I have a DIY 3D printer (running Mach3) that I am wanting to add a filament cooling fan to. I would like to use a simple 40mm PC PWM fan (4 wires) and have Mach3 control it using the spindle speed PWM... is this possible? I am using a Campbell Combo Board. As I mentioned the fan has 4 wires (12v, grnd, PWM, and tach). 12v & grnd I think are obvious, but where does the PWM wire need to connect and is the tach wire even needed? Don't really care about precise RPMS, just want to be able to have an off, low, med & high speed that is controlled by Mach from the g-code.