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Encoder/Controller Issue?

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  • #16
    Originally posted by 5294-jjkd View Post
    We have six Neverest motors this year, four with encoders, never a problem. In your picture, I see two motor controllers with encoders plugged in, but your previous messages indicated that only one was failing. Do both fail? What is the exact error message on the robot phone?
    This leads me to think that some type of physical strain is causing the encoders to error (which may explain why the seemingly bad motor miraculous came back to life and started working). Our robot is rather heavy and the motors buckle quite a bit. Have you ever heard of physical straining on motors causing this type of behavior (of course physical strain can break the motor or encoder, but in our case it was only "broken" temporarily)

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    • #17
      I seem to recall an older thread that involved a motor being run in a particular way that caused wear resulting in encoder problems. I will try to find it.

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      • #18
        This is the thread I was thinking of, unfortunately I don't see an obvious relationship to your problem....

        http://ftcforum.usfirst.org/showthre...t=Encoder+wear

        You may want to try connecting the motor controller to a PC and use the core device discovery program to exercise the functionality of a 'good' motor and compare to a 'bad' motor, see if there is a difference in behavior.

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        • #19
          Originally posted by 5294-jjkd View Post
          This is the thread I was thinking of, unfortunately I don't see an obvious relationship to your problem....

          http://ftcforum.usfirst.org/showthre...t=Encoder+wear

          You may want to try connecting the motor controller to a PC and use the core device discovery program to exercise the functionality of a 'good' motor and compare to a 'bad' motor, see if there is a difference in behavior.
          I have just read this thread, and I'm intrigued by the possibility of the fault being related to the the encoder issues I discovered a while back...

          Taking what has been discovered at face value:

          1) After a parts replacement, the system seems to work fine for a while.
          2) After some usage, a fault condition occurs that seems to be related to the encoder.
          3) Cables and modules seem to be hooked up correctly.
          4) There is a time factor involved that seems to effect either the motor, or the controller... it's not clear to me which...

          I can throw out one off-the-wall scenario...

          What if a mechanical failure in the encoder electronics is causing undesirable voltages to appear on the encoder cable which is effecting the Motor controller.
          This could possibly be grounding on the +V line, or worse still, +/- 12V leaking onto any of the lines.

          Possible justification...
          We know that if the shaft of the andymark motor is pushed into the motor body, this can cause odd things to occur with the encoder.
          -- observed: Heavy loads in one direction on a NR40 causes the helical gear to push the encoder magnet out and reduce the number of encoder pulses.
          -- reported: At least one team reading incorrect encoder counts on NR3.7 motors.. suspect due to miss aligned encoder magnet.
          -- proposed: Changes were being made to the encoder housing to prevent this. We don't know what if any changes have been made.

          So, now with the addition or more gearbox combinations, perhaps a new fault is occuring that requires a certain amount of time to appear.
          eg: a re positioned component is being pushed out or alignment causing wear, or chafing, or vibration, or shorts.

          So, some new tests could be used to determine if this is possible. And it really relies on some post failure testing:

          1) Identify a controller / motor combination that has "failed". That is: you can't connect to the controller with the motor/encoder attached.

          Test 1) Disconnect the encoder cable and determine if the combination now runs.
          --- If it does, we know the failure is directly related to some part of the encoder pulse generation/transmission/reading portion of the system. But that it's not fatal to the controller
          --- If it doesn't, we know that the fault is causing a fatal failure on the controller.

          Test 2) Replace JUST the Bad motor with a new motor and reconnect the encoder. Does it run?
          --- If it does, we know the failure was originating on the motor, and it is most likely due to a fault in the encoder electronics.
          --- If it doesn't, it may still be that the fault is causing a fatal failure on the controller. But, remove the encoder cable and see if it starts running.
          --- --- If it does, this points to the final failure being on the Motor controller Encoder reading logic, caused by the original failure on the motor.

          Test 3) would be to replace the Motor controller, but this will probably lead to another expensive failure, so I resist doing this.

          I'd be really interested to hear the results of tests 1 and 2.

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          • #20
            Originally posted by Daniel_10237 View Post
            When our encoder wires are plugged into the core motor controller the board throws and error and dies. Any ideas as to why this is happening?
            Another set of problems with motor controllers... there seem to be several people seeing these.

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