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.

wrote:
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.

How do you *know* it is "one LED"? I suspect it is a "bicolor"
LED (almost a sure bet if it has more than two leads -- still
possible even with just *two*).

You might want to notice the ranges of colors and consider
what color *mixes* could make them (e.g., red + green LEDs in
the same package will yield yellow-ish -- plus variations from
red *to* green depending on the mixing rates)

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?

** Bi-colour LEDS like this have been around for 30 years.

http://www.effled.com/images/product...lor_LED_RG.jpg




.... Phil

In article ,
says...

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.

It could be the plastic windows on those cheap things turning yellow?

--
If there is a no_junk in my address, please REMOVE it before replying!
All junk mail senders will be prosecuted to the fullest extent of the
law!!
http://home.comcast.net/~andyross

On Thu, 06 May 2010 01:20:36 -0500, mister_friendly wrote:

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.

They could be RGB leds. These devices, now very cheap on ebay, are
externally identical to an ordinary two pin led though they contain three
emitting diodes in the same package plus a small circuit that flashes
each of them independently.
http://www.youtube.com/watch?v=PPtg4mFC_-k

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.

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.

"Meat Plow"


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.


** Fraid that is simply not true.

Nearly ALL high intensity / high efficiency white LEDs are made using
phosphors that convert blue or purple light to yellow.



..... Phil

On Fri, 7 May 2010 17:29:19 +0000 (UTC), Meat Plow wrote:

Well then I am uninformed on newer technology ...

Says it all.

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?

Meat Plow wrote:
On Fri, 07 May 2010 22:47:07 +0000, Cydrome Leader wrote:

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?

You're one of those newsgroup assholes who will argue with anyone about
anything, ****k off.

Maybe you should take your yellow and purple LEDs and leave if you don't
like it here.

On Tue, 11 May 2010 17:07:56 +0000, Cydrome Leader wrote:

Meat Plow wrote:
On Fri, 07 May 2010 22:47:07 +0000, Cydrome Leader wrote:

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?

You're one of those newsgroup assholes who will argue with anyone about
anything, ****k off.

Maybe[SLAP]

Maybe you should learn what the words **** off mean?

Meat Plow wrote:
On Tue, 11 May 2010 17:07:56 +0000, Cydrome Leader wrote:

Meat Plow wrote:
On Fri, 07 May 2010 22:47:07 +0000, Cydrome Leader wrote:

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?

You're one of those newsgroup assholes who will argue with anyone about
anything, ****k off.

Maybe[SLAP]

Maybe you should learn what the words **** off mean?

why don't you come teach me?