Duet 3 Mini5+ sensorless homing not working

obzocker

Hello everyone,
i'm currently trying to configure the sensorless homing for my Duet 3 mini 5+ but i can't get it to work.
The Axis keeps crashing regardless of the sensitivity (M915 S-64 or S63) or other Parameters.
I can only get the Axis to "stop" if I set the motor current to 200ma, but this only "stops" the Axis but you can hear that the motor wants to turn further.
I have also tried to to set the stealthChop range with M569 but that made the Axis only crash even harder.

config.g

homex.g

Is there anything obvious I'm missing?

I appreciate any input.

dc42

What firmware version are you using? There was a fix to the stall detection sensitivity setting in release 3.3.

obzocker

@dc42 I'm running 3.3

Phaedrux

M915 s-64? Is that what you're normally using or just for testing?

Did you calculate your H value?

Have you tried different motor currents?

obzocker

@phaedrux M915 S-64 was just for testing. I tested everything from -64 to 63.

I wasn't sure how to calculate the H value correctly. In the documentation of the "Compact but powerful motor" from e3d it says 1.68 amps per phase as rated current. The motor has 2 Phases, so do I need to use 1.68 or 3.36? Either way I tested it with H400 and no parameter. I tested many speeds but never got under 70mm/s, because the documentation of the sensorless homing from the duet highlights that higher speeds are important.

I have tried currents from 200ma to 400ma.

gloomyandy

@obzocker Take a look at this thread https://forum.duet3d.com/topic/24533/help-with-sensorless-in-duet-3-mini-5?_=1628841579208 You will need to add V40 to your M569 settings.

obzocker

@gloomyandy as i described earlier the V40 Parameter makes to Axis crash even harder. I have tried it exactly as your the post states (remove H Parameter, Add V40) and it doesn't work.

What makes this interesting(and frustrating) that the stealthChop seems to override the motor current settings. I set the motor current to 60mA. I couldn't even do a manual move but the homing moves and crashes the Axis at full force as if I set the motor current to 1000mA

Furthermore if i try to stop the motor before the Axis end with my hand I somewhat randomly get the error "Warning: high temperature reported by driver(s) 0", which makes no sense since the whole board was powered on for about 3 min. it has sufficient airflow, the fans where at 100%(MCU temps were 32degress celsius)

order of M569 and 913 is irrelevant (produces same results)

obzocker

@gloomyandy I again tried the solution. This time I change the the S Parameter to -40
Now the motor stops at the end, but first I get "Error: short-to-ground reported by driver(s) 0
Warning: high temperature reported by driver(s) 0"
And then I get the Error" short-to-ground reported by driver(s) 0" every 5 seconds.

What can I do? I double checked, the motor wiring is correct.

gloomyandy

@obzocker I'm not really sure why you are getting those warnings, the only thing I can see is that you will be operating the motors at a pretty low motor current (30% of 800mA), which may cause some problems.

You may want to try searching the forums for "short-to-ground" to see if others have had similar problems.

obzocker

@gloomyandy @gloomyandy Ok. The sensorless homing works now.

The problem is that the motor current was to low.
Sensorless homing only works(for me at least) for currents between 480mA-800mA

The documentation highlights that you should/could lower the motor current ("Try to use as low a current as possible") but never states that motor currents which are to low may also not work.

Whats weird is that the lower motor current while in stealthChop seems to effect the sensitivity of the sensorless homing.
When the motor current gets lowered, the overall force/strength of the motor does not change. The only difference is that with higher "motor currents" (M913 between 60 and 100 of 800mA) the sensorless homing works, but with lower "motor currents" (M913 below 60) the Axis crashes like if no sensorless homing is configured. Even at "motor currents" of 1% the motor has the same force/strength as 800mA

Am I missing something obvious?