ok, thank you for your answer, how to assign to the fan a command which is not foreseen in the standard code for my stepper motor

I think you are a little limited to the understanding of the question that I ask

you didn't understand the question, sorry, how to substitute or have the slicer interpret the fan control by a stepping motor...

Imagine I want to use a stepper motor to drive my cooling instead a normal fan to be understand by any slicer, this is my question

@bearer said in Using a rc servo to drive my cooling (fan0):

Not sure what you're actually trying to achieve here; but lets for a second assume you're using an RC servo to control the angle of a baffle or something like that?

The difference between a fan output and a servo is the servo needs a specific pulse length to correlate to a given position; while the fan only need a duty cycle proportional to the desired speed (slightly simplified). DuetWebControl will only display slider for control of fans, not servos associated with tools afaik.

So to have a chance at making a (configured) fan output generate servo compatible pulses you'd have to adjust the frequency for the output to give you a chance of re-creating the absolute pulse lengths needed by the servo which probably mean you loose pretty much all the available resolution

ref https://en.wikipedia.org/wiki/Servo_control

setting 50Hz fan output gives you the correct period of 20ms. but of these 20ms the servo only respond to a pulse length of 1 to 2ms.

basically you can only adjust the slider between 5%(1ms) and 10%(2ms) to control the full range of the servo without changing something in software or hardware i think.

I'd try to increase the the frequency and see how low a period the servo will accept to increase the granularity of control when controlling it with M106 as if it was a fan. Or dive into the firmware or DuetWebControl to make some changes, but thats not so trivial.

(or I could be completely wrong and someone else will give you another answer)

Thanks for your reply, i know it and i tried, thats why i need to use the servo
M950 P0 C"fan0" Q50
M280 P0 S90

If i use pwm for servo,
It give me ~1 to 2ms, i mesure it with my scope From 0 to 180°.
If i use pwm signal from fan, it does not work, like you describe.

I just want to know how to handle servo in place of Fan regulation to be interpreted correctly by a slicer and a duet web interface

Hello,
I use a servo connected to a valve to drive my cooling (i made a 24 to 5v pwm converter, hardware is ok)
I want to know how i can assign this servo like a fan0 ?
I use the following code, it work perfectly when i send manual command, but the servo could not be driven by "cooling" (fan disappear in the web interface and cannot be done by slic3r or other slicer)

M950 P0 C"fan0" Q50
M280 P0 S90

Any idea or solution ?
Thanks in advance

Yann

I'm using

Duet3d Ethernet
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