On Sun, 26 Dec 2010 13:11:39 -0600, AZ Nomad
wrote:

On Sun, 26 Dec 2010 12:19:56 -0600, zzzzzzzzzz wrote:
On Sun, 26 Dec 2010 11:15:58 -0600, AZ Nomad
wrote:

On Fri, 24 Dec 2010 06:25:05 -0600, G Morgan wrote:
Home Guy 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.

Standards light dimmers use PWM, not variable voltage.

Actually, phase control, not PWM. Similar to, but not to be confused with.
With a nonlinear load, like an LED, it's quite different.

Who said anything about phase control?

Dummy, common incandescent (triac/SCR) dimmers use PHASE CONTROL, not PWM.
There *is* a difference.

PWM is pulse width modulation, control of power by duty cycle.

No, it is PHASE CONTROL. Dimming is done by controlling the firing angle of a
triac or SCR. For an incandescent (resistive load) this works out to be
similar to PWM, but it is a *lot* different when you're talking about a load
as nonlinear as an LED. PWM is often used to dim LEDs, but from a DC supply.
PWM works just fine on non linear loads as its output isn't operated linearly.

PWM works, phase control doesn't work well.

The output of PWM is either on or off. What controls average power is the
percentage of the time that the device is on. LEDs do fabulously well with PWM
actually.

It would help if you had slight clue.