Leds colors, just wondering...

M

martin

Guest
Hey Ive always wondered about the voltage as related to the colors of LED's.

Depending on the color of the Led you use a different Voltage.

But what I don't understand is why? Aren't all leds the same with just a
different resin or what ever plastic surrounding it to make the color. eg
RED, or GREEN resin. I don't understand why different colors require
different voltages.

Can anyone answer my question ??

Thanks.
 
On Mon, 20 Dec 2004 12:55:31 -0600, "martin" <martin@123.com> wrote:

What would happen if you put a Red "photon" inside a clear LED or can you
have a clear bright photon inside a red plastic LED.
Click to expand...
Ah. The infamous clear bright photon. I cannot wait for your explanation of
those, John. ;)

Jon
 
martin wrote:
Hey Ive always wondered about the voltage as related to the colors of LED's.

Depending on the color of the Led you use a different Voltage.

But what I don't understand is why? Aren't all leds the same with just a
different resin or what ever plastic surrounding it to make the color. eg
RED, or GREEN resin. I don't understand why different colors require
different voltages.

Can anyone answer my question ??

Thanks.
Click to expand...
It has to do with the energy per photon. Electrons gain energy by
falling through the voltage across the junction, and give that energy
up into a photon (if you are lucky). Blue photons have about twice as
much energy, each, as red ones do. The junction has to be designed to
produce the needed drop and also to be transparent to the photons
produced. Each color requires a different kind of junction material
and structure.

--
John Popelish
 
John Popelish wrote:
martin wrote:

Hey Ive always wondered about the voltage as related to the colors of LED's.

Depending on the color of the Led you use a different Voltage.

But what I don't understand is why? Aren't all leds the same with just a
different resin or what ever plastic surrounding it to make the color. eg
RED, or GREEN resin. I don't understand why different colors require
different voltages.

Can anyone answer my question ??

Thanks.

It has to do with the energy per photon. Electrons gain energy by
falling through the voltage across the junction, and give that energy
up into a photon (if you are lucky). Blue photons have about twice as
much energy, each, as red ones do. The junction has to be designed to
produce the needed drop and also to be transparent to the photons
produced. Each color requires a different kind of junction material
and structure.
Click to expand...
Of course, no simplified explanation is correct. But you might search
Google for more details, like:
http://www.physics.gatech.edu/advancedlab/labs/photoelectric/photoelectric-3.html


--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:41C705B0.F8100544@rica.net...
John Popelish wrote:

martin wrote:

Hey Ive always wondered about the voltage as related to the colors of
LED's.

Depending on the color of the Led you use a different Voltage.

But what I don't understand is why? Aren't all leds the same with just
a
different resin or what ever plastic surrounding it to make the color.
eg
RED, or GREEN resin. I don't understand why different colors require
different voltages.

Can anyone answer my question ??

Thanks.

It has to do with the energy per photon. Electrons gain energy by
falling through the voltage across the junction, and give that energy
up into a photon (if you are lucky). Blue photons have about twice as
much energy, each, as red ones do. The junction has to be designed to
produce the needed drop and also to be transparent to the photons
produced. Each color requires a different kind of junction material
and structure.

Of course, no simplified explanation is correct. But you might search
Google for more details, like:

http://www.physics.gatech.edu/advancedlab/labs/photoelectric/photoelectric-3.html


--
John Popelish
Click to expand...
Thanks John,

But if I may, so your saying that the color of the LED is not caused by the
plastic surounding the little diode device? Do they put it in a RED medium
to enhance the color.
What would happen if you put a Red "photon" inside a clear LED or can you
have a clear bright photon inside a red plastic LED.

Thanks.
 
martin wrote:

But if I may, so your saying that the color of the LED is not caused by the
plastic surounding the little diode device? Do they put it in a RED medium
to enhance the color.
Click to expand...
The colored plastic makes it easy to tell what color light the LEDs
will produce when they are off, and increases the on to off contrast
in many applications. The dye darkens the appearance when no light is
coming out.

What would happen if you put a Red "photon" inside a clear LED or can you
have a clear bright photon inside a red plastic LED.
Click to expand...
You get red light when it is on, and a but not internally illuminated
object when it is off. If you are not interested in looking at the
LED, directly, but shining a beam of red light on something else, the
clear lenses are usually used.

--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:41C76AB3.D093AB7F@rica.net...
martin wrote:

But if I may, so your saying that the color of the LED is not caused by
the
plastic surounding the little diode device? Do they put it in a RED
medium
to enhance the color.

The colored plastic makes it easy to tell what color light the LEDs
will produce when they are off, and increases the on to off contrast
in many applications. The dye darkens the appearance when no light is
coming out.

What would happen if you put a Red "photon" inside a clear LED or can
you
have a clear bright photon inside a red plastic LED.

You get red light when it is on, and a but not internally illuminated
object when it is off. If you are not interested in looking at the
LED, directly, but shining a beam of red light on something else, the
clear lenses are usually used.

--
John Popelish
Click to expand...
Thanks John.

Mystery solved.
 
martin wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:41C76AB3.D093AB7F@rica.net...
(snip)
You get red light when it is on, and a but not internally illuminated
object when it is off. If you are not interested in looking at the
LED, directly, but shining a beam of red light on something else, the
clear lenses are usually used.

--
John Popelish

Thanks John.

Mystery solved.
Click to expand...
The red encased red LED should have been described as, "You get red
glowing object when it is on, and a dark red, but not internally
illuminated
object, when it is off.

I appologize for getting in a hurry. But you appear to have figured
out where I was going.

--
John Popelish
 
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