Variable Resistance Type Dimmer, Light 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

Circuit Diagram and Parts of Variable Resistance Type Dimmer

1. Variable resistance
2. Variable knob.
3. Brush
4. Luminary (lamp)

Working principle of Resistance Type Dimmer
Variation of current in the lamp varies its brightness. Variation of current is obtain by varying resistance O by connected in series with the lamp.
Operation : Variable knob (2) when slided the resistance in the lamp circuit varies. This varies the brightness of lamp. It is a manual operation. This is the old fashion.

Advantages of Resistance Type Dimmer

1. Simple operation
2. Maintenance required is very less.
3. Cheaper in cost
4. Portable unit.

Drawbacks of Resistance Type Dimmer

1. Due to resistance, all the while in the circuit, there is a power loss.
2. Power loss produces heat and the unit becomes hot, so it needs heat dissipation arrangements.

1.2 Salt Water Dimmer

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

3. Electronic Dimmer

3.1 Thyristor operated dimmer

3.2 Triac Operates Dimmer