M906 / M913 behavior question



  • I wish to have the stepper idle current, on one axis only, to be at different percentages under different end locations. The global idle current is 30 percent.

    For example #1 - Is this 80% of FULL power or 80% of IDLE power?
    M913 U100 ; Set normal current U
    G1 U50 ; Absolute
    M400 ; Wait for move finish
    M913 U80 ; 80% normal current ( 80 percent of what ? )

    For example #2 -
    M913 U100 ; Set normal current U
    G1 U10 ; Absolute
    M400 ; Wait for move finish
    M913 U??? ; 100% IDLE current is what is desired


  • Moderator

    M913 is a percentage of M906. Does that help?



  • @Phaedrux Not quite. For example a given M906 can have TWO values - one is for running current and the other is for idle current. So does the M913 percentage apply to BOTH 906 run/idle values or does it apply to just the RUN value - big difference. Hope I've stated that adequately.


  • Moderator

    Ah, I see what you mean. No, as far as I know the idle hold current would take precedent and override the M913 modification.



  • @Phaedrux You may be correct but perhaps DC42 could chime in here. Idle holding current requirements should be able to be independently controllable especially for extended axes (UVW etc) where needs (such as in my case) may differ from those of the primary axes. In fact ideally, ALL holding currents might preferably be independently specified.


  • Moderator

    As far as I'm aware the idle current is applied across all axis and not currently possible to set it per axis.

    @dc42 will have to confirm or deny.



  • @balrags said in M906 / M913 behavior question:

    @Phaedrux You may be correct but perhaps DC42 could chime in here. Idle holding current requirements should be able to be independently controllable especially for extended axes (UVW etc) where needs (such as in my case) may differ from those of the primary axes. In fact ideally, ALL holding currents might preferably be independently specified.

    Just out of curiosity, if the idle hold current is set for the worse case axis, why would that be a problem for other axes? OK, it might be slightly higher than is strictly necessary for some of those axes but does that really matter?


  • administrators

    @Phaedrux said in M906 / M913 behavior question:

    As far as I'm aware the idle current is applied across all axis and not currently possible to set it per axis.

    Correct.

    The idle current is the specified percentage of the current set by M906, regardless of any use of M913.


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