Homing sensorless

luc

Yes you'll need to tune sensitivity, speed, and motor current.
If you already have endstop switches, why use stall detection?

For sensitivity, speed, and motor current on which parameter do you suggest me to act? On M915? and/or....?

I would like to use sensorless homing as I have transformed X and Y with linear guides and I would like to gain space in their run (if I can)

Phaedrux

Yes, 915 sets the sensitivity for starters

https://duet3d.dozuki.com/Wiki/Gcode#Section_M915_Configure_motor_stall_detection

Set it so that it stalls immediately, and then lower it until it moves freely.

Lower the motor current until you can no longer move the axis and then increase it until you just get reliable movement.

Then you can test stalling itself. You will need to have a speed fast enough to actually produce enough back emf to trigger. So you won't likely be able to do a single fast pass followed by a slower bump pass. Just a single fast move.

Phaedrux

The stall detection wiki page I posted earlier has a lot of detail. What step are you getting stuck on? What settings have you tried? It's not a feature that you just turn on and go, you have to do some tuning for your particular printer. And even then results can vary.

luc

@Phaedrux
If the compilation of the codes is correct and also their positioning in config.g and the various home ...., I try with sensitivity.

More than "stuck" I was uncertain about the correct construction of the "home" files and undecided about the parameters that I should now modify.
If I understand correctly, you suggest me to intervene on:
M915 X Y S3 F1 H400 R0

so I drop H400 to 100 and try (the wiki suggested 400 for 0.9 ° engines)

Then say
"Lower the motor current until you can no longer move the axis and then increase it until you just get reliable movement"
are you referring to M913 or M906?
M906 it seems to me that it is something else or wrong?

"Then you can test stalling itself. You will need to have a speed fast enough to actually produce enough back emf to trigger. So you won't likely be able to do a single fast pass followed by a slower bump pass. Just a single fast move. "
F3000 in the "home ..." file seems adequate ... what do you suggest?

Phaedrux

@luc said in Homing sensorless:

M913 or M906?

Whichever you prefer. M906 is an absolute value and must be set. M913 is a percentage of the M906 value and can be used after to drop and reset the current to a percentage.

Sensitivity is S. So try increasing that until it stalls immediately. 64 is the highest value.

H400 would be good if you have 0.9 motors for starters.

F3000 seems ok, but you're going to have to test different values yourself on your printer. I can only guess.

luc

@Phaedrux said in Homing sensorless:

@luc said in Homing sensorless:
Sensitivity is S. So try increasing that until it stalls immediately. 64 is the highest value.

M915 X Y S3 F1 H400 R0
(https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing Higher values reduce the sensitivity; lower values make false stall detection)

I do tests starting from -50 and gradually I edit.

For now I thank you very much, for correctness I will update later.

luc

Does not work.
Tried:
with S-50 "
F4800 instead of 3000

Doubt: M915 should be put in "config.g" or in the "home ..." files?

My system is 12 volts .... doesn't it work for this?

Phaedrux

@luc said in Homing sensorless:

Higher values reduce the sensitivity; lower values make false stall detection

Serves me right for posting after 1am.

Phaedrux

@luc said in Homing sensorless:

Doubt: M915 should be put in "config.g" or in the "home ..." files?

Either one will work. Whatever makes most sense for you. Having it in the homing file will make it easier for tuning because you won't be prompted to reboot the board every time you edit config.g. It will just get run along with the homeall when you try to home.

Yes 12v should work.

dc42

Two things:

If you only use stall detection for homing, then you should never need to change the stall detection settings. In which case you can put the M915 command in config.g.
There is a minimum speed for stall detection to work, so the 2-stage fast-then-slow homing that is often used in homing files is not appropriate when using stall homing.

luc

@Phaedrux said in Homing sensorless:

Serves me right for posting after 1am.
It seems to me that you are in Canada ... I Italy ...
The alarm sounds to me and you go to sleep! eh eh eh

luc

Today I try again. Yesterday it seemed to me that at the first "bump" it worked (the trolley went back) and then at the second no longer because the engine did not stop. I have to check better because I was confused!
Probably as DC42 says in point 2 I will not be able to use the second bump.
Let's see .... today I make other attempts.
Meanwhile, thank you again for your patience!

Phaedrux

@luc said in Homing sensorless:

I will not be able to use the second bump.

That's right. Because it is too slow. You can still back off from the stalled state position a few mm if you want, but no sense trying to home again more slowly because it won't help accuracy and it likely won't stall the same way.