Dimmer how does it work

Dimmer switches can easily be installed by electricians or by people who are knowledgeable about hooking up these types of devices. Keep reading to understand how dimmer switches work and how they can benefit your home environment. Dimmer switches simply raise or lower the brightness in electric light bulbs. They are often used in homes and businesses to conserve energy and to control the lighting environment. You can automatically set the lights to dim at a certain time with timers or smart controls, or adjust the light level manually.

The key to using a dimmer switch is knowing how to get the best results out of the device, so it helps to understand how it works.

Dimmer switches use simple electrical principles to function depending on their type. Your basic dimmer switch simply reduces the amount of electricity flowing through a circuit to reduce the brightness of a light. However, modern dimmer devices work differently. When this happens, it diverts electricity from the light bulb. The amount of electrical current flowing through the lightbulb is reduced.

A dimmer switch changes the direction of electrical flow every time that it is used to dim or brighten the lights. The flow of electricity always alternates between positive and negative. When the circuit alternates it will automatically shut the circuit off or on. A modern dimmer switch " chops up " the sine wave. It automatically shuts the light bulb circuit off every time the current reverses direction -- that is, whenever there is zero voltage running through the circuit.

This happens twice per cycle, or times a second. It turns the light circuit back on when the voltage climbs back up to a certain level. This " turn-on value " is based on the position of the dimmer switch's knob or slider.

If the dimmer is turned to a brighter setting, it will switch on very quickly after cutting off. The circuit is turned on for most of the cycle, so it supplies more energy per second to the light bulb. If the dimmer is set for lower light, it will wait until later in the cycle to turn back on.

That's the basic concept, but how does the dimmer actually do all of this? In the next couple of sections, we'll look at the simple circuitry that makes it work.

So this then would be the modified waveform coming out of the forward phase dimmer. So this is how a standard dimmer works. A dimmer with the output characteristics explained here, is known by many names, including standard dimmer, household dimmer, incandescent dimmer, Triac dimmer, magnetic dimmer, forward phase dimmer, leading-edge dimmer. I will refer to this throughout the remainder of the article as a forward phase dimmer. Keep in mind that these dimmers were developed for dimming conventional light sources.

Particularly incandescent lamps. They will react to how much power is delivered to them, regardless of the waveform. When the lamp is low voltage and a transformer is used to convert the line voltage to 12 volts, for example, to apply to that lamp, then the addition to the lamp itself, some complexity is introduced by the transformer.

Now conventional wire rounded magnetic transformers are compatible with this type of dimming or forward phase dimming, so long as certain factors are implemented in the dimmer. For example: The power delivered during the positive half of the cycle must equal the power delivered to the negative cycle. So that any DC component the power delivered is within the tolerance of transformers, and out of tolerance, DC component would cause the transformer to saturate, leading potentially to its failure.

At one point the history of light source development, the electronic transformer was introduced, with a very different set of characteristics from those of a magnetic transformer. One key difference is that it is not all compatible with a sudden voltage rise, which occurs twice during each cycle. The solution to dimming electronic transformers is, to swap the sequence of power delivery to the lighting load each half-cycle, instead of opening the switch at the beginning of the cycle, the switch is closed and at that point, the power is delivered for a time.

Then after a predetermined delay, the voltage is turned off and power is no longer delivered for the remainder of the half-cycle. Dimmers that produced this backward waveform, are more known by the following terms: elv or electronic low voltage dimmer, simply electronic dimmer, reverse-phase dimmer or trailing edge dimmer.

So we can then dim line voltage incandescents with either forward Phase or reverse-phase dimmers. The triac that is used to perform forward Phase dimming, cannot be operated in the reverse-phase matter and so different electronics are used for reversed-phase dimming — typically a FET or an IGBT.

These electronics are comparable more expensive than a triac and their current ratings are typically lower. So if you use reverse phase dimming you will pay a premium and your load capacity will be somewhat lower, compared to the forward phase dimmer.

I should mention here, that some electronic low voltage transformers have been modified, specifically to be compatible with forward phase dimmers. The manufacturer of the elv transformer must state, that it is compatible with forward phase dimmers or an electronic transformer should always be paired with a reverse-phase dimmer. While phase control is still the primary dimming method, it is not the only method.

So other methods of dimming became commercially available. All of which have carried forward in one form or another to LED dimming. The signal is used to communicate to what level the light output should be set and the ballast driver uses some mechanism beyond the scope of this article, to achieve that lighting level.

For this reason, I refer to dimmers that use these methods as indirect dimmers. A light source that includes indirect dimming capability will be looking for a variable control signal, separate from the power delivered, that power typically being switched on and off by the controlling dimmer, in addition to the variable control signal.

The first type of control signal I will discuss is the variable low voltage output — sometimes referred to as zero to ten dimming. Such a device will react to a control signal, that varies between 0 and 10 volts DC, to regulate the light output.