, Resistor or Photoresistor), Dependent batteryformedby twoAA cells. ratio. resistance LDRwitha highdark-to-light Useanygeneral-purpose youdon'tneedan ON-OFF forshortdurations Sincethecircuitis operating switch.Justputthecellsin the batteryholderwhenusingthe unit. to the rangeof yourworkinglightintensity. Pl adjustssensitivity is notcritical. Theammeter ofthePhotometer. FigureI showstheschematic Anytypewithfullscalerangingfrom100uAto 1 mAcanbe used. device aschassis.The view,usingaterminalstrip a mounting Figure2shows canbe housedin a smallplasticbox.ThemeterandLDRareplacedon the frontpanel. youneedto adjustP1.Tryvalues usedis outof specification, lf theammeter between10,000 and 100,000ohms.The LDRcan be housedin a small ontheapplication. opaquetube,depending

250

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Figure I

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PartsList - Photometer Resistor) LDR - AnycommonLDR(LightDependent M1

- 0-200uA - meter- see text

P1

- 100,000ohm trimmerpotentiometer

R1

- 10,000ohm,114W,5% resistor

81

- 3V - two AA cells

ldeasto Explore or to learnmoreaboutthe circuit: To get betterperformance .

in placeof the LDR. Try to use a phototransistor

o Replacethe ammeterby a commonmultimeter. o Youcan replacethe LDRby an NTCand convertthe deviceintoa meter. temperature Scienceprojectsusingthe device: canbe conducted lightmeasurement o Anyexperiment thatinvolves usingthisdevice. o Youcan calibratethe meterscaleusinga commonphotography photometeras reference.

258

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GENERATOR SEQUENCE G/P) putto workbyusingit asa sourceof clockpulsesfor Anastablemultivibrator, is thebasisforthiscircuit. a 4017counter, or as a in a rangeof one-of-ten randomnumbers Wecanuseit to generate projects in other applications. or 0-to-9counterin science onepulseeachsecondfor Youcanalsoadjusttheclockso thatit supplies orat home.lf youalterthe experiments usingthecircuitasa timerinscientific timerangecan be changedso that it suppliesone clockpulsefrequency, pulseeachminuteor ten minutes.In thiscase,thetimerangewillriseto 9 (in1- or 1O-minute steps)! or 90 minutes minutes youcanchange the generator demonstrations, inlogiccircuits Asa sequence switch a momentary connecting of the555to monostable, astableoperation it. or anysensorthatcanbe usedto trigger uponthe andR3depends from6 to 12Vsupplies, Thecircuitcanbepowered ifthesupplyvoltageis6V. Usea 470ohmresistor voltageofthepowersupply. power is 12V. supply used if the Usea 1,000ohmresistor the pulseraterangeandcan be altered.Values C1 determines Capacitor thathighervaluesmean between1 and1,000uF canbe used.Remember lowerpulserate. used. onthecapacitor Pl adjuststhepulseratewithin100:1,depending The diagramof the SequenceGenerator. Figure I showsthe schematic theclockpulsesanda 4017CMOSlC, circuitusesa 555lCtimerto generate to drivetenLEDsas indicators. a counterand1-of-10decoder printed-circuit boardis shownin placement on a homemade Components to mountit. boardor breadboard Figure2, Youcanalsousea solderless capacitor, pieces, suchastheLEDsandelectrolytic ofthepolarized Positions shouldbeobserved.

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2

4

7

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1

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5

6

9

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Figure I

PartsList - SequenceGenerator lC1 - 555- Integrated circuit, timer ,C2 - 4017- CMOSIntegrated circuit,counter LEDs- Gommon red,yellowor green P1

- 1,000,000 ohmpotentiometer

Rl,2 - 10,000ohm,114W,5% resistors Rg

- 470ohm,114W,5% resistor

Cl

- 10uF/l6WVDCelectrolytic capacitor

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P1

+6/1?r/

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Figure2

ldeasto Explore To learnmoreaboutthe circuitor to get betterperformance: o Wirea momentary switchbetweenlO1'spin 3 and lO2'spin 14 to controlthe counter.You can stopthe counteranytimewiththisswitch. a Explainhowcounterssuchas the 4017work. o Couldyou alterthe circuitso that it countsto any valuebetween2 and9?

