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Isolating a Wiper Motor Ground

Discussion in 'DIY Motion Simulator Projects' started by Ursine, Jul 30, 2011.

  1. Ursine

    Ursine New Member

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    Some wiper motors will have the case grounded, which will be a problem when attaching to a metal frame. If the motors are run in opposite directions it will short out your power supply.
    I spent the morning trying to see how difficult it would to isolate the ground. Fortunately it's not too hard. There are lots of different wiper motors out there but this is how my particular model looks. First chect to see if you're lucky enough to have a motor that's not grounded in the first place.

    1. Remove the motor case.
    MotorFix1.jpg

    2. Remove the gear cover. Mine simply snapped on and off.
    MotorFix2.jpg

    3. Before I could remove the rotor, I had to remove the C clip on the worm shaft.
    MotorFix3.jpg

    4. The metal screw eyelets are where the motor is grounded to the case. There is one spot on top (indicated by the circle) and one underneath.
    MotorFix4b.jpg

    5. On the back of the board I used a Dremel with an abrasive wheel to cut the traces to the grounded eyelet.
    MotorFix6.jpg

    6. On the top I had an over temp/current device that I also cut the trace to.
    MotorFix7.jpg

    7. I've replaced the ground with bits of insulated wire.
    MotorFix8.jpg

    8. Replace the circuit board. I've removed the over current device on mine. I decided I didn't need it.
    MotorFix9.jpg

    9. I had to tie back the brushes with thin bits of wire before I could replace the rotor.
    MotorFix10.jpg

    10. Replace the housing and gear cover. A few drops of light machine oil on the bearings or bushings would be a good idea. Also check for damage to the geartrain. Mind had nylon gears. Be sure there's ample grease in the gearbox.

    Finally make sure you don't have continuity between the motor leads and the case. On my gear cover, there was a tab to ground the common motor lead to the case. I removed it.

    Enjoy,

    Dave
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  2. bsft

    bsft

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    That looks like a BIG job to isolate the ground.
    I just cut the wires on the outside of the motor first and then applied power to find what was what
    [​IMG]
    [​IMG]
    Perhaps try this first before removing the motor housing, you may find you can isolate with less hassle. If that does not work, then go to plan b.
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  3. Ursine

    Ursine New Member

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    I tried that first with mine. I always had some continuity to the case no matter what wiring combo I used. I agree, try to snip the wires and power it first... stripping down the motor is a last resort.

    Dave
  4. EL-CORAZON

    EL-CORAZON New Member

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    Hi .just done this my self :D and as I was in the mud. 8) I modified just A little bit more

    Attached Files:

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  5. EL-CORAZON

    EL-CORAZON New Member

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    If u want to do this isolation mod... the first post is the way.. you have to isolate the current inside the motor
  6. bsft

    bsft

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    Failing that, mount the motor on a piece of board, paint it then screw it down, and mount the rod end to a block of timber on the top part of the frame. Paint it and no one will notice, and you solve any further issues with voltage - current change. Wood does not conduct any power.
    Besides, since when does an unisolated motor feed current back to the controller to damage it. The controller is telling the motor what to do. As far as I know anyway. :uups:
  7. kubing

    kubing Member

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    daihatsu Mira wiper has an external ground wire attach to their case..just cut the ground wire to the body..done. no need to open the whole case to do that. :D
  8. Christopher.j.elliott

    Christopher.j.elliott Member

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, Arduino, Motion platform, 4DOF, 6DOF
    Hey Dave is it possible to use or have you tried using 2 separate l298n controllers for each motor from the arduino?
    i cant seem to get the housing off my motors and was wondering if the route i described would fix the issue of having a grounding by passed?
  9. Christopher.j.elliott

    Christopher.j.elliott Member

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, Arduino, Motion platform, 4DOF, 6DOF
    inside my motors , i have no wire brush touching the inside side of the motor. i haven't cut and soldered because i haven't been able to figure out which is the earth ground wire. but what if i were to run a ground wire from the casing on the motor to the ground of the terminal thats on the power supply unit and ground it that way? anyone try that?