bicolor led driver

[[email protected]]

Hi all
I need to build a bicolor led driver using a single input that
alternates between 8-12V every 2 seconds. So at 8V, the LED lights to
one color, and at 12V the other. Any ideas will be welcome.

 

[krw]

Hi all
I need to build a bicolor led driver using a single input that
alternates between 8-12V every 2 seconds. So at 8V, the LED lights to
one color, and at 12V the other. Any ideas will be welcome.

How about a diff amp:
VCC VCC
+ +
| |
| |
V -> V ->
- -
| |
| |
| |
|/ \|
In o-----| |-o 10V
|> <|
| |
--------
|
.-.
| |
| |
'-'
|
|
===
GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

If you haven't a separate Vcc larger than Vin+Vled, the Vref and Vin
can be scaled with resistor dividers.

 

[D from BC]

Hi all
I need to build a bicolor led driver using a single input that
alternates between 8-12V every 2 seconds. So at 8V, the LED lights to
one color, and at 12V the other. Any ideas will be welcome

Sounds like a 555 project.
D from BC

 

[pklammer]

Hi all
I need to build a bicolor led driver using a single input that
alternates between 8-12V every 2 seconds. So at 8V, the LED lights to
one color, and at 12V the other. Any ideas will be welcome.

How about with one bicolor LED and one resistor?

If the 8 and 12V are low enough impedance (can sink and source LED
current), and if you can afford a little waste current (heat), and can
supply constant 10V (is the 12V constantly available somewhere?), then
tie one end of a bicolor LED to 10V through some current-limiting
resistance, and the other end to your 8/12V source.

I've done this with an SPST switch and 4 resistors to operate a red/
green LED depending on the switch closure.