I am new into this hobbie. I built a spirograph and I keep buring up the potentiometers. I am running 12 volt pc fans for the scanners(using a wall wart). The current on each fan is .16 amps. The pots I am using are 1K - 1meg ohm. Do I need a resistor in the circut? Also the speed of the fans are almost on and off. I have a hard time controlling the fan speed. All advice welcomed.