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slipring1.jpg

I’m working on a new project and I need an electrical connection that can rotate 360 degrees. I could purchase a slip ring, rotating electrical connector, or better yet a rotary transformer. Then again, I could just try to make one from a DC motor. Do you have any suggestions for making, or *gasp* buying, a slip ring connectors? If so leave them in the comments. Thanks!

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Marc de Vinck

I’m currently working full time as the Dexter F. Baker Professor of Practice in Creativity in the Masters of Engineering in Technical Entrepreneurship Program at Lehigh University. I’m also an avid product designer, kit maker, author, father, tinkerer, and member of the MAKE Technical Advisory board.


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Comments

  1. Chris W says:

    Would a motorcycle or car alternator be too big? They have heavy duty brushes for the field, and mounting surfaces.

  2. Sam Littlewood says:

    How about using ballraces? – one for each conductor. This is what the electric ‘Round the pole’ flyers use.

    1. Marc de Vinck says:

      I have to look into that. Sounds interesting. Thanks!

    1. Marc de Vinck says:

      That does look perfect. How did I miss that?

  3. anachrocomputer says:

    To give a good answer to this question, we really need to know more about the application. First of all, how many volts will be across the joint? 12V DC and 240V AC solutions would be quite different. How much current must the joint carry? How fast must it rotate? And how much friction is tolerable?

    1. Marc de Vinck says:

      Good point!

      5-12V DC
      Low speed
      Long life
      4-6 conductors

      I think the link above is perfect. I missed that one on my search! [Thanks, Akiba]

  4. RonW says:

    Something I have have done is to use the bearing(s) and a slipring for power, then LEDs and photodiodes for signal. A low cost AVR or PIC can decode / encode the data signals over the optical links (one in each direction).

    To insure smooth power for the electronics in the rotating section, I used an electrolytic capacitor across the power feed.

  5. craig says:

    For supplying 12V power to my R2-D2 droid domes that rotate(make issue #2) I used a 1/4″ stereo headphone jack and plug. I mounted the jack in the top center of the body, and the plug is on a rigid coax that is mounted to do a gentle arc from inside the dome to the plug. The beauty is that because of the curve of the rigid coax, the two did not need to be mounted dead center, or even near center. The trick is to use the tip and mid section of the plug/jack, NOT the shield as that gives intermittant contact when rotating. Also, switch off power when plugging/unplugging it or for a split second the tip will short out the tip and midsection spring contacts. I ran up to 5 amps for 10 minutes through mine once I ‘broke it in’ as a test and it never even got warm.

    1. Marc de Vinck says:

      5 amps…through a headphone connector? Wow!

      How about lifespan? I guess an R2D2 robot is intermittent use and not an issue. Also, when it wears out, it certainly is a cheap fix.

      I would love to check it out? Any link to a build, or more info that we could share with our readers?

  6. Aud1073cH says:

    A common use of rotary transformers is VCR head drums.
    Old VCRs are cheap at second hand stores, or free if you find one being thrown away.

    http://en.wikipedia.org/wiki/Rotary_transformer

    The motors are usually 2 or 3 phase brushless, and the controllers sometimes on the motor PCB, or nearby. You may also be able to attach a microcontroller to do the job.

    Don’t forget to save the other parts, like tape drive motor, rollers, optical sensors, etc.

    1. Marc de Vinck says:

      Thanks! Since I only need an actual electrical connection, the driver board isn’t even an issue. I have an old VCR (from the trash) that I should rip apart.

  7. Mike says:

    Someday I want to have a project with the $’s behind it to use something from these guys:
    http://www.meridianlab.com/index.html

    nanoamperes through 1000′s of amps and Any Voltage
    (Depending on the model)

    Ah….someday…..

  8. James says:

    If you just needed power and you had access to both ends of the shaft you could use a second DC motor as a generator. Spin the body with the first motor and lock the shaft on the other end.

  9. craig says:

    When I say I ‘broke-in’ the large 1/4″ stereo headphone jack/plug, I sat watching TV for awhile holding the spring loaded tension parts tight against the inserted plug and twisted the plug back and forth. This made the actual contact points conform to a larger surface rather than a pin-point. I ran a 100W razor scooter motor through the plug as a test. Occasionally I bogged down on the wheel to put a load on it. Now I was certain it was good for dome lighting & electronics. I put a thin dab of dialectric grease on it, and after many outings at conventions and museum tech nights, it looks the same as day one. Not wearing out one bit. My dome motor spins the dome uber fast too. People think it’s going to spin right off the droid it’s so fast.

    1. Marc de Vinck says:

      OK, you sold me. I’m going to try it out. Thanks!

  10. Jonathan Foote says:

    Carl Pisaturo has a nice tutorial on how he makes slip rings for high-speed applications. He uses epoxy and turns the whole assembly in a lathe.
    http://www.carlpisaturo.com/_ElNo_SLIP.html

  11. Hugh Doherty says:

    Hi, Following a suggestion on a model-making site, have you considered a 1/4 inch stereo jack. won’t handle much current, maybe not long life but cheap for a trial.
    regards,
    Qdoc

  12. Hugh Doherty says:

    Hi,
    Following a suggestion on a model-making site, have you considered a 1/4 inch stereo jack. Maybe not handle much current or have long life but cheap enough for a trial.
    Regards,
    Q

  13. anil says:

    Interesting blog………………….!!!

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