Multiplexing circuit

[brobl]

Hey all,

I'm trying to figure out a way to multiplex three circuits(12V, 0.5A MAX) using 2 LEDs from a DSP evaluation kit as the decoder bits. When the LEDs turn on, the voltage change is a little over 1V (2.5 - 3.6). I'm stumped as to what to do with these specifications. Any help would be appreciated. Thank you!

btw, These three circuits are used to control fan speeds on a standard 12V fan.

 

[Harald Kapp]

Sorry, this is rather unclear. Can you explain in more detail?
I wouldn't know how to use LEDs for decoding. Normally they are used as indicator lights. Also what exactly do you want to multiplex? Are there 3 supplies which are multiplexed onto one fa, or are there trhee fans multiplexed onto one supply?
Maybe multiplexing isn't what you want at all (http://en.wikipedia.org/wiki/Multiplexer describes whar we understand as multiplexing, it may not be what you desire).

Harald