On Dec 26, 11:51*pm, wrote:
On Sun, 26 Dec 2010 20:27:58 -0800 (PST), JIMMIE



wrote:
On Dec 26, 2:54*am, wrote:
On Sat, 25 Dec 2010 22:36:45 -0600, wrote:
I like doing experiments like this and I will be back as soon as my
high intensity LEDs arrive because this is my plan. We will see.
I have no problem admitting when I am wrong but I want to see it.

Go for it. *I do this stuff all the time, though with indicators, not
for illumination. *

OK Here you go

These are garden variety indicator LEDs (what I had handy)
There is a 270 ohm in series with 4 LEDs and a 1k pot wired as a
rheostat.
With the pot set to 0 ohms get a tad over 15M/A and the LEDs are as
bright as you can expect from these, may even be overdriven. I al
dropping 4.11v over the 270 ohm resistor.
Turning the pot down toward 1k ohms dims the LEDs quite smoothly
At 1K ohms plus the 270 I get 3.7 MA or so and I am dropping 4.8 volts
across the resistors.http://gfretwell.com/electrical/LED%...experiment.jpg

I agree it is not exactly linear but I also do not understand how this
small variance makes any real world difference since most of the
voltage is still being dropped across the LED string. You certainly
would have a hard time seeing it on your electric bill.

You should see the PWM method. brightness is variable from next to
nothing to full bright. They also retain their color while white
lights turn yellow using your method.

Jimmie

I think most people find the color change to a softer color is part of
the reason they want to dim the light.
You usually dim accent lights or to turn task light to accent light.
Bear in mind in my house I have a bunch or rope lights and 15w sign
bulbs for our normal lighting and we use task lighting where we are
reading or doing some kind of work. That is why my under cabinet light
will probably be the 9 LEDs from a $2 flashlight and on a dimmer.
I just want enough light to mix a drink. ;-)
The light follows you wherever you go in the house but it is generally
fairly low level light. (rope light under toe kicks and overhead in
crown moldings) on motion sensors.
Outside most of my motion lighting is 15w sign bulbs but there are
lots of them. I hate that "Stallag 13" look you get with Par 38s.

The yellow lights didnt look good at all to me, of course this may
have something to do with the color of my counter top too. I have been
thinking of experimenting with combining different color LEDs in the
same cluster. Replacing one of the LEDs with a yellow one might not be
a bad idea. LEDs arent ideal for task lighting so why use them for
that. I used to have some light fixtures that had fluorescent, 60 watt
incandescent and night light type bulbs all in one fixture. I can see
where combining fluorescent and LED in an under-cabinet light would
have some advantages.