29-03-2012 09:44
For a project I needed to control a dual color LED with 2 digital lines. Since the LED indicator was added late in the project it was not possible anymore to change the software in the microcontroller. The industrial design of the product however only allowed for a 2 pin LED.
Attached circuit allows use of the dual color (2pin) LED with 3 colors, since it alternates between bot LED's when both control lines are high. The basic circuit behind it is the ancient two transistor multivibrator.
The capacitor values are not critical, but care must be taken to avoid frequencies like 32kHz or 38kHz, as these may cause problem with infra red remote control receivers.
D1 and D2 represent the dual color LED. Resistors R1 and R2 are different in this drawing to indicate thay can be used to optimize brightness of the different colors in the LED.
Transistors are standard NPN types.
Volhout
Post edited by Volhout
on 30-03-2012 14:17 Post edited by Volhout
on 30-03-2012 14:19 Post edited by Volhout
on 30-03-2012 14:19 Post edited by Volhout
on 30-03-2012 14:22
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