In article , Jeff Thies wrote:

Hey Don,

What do you know about what circuitry is in the commercial LED lamps
and dimming compatibility.

For those who don't know, Don Klipstein knows more about lighting
than anyone I know of:

http://members.misty.com/don/ledx.html

We'll see if he is around and interested.

Sadly, I have yet to look inside any retail-available LED lights over 2
watts, nor most 2 watts and under. I don't remember too well what the
packages that I looked at so far say.

Best I can say is, look at the fine print on the packages for
compatibility with dimmers.

The Philips ones at Home Depot *may* be a good bet. However, I did
little more than glance at their photometric and color specifications
after getting "sticker shock".

So far, I am seeing only here-and-there applications where LED "bulbs"
appear to me more appropriate than CFLs or incandescents, mostly for light
output near or less than that of a 25 watt incandescent and with a lot of
"on time" per day.

One more thing: Most white LED units claiming 100,000 hour life
expectancy, especially cheaper and non-major brand ones, significantly
fade in 4,000 to 50,000 hours. I generally recommend green or blue LEDs
for nightlights. Any LED "security lighting" that must be at least
basically white should be by or have LEDs made by *major* brands of
"lighting grade" LEDs, such as Philips/Philips-Lumileds, Cree, Nichia,
Osram/Sylvania, Citizen/Cecol, and the like.
Also, the usual "bullet shape" low power LEDs are unlikely to get past
10,000 hours before significantly fading if they are white unless they are
greatly underpowered. I know of one LED nightlight "bulb" that does make
use of underpowering to achieve true long life from cheap white low power
LEDs. That is the Feit 3-LED candelabra base one.

One more thing: For outdoor or basement nightlighting or security
lighting, I strongly recommend that any white lights (LED or otherwise)
be of cooler color (more bluish, higher color temperature). This is
because night vision is significant in such dimmer lighting environments,
even if colors and sharp outlines are visible. A spectrum richer in
mid-green to mid-blue favors greater illumination in this case.
--
- Don Klipstein )