261

Frrffi f8 $oucmrGmcnnr Scienceanduncommon uses: o Wirethe 555as a monostable multivibrator and usean LDRas sensorto triggerit.Thecircuitwilloperateas a pulse-of-light counter. o Usethiscircuitina project pulses aboutcomputers.You canproduce to be countedusingtheexperimentalflip-flop in thisbook. described o Experiments onESP(Extra-Sensory Perception) canbeconducted usingthiscircuit. Random numbers ina scaleof 1-to-10 canbegeneratedusingthiscircuit.

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(E/P) TNJECTOR STGNAL (multiin doingsomeservicingon youraudioequipment lf you'reinterested find this squarewavegeneratorto media,for instance)you will undoubtedly be a handytool.Youcanalsousethiscircuitin RFstagesin AM/FMreceivers, as highas 100MHz. harmonics arestrongin frequencies sincethe oscillator In this arrangment,frequencyis determinedby capacitorC2, resistorsR1 and R2,and D1. Thefrequencycan be alteredby the valuesof resistorsand/ or capacitorsselected.In our circuitthe oscillatorrunsat about1,000Hz. The outputsignalwaveformis squareand the outputswingsthe full power supplyvoltage,whichcan be anythingbetween3 and 12 volts (we recommenda 3-voltpowersupplyif you want a portableunit).Supplycurrentis typicaly10 uA, extendingbatterylife. Figure I showsthe completeschematicdiagramof the SignalInjector.lC1 is by C2,R2 is determined Frequency a 555timer,wiredas an audiooscillator. and R1.Youcan changeC2 withina largerangeof values. Figure 2showsthe homemadePGboardwherethecomponentsaremounted. A small3V batterycan also be usedif you wanta very compactmounting. 'Tronf'ofan audio(or RF) A signalinjectoris usedfrom the "bacK'tothe circuit.Forinstance,to usethe signalinjectorwith an AM receivelapplythe signalfrom the probeat the baseof the outputtransistor.lf that stageand everythingafterit operatescorrectlythe signalwillbe heardin the speaker.lf the outputstageprovesto be OK, movebackto the baseof the drivertranapplythe is working.Then, outputsignalwillbe higherif everything sistor.The volume it the towardsthefrontof thecircuitby injecting at signalprogressively control,detectorstage,lF stagesand the mixer. Thecircuitcan be housedin a smallplasticboxandconnectedto the external circuitthrougha probeand an alligatorclip. Figure 3 representsa possible housingarrangement. Totestthe signalinjector,applythe signalto the inputof any audioamplifier.

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PartsList- SignalInjector lC1

- TLC7555CMOSintegrated circuit- timer

D1

- 1N4148or 1N914general-purpose silicondiode

resistor R1,2 - 10,000ohm,114W,5% C1

- 10 uE 6 WVDCelectrolytic capacitor

C2

- 0.047to 0.1 uF ceramicor metalfilmcapacitor

C3

- 0.01uF ceramicor metalfilmcapacitor

S1

- SPSTtoggleor slideswitch

81

- 3V - two AA cells

PP1 - Probe G1

I

- Alligator clip

ldeasto Explore To learnmoreaboutthe circuitor to get betterperformance: o Whathappenswiththe waveshapeif D1 is removed? o Whycanthe circuitbe usedin frequencies as highas 100MHzif it generates a 1,000Hz signal? o Replacethe lC witha common555 (bipolar). The circuitwillwork, version. is higher than in the original the current drain but o RemoveC3 and powerthe circuitfrom a 5V powersupply.The signalinjectorcan nowbe usedin TTL logiccircuits.

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o Rl and R2 areshownas fixedresistorsin this project. Youcan (1,000,000 changetheseresistors to a potentiometer ohms,for ingenerate stance)inserieswitha 1,000ohmresistorto signalswithina largerangeof frequencies andduty-cycles. Scienceprojects usingthesignalinjector: o Thecircuitcanbe usedas a simplebio-stimulator in biological experiments. power levels high Stimulation as asthe supplyvoltagecan beachieved. Theselevelscanbe usedin directnervestimulation. o Wirea piezoelectric transducer orcrystalearphone to theoutputof thissignalinjector. A toneof about1,000Hzwillbe produced andcan be usedin experiments.

