On Dec 24, 9:01*am, Nate Nagel wrote:
On 12/24/2010 07:25 AM, G. Morgan wrote:





Home *wrote:

I'm seeing more LED lightbulbs turning up on store shelves.

I don't think I've seen one yet that is ok to use with a dimmer switch..

I can understand why CFL's can't be put on a dimmer - but why not LED
bulbs?

This is new, last 3 years. *They had to develop a ballast that was
adjustable. *CFL's and LEDS are not a good comparison.

They're crazy-priced as is. *Not being able to dim them makes them even
less desirable as a replacement for incandescent bulbs.

L.E.D.S. Are going to difficult (impossible) to dim. *Remember
they are DIODES that only need .7V *to illuminate. *AFAIK ---
LED's are not dim-able.

sure they are, I had a LED dash light kit in my old 944. *It didn't dim
linearly like the incandescents though, so a slightly different dimmer
would be required. *I thin kthe difficulty is with dimming with AC.

nate

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LEDs arent dimable in the normal since of the word. The current to
them can be pulse width modulated to produce what we percive as a
dimming of the light. This is accomplished by switching the diode off
and on at a high enough rate that our eyes cant see the flicker.
Dimming is controled by changing the ratio of off to on time. You may
have noticed that LED Christmas tree light are a good bit dimmer than
the typical LED lamp found on an appliance like the computer you are
working at now. This is because the computer supplies a constant DC
voltage and the LED is on 100% of the time while the Christmas tree
lights are powered by a varying AC voltage that will only turn them on
for about 40% of the time.