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Using Dimmers With LED

Dimmer Switches work by reducing the power delivered to your light bulb, they do this by trimming a section of waveform, either on the Leading Edge or Trailing Edge of the wave. Manufacturers have designed their LEDs to be compatible with the majority of common Trailing Edge household dimmers. Trailing edge dimmers are slightly more complicated and more expensive than the Leading Edge dimmers but they have many more desirable features such as smooth control, silent running, soft start and multi-way dimming that greatly enhance the life of the LEDs.



How Do Trailing Edge And Leading Edge Dimmers Work?


Trailing Edge: Trailing edge dimmers are designed to fade the voltage to zero rather than switch it abruptly off, by applying a resistance to create a ramp. This increases the amount of heat dissipated, since the resistive period generates heat.


Leading Edge: Predominantly used with Incandescent or Mains Halogen light bulbs Leading edge dimmers are compatible with resistive or inductive loads and are able to reduce the load by shortening the cycle at the leading edge of the input waveform.

Trailing Edge Waveform


Leading Edge Waveform



How Many Light Bulbs Can Be Used With A Dimmer?


All dimmer switches have a minimum and maximum rating (watts). Unfortunately LED loading cannot be calculated the same way as a traditional Incandescent or a Mains Halogen light bulb. A good ‘Rule Of Thumb’ to apply ,which is used by most manufacturers, is to take the maximum rating of the dimmer switch and divide by 10 (or in other words use 10% of the Max rating). As an example if you have a dimmer switch with a maximum rating of 400w (rule of thumb translates to 40w) you can run 5no 7.1w Dimmable LED light bulbs (see example below for further explanation).


Dimmer Loading Example


It is worth mentioning at this point that all manufacturers state that their LEDs are designed to be compatible with the majority of common household dimmer switches but they cannot 100% guarantee that they work with them all as there are so many makes and models on the market today.