Life extension circuit diagram about lighting bulb

Probe domestic switch needle KG300B head diameter 3.0 normally closed switch needle total length is 5

The AC switch is composed of diodes D1~D4 and a thyristor SCR as shown. Resistor R1 is the current limiting resistor of the bulb, and R2, R3 and capacitor C form a delay trigger circuit. At the moment of turning on the light, the capacitor C can be regarded as a short circuit, and the thyristor is turned off because it is not triggered. After the AC power is rectified, a loop is formed through R1 and the bulb, and the voltage on the bulb is extremely low, causing the bulb to turn red. As C is charged, when the voltage on C reaches the trigger voltage of the thyristor, the thyristor is fully turned on, causing the bulb to illuminate normally.