The figure below shows a project of automatic night lamp circuit. The circuit will automatically turn on the LEDs when the room gets dark for example at night when you close your room lights and automatically turn off the LEDs in the morning.
The circuit is using only few general components
and can be directly operated from 220 volt AC. The 1uF / 400V capacitor converts AC high voltage to low which is then rectified by the four 1N4007 diodes and converted to DC voltage. A 220uF capacitor is used to filter the AC ripples. A 12V 1 watt zener diode steps down the DC voltage to 12 volt to operate the circuit.
A LDR is used to detect the darkness in the room. A 100K variable resistor is used to adjust the sensitivity of the circuit. The circuit is using 6 LEDs, you can use any color as desired. The circuit is not using any transformer and directly connected to the AC therefore do not touch any component of the circuit when it is connected to the AC mains.
Note: Many points of this circuit are at AC mains voltage. It could give you lethal shock if you are not careful. If you don't know much about working with AC line voltages do not attempt to construct this circuit.
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