||Light Detector Circuit
Mick Devine, UK
Variable resistor R1 adjusts 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 resets the circuit. The output device may be a low power piezo buzzer.