How to turn on fan when stepper drivers turn on?

Is there a PWM solution that can turn on the fan when the stepper drivers power up?

To provide some cooling, I'd like to put a small fan near the board to get some air circulating, it only needs to run when the stepper drivers are on.
PWM would be very hand in this case, then I can set it to 50% or so, whereas now if I hook up the fan it will be on full speed all the time which is noisy.
I'm using an solid state relay for the heatbed which runs off a spare arduino pin, freeing up one of the ramps1.4 mosfets for the extra fan.

I did lots of googling and I searched this subforum but I didn't find what I was looking for.

There is a board fan pin that does exactly that. It assumes only when printing we need cooling so it turns fan off when motors are off.

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Thanks!

Though I can't seem to find the setting in configuration.h
Is it in configuration.h or where should I look?

For future googlers who come looking here this may also be of interest/use to you:
[github.com]
[captain-slow.dk]

Edited 1 time(s). Last edit at 11/16/2015 07:44AM by TTN.

#define FAN_BOARD_PIN yourpinnumber

should do. In config tool it is in features section.

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I can't find it in configuration.h (got it from github) I'll just define it in configuration.h and that should do the trick.

Thanks!

EDIT: worked

Edited 2 time(s). Last edit at 11/16/2015 05:55PM by TTN.

Is it possible to set a PWM value for the FAN_BOARD_PIN?