Ultra simple car interior light dimmer circuit of a pulse width modulated (PWM) energy saving dc lamp dimmer is described here. With the help of this circuit, you can control the intensity of the dome lamp in your car from near 5% to 90% using a single potentiometer. The circuit is designed for cars with negative ground.
The circuit works off 12V dc supply from the car battery and is capable of driving dc incandescent lamps of wattages up to 24W!
The design is based on IC1 (40106) astable multivibrator whose output is low for a period determined by R2 and high for a period determined by R1 and P1. Output from IC1 (at pin4) is applied to the base of transistor T1.Transistors (T1&T2) are switched on and the lamp is energized during the negative period of the output pulse of IC1. When the resistance of P1 is at maximum, the brightness of the lamp is at minimum level.