Originally Posted by Ichthy
I just bought a new potentiometer for my DIY stirplate. *disclaimer* I don't understand very much electrical lingo.*
The potentiometer is rated at 25 ohms and 3 watts - it is the part recommended in the often used stirplate thread. I'm powering a 12 volt computer fan and am using an AC converter that is rated at 9V output.
My issue: I soldered the connections to the potentiometer and when I turn on the power the potentiometer heats up rather quickly and becomes too hot to hold in your hand. There is no smoke or sparks and the fan is turning fine. I have full range of speed adjustment.
My question: Is this heating problem an issue? I'm wondering if I've to powerful an input and it's overloading the potentiometer?
And advice would be much appreciated!
If your aiming for 9V and you have 12V the resistance of the pot (potentiometer) should be set to 3/12ths of the total resistance (the other 9/12ths being the fan). This also means the 3/12ths of the power going into the circuit it turned into heat by the pot (the other 9/12ths to power the fan).
But more on topic, if the third wire doesn't fix it fully; you may be exceeding the 3watts the pot is made for. Many small fans use 10+ watts. Is there any markings on the fan as far as wattage or amperage?