View Full Version : 1 fan, 2 rails.

03-03-2005, 02:31 AM
I want to power one fan, from two rails.

I want to have the fan, and onto the line goes one 12v, and another 12v.

line 1 will be active first, then line 2... then line 2 will turn off, and line 1 will turn off after that.

I want to know,

Will the voltage/wattage/amperage double?
how can I stop the each line from shooting its 12v up the other


03-03-2005, 08:00 AM
Why? Will there ever be a time when source 2 will be on without 1?

03-03-2005, 09:51 AM
Use a diode (1N4004) forward biased in each 12v line, that will isolate each rail from the other.

The fan will run on whichever line is active, or both if they are active at once, without any pain if diodes are used.

03-03-2005, 10:40 AM
thank you godfather!!!

Graham L
03-03-2005, 01:54 PM
Or use even higher technology and use 1N5819s (Schottky diodes, with lower forward voltage). ;)

Connect the ends with the "band" together, they go to the fan +ve, the free ends go to the separate supplies.