1. Description of Dimmers
Dimmers allow to use one light for many purposes and to modify instantly the atmosphere of a room with a simple adjustment. They will also save energy when used at lower levels on light intensity. Look for full-range dimmers so that you can vary the light continuously from zero to full brightness. Dimmers can be used with incandescent lights, including low-voltage systems, and with many fluorescents lamp too.
Except for some new screw-base compact fluorescents, fluorescent lights must have their own dimming ballasts and should never be installed in sockets for dimmable incandescent. Dimming incandescent lamps should extend their life; however, if halogen lamps are dimmed frequently, manufacturers advise operating them occasionally at full light output.
There are several choices of wall-mounted dimmers: toggle, rotary, sliding, solid-state touch, and new integrated systems with remote controls that can recall previous lighting levels. If several high-wattage incandescent lamps are to be controlled at one point, add a hard-wired dimmer. For plug-in lamps that do not have a dimming switch, you can purchase an adapter for a socket or cord dimmer.
2. Light Dimmers
Solid-state light dimmers work by varying the "duty cycle" (on/off time) of the full AC voltage that is applied to the lights being controlled. For example, if the voltage is applied for only half of each AC cycle, the light bulb will appear to be much less bright than when it gets the full AC voltage, because it gets less power to heat the filament. Solid-state dimmers use the brightness knob setting to determine at what point, in each voltage cycle, to switch the light on and off.
Typical light dimmers are built using SCR and the exact time when the SCR is triggered relative to the zero crossings of the AC power is used to determine the power level. When the SCR is triggered it keeps conducting until the current passing through it goes to zero. By changing the phase at which you trigger the triac you change the duty cycle and therefore the brightness of the light. Triacs and thyristors are sensitive to over currents. When dimming normal light bulbs, short circuits are quite probable because of burnt filament. For this reason, light dimmers must have their own fuse, which protects them against failures.
Dimmer circuits normally use coils that limit the rate of current rise. Typically, filtering in light dimmers causes the current rise time (current rises from 10% to 90%) to be in range of 30 to 50 microseconds. This gives acceptable results in typical dimmer applications at home (typically this limitation is made using 40.100 mH coil).
The coil itself does not usually solve the whole problem due to the inductor’s self-capacitance: they normally resonate below 200 kHz and look like capacitors to disturbances above the resonance frequency. That's why there must be also capacitors in order to suppress the interference at higher frequencies.
Normal light dimmers are designed to only dim non-inductive loads like light bulbs and electric heaters. Normal light dimmers are not suitable to dim inductive loads like transformers, fluorescent lamps, neon lamps, and halogen
lamps with transformers and electric motors. There are special dimmers available for those applications.
Fully loaded halogen transformers usually dim quite well. Some of the electronic transformers are made dimmable and work well with traditional light dimmers. The ones which are not meant to be dimmed can be damaged by the dimming and even damage your dimmer.
Fluorescent light bulbs (including compact fluorescents) are more energy-efficient than regular bulbs due to the different method they use to produce light. Regular bulbs (also known as incandescent bulbs) create light by heating a filament inside the bulb; the heat makes the filament white-hot, producing the light that you see. A lot of the energy used to create the heat that lights an incandescent bulb is wasted. A fluorescent bulb, on the other hand, contains a gas that produces invisible ultraviolet light (UV) when the gas is excited by electricity. Most compact fluorescent lamps (CFL) have ”integral" ballast, built into the light bulb, whereas most fluorescent tubes require separate ballast independent of the bulb. Both types offer energy-efficient light.
A dimming compact fluorescent light bulb is specially designed for use with dimming switches. Regular compact fluorescent bulbs should not be used with dimming switches, since this can shorten the bulb’s life.
Until recently, screw-in CFLs were not compatible with conventional household dimmer switches. However, new screw-in products that have been introduced can be used with dimmer switches, allowing for even more energy savings. To prevent any hazard, it is best to check the package for compatibility with dimmers, or for a safety warning.