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DIY Stirplate (Alarm Magnets, 24v fan)

I found a 24v computer fan in a server at work. Since it is using more voltage, when I plugged the fan into a 5v power supply with output of .35 Amps, the fan still ran very fast- even when I turned it all the way down with a 25ohm Potentiometer.

I’ll try it with a 12v fan which I am sure will slow it down.

Does anyone use a different ohm potentiometer?

I use three 10ohm resistors in mine with a 25ohm rheostat. (12volt .30amp fan w/ a 12volt 500ma DC Converter) And have it wired so that I can use just the rheostat or switch to the rheostat plus the resistors. Giving me two different variable speeds.

baratone, would you post your schematic please? i doubt I’ll understand it, but just to see. What does the resistors do?

I don’t really have a schematic, but I’ll see if I can come up with something.
The resistors are wired in series giving me 30ohms of resistance in conjuction with the 25ohm rheostat on one side of my three postion switch(1 watt 10ohm Metal-oxide resistors). the other side just runs the 25ohm rheostat.

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