As we have already published various type of lamp dimmer like condenser lamp dimmer, light dimmer using triac etc. Now here is a lamp dimmer for dome lamp in car, gives a fairly linear control over the lamp brightness from low to high intensity. The main advantage of the circuit dome lamp dimmer is it consumes little power because it is a pulse-width modulated chopper circuit. You can also control the intensity of a halogen bulb or control the speed of a mini drill by using the circuit.
Circuit Description of Dome Lamp Dimmer
The circuit of dome lamp dimmer is build around timer IC NE555 (IC1), and a MOSFET. IC1 is used as astable multivibrator in order to produce square wave capacitor C1 is charge and discharge from the output of IC1 via diode D1 and D2. Adjust potmeter VR1to control the RC time constant-during the charge-discharge cycle and get the timer output with the desire pulse width. By this way the brightness of lamp can be varied from low to high by adjusting potmeter VR1. Use a suitable heat sink for the MOSFET T1 to handle the load current.
BEP NOTE: As we know that most cars run only one wire to power the lamp and use the car body for return current path. Connect ground path of the circuit to the car body.
PARTS LIST OF DOME LAMP DIMMER
Resistor (all ¼-watt, ± 5% Carbon)
R1 = 1 KΩ
R2 = 47 KΩ
VR1 = 22KΩ POT
C1, C2 = 0.01 µF
IC1 = NE555
D1, D2 = 1N4148
T1 = IRF540
B1 = 12V bulb