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18781Re: [RoboMower] Stuttering wheel motor

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  • Lee Hart
    Jun 3, 2014
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      Thanks for all your suggestions, guys. I got it fixed! My RoboMower is
      happily mowing away as I write this. :-)

      I tried setting up a new small perimeter wire, but the mower still
      stuttered along. That wasn't it.

      The thermistor (or some kind of temperature sensing device) is riveted
      to the side of the metal shroud around the right motor. It is not in
      series with the motor; it just had small white wires that go back to the
      main board. So that wasn't it.

      Removing the shroud let me inspect the brushes. With the motor out, I
      could also run it. I connected it to a 12v battery charger with a car
      tail light in series; it ran smoothly. I attempted to hold it to see how
      much torque it had, and whether there were any dead spots or torque
      pulsations when rotated slowly, which could be caused by bad brushes.
      There were none; so the motor is fine.

      But I did notice that the quick-connects to the motors were a
      surprisingly loose fit. It turns out that the 0.187" quick-connects have
      a sub-standard thickness; so the standard female terminals they used
      don't fit tight. With the motor back in and running, wiggling these
      terminals caused the stuttering. Aha!

      I pinched the female terminals a bit to tighten them up. I put it all
      back together, and it works!

      PS: This was my first look inside. Getting the cover back on is even
      worse than getting it off! What sadist designed this thing? FIENDLY

      I also get the impression that they know little about designing
      electronics for outdoor use. Everything is built the same way as indoor
      electronics. No moisture proofing, no conformally coated PC boards, no
      allowance for bugs or dust, no wide-temperature-range parts.
      I do not waste my life in friction when it could be turned into
      momentum. -- Frances Willard
      Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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