Touch Dimmer Circuit

We have already posted dimmer using capacitor called “Condenser Lamp Dimmer”. Now here is a lamp dimmer using triac with touch facility.

Circuit Description of Touch Dimmer Circuit Using Triacs

The heart of the circuit touch dimmer using triac is the S576 (IC1) which provides an uncomplicated and elegant method to fire the triac.

circuit diagram of simple touch dimmer using triacs

The IC is not very sensitive to power glitches and work on the 15V dropped by R2 and C2, Zener Diode ZD1 clamps the voltage at 15V, while D1 and C3 smoothen the supply. Interference is reduced by the RC snubber. Resistor R7 and R8 are necessary and provide the touch plate. The triac firing signal is fed through D2, while R3 and C4 synchronise the circuit to mains frequency.

When the touch plate is touched briefly fro 50-400ms, the lamp or load toggles between on and off. When the plate is touched for longer periods, the load (i.e. the lamp) cycles between maximum and minimum power in a period of 6.5 secs. The 50ms lower limit is set to avoid false triggering by picking up interference. The circuit can handle any amount of non-conductive power if the amperage of the triac is changed.


Resistor (all ¼-watt, ± 5% Carbon)

R1 = 10Ω

R2 = 1 KΩ/1W

R3 = 1.5MΩ

R4, R7, R8 = 4.7 MΩ

R5 = 470 KΩ

R6 = 120 KΩ


C1 = 10 nF

C2 = 220 nF

C3 = 100 µF/25V

C4 = 470 pF

C5 = 47 nF


IC1 = S576

ZD1 = 15V

D1, D2 = 1N4006

TRIAC1 = As per power needed


F1 = 2Amp fuse

Touch Plate