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?