Connect Mosfet to other pins

Hi

Is it save to connect an external Mosfet (a small board) directly to any other pins on Ramps then D8 - D10?

I'm asking because my D8 port broke while the hotend was connected directly to it. My hotbed is connected to an external Mosfet on D10 and I have an additional external Mosfet in spare. So I could use it for the hotend but I'm not sure if other pins can handle it. As a quick fix I connected the hotend to D9, but this way I had to disconnect the fan.

Another possibility would be to replace the Mosfet on D8, but I would only try this if there is no simpler way to operate the external Mosfet. Btw. D8 isn't totally broken. However it needs a very long time to power up. The corresponding LED starts to glimm after 20 seconds and then it gets brighter and brighter, until it reaches full brightness sometime later. Currently I can still use D8 for powering the cooling fan in a kind of imprecisely way.

Edited 1 time(s). Last edit at 07/27/2019 09:10PM by BeSpace.

You can use any unused PWM capable IO pin

On the mega these are
Digital pin 2 (PWM)
Digital pin 3 (PWM)
Digital pin 4 (PWM)
Digital pin 5 (PWM)
Digital pin 6 (PWM)
Digital pin 7 (PWM)
Digital pin 8 (PWM)
Digital pin 9 (PWM)
Digital pin 10 (PWM)
Digital pin 11 (PWM)
Digital pin 12 (PWM)
Digital pin 13 (PWM)
Digital pin 44 (PWM)
Digital pin 45 (PWM)
Digital pin 46 (PWM)

You will have to find out where each of these pins goes to on the ramps to see if you can use it.

this will help [reprap.org]

NB you also need a mosfet that can be turned on with 5v, a lot of the external mosfets are designed to be turned on with 12v (being the output of the on board mosfets)

Edited 1 time(s). Last edit at 07/27/2019 11:09PM by Dust.

Quote
Dust
NB you also need a mosfet that can be turned on with 5v, a lot of the external mosfets are designed to be turned on with 12v (being the output of the on board mosfets)

Ok I get the point. I will check if the Mosfets can be triggered by 5v.
Another option would be to solder a simple board with an Z34N, a resistor and a diode to drive the fan on a PWM pin. Have everything laying around. Can somebody tell me if the MOSFET will need a heatsink for a 12V , 0.18A fan? The power seems low, but I’m not sure how the PWM impact will be.

Edited 1 time(s). Last edit at 07/28/2019 10:14AM by BeSpace.