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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 Gold Contributor

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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:

    • Like Like x 1
  5. EL-CORAZON

    EL-CORAZON New Member Gold Contributor

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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. Tags..(VR)

    Tags..(VR) Member

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    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. Tags..(VR)

    Tags..(VR) Member

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    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?
  10. dieser

    dieser Member

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    Do they need to be grounded just on a metalframe?
    when i´m going to build a woodframe, do the wipers need grounding?

    thanks for clearing things up! ;)
  11. Zed

    Zed VR Simming w/Reverb Gold Contributor

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    It depends on the setup. If the motors are totally isolated, then you may be ok, but anything that connects the motors electrically could allow short circuits. You would want to meter it out before applying power or you can fry parts. Opening the motors to unground them isn’t hard though.
  12. Sam Neall

    Sam Neall Member

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    I tried to use wiper motors for my sim but I upgraded to more powerful motors. I just bought a couple more to make a rc tank and this tutorial has definitely helped me out. Thanks.
  13. Peter_the _machinist

    Peter_the _machinist Member

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    Hi, I've connected grounding brush with my "-" brush inside my wiper motor and it's all working fine but in the second and third I did the same and I've damaged them (probably I've touched isolation of the motor with my soldering iron or damaged isolation when I was trying to put enclosure back on). So my question is can I do it only one of them to avoid short ciructs or I need to buy fourth one and try it again?
  14. dope-walker

    dope-walker New Member

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    Hello,
    i have a quest to this....

    I have a 24v Bosch 0390442451 whiper motor.

    the way I understand it. Some wiper motors have the housing grounded, which is a problem when attached to a metal frame. If the motors run in opposite directions, your power supply will be shorted out. Which in turn destroys the motor h bridge

    But honestly I don't understand.
    So I understand it that if I hang my continuity tester on one of the poles and then go to the housing, there should be no continuity.
    That's the way it is. if I of course use the brown mass cable then of course it is already like that. Does that fit now? I don't know


    But is this ok or must i do more? motor.JPG
    • Disagree Disagree x 1
    Last edited: Jul 15, 2021
  15. Abram Manoge

    Abram Manoge Member

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    Yes some motors are just grounded on the outside with the wire that goes on the screw. It should be fine
  16. Martin Dixon

    Martin Dixon Member

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    Hi everyone,

    I have tried to follow the guide but am clueless could some one help me and tell me how to isolate my motor so that i get it right and dont mess up my motors i have striped it down but dont know what i need to cut or solder.

    20220211_194108.jpg 20220211_194134.jpg
  17. Martin Dixon

    Martin Dixon Member

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    Sorry for the double post please could some one help
  18. Zed

    Zed VR Simming w/Reverb Gold Contributor

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    You don’t need to isolate the motors if you don’t have any metal connections that tie the motor frames together. That can be through output arms, motor mounting, etc. If you use nonconductive mounts, actuator rods, or your motion frame isn’t metal (the ultimate test being a continuity check from motor to motor) you don’t need to isolate the motor windings/connections. But you have to be absolutely certain that the motor frames don’t have an electrical path between them.

    Some motors may be difficult to isolate properly depending how they are constructed. The ultimate test is to check for continuity between the terminals and the motor case with a test meter. As long as you have a current path from the terminals to the motor case, you can’t use them where there is a metal path of any kind from motor to motor.

    Unfortunately, just looking at the brush holder board isn’t enough information to tell where the path is from terminals to motor frame. It looks like the mount holes on that brush holder are the contacts to the motor terminals. It could be one of those is hard mounted to the motor frame. Check the mounts for that brush holder for continuity to the frame. I’d guess one of those is insulated and one isn’t but you’d need to test. Depending on how it’s built and how your sim is built, you may need to just isolate the motors and push-pull connections from the seat frame.

    If you go that way just remember the motors themselves will be electrically hot and any accidental metal bridging between them will short out your bridge. This is also only safe when voltages are low. If you are running with anything more than 40 volts on your motor supplies, that can start being lethal if you get across it. I only mention this since the motor cases are hot electrically if you can’t isolate them. They would be the same as bare wires for curious hands. Even 12 volts has been lethal under very wrong circumstances.
  19. Martin Dixon

    Martin Dixon Member

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    Thank you for your reply I have tested it and I get continuity through the case I think I'm just going to mount the motors on wood and same for the push rods behind my seat to be safe as it seems the easiest way to do it until I get better motors.

    Thanks again martin