LEDs and dimmers

[boghog]

I am new to LEDs. Can you please explain if their non-dimmable behaviour is caused by the LED bulb or the transformer?
I bought a cheap LED downlight and I tried it with my living room's dimmer and it doesn't dim down, just flashes when really low. After some more research I found that there are some dimmable LED downlights on the market. Do these work with "normal" dimmers, i.e. the dimmers you find in the switches section in B&Q, or do they require some special LED dimmers?
Also, when they specify the angle of the beam, do they measure from zenith/height to edge of cone, or edge to edge?
Thanks

 

[Taylortwocities]

Some LEDs are dimmerable some are not, its in the spec.

The other thing to consider is the dimmer itself. Most dimmers are made to work with tungsten/halogen lamps. If you llok at the back of one, it will say something like 40-250W or 60-400W. That means you have to pull 40watts from the dimmer for it to work. Your LED lamp is 5 or 6 watts so there's not enough load for it to work.
You'd need a LOW LOAD DIMMER

plus a LED lamp that works with the dimmer

 

[bernardgreen]

All Light Emmitting Diodes are dimmable.

That is until they are packaged into a light fitting with "something" that provides them with the current they need to light up.

The brightness of an LED is ( almost ) directly proportional to the current ( not voltage ) passing through the LED. Vary that current and you vary the brightness. Simple.

It amazes me that there are so few domestic light fittings using LED that are designed from the start to have a means of controlling the current through the LED to provide smooth and reliable dimming. It might be that concentrating on the domestic market the manufacturers make more profit from making LED "replacements" for existing types of lamps as those lamps fail and cannot be replaced. If the existing lamp was not in a dimmable circuit (which is the vast majority ) then all is well and sales are easy to make.

The problem arises when an old lamp ( incandescent ) that was dimmable with a simple dimmer is replaced with an LED lamp then the "something" in the LED lamp that controls the current through the LED fails to be able to work together with the simple dimmer that did control the simple lamp.

The "something" is a most often a form of current control that requires a steady mains supply to oeprate correctly. The phase chopped mains from a simple dimmer messes up the current control. In the worse case the LED can be over driven and burn out as the "something" tries to cope in a situation it was not designed to work in.

 

[boghog]

Thanks, that makes sense.