Fans Triggered From Stepper Driver Temperature

dhusolo

On my CoreXY I have a 12v fan on my X and Y stepper. I would've like to have them turn on automatically when the corresponding stepper driver (0.1 and 0.2) on my Duet 3 reaches a certain temp however looking at the object model I don't see temperature readings for each individual stepper driver.

Besides using the MCUs internal temperature as the trigger to turn on the fans, does anyone have a better option?

M950 F3 C"0.out5+0.out5.tach" Q500    ; Fan 3 uses out5, and using out5.tach as a tacho input
M106 P3 C"RT Stepper Fan" S0 H-1      ; connected to P0.2 set fan 3 value. Thermostatic control is turned off
M950 F4 C"0.out4+0.out4.tach" Q500    ; Fan 4 uses out4, and using out4.tach as a tacho input
M106 P4 C"LT Stepper Fan" S0 H-1      ; connected to P0.1 set fan 4 value. Thermostatic control is turned off

droftarts

@dhusolo stepper drivers don’t report current temperature. They only report a warning message (at 100C) and a shutdown message at around 130C. You can add a thermistor mounted directly on the driver, or just use the CPU temperature as a proxy, which is reasonably accurate as there is a shared ground plane on the Duet, which acts as a heat sink. See https://docs.duet3d.com/en/User_manual/Connecting_hardware/Temperature_configuring_mcu_temp

Ian

deckingman

@dhusolo I did exactly that when I had printed motor mounts. I stuck a small bead thermistor onto each stepper with a small dab of epoxy adhesive and use these to thermostatically ramp up the fan speed as the stepper motor temperature increased.

I did away with it all when I changed to aluminium motor mounts. These being bolted to the aluminium frame act as a giant heat sink, which keep the motors passively cooled.

dhusolo

I've configured fans to run off MCU temp in the past so I'm familiar with how to do it, I was just curious if there was a different option.

I have the fans configured as this:

M308 S2 Y"mcu-temp" P"0.mcu-temp"
M950 F3 C"0.out5+0.out5.tach" Q500
M950 F4 C"0.out4+0.out4.tach" Q500
M106 P3:4 H2 T20

However neither of the fans will spin even though the MCU-Temp is at 32c.
If I configure M106 as either of the following 1 fan will work.

M106 P3 H2 T20
M106 P4 H2 T20

droftarts

@dhusolo said in Fans Triggered From Stepper Driver Temperature:

M106 P3:4 H2 T20

As far as I'm aware, you can't set two fans at once with M106; the P parameter takes only one fan number. If you send that command from the console, what does it report?

Ian

dhusolo

@droftarts It simply echoed

M106 P3:4 H2 T20

But you were correct. I was able to get them both to run with

M106 P3 H2 T20
M106 P4 H2 T20