Tell us about yourself!
hey nice project! A really simple way to slow a DC fan down is to get two crocodile / alligator clips and a length of stainless mig welding wire. break the live wire feed to the fan, clip the feed to one end of the wire and attach the other clip to the wire a few inches along move the other, then move the clip along and watch to see the fan speed or slow depending in the direction you move it. you can also measure the resistance of the welding wire. It's 'poor boy' resistance wire.