Allocate tool heater as fan

bilsch

I did something stupid and kinda killed one of my pwm fans ( fan1 ). Short of desoldering / replacing that mosfet is there a way to drive an external fan from one of the expansion ports?

I actually have another need for doing this to control a water pump which is 12v and my systems are all 24v. I want to get PWM so I can control the speeds else I could just go on/off.

I was looking over the wiring diagram. I don't see anything on the expansion header that calls out as a fan3+ pwm so I'm not sure what to look for.

Is this possible?

dc42

Firmware 2.02RC3 allows you to use a heater output as a fan, e.g.:

M307 H2 A-1 C-1 D-1 ; disable heater 2 to make it available
M106 P3 A2 S0 ; fan 3 uses logical pin 2, which is heater 2

then you can do e.g. M106 P3 S0.5

HTH David

bilsch

@dc42 nice thanks!

bilsch

@dc42 Also does this work for the pwm on the other extruder heaters? For instance extruders 3..5 or whatever? Are there separate breakout pins for the fans - how does that work with the expansion board?

dc42

Yes it works with all heaters.

The fans on the DueX expansion board are controlled using the I2C interface to the DueX, so there are no corresponding pins on the expansion header.

bilsch

@dc42 So if I want to map heater 3 to fan 3, I would use the following correct?

M307 H3 A-1 C-1 D-1 ; disable heater 2 to make it available
M106 P3 A8 S0 ; fan 3 uses logical pin 8, which is heater 3

Is that correct? And I could also change P3 to P0 if I want to override the first fan?

dc42

Heater 3 is logical pin 3, not 8. https://duet3d.dozuki.com/Wiki/Using_servos_and_controlling_unused_IO_pins#Section_Logical_pin_numbers

bilsch

@dc42 Got it working thanks!

I had to set it to inverted - guessing its just the mosfet I'm using?

dc42

@bilsch said in Allocate tool heater as fan:

@dc42 Got it working thanks!

I had to set it to inverted - guessing its just the mosfet I'm using?

Heater outputs on the expansion bus are inverted.