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Voltage reduction

Y

yokomo

Golden Member
I want to put 4, 3way toggle switched that will control 4 diffrent fans in my pc. One side or the switch I would like it to be 12volt and on the other side 6 or 7 volts... You cannot just put in a resistor for this if I am correct? So what would be the cheapest smallest and easiest..
 
you could get a breadboard and resistors like from circuits classes and ghetto rig it using voltage dividers, or just get one of those fan controllers with 4 knobs that continuously adjust voltage betweeen 0 and 12 volts if you aren't set on switches or fixed voltages.

pm me if you need help with how to build a circuit to give the right voltages
 
I'm guessing that you want to either have 12 volts or 6 volts applied to each fan from the same 12 volt power supply?

What you could do is use a volt/amp meter to measure the current draw each fan. Assuming that the fan will always draw about that same current, you can figure out the size of a resistor (6volts/??milliamps = ??kohms) that you can switch in series with the fan that will drop the voltage it sees from 12 volts down to 6 volts.

What I would do is arrange the switchs so that they put two fans in series (rather than parallel). Two identical fans should split the 12 volts equally between them.

Actually I wouldn't do this at all. :laugh:
 
If you want to do things like the big boys, you could rig up a voltage-regulator circuit using a LM317 or similar. You have to know how to calculage current and voltage, and calculate resistance in series and parallel.
Of course, you could always just buy a fan controller yourself, but where is the fun in that???

But as another poster said, if you want 6V fans, put two in series.
If you want 7V fans, wire the fan up to the +12 and +7V lines. 12-5=7.
Both of these can be done with cables that you probably already have, and a few inches of electrical tape.
 
Dude, just use one potentiometer. Hook one side of the pot to +12, one to ground, and hook the fan between the middle of the pot and ground. Simple adjustable voltage divider. Or you could just use the 5 volt supply if you're not too picky.
 
What bobsmith said. I'm doing this. Grab a bunch of potentiometers from radio shack.
 
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