礼貌灯电路

礼貌灯电路
礼貌灯电路--CourtesyLight15secondsdelayedswitch-offAgoodideaforbedroomlamps
Parts:R1____________470R1/2WResistorR2____________100K1/4WResistorR3______________1M51/4WResistorR4______________1K1/4WResistorC1____________330nF400VPolyesterCapacitorC2____________100F25VElectrolyticCapacitorC3,C5__________10nF63VPolyesterorCeramicCapacitorsC4_____________10F25VElectrolyticCapacitorD1,D2________1N40071000V1ADiodesD3_________BZX79C1010V500mWZenerDiodeD4__________TIC206M600V4ATRIACQ1____________BC55745V100mAPNPTransistorIC1____________7555orTS555CNCMosTimerICSW1____________SPSTMainssuitedSwitchDevicepurpose:Thiscircuitisintendedtolettheuserturnoffalampbymeansofaswitchplacedfarfrombed,allowinghimenoughtimetoliedownbeforethelampreallyswitchesoff.Obviously,userswillbeabletofinddifferentapplicationsforthiscircuitinordertosuittheirneeds.Circuitoperation:Duetothelowcurrentdrawing,thecircuitcanbesuppliedfrom220Vacmainswithoutatransformer.Supplyvoltageisreducedto10VdcbymeansofC1reactance,atwodioderectifiercellD1D2andZenerdiodeD3.IC1isaCMos555timerwiredasamonostable,providing15secondson-timesetbyR3C4.WhenSW1isclosed,IC1output(pin3)ispermanentlyon,drivingTriacD4whichinturnfeedsthelamp.OpeningSW1operatesthemonostableand,after15seconds,pin3ofIC1goeslowswitchingoffthelamp.Notes:Thecircuitiswiredpermanentlytothemainssupplybutcurrentdrainisnegligible.Duetotransformerlessdesignthereisnoheatgeneration.ThedelaytimecanbevariedchangingR3and/orC4values.TakingC4=10F,R3increasestimingwithapprox.100Kpersecondratio.I.e.R3=1MTime=10seconds,R3=1M8Time=18seconds.LowGate-currentTriacsarerecommended.Useawellinsulatedmains-typeswitchforSW1.Warning!Thecircuitisconnectedto220Vacmains,thensomepartsinthecircuitboardaresubjectedtolethalpotential!.Avoidtouchingthecircuitwhenpluggedandencloseitinaplasticbox.ThiscircuitwasawardedwithpublicationinELECTRONICSWORLDCircuitIdeas,April2001issue,page299.