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.

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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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