Bi-Color LEDs

[spartadrive_in]

Hi. I'm working on a custom EFX box and had a question.

(For simplicity I will talk about the path for the LED switch only.)

How do I wire a bi-color Led? I know that switching the polarities will do it BUT here is the question:

Using a SPDT switch how do I make that work? I suppose that I need to incorporate some sort of switching transistor?? in order to supply it with +9V or -9V?

let me know please. Thanks.

[Enzo]

A DPDT would allow you to flip the diode. I can't offhand think of how to do it with a SPDT unless you actually do have both polarities of 9v. In that case it is simple. Wire one end of the LED to ground. switch the other end between pos and neg rails.

ANother option is a different LED. SOme reverse polarity for color change. Others are two LEDs in one package mor or less in parallel wit a common end.

Check out example, common cathode, separate anode for each color - LED has 3 legs.

http://www.jameco.com/Jameco/Products/ProdDS/104889.pdf

[spartadrive_in]

Yea a 3 lead is what I could use even better. I have a Radio Shack 2 lead LED. How would I supply a -9V as well as +9V?

Where can I get a 3 lead LED then? Expensive? That will be an easier idea.

Thanks.

[Don Moose]

If you're in the US or Canada - digikey
If in the Commonwealth - Maplin

Search for LED - the narrow it down by package (thru-hole 3-lead radial) and from there pick your color pair. Digikey's prices ranged from 0.60USD to 1.50USD in singles. 10-packs and 100-packs were cheaper on a per-part basis.

Hope this helps!

[spartadrive_in]

Awesome I saw that site. I found some on eBay that sold for about $0.50 each so I've already went with those. Thanks.

[Enzo]

I don't use Digikey nearly as often as Mouser and Allied, but they do seem to have the king of LED selections.

Another company I use only once in a while , but who has odd little project things I can't find as easily elsewhere is Jameco, from whose site I took the example I posted. I think they were 29 cents or something.

But to use your 2 wire bi-color LED, you have to reverse polarity, simple as that. If your effect uses only 9v as from a battery, then you have to end for end the diode. If you actually have pos and neg 9v rails in the project you'd switch between them.