Connecting a "pancake" stepper to my dual hybrid BB

Discussion in 'Guides, Mods, and Upgrades' started by GrodanB, Feb 15, 2017.

  1. GrodanB

    GrodanB Well-Known Member

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    Since I do not find this when searching and I assume I'm not the only one thinking about this modification I wanted to double check how this is supposed to be connected.

    Have OMC 13 and 18 and the original Wantai 40 Ncm in front of me...

    Looking at the datasheet it seems like the colors is the same for the 13 and 40.
    A=RED and BLUE and B=BLACK and GREEN. Easy enough...
    But then it gets interesting...

    On the Duet (since it claims to have the same connection as the RUMBA I assume it is valid for the Rumba) the colors is:
    A=GREEN and BLUE
    B=BLACK and RED.

    Then looking at the connector of the Wantai... this seems to be how it is connected... BUT the cable is twisted:
    BLUE and RED
    BLACK and GREEN

    Is this the recommended twisting?

    But regardless of this I shall connect 1A(board) to 1A(Motor) and 2A to 2A... and same for B?

    To make things more irritating the connector I got from OMC for the 18 also uses the same coloring as the 13 datasheet... and not the one in the BB/Duet uses...
    (writing this I think I know but it would be nice to double check.)
     
  2. Ephemeris

    Ephemeris Well-Known Member

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    Yes I had the same situation. My pancakes are Blue-Red-Green-Black. Twist Blue-Red together and Green-Black together.

    You could wire this up several ways and it will work give or take a sign reversal. I went with

    Code:
    Stepper Blue   = Duet Red
    Stepper Red    = Duet Blue
    Stepper Green = Duet Green
    Stepper Black  = Duet Black
    This made my polarities in config.g

    Code:
    M569 P0 S1                               ; X-axis (Drive 0) goes forwards
    M569 P1 S1                               ; Y-axis (Drive 1) goes forwards
    M569 P2 S1                               ; Z-axis (Drive 2) goes forwards
    M569 P3 S0                               ; Extr-1 (Drive 3) goes backwards
    M569 P4 S0                               ; Extr-2 (Drive 4) goes backwards
    
    Important thing is once you wire it up and before you power up, move the carriage and bed manually to a safe position. Then when you power up, BEFORE HOMING, issue small movement commands to determine if polarity is what you expect.
     
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  3. GrodanB

    GrodanB Well-Known Member

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    Great thanks.

    One feels/seems like an idiot when confronting this...

    I plan just to change the direkt driven extruder. But have you changed the X also?

    I have been thinking about weight loss in the moving parts... Y and X seem unnecessary since they are stationary. But X and extruder seem interesting.

    When bed leveling I see that the sag seem to happen on the side with the stepper motors...

    Should I just divide the e-steps by 2 to get close to the correct value? Or is it recommended to got to 32 microstep to "regain" the lost steps?
     
  4. Ephemeris

    Ephemeris Well-Known Member

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    Any mass loss of the X-carriage makes it conceivable a small stepper motor could be used for X.

    For the Duet WiFi, I recommend you set all the steppers to 16x microstepping and enable interpolation. The relevant config.g gcode looks something like this

    Code:
    ; *** Set the microsteps/step and microsteps/mm for each motor
    M350 X16   Y16   Z16   E16:16   I1       ; Set microstepping to 16x for motion and 16x for extrusion
                                             ; The I parameter turns 256x interpolation on (1) or off (0)
                                             ; Interpolation to 256x microstepping only works if you set
                                             ; the microstepping to 16x and use the I1 parameter.
                                             ; The I1 parameter does nothing for any other microstepping value.
    
     
  5. GrodanB

    GrodanB Well-Known Member

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    Why do you switch the red and blue? And not the green and black?

    My divide by two was unnecessary since after removal I saw that the old stepper was a 1.8 degree stepper to... so the old value of 417.5 should be a good start value.
     
  6. Ephemeris

    Ephemeris Well-Known Member

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    Why? Because it was the way my cables were already wired :) There is no canonical right answer to wiring these things.

    If you swap the leads in a coil pair what happens? The stepper rotates in the opposite direction. Swap the two pairs for each other what happens? The stepper rotates in the opposite direction. Do both? The changes cancel out and the stepper rotates the way it was already. Each permutation works fine. None of them are really wrong.

    If you install the cable 'backwards' you swap coils and reverse the polarity on both pairs so that TRIPLE reverses the motor direction which of course is the same as reversing the direction once. This is handy when a motor is wired wrong and you don't have time to fix it in software, you just flip the connector 180 degrees and off you go.

    The only wrong permutations are when you make pairs from wires that aren't for the same coil. Then the motor won't work.

    You might enjoy this reference: http://www.reprap.org/wiki/Stepper_wiring
     
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  7. GrodanB

    GrodanB Well-Known Member

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    Weird this happen now... suddenly I cant start without a thermal error... need to fault trace... do not know what happen...
     
  8. jfb

    jfb Well-Known Member

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    That was interesting - thanks. :)

    Unfortunately, I made the mistake of following further on that thread and that lead me to the NEMA website, where I foolishly downloaded the "NEMA Standards Publication 16 (NEMA ICS 16-2001) - Motion/Position Control Motors, Controls and Feedback Devices", which is one of the most tedious documents I've ever seen :oops: Informative, but oh so tedious!

    If you happen to be interested (or suffering from insomnia), you can get it here https://www.nema.org/standards/page...ol-motors-controls-and-feedback-devices.aspx?
     

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