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IndustryArena Forum > CNC Electronics > Servo Motors / Drives > "master encoder state error" AB ultra100 error message
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  1. #1
    Join Date
    Jun 2005

    "master encoder state error" AB ultra100 error message

    I have finished installing Allen Bradley ultra drives and motors on my machine and it is moving fine but the drives keep randomly faulting out and the ultramaster software gives me the error of "Master encoder state error" Which I understand is referring to the step and direction signals that are wired to the same pins that an input encoder A+ and B+ signals would use if it were in Position Follower (Master Encoder) mode which is used when one servo is to be electronically geared/coupled to another by using it's encoder signals to keep them in sync.

    I have the drive wired up for step and direction control and set up as Position Follower (Step/Direction). I have followed the connection guide and have the step+ and direction+ wires hooked to their pins. I have the Step- and Direction- wires hooked up to PC ground. This method of hooking up the drive is commented on by Allen Bradley as "External Step/Direction Interface via Single-Ended TTL Line Drivers (not recommended)"

    I used this same drive/motor combo years ago on a machine and it worked great. So I am at a loss as to why I would be having this error and I can not find any documentation on what the error means or what causes it within the drive.

    I am using CandCNC's UBOBIII break out board and Mach3

    Anyone have any experience or knowledge that might help?

    Thanks in advance, ShapeShaver

  2. #2
    Company Representative
    Join Date
    Feb 2007
    Sounds like your getting random noise on the encoder lines (or comutator lines) that is confusing the state decoder. Is this a Brushless or AC servo ?
    Manufacturer of CNC routers and Viper Servo Drives
    www.LarkenCNC.com and www.Viperservo.com

  3. #3
    Gold Member
    Join Date
    Sep 2010
    i agree step/dir line noise. as manual said, non differential input is not recommended.

    are the step/dir lines run in a shielded cable with shield tied to ground at at least one end? if not, try that. if it doesnt fix, tie shield at both ends and try it. if that doesnt do it see if u can move this wire away from any motor leads of power leads. if that doesnt work sounds like time to buy a $ 100 single ended to differential line driver and stick at the mach3 location and do it right.

  4. #4
    Join Date
    Jul 2013

    It's a bit late, but i hope it has some use for others.

    Could it be that instead of ''Master encoder state error'' u ment ''Motor encoder state error''? (as the editor software is called Ultra Master, maybe a mixup?)
    I have the full list of error codes here and that one is not among them.

    If you indeed ment ''Motor encoder state error'' this is what the Troubleshooting Guide has to say about it:
    Motor Encoder State Error
    Error code: 20

    Posible cause:
    The motor encoder encountered an illegal transition.

    -Replace the motor/encoder.
    -Use shielded cables with twisted pair wires.
    -Route the feedback away from potential noise sources.
    -Check the system grounds.

    Posible cause:
    Bad encoder.

    -Replace motor/encoder.

    I hope this helps at all.


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