This circuit turns on a lamp when the night comes and turn it off in the morning. The circuit operates only with incandescent lamps and sensitivity is adjusted by P1. Since the control is a half wave type, the lamp will glow not with is total power but less. A diode bridge can be added to a full-wave control. The SCR must be mounted on a heatsink. The SCR is according the AC power line. Any LDR can be used as sensor.
Night Switch
