Need help with a speed control for fan

[Perry Holbrook]

I'm building a very over engineered fire pit. One of the features is a supply air fan that blows up through the flame, mainly for getting the fire started quickly. I bought a small fan from Surplus Center that has a 12 vdc motor. I also bought a speed controller on Amazon that takes 12vdc input. It says it is 6v-90v 15A. It has a potentiometer that is stamped B10K. It only turns about 3/4 of a full revolution. Everything works fine and and it looks like the fan will supply enough air, maybe to much.

However the pot only gives me control in the first 1/4 turn or so (goes from nothing to full speed in that 1/4 turn).

My question is, if I change the pot will I get a fuller range of control, if so, what size pot should I get?

Thanks,
Perry

[Paul F Franklin]

Try putting a 33k resistor in series with the high end of the pot. You can identify the high end using a multimeter. With the pot turned all the way down, you will measure 0 ohms (about) between the center terminal and the low terminal. The other terminal is the high end.

This should shift the range so the whole pot rotation gives you about the same range as the first 25% did before the change.

It's possible the controller won't like the added resistance, but I doubt it.

[Perry Holbrook]

Thanks Paul. I'll give that a try.

Perry