This light dimmer is used to dim the intensity of 12V light bulbs using the well-known 555 timer that is configured as an astable multivibrator. The pulses from pin 3 are used to control the VMOS transistor BUZ20, BUZ72 or 10N10. The maximum dissipated power must not exceed 40 watts. You may use the transistor without a heatsink if the power does not exceed 10 watts.
The 555 IC powering is done through D2 diode and is filtered using C3 capacitor. The resistors can be 0.25W or 0.5W with a tolerance of ±5%.