Filament Light Dimmer Circuit

filament light dimmer using bt136 triac DB3 diac

Filament Light Dimmer Circuit

This simple triac dimmer can be used to control incandescent filament lamps up to 200W. The circuit operates on the phase-control principle.

filament light dimmer circuit using bt136 triac DB3 diac

R1 10kΩ 0.5W
R2 100Ω 0.5W
VR1 500kΩ Potentiometer
C1 330n (0.33µF)
C2 100n (0.1µF)
D1 DB3 Diac
Q1 BT136 Triac
L1 Filament Light

The main control is provided by VR1. This determines the rate at which C1 charges and hence the point along the mains waveform at which the voltage on C2 reaches the breakdown voltage  of the diac (D1), which is when the triac is triggered.

BT136 triac pin configuration Passivated, sensitive gate triac DB3 Diac trigger diode
BT136 Triac pin configuration DB3 Diac

Interference suppression is provided by R2 and C2.

This light dimmer is directly connected to mains. So be careful.

The potentiometer should have a plastic spindle.

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