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(E) METALDETECTOR Youcan use this simplemetaldetectorto locateplumbingpipes,electrical wiringinsidewalls,find a lostwatchor coin at the beachor evena treasure with goldcoinsburiedyearsago by pirates. whereyoucan showthe magnetic Youcanalsousethe circuitin experiments diamagnetic, propertiesof materials.The betweenparamagnetic, ditferences and nonmagneticmaterialscan be shown.Interestingexperimentscan be conductedusingthe metaldetectordescribedhere. This circuitwill detectthe presenceof metallicobjectsthroughany nonconductivematerialsuchas dirt, wood,stone,plasteror plastic. With a littlepractice,you will be able to detectmetallicobjectsto depthsof overseveralinchesand will giveyou a fairlygoodideaof theirsize. methodto detectan object. Our circuitusesthe beat-frequency in Thefrequencyof the searchcoiloscillatorchangeswhenthe conductance the field of the searchcoil changes.Therefore,when metalscomewithina shortdistanceof thecoil,thefrequencyis changed,whichin turnchangesthe pitchof the audiblesound. The soundis producedby the speakerof a commonAM receiverthat tunes the coiloscillator. A schematicdiagramof the MetalDetectoris shownin Figure 1. Observe Youcan also use a oscillator. that the circuitis a very simpleone-transistor power the supplypolarity. general-purpose inverting transistor, PNPsilicon usinga terminalstrip of the electroniccomponents, The physicalarrangment part of this projectis the search as chassis,is shownin Figure2.Thecritical coil. The searchcoil is woundin a large6-inchplasticFrisbee.Beginby securing one end of the enameledmagnetwire form (18 to 22 AWG)with masking forma loopin the magnetwireforthe center tape.On thetenthwrap(haltway) tap,thencontinueuntilyou completethe 20 turnsof wire.

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lunPnlec$lorlltcHlcrlmcntor to securethe coilwirefirmly,as one looseloopin the coil It is veryimportant willcausethe detectorto be unstable. To use: Fix a smallportableradiocloseto the oscillatoras shownin Figure 3. Tunethe radioto a freepointof the rangebetween550and 1,600kHz.Adjust tunethissignalas a whistle.lf youcan'tfind CV in thesearchcoiloscillatorto the oscillatorsignalin theAM band,reduceor enlargethe searchcoilby a few turns. Passingthe searchcoil over a metallicobjectwill changethe pitchof the changeoccurs,you shouldbe directly whistle.Whenthe mostpronounced overthe metalobject.

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PnFGrt5 ftfiilromau PartsList - MetalDetector Q1- 8C548general-purpose NPNsilicontransistor Ll - Searchcoil- seetext CV- 365pF - anyvariablecapacitor (fromnonworking AM radio) C1 - 2,200pF ceramiccapacitor C2- 0.1uFceramiccapacitor Rl - 10,000ohm,114W,5% resistor 51 - SPSTslideor toggleswitch 81 - 6 or 9V - fourAA cellsor 9V baftery

ldeasto Explore Togetbetterperformance or to learnmoreaboutthecircuit: o Makeexperiments withditferent kindsof materials to seehowthe detectorworkswitheachone. o Explain whathappens whena metalobject is introduced in a magneticfield.ls thereanywayto identifythe metalbeingdetected? o Thecircuitcanalsobe usedas an RFsignalgenerator. Togetthe signalfromthisoscillator, probe connecta to thecollector of thetransistorwitha 1,000pF capacitor andan alligator clipto theemitter.

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forhc trncilmcmcl IunProiecls Scienceprojectsand uncommonapplications: o Severalexperimentsinvolvingmetaldetectioncan be conducted usingthissimplemetaldetector.An examplewouldbe a workto show andnon-magnetic diamagnetic betweenparamagnetic, the differences materials,as suggestedearlier. o The searchcoil can be modifiedto applyRF signalsto plantsor on to find the effectsof RF (RadioFrequency) animals.Experiments plant growth this made with circuit. germination be can or seed

218

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SET(E) GRYSTAL no batterypowerat all canbe whichrequires radioAM receiver A complete crystal Theclassiccircuitof thewell-known createdwitha fewcomponents. or diodeas detector, canbe basedon a germanium radioor crystalreceiver if youprefer,theoriginalgalenacrystal. antennatuningcoil Figure I showsthe classiccircuit.L1 is a proprietary (365to 500 variablecapacitor woundon a papertubeandCl is a matching radios. transistor canbe foundin old non-working pF).Avariablecapacitor Youcanalsofindthediodein thesesetsanduseit forthisproiect. is Virtuallyany diodecan be used,and the onlyothercircuitcomponent higha be must Theearphones acrossthe output. C1,connected capacitor (headphones). type impedance good groundconnection is essentialfor aerialandgoodphysical Anexternal reception. ThecircuitwilltuneAM bandradiostationsnotfarfromyourhome. layoutis shownin Figurc2. Component wireon a f -inch L1 is formedby 100turnsof No.22to 28 AWGenamelled papertube. diameter

PartsList - CrystalRadio D1

- 1N34or anygermanium diode

L1

- Coil- seetext

CV

- 365to 500pFvariablecapacitor

C1

- 470pF ceramiccaPacitor

- High{mpedance (2,000to 10,000 ohms)phone PHONE 2t2

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Figure 1

Figure2

ldeasto Explore Tolearnmoreaboutthecircuitor to getbetterperformance: o Usean audioamplifier to getbetterreception. o Replace thecoilby 100turnsof No.22lo 28 wireon a ferriterod. SciencepQects: o Thissetcanbe usedto demonstrate howold-timeradioreceivers operated. Explainhowa galenadetector works.

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withthis temperature-dependent experiments Youcan conductinteresting pitch Thesensor temperature of a sensor. the Tone depends upon oscillator. of this silicondiode.The reverseresistance is a commongeneral-purpose junction temperature.The circuitcanoperate onthe diodeisslight,dependent -20and+100degreesCelsius. rangetypically between in a temperature canbealteredina large rangedepends uponCl.Thiscomponent Frequency to uF rangeof values.Valuesbetween0.01and 0.47 can be substituted produce tonesin theaudiorange. "clicks" of uponthetemperature witha ratedependent lf youwantto produce Metal film or 1 uF. 0.47 and with values between the sensor,try capacitors canbe usedin thiscircuit. ceramiccapacitors nearthepointwhereit beginsto run. Pl youcanputtheoscillator Byadjusting makingit operateas a risewilltriggertheoscillator, Then,anytemperature temperature alarm. fromtwoorfourAAcells,andcurrentdrainis low. Thecircuitcanbepowered diodecanbeprotected silicondiode.The Thesensoris anygeneral-purpose andwater. againstmoisture is shownin Oscillator Theschematic diagramof theTemperature-Controlled wirefor FigureL Thesensorcanbewiredto thecircuitbya longtwisted-pair remoteoperation. layout,usinga terminalstripas chassis,is shownin Figure2. Components youcanalsomountit on purposes, forexperimental Asthecircuitis intended board. a solderless should suchasthediodeandpowersupply, components, Position ofpolarized be observed.

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IunProlccts foltln Hnulmomcl Iled OsciIlator PartsList- Temperature-Contro NPNsilicontransistors Q1, 2 - 8C548general-purpose Q3

- 8C558general-purpose PNPsilicontransistor

D1

- 1N914general-purpose silicondiode

P1

- 1,000,000 ohm potentiometer

resistors R1,2 - 10,000ohm,114W,5% R3

- 1,000ohm,1/4W,5%resistor

Cl

- 0.047uF ceramicor metalfilmcapacitor

S1

- SPSTtoggleor slideswitch

81

- 3V or 6V - two or fourAA cells

S P K R- 4 o r I o h m s - 2 o r 4 i n . l o u d s p e a k e r

ldeasto Explore To learnmoreaboutthe circuitor to get betterpedormance: o By replacing circuitwilloperD1withan LDRor phototransistorthe oscillator. ate as a light-controlled o Explainwhy the resistanceof the sensorvarieswithtemperature, thiscircuit. controlling o Replacethediodewitha transistor(conection is madeusingcollector and emitterterminals).Explainwhythisdevicecan alsobe usedas a temperaturesensor.

200

ftltfct|'Iffi|tG|lI Scienceprojects or uncommon uses: o Youcan usethis circuitas a biofeedback deviceby replacingthe Thesubject,holdingthe sensorin hand, sensorwithtwoelec,trodes. canlearnhowto controlthetonethroughstressandbreathing management.The circuitalsooperates asa liedetector usingthisconfiguration. o Anyexperiment involving temperature variations canbeconducted usingthiscircuit.

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SIREN (E/P) FREQUENCY-MODULATION Actingon a capacitorcharging,one oscillator(pins1,2 and 3 of lC1) can modulateanotheroscillatorin frequency,as describedin this project.The producedtonesthusrunfromhighto lowandvice-versaat a ratedetermined by the firstoscillatorfrequencyand also by P1 and P2 adjustments. The circuitcan be usedas a siren,part of alarms,gamesand manyother With a 12Y powersupplythe outputpoweris up to a wattage applications. representing an excellentaudiolevelin a loudspe,aker. The basiccircuithas tone, modulationrate and depthadjustedby trimmer potentiometer.There thatcan be changedto alter arealsosomecomponents the performanceof the siren.G1, for instance,determinesmodulationrate depthand rateand andcan rangefrom 1 to 47 uF.C2 determinesmodulation can also be alteredwithina large rangeof values.C3 determinetone frequency,rangingfrom0.01to 0.1 uF. Powersupplycan rangefrom6 to 12V.Witha 12Vpowersupplycurrentdrain is as highas 2 or 3 amps.Fl is importantto preventproblemswith shorts. Ql is a powerFET and equivalentscan be used.Youalso can replacethis transistorwith a DarlingtonNPN powertransistorsuch as TlP110,but you mustalsoadda seriesresistorwithbaseterminal.Usea 10,000ohm resistor tor this task. Siren is shownin Figure 1. The schematicfor the Frequency-Modulation Observethattwo gatesare usedas oscillatorsandthe othertwo of a 40938 lC are usedas butfer-inverters. boardis shownin Componentsplacementon a homemadeprinted-circuit purposes the circuitcan also be mountedon a Figure 2. Forexperimental solderlessboard,andit is importantto placethetranslstoron a largeheatsink. should capacitors, suchas electrolytic Positionof the polarizedcomponents, be observed. typefor betterperformance.Installingit The speakershouldbe a high-power in an enclosurewill providebettersoundlevel.

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Siren PartsList- Frequency-Modulation lC1

- 40938CMOSIntegrated Circuit

Q1

- lRF630or equivalent PowerFET

SPKR- 4 or 8 ohms,4- to 8-inchspeaker- see text F1

- 5A fuse

R1

- 100,000ohm,114W,5% resistor

R2

- 4,700ohm, 114W,5%resistor

resistors R3,4 - 10,000ohm,114W,5% P1

- 2,2OO,OO0 ohm trimmerpotentiometer

P2

- 47,000ohm trimmerpotentiometer

P3

- 100,000ohm trimmerpotentiometer

C1

- 4.7 uF,16WVDCeletrolytic capacitor

C2

- 1,000uF,16 WVDCelectrolytic capacitor

C3

- 22 uF,16WVDCelectrolytic capacitor

C4

- 0.022uF ceramicor metalfilm capacitor

ldeasto Explore To learnmoreaboutthecircuitor to getbetterperformance: o ExplainhowPowerFETswork. o AlterCl , C2 andC3to createnewsounds.

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Figure2

o Wire pins 1 and 5 togetherand to an externalcontrolcircuit.The sirencan be controlledby externallogiccircuits. o Determine the logiclevelin pins10 and 11 whenpins1 and 5 go low.Whatwill happenwithcurrentdrainin this case? o ReplaceQ1 by a TlP31or 8D135to operatewith lesspower.The powersupplyshouldbe reducedto 6 or gV in this case. Scienceprojectsand uncommonapplications: o ReplaceR1 with an LDR and experimentwith a light-controlled siren. o Usethis sirenas part of alarms. o Usingthis sirenyou can generatespecialsoundsto experiment withanimalconditioning. o Modulatedultrasounds can be producedby reducingC4 to values pF. as fowas 2,200or 4,70O

205

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colNTossER(E/P) theflippingof a coinby merelypressingS1' Of course, Thiscircuitsimulates can't version,if usedfor importantdecisions(or experiments), the electronic be loadedor weightedand is 100%random. in a frequencyrate deterThe circuithas two LEDsthat flick alternatingly, minedby C1,whenpoweris ON.Whenyou press51 the circuitstopsimmediatelyandonlyone LEDremainsON. Powersupplycan rangefrom5 to 12 volts,andthismeansthatyoucan use version. AA cellsin a Portable Cl, to the intendedapplication: can be alteredaccording Somecomponents use also for instancecan be alteredin a rangefrom0'01 lo 0-47uF.Youcan a touchsensorto stopthe tosseror increaseR1'svalueto up to 10,000,000 ohms. The schematicdiagramfor the coin tosseris shownin Figure 1. Only one g"t" " 49gglC is uied as oscillatorto producerandompulsesin this circuit' boardis shownin componentsplacementon a homemadeprinted-circuit Figire2. The circuitcan easilybe housedin a smallplasticbox. casuchas the LEDsand electrolytic Positionof the polarizedcomponents, pacitor,shouldbe observed.

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Figure I

PartsList - CoinTosser lcl

- 40938CMOSIntegrated circuit

LEDs- Commonred,yellowor green S1

- SPSTMomentary switch

R1,2 - 10,000ohm,114W,5% resistors R3

- 1,000ohm,1l4W,S%resistor

C1

- 0.1uF ceramicor metalfilmcapacitor

C2

- 100uE 16WVDCelectrolytic capacitor

Glhlm

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Figure2

ldeasto Explore Tolearnmoreaboutthecircuitor to getbetterperformance: canbe usedto driveincandeso Insteadof usingLEDs,transistors centlamps. o Sl can be placedas far as you wantfromthe circuit.Common parallelwirecanbe usedforthistask. thatthe o Explainhowa flip-flopworksandhowyoucanguarantee circuitis 100%random.

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mFa ..': r0 Grhlrcu Science anduncommon applications: o YoucanconductESP(Extra-Sensory Perception) experiments using thiscircuit.51 canbe placedfarfromthe LEDsfor betterresults. o Experiments withprobability theorycan be conducted usingthis circuit. o Tryto couplea sequence generator to the oscillator usedin this circuitto geta 1-to-10ratflecircuit.

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(E) PLASMAOSCILLATOR feedback thatcanbe usedin an uncommon medium A flameis a conductive canbe Thisconfiguration of an audiooscillator. loopto controlthefrequency flame. a of of theconductivity usedas a confirmation matbythe'Tourth" inthisprojectis controlled described Theaudiooscillator "plaSma" part of an or an ionizedgaS,and Canbe usedas ter state,the physics. in experiment interesting by a simplematchor a candleandtheflickering Theflamecanbe produced sound. thegenerated etfectwillmodulate on the between1 and 500 Hz, depending The circuitrunsin frequencies andflamepositions. electrodes is shownin Figurel.The high of thePlasmaOscillator diagram A schematic in thisproject.A flametypically of a 40938is fundamental inputimpedance in the rangeof tenthsof megohms. hasa resistance positioning is shownin Figure2. Theprintedcircuitboardforthecomponents Sensordetailsarealsogivenin thatfigure.Twowires,oneplacednearthe other,withabout1 inchof baredlengthas shownin the figure,formthe "plasmasensof.Theflameshouldinvolvethetwobaredwiresat the same to operate. currentto flowandtheoscillator timeto allowthefeedback can replacethe transistor transducer An outputstageusinga piezoelectric canbepowered Witha lowercurrentdrainthisconfiguration andloudspeaker. fromfourAA cellsor a 9V battery.

-

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Q1 8D135 OR TIP31

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Figure I

PartsList- PlasmaOscillator lOl

- 40938CMOSIntegratedCircuit

SPKR- 4/8 ohm 4-inchloudspeaker Q1

- 8D135orTlPSl PowerNPNsilicontransistor

R1

- 10,000ohm, 1l4W,5olo resistor

R2

- 1,000ohm, 114W,5%resistor

X1

- Plasmasensor- see te)ft

C1

- 1,000to 4,700pF ceramicor metalfilmcapacitor

t05

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SPKR

X1

+61+12V

Figure2

ldeasto Explore or to learnmoreaboutthecircuit: Togetbetterperformance o Explain whythecircuitdoesn'toperateusinga neonorfluorescent lampas a plasmamedium. o Explain is. what"plasma" o Youcanalterthiscircuitto useit as a flamealarm.

300

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applications: Science a Otfcourse,thebasicideaofthisprojectisto useit inanexperiment plasma. gasloseselecinvolving Plasmais produced whenanionized trons.Thethe gasconvertsin a "soup"of freeelectronsandionized atoms. o Usedifferentkindsof flames,suchasthoseproduced bymatches, gas,paper,etc.,andcompare pitch. theirconductivity tone by'the

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