Meat Plow wrote:
On Thu, 06 May 2010 15:21:52 +0000, Cydrome Leader wrote:
Meat Plow wrote:
On Thu, 06 May 2010 01:20:36 -0500,
rote:
I keep seeing these little solar power sidewalk lights. Last year they
were all white (blueish white). Lately I see them where they change
color. Yet, they only have one LED. How can a LED change color? I
thought the color was determined by dopeing it with a metal. So how can
they change? This has me puzzled.
Bi-color LED have two LED inside with a common cathode. Change the
polarity and you switch on the other LED.
this probably has nothing to do with bicolor LEDs. Who the hell would
make a red/green sidewalk light anyways?
Anyways, white LEDs are sort of like flourescent lights. They junction
makes bright blue light and there is a phosphor that then converts this
into "white". Quite a bit of the blue leaks out.
The quality of white can vary (and does so more with cheap LEDs) in
addition to the phosphor actually aging.
so a visible color change from a cheap white LED isn't all that
surprising.
The OP asked how an LED can change color and I gave an answer. You got a
problem with that? And most white light LEDs are made from yellow and
purple junctions and are not in the least like a ****ing fluorescent
light.
yeah, that's it. taking one color and using it to excite a phosphor to
emit another color is nothing like a flourescent light at all.
you called me, cree and nichia on our conspiracy.
So tell me, what's the forward drop on an LED with "yellow" and "purple"
junctions again, and how are the wired again?