I'm trying to run a cooling fan off a RAMPS 1.4 but the D8, D9, and D10 outputs are all full from the dual extruder and bed. Any ideas how to go about this? Then only way I can think of is having 12v run to the print head and then using logic from another pin on the ramps to switch it. I know I can grab 5v from the AUX pins but I don't know how to switch that.
