Shouldn't you be using the MKS_BASE for your board?
RAMPS by itself has only three MOSFET controlled outputs, so you need to add some extra circuitry.
Use the EEB setting and add something like this fan control: [www.ebay.com]
Then you just modify Marlin to use that controller for the fan.
That fan controller happened to be the first one found with a search using "ramps fan controller"
RAMPS by itself has only three MOSFET controlled outputs, so you need to add some extra circuitry.
Use the EEB setting and add something like this fan control: [www.ebay.com]
Then you just modify Marlin to use that controller for the fan.
That fan controller happened to be the first one found with a search using "ramps fan controller"