Dimmer Switches work by reducing the power delivered to your light bulb.
They do this by trimming a section of a waveform, either on the leading edge or trailing edge of the wave.
Manufacturers have designed their LED light bulbs 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’ versions 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 LED light bulbs. For a more comprehensive rundown of dimming and dimmer switches in general, check out our Dimming for Dummies guide.
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 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 can reduce the load by shortening the cycle at the leading edge of the input 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 – one that 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 five 7.1W dimmable LED light bulbs (see example below for further explanation).
[…] Okay, so there are numerous types of dimmer switch available, but by far the most popular are the two that we’ll be concentrating on today – leading edge and trailing edge phase-cut dimmers. […]
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[…] For further information read our guide on dimming LED lamps. […]
I have 29 GU10 LED SMD with 7W , which dimmer switch I need to use , Thank you
There is a rule when calculating LED wattages that which is W*10. So for your concern, 29*7*10 = 2,030W which is very large. You would need to find a dimmer which can cope with loads above 2,030W. This would require a very specialist dimmer (that we don’t sell). I think the best advice would be to consult an electrician.
I have a much smaller situation. I’m just connecting under counter lighting in a kitchen using Kichler LED lights, and the lights flicker when we dim them. The whole house has push button switches which is also challenging to find what will work with the LED fixtures. I’m afraid that I need to find a lighting engineer. Please help!
Most LED lighting manufacturers test which dimmers their lights work on. Flickering is a typical side effect of a dimmer switch that is not compatible with the lights you are using. I’m afraid there is no easy workaround to solve this apart from requesting from the lighting manufacturer which dimmers they recommend, and then installing these dimmers into your lighting circuit.
[…] Determining how many light bulbs you can use with one dimmer switch takes a little calculation. You can learn more here. […]
l have 7x 50watt halogen street lamps and want to dim them, any suggestions?
You could do this on a standard dimmer switch, so long as it’s maximum load for halogen exceeds 350W – there are many 400W dimmers available if you do a quick search online.
I’ve just bought a Celling light . And the led driver says 40-60w . Ac165-265v . 50/60/hz can you get me a switch please for it
Is the LED Driver dimmable?
Hi Matt: In using a universal slide dimmer switch the manufacturer list the maximum rating Watts as follows: for dimmable LED/CFL 150-Watts; for Incandescent/Halogen 600-Watts. Would you still require the 10% rule in calculating the number of dimmable LED light bulbs given the manufacture makes the distinction between the maximum wattage for the different types of bulbs? If you use the dimmers LED maximum watts as 150W, then the following would be true: I have a light fixture requiring 6 bulbs. The dimmable LED bulbs are 7.1W per bulb. Therefore 6 LED dimmable light bulbs X 7.1W each = 42.6… Read more »
I don’t think you need to use the 10% rule in this case as the dimmer switch states a rating of 150W. So you should be able to add up to 150W of LED bulbs onto the dimmer.