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.

[darron]

does it really NEED to be a SPDT switch? it could of course easilly be done using a DPDT.

as an alternative, you can also buy bipolar LEDs which have three legs. one neutral leg and one leg for each colour. you could use that with a SPDT. those sort of bipolar LEDs are actually more familiar to me than the one you described. that could easily be used with a SPDT switch and sort out your problem.

[head_spaz]

Shown are two simple circuits from my archives, for use with a single
ended power supplies.

The top is circuit is inefficient because there is wasted current
draining thru the resistor in parallel with the LED. (in either state.)

The bottom circuit is more efficient, but requires two separate LEDs.

There are more options when using bipolar supplies and multiple pole
switching.

Comments welcome.

[head_spaz]

With a bipolar supply... the task is easy.

[darron]

but the bipolar power supply in itself is pretty inconvenient in most cases. why not just get a three leg led, or use two leds? maybe it's different in the states but the three leg leds are more common to me.

[head_spaz]

If you'd rather use a TRI-LED... here's a simple way to hook it up.