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This project automatically turns on a night lamp light when bedroom light is switched off. This is a LDR (Light Dependant Resistor ) based circuit. The lamp light remains ‘on’ until the light sensor senses daylight in the morning. A super-bright white LED is used as the night lamp light. It gives bright and cool light in the room. When the sensor detects the daylight in the morning, a melodious morning alarm sounds.

 

 

The circuit can be easily assembled on a general-purpose PCB. Enclose it in a good-quality plastic case with provisions for LDR and LED. Use a reflective holder for white LED to get a spotlight effect for reading. Place LDRs away from the white LED, preferably on the backside of the case, to avoid unnecessary illumination. The speaker should be small so as to make the gadget compact.

 

Resistor -------------------------------- R1,R7----------------------------- 1K
Resistor -------------------------------- R2,R5 ---------------------------- 150K
Resistor -------------------------------- R3 --------------------------------- 120K
Resistor -------------------------------- R4 -------------------------------- 220K
Resistor -------------------------------- R6 --------------------------------- 580K
Resistor -------------------------------- R8 --------------------------------- 560K
Capacitor ------------------------------ C1 ---------------------------------- 1000µ /25V
Capacitor ---------------------------- C2,C3 ------------------------------- 0.01µ
Diode ----------------------------- D1,D2,D3,D4 ------------------------- 1N4007
Diode --------------------------------- D5,D6 ------------------------------ 1N4001
Zener Diode --------------------------- ZD --------------------------------- 3.3V / 0.5W
LED ----------------------------------- LED -------------------------------- white
Light Dependent Resistor ----------- LDR1,LDR2 ---------------------------
Transistor ---------------------------- T1,T2 -------------------------------- BC548
Integrated Circuit -------------------- IC1 ---------------------------------- 7806
Integrated Circuit -------------------- IC2 ---------------------------------- NE555
Integrated Circuit -------------------- IC3 ---------------------------------- UM66
Transformer ------------------------- X1 ---------------------- 230V to 0-90V 500mA
Speaker ---------------------------------- SP ---------------------------------- 8µ 4.5W

Circuit Designed by : D. Mohan Kumar
Source:

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