DIYbanter - View Single Post - Why aren't many / most LED light bulbs dimmable?

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On Fri, 24 Dec 2010 12:43:40 -0500, wrote:

On Fri, 24 Dec 2010 12:11:20 -0500, Jeff Thies
wrote:

I hadn't thought about this, but aren't light dimmers just varying
the fraction of a half wave (pulse width)? It would seem to me that it
should work with LEDs (although not particularly well) but I don't know
what circuitry is in an LED light.

The problem is the clock rate. LEDs respond virtually instantly and at
60 or 50hz the flicker would be horrible.

As can be seen with LED Christmas lights. It's fairly cheap to double that
(full wave bridge or more LEDs), which would solve the problem.

You could either clock your chopper a lot faster or just vary the
current.

How do you "just vary the current" efficiently, without chopping it? It
doesn't have to be a lot faster but you're right, 60Hz doesn't cut it IMO.

Since the currents are so low, a rheostat may not be out of the
question.

Huh? Sure they are. You might just as well use incandescent lights.

As soon as Hosfelt gets my box here I am going to start playing with
some high intensity LEDs to see what I can do with them,
My goal is dimmable under counter lights that run off a wall wart with
a very low profile. (perhaps even recessed into the cabinet bottom)

Good luck with that.