The dimming process seems simple enough – the push of a button or the pull of a lever makes your lights brighter or darker. However, there are actually many kinds of dimmers, designed to function with different light sources and lighting systems. For your lighting system to work properly, you need to choose the right one.
I'll explain how different kinds of dimmers work, and what kind of dimmer you need to use with your lights. We'll cover dimmers made for use with the following:
- Incandescent Lights
- LEDs and CFLs
- Line Voltage Systems
- Low Voltage Systems
- Magnetic Transformers
- Electronic Transformers
- Hardwired Lights
- Plug-in Lights
Standard Incandescent Dimmers
If you are not dimming anything fancy – just your standard incandescent, halogen, or xenon lights – you should use a standard incandescent dimmer. This switch uses an electrical component called a triode alternating current switch, or a triac. To dim, the dimmer turns the lights on and off very rapidly, about 120 times every second. The flashing happens too rapidly for us to notice. This process is similar to how video works – the still frames move so quickly that what we see looks smooth and continuous. For brighter light, the triac keeps the lights "on" more than "off." For dimmer lights, they're "off" more than "on."
LED & CFL Dimmers
Standard incandescent dimmers can cause newer light sources to malfunction. When used with the wrong switch, LEDs and CFLs won't dim fully, may turn off unexpectedly, and could fail to turn on. To ensure all your lights dim correctly, you need a compatible dimmer. Take Lutron's new C-L dimmers, for instance. Using HED technology – the advanced circuitry necessary to dim most high efficiency lights – C-L dimmers smoothly operate LEDs, CFLs, and even mixed loads with incandescent lights. Always make sure your light bulbs are manufactured for dimming, and are listed as compatible with the dimmer you choose.
Line Voltage & Low Voltage Dimmers
If your lights run on line voltage – the standard voltage supply in your home (120V), or low voltage – a reduced supply (12V or 24V), you'll need a dimmer that runs on the same.
For line voltage systems, you can use a standard, basic dimmer. Since they operate on your home's regular voltage, you can simply wire them into your system – no big deal.
Low voltage lighting systems can be a little more complicated, because you have to find a switch that will work with your lights and your transformer. If you use a line voltage dimmer with a low voltage system, or a dimmer that isn't compatible with your transformer, it could cause problems like overheating, loud buzzing, flickering lamps, or damage to the lamp, dimmer, or transformer.
Electronic & Magnetic Dimmers
This distinction is important when finding a dimmer for low voltage lights. Low voltage lighting systems need transformers to decrease line voltage to their required voltage supply. Transformers are either electronic or magnetic.
Magnetic transformers are made of copper wrapped around a steel core, which is inductive. This just means it can store energy in the form of a magnetic field. When you use a magnetic transformer, you'll need a magnetic dimmer. Many magnetic dimmers use a technology called standard phase control when dimming, which causes a delay before the dimmer starts conducting.
Electronic transformers use capacitive electronic circuitry, which stores electric charge. You'll need an electronic low voltage dimmer to control this kind of system. Most electronic dimmers use reverse phase control to function, delaying the time at which the dimmer stops conducting.
Note: You can mix line voltage and low voltage fixtures on the same circuit, but you always have to use them with the correct low voltage dimmer. The load can't exceed the dimmer's capacity. Never mix electronic and magnetic dimmers on the same dimming circuit.
Hardwired & Plug-in Dimmers
Finally, there's the style issue. For large-scale lighting systems like recessed lights, under cabinet lighting, or display lighting, you'll always want to use a hardwired dimmer, installed in the wall like a regular light switch. However, if you only need to dim a single fixture, like a lamp, you may find a plug-in tabletop dimmer will give you more freedom.