[sdiy] Bi-Color LED Question

Scott Gravenhorst music.maker at gte.net
Sun Nov 9 22:58:05 CET 2008

"Ken Elhardt" <ken.elhardt at gmail.com> wrote:
>I hooked up a bi-colored LED (red/green) I bought years ago to try it
>out and I'm curious about something.  I can get the green portion to
>light, and the red, but not at the same time.  If I have power applied
>to the green and then hook power to the red, it shuts off the green as
>if the red has priority over the green so I can't get yellow out of
>the thing.  Is this how all bi-colored LED's work?

It sounds like the device has 3 leads, one for a common and one each for each of
the 2 LEDs inside.  If you simple connect the two "hot" leads together through a
resistor, only one LED will light because the diodes do not share current as you
might expect, one will turn on and starve the other.  

Use a separate resistor for each "hot" lead and both can light simultaneously.

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