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Posted to sci.electronics.repair
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Color changing LEDs
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?
http://www.pentairpool.com/pdfs/Inte...andscapeOM.pdf
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.
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