黑暗激活LED或燈閃光電路
黑暗激活LED或燈閃光電路--Dark-activatedLEDorLampFlasher
Simplephoto-sensitivecircuit3VbatterysupplyParts:R1_________________Photoresistor(anytype)R2________________100K1/2WTrimmerCermetR3,R4______________10K1/4WResistorsR5________________470R1/4WResistorR6_________________47R1/4WResistorC1________________220΅F25VElectrolyticCapacitorD1______________1N414875V150mADiodeD2_________________LEDAnytypeandcolor(SeeNotes)Q1,Q2____________BC33745V800mANPNTransistorsSW1_______________SPSTSwitchB1__________________3V(Two1.5VAAorAAAcellsinseries,etc.)Circuitoperation:ThiscircuitadoptstheratherunusualBowes/Whiteemittercoupledmultivibratorcircuit.Theoscillationfrequencyisabout1HzandissetbyC1value.TheLEDstartsflashingwhenthephotoresistorisscarcelyilluminated.TheonsetofflashingcanbesetbytrimmingR2.Notes:BestresultsinflashingfrequencycanbeobtainedusingforC1avalueinthe100to1000΅Frange.Todriveafilamentlampthefollowingchangesmustbemade:Usea2.2to3V,250-300mAlampinplaceoftheLEDR2=10K1/2WTrimmerCermetR3,R4=1K1/4WResistorsR6=1R1/4WResistorC1=470to1000΅F25VElectrolyticCapacitorInLED-modeoperationthestand-bycurrentconsumptionislessthan400΅A.InLamp-modeoperationthestand-bycurrentconsumptionisabout3mA.
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