DCC++ & pololu mc33926 motor shield current feedback

RudolfM Dec 4, 2020

  1. RudolfM

    RudolfM New Member

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    Hi all,

    I use Arduino uno with motor shield Pololu. Programmed with DCC++ base station software and communicating via DCC++ controller.

    All works well.

    The one problem I have is that the current feedback is not working, I can't see any current drawn on the screen.

    I understand that the current feedback is done via A0 & A1 pins, do I need to use a resistor on motor shield before the signal goes back to Arduino Uno?

    Could you please advise.

    Thank you.

    Rudolf.
     
  2. schufti

    schufti TrainBoard Member

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    Hi,
    first: did you connect the FB from the motor shield to A0 on the arduino?
    second: IMHO I think they made an error on the conversion factor for the pololu board.
    in motordrivers.h I suppose it should be 9.3 instead of 18 (lines 34 & 35)
    third: if that didn't help: can you measure anything on the FB pin to gnd when some trains are in operation?
     
  3. S t e f a n

    S t e f a n TrainBoard Member

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  4. schufti

    schufti TrainBoard Member

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    Hi,
    to put it right, there is no "not recommended" to read anywhere. Instead I find the pololu MC33926 under "Boards currently supported / Easy to use boards".
    Only a remark (3A - current sensing is not appropriate for most programming) limits its use for programming.
    BUT that is based on the problem (low resolution) I try to give a hint for possible fix - obviously no one is interested, so am I now.
    Instead stay with the obsolete boards or add complexity with additional sensing boards - to each his own.
    It is the same as with 28 speed steps - a simple patch to be in line with NMRA standard minimum requirements, no one seems interested, so am I now (works for me).
     
  5. S t e f a n

    S t e f a n TrainBoard Member

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    Well, to me it didn't sound like a recommendation.
     

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