Automatic Evening Lamp
Automatic Evening Lamp
Automatic Evening Lamp
AutomaticEveningLamp
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HOME>>CIRCUITLAB
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AutomaticEveningLamp
D.MohanKumar
Presentedhereisasolutionforswitchingoffoutdoorlampsevenwhenyouarenotathome.Thelampturnsoninthe
evening and turns off in the morning so that there is no need for manually switching it on/off. The circuit is directly
powered from AC mains and can be enclosed in a plugin type adaptor box. It can drive a bulb, CFL, tubelight, LED
lamp,etcupto200W.AuthorsprototypeisshowninFig.1.
Circuitandworking
The circuit uses a transformerless power supply to generate lowvolt DC. As
capacitors C1 and C2 are connected in AC lines, these should be Xrated
capacitors. This minimises space and makes the unit lightweight. Unlike an
ordinarycapacitivepowersupply,amoreefficientpowersupplydesignisused
for spikefree operation. Phase (L) and neutral (N) lines have identical circuits
soreversalinpolaritywhilepluggingwillnotaffectthecircuit.105K(1F)400V
ACcapacitorsareusedthatcandrop230VACtolowlevelAC.ResistorsR1and
Fig.1:Authorsprototype
R2 protect the power supply from instant inrush current. Bleeder resistors R3
andR4,paralleltoC1andC2,removethestoredcurrentfromthecapacitorsat
powerofftopreventshockfromstoredenergyinthecapacitors.
A fullwave rectifier bridge comprising D1 through D4 (1N4007) rectifies low
voltACtoDCandsmoothingcapacitorC3givesripplefreeDCforthecircuit.Theoutputvoltagefromthepowersupply
is sufficient to operate the circuit including the relay. Green LED1 indicates poweron status. Resistor R5 limits LED
current.
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Fig.2:Circuitdiagramofanautomaticeveninglamp
ThecircuitisasimplebistablearrangementusingpopulartimerIC555(IC1).Linkingitsthreshold(pin6)andtrigger
(pin2)controlsitsflipflopoperation.Whenthethresholdinputishigh,itresetstheflipflopandkeepstheoutputlow.
When the trigger input is low, flipflop triggers and output turns high. So the combined action of threshold and trigger
inputs gives the bistable switching action to control relay driver transistor T1. The bistable action of IC1 is controlled
by LDR1 and resistor R6 (470k). The value of 5mm LDR can be up to 1 megaohm, depending on the ambient light
conditions.A1MvariableresistorinplaceofR6canmakethesensitivityadjustmenteasy.
Duringdaytime,LDR1haslowresistance,whichmakesthresholdpin6ofIC1high.Thisresetsthetimerandtheoutput
ofIC1remainslow.IttakestransistorT1tocutoffstate.Therelayisdeenergised,sothelampremainsoffduringday
time.
Fig.3:ActualsizePCBlayoutofanautomaticeveninglamp
Fig.4:ComponentlayoutofthePCB
Download:http://www.electronicsforu.com/electronicsforu/circuitarchives/my_documents/my_files/pg_83_Fig_3_Circuit
Dec_14_Automatic_Evening.zip
When the intensity of sunlight reduces in the evening, LDR1 offers more
resistance and the current through it ceases. This makes both threshold
and trigger inputs of IC1 low and the timer changes its output to high.
Transistor T1 is switched on due to saturation action. The relay is
energised, contact changeover takes place and line is extended to bulb
B1. As the circuit is complete, the bulb will be switched on. It will remain
litthroughoutthenight.
Inthemorning,thesituationwillgetreversedthresholdpin6andtrigger
pin 2 go high, timer reverses its output. Transistor T1 goes into cutoff
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AutomaticEveningLamp
region.Therelaywillbedeenergisedandthebulbwillgetswitchedoff.
CapacitorC5atthebaseoftransistorT1givesaslightlagduringon/offof
T1 for the clean operation of the relay. Freewheeling diode D5 eliminates
back EMF from the relay coil and protects T1 during its switch off. Red
LED2indicatestheactuationoftherelay.
Constructionandtesting
An actualsize, singleside PCB layout for the automatic evening lamp is
shown in Fig. 3 and its component layout in Fig. 4. After assembling the
circuitonaPCB,encloseitinasuitableplasticcase.
Give sufficient spacing between the power supply section and the
remainingcircuit.ProvideholesonthefrontsideoftheenclosureforLEDs
and LDR. Connect phase line (L) to the common contacts of the relay and
neutral line (N) for the bulb to the N/O (normally open) contacts of the
relay. A 5V PCB relay is used. Ratings of the relay must match with the
load.SincethecircuitisdirectlypoweredfromhighvoltAC,extremecare
isnecessaryduringtesting.
FirstassemblethepowersupplysectionuptogreenLEDandconnecttoAC
lines. If the green LED turns on, power supply section is alright. After
disconnectingthecircuitfrommains,assemblethecircuitaroundIC1.Test
this part using a 9V battery connected across capacitor C3. If relay RL1 energises after masking LDR1, the bistable
sectionisworking.
Now the relay connections can be done. Keep the unit outdoor in a place where sufficient light is available. Light from
thelampshouldnotfallonLDR1.
Caution. Since this circuit has mains voltage on board, extreme precautions need to be taken. Do not troubleshoot
whenitisconnectedtothemains.Testonlyaftertakingadequateprecautionstopreventshockhazards.
TheauthorisalecturerinagovernmentwomencollegeinKerala
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PostComment|6Comments
15 22 18
ABHAY 48daysago
CanIlesswattagebulbatop..?
Reply 1Reply
ANUDEEPMANTHU 39daysago
YesMr.Abhay...Youcanreplacethebulbwithanyotherappliancewiththenominalvaluesnotexceedingtherelay
specifications...butastheconceptisaboutlightyoucanuseabulbofanywattagewiththevoltageandcurrentratings
notexceedingtherelayspecifications.
Reply
ANUDEEPMANTHU 39daysago
Thisprojectisveryusefulsir.Butwhysomanyresistorscapacitortransistorandtimer...?WecansimplyconnecttheLDRin
serieswiththerelaycoil...AndtheconnectthebulbthroughNOterminaloftherelay.Thensamefunctioncanbe
achieved.WhenLDRresistanceislowrelaycoilisenergizedandtherelaytripstoNCandbulbdoesnotglow.Ontheother
handwhentheLDRresistanceishighindarknesstherelaycoilDeenergizesandthebulbcktclosesandthebulbglows...
Hencethesamefunctioncanbeachieved...
Reply
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AutomaticEveningLamp
raj 39daysago
canIgetthespareskits
Reply
bilalahmed 29daysago
caniuse3wattultrabrightledsinsteadofbulb
Reply
MicrosoftOLEDBProviderforSQLServererror'80040e21'
MultiplestepOLEDBoperationgeneratederrors.CheckeachOLEDBstatusvalue,ifavailable.Noworkwasdone.
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