Light Detector

This is a circuit diagram of light detector. This circuit can be used as a sensor of automatic lamp switch, thic circuit also can be used for anti theft alarm circuit.

Schematic diagram:

electronic circuit diagram

Use variable resistor R1 to adjust the light threshold at which the circuit triggers. R1's value is chosen to match the photocells resistance at darkness. The circuit uses a CMOS 4001 IC. Gate U1a acts as the trigger, U1b and c form a latch. S1 to reset the circuit. You may used piezo buzzer or LED as output indicator, you may use both of them.