Bi polar LED's

[Ryan Harding]

The ones that can be green/red!

How do they work?

 

[williB]

they accually conduct in both directions..
on the inside they are hooked up with the cathode of one connected to the anode of the other and visa/versa on the other side..
So for example when the current flows in one direction the red will be lit, when the current flows in the other direction the green will be lit..

 

[Oznog]

If you give it AC, then the red and green will mix to make yellow.

 

[evandude]

some of them are 3 leads... in all cases it is just 2 LED elements in one case. if it's 2 leads, it will be one color in each direction, if its 3 leads, it is two anodes with a common cathode, or vice versa.

 

[John Sorensen]

Nowadays you can get tri-color (RGB) leds and make any color.

j.

 

[Ryan Harding]

so how is this possible, what other components do you need for this, to make it 'decide' what colour it will be?

 

[John Sorensen]

RGB LEDs are three LEDs in one package, usually (but not always) with a common anode or cathode (you can get them either way, pretty sure). You just need to control the current through each LED (with a current source/sink, or PWM, or whatever) in order to mix the colors the way you want. If you turned them all full-on it would look white (at least at a little distance).

If you just want something to look pretty and interesting, you could use this flasher/fader thing:

https://www.goldmine-elec-products.com/prodinfo.asp?number=G13897&variation=&aitem=5&mitem=5

j.

 

[Styx]

so how is this possible, what other components do you need for this, to make it 'decide' what colour it will be?

it all depends on what lead you pull to +5V (via a resistor) or down to ground. All you need is a PI (they can sink 10mA ???)

They are quite handy (well the 2colour ones I think) for indicating what is happening

 

[Zener_Diode]

there are a spicifics LEDs that change there colors depends on a current flew threw them. As the current is higher the materal they are built from getting worm and emitting other color.

as you can see(if you will play with this LED) the color go from green (the cold one) to red(the hot one).

is it answer enoght for you?

p.s. sorry for my mistakes.

 

[John Sorensen]

there are a spicifics LEDs that change there colors depends on a current flew threw them. As the current is higher the materal they are built from getting worm and emitting other color.

I've never seen such a thing. I've seen red LEDs that when you get them real warm they look kind of orange and green ones that when they get really warm look yellow, but that doesn't last long, because then they turn black.

j.

 

[absolution]

| Think of it like this with the 2 diodes back to
| back. when one polarity is give a single side
|'''''''''''''''''''| will conduct then if the polarity is reversed the
| | other side will conduct
.... .....
\/ /\
''''' '''''
| |
|...............|
|
|

 

[absolution]

well my text pic got messed up when it transfered to the forum but u should get the idea. and remember colors and conductive paths are determined on how you dope the materials

 

[jrz126]

there are a spicifics LEDs that change there colors depends on a current flew threw them. As the current is higher the materal they are built from getting worm and emitting other color.

I've never seen such a thing. I've seen red LEDs that when you get them real warm they look kind of orange and green ones that when they get really warm look yellow, but that doesn't last long, because then they turn black.

j.

That means you are running too much current through them.

 

[Exo]

bad post, nm...

 

[Zener_Diode]

read this
**broken link removed**