Triac Operates Dimmer, Electronic Dimmer

Dimmers

Different lamps/luminaires produce light with constant brightness once they are switched on.
For the following spots, the variation of brightness of the lamps is required.

For (i) Photo studios (ii) Stage (iii) Drama theatres (iv) Decorations (v) Various functions.

The device for controlling the brightness is a "Dimmer".
Dimmer is an electrical and or electronics device. It basically changes the current or voltage which is the cause of varying brightness of luminaries.

Let us study the circuit arrangements and operation of these dimmers.
1. Variable Resistance Type Dimmer
1.1 Resistance Type Dimmer

1.2 Salt Water Dimmer

2. Dimmer Transformer
2.1 Autotransformer Dimmer
2.2 Two Winding Transformer Dimmer

3. Electronic Dimmer

Electronic dimmers are very compact and handy.
These circuits make use of solid state devices like SCRs, TRIAC, DIAC.
These are used to control the intensity of lamps.
In comparison to resistance control dimmer, the power loss in this system is negligible,

These are two types of circuits possible hence two types are possible

3.1 Thyristor operated dimmer

3.2 Triac Operates Dimmer

Circuit Diagram of Triac Operates Dimmer

Triac and Diac are used to change the intensity (brightness) of the lamp.
Operation of Triac Operates Dimmer

The resistance R1, and capacitor C1 are connected in series.
The capacitor is made to charge through the Ri resistance.
When the voltage across reaches above the breakover voltage of DIAC, it starts conducting.
The voltage across the capacitor now gets applied to TRIAC gate and the TRIAC is turned ON. The charging of the capacitor can be controlled by the variable resistor R1, which indirectly controls the firing delay of TRIAC.
Thus the intensity i.e. brightness of the lamp can be controlled.

Application of Triac Operates Dimmer