Smart 230V AC Bulb Holder

The Smart 230V AC Bulb Holder functions as an automatic dusk-to-dawn lighting controller by combining light-sensing circuitry with a relay-driven power switch. At the front end, a GL5528 light-dependent resistor (LDR) acts as a variable light sensor, forming a voltage divider with a 100-kilo-ohm resistor (R2) to detect ambient light levels. During daylight hours, the low resistance of the LDR alters the input conditions of the circuit. As night falls, the resistance of the LDR increases significantly, triggering a change in state that is processed alongside an NE555 timer IC (IC2). The NE555 timer stabilizes the control signal to prevent rapid toggling or flickering as light levels transition at dusk and dawn. The control signal then drives a PC817 optocoupler (IC1), which provides essential galvanic isolation between the low-voltage control section and the high-voltage mains section. On the power side, incoming 230V AC mains voltage is stepped down and rectified using a bridge rectifier (BR1), a 1N4007 rectifier diode (D1), and a 12V Zener diode (ZD1) to supply stable DC power to the active components. A 220uF buffer capacitor (C2) smooths out voltage fluctuations to ensure steady operation. Finally, when the control logic commands the light to turn on, a 12V single-changeover relay (RL1) clicks over, physically closing the 230V AC circuit connected to the bulb holder and illuminating the lamp.