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Slip Rings — Parallax Forums

Slip Rings

ajwardajward Posts: 1,130
edited 2012-07-31 18:25 in General Discussion
Hey All...

Has anyone experience transferring power and/or signals through a slip ring? Something like a continuously rotating sensor array.
Just toying with some ideas here. (Like I don't have enough unfinished projects going on! :-| )

Thanks for any wisdom!

Amanda

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-07-31 11:10
    Slip rings have been in use one way or another for a long, long time. There is always a certain amount of corrosion and noise associated with them. i suppose platinum would be best, maybe wetted with mercury. Getting digital data through them would not be easy.
  • Ken GraceyKen Gracey Posts: 7,410
    edited 2012-07-31 11:14
    A while back I caught this video from Limor:

    http://www.adafruit.com/blog/2012/03/12/slip-ring-video/
  • skylightskylight Posts: 1,915
    edited 2012-07-31 11:24
    @Ken, that looks great I can just imagine that used on a boe-bot with a continous rotation servo mounted ping for 360 degree view of the environment.
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2012-07-31 12:14
    There are quite a few small ones on ebay and some are pretty inexpensive

    http://www.ebay.com/sch/Electrical-Test-Equipment-/92074/i.html?_nkw=slip+ring

    If you need something really heavy duty 150Amps or higher I have s source for those but they will need to be cleaned up before using them.

    Robert
  • ercoerco Posts: 20,261
    edited 2012-07-31 13:18
    Cheap telephone swivel jacks might work for light duty use: http://www.ebay.com/itm/2X-PHONE-ACCESSORIES-SWIVEL-JACK-FOR-LANDLINE-PHONE-KEEPS-CORD-FROM-TWISTING-/110927524362?pt=US_Phone_Cords_Jacks_Plugs&hash