Dimmers are used for controlling brightness of the light. Dimmers are used to change the waveform of the voltage applied to the light. Dimmers are used for controlling voltage of resistive loads lights i.e. for CFL’s, Bulbs, resistive incandescent, LED lights etc.
Dimmer chops the voltage applied to light. Which will allows chopped part of voltage to pass to light. Dimmers are available in different sizes and ratings, they have sizes as small as size light switch to control domestic lighting and have as higher rating for controlling lighting installations in theatres and architectural lightings.
Above pic shows small size of dimmer used domestic lights
Dimmer is wired in series with the lamp. The lighting dimmer control is done by potentiometer. To control voltage in lighting potentiometer needed to be rotated to control the voltage.
From above pic you can see how Dimmer is wired in circuit.
Dimmers are available in different ratings from 600-1000 W rating, depending upon the rating of light. Remote controlled dimmer switches are also available. X10 models are available for house lighting and Modern professional dimmers DMX and DALI models are generally digitally controlled.
Also Modern dimmers are semiconductor controlled instead of old resistive controlled as semiconductor dimmers have more efficiency. In old resistive controlled dimmers voltage is dissipated across resistance but as semiconductor controlled dimmers is solid state dimmers i.e. they can switch between low resistance as ÖN State and high resistance as ÖFF state so they have low power dissipation and leads to higher efficiency and saving of power. Due to these semiconductor dimmers they smaller sizes of dimmers are available in the market. These semiconductor dimmers can have easily remote control operation available. These switches generate heat and radio-frequency interference that can be avoided by placing inductor as part of circuitry.
Semiconductor based Dimmer internal circuit is shown above
Dimmer have following types:-
1. Rheostat Dimmers
2. Saltwater type—Liquid Dimmers
3. Coil Rotation Transformer
4. Auto-Transformer Dimmer
5. Solid State Dimmer
Dimmers have three types of curves:-
Analog dimmers O/P wasn’t directly proportional to Input, An analogue dimmer dim slowly at first, quickly in middle and slowly at top.
Usually televisions uses Square Law curve. Which allows finer control of light at top, this is done to allow accurate trimming of color temperature of lighting. Theatrical dimmers use softer “S” or linear curves.
Digital dimmers can be designed for any shape of curve for operation.
Dimmers Preheat function:-
Dimmers also provide preheat function. Whenever there is switching of high intensity incandescent lamps this will reduce the life of lights due to high inrush current. These high current usually occurs due to switching from cold to hot state. This can be avoided by setting dimmer between 5% to 10% as light will appears to be off at that level but it will provide preheating of light i.e. it will leads light not getting cool down. This will leads to higher life of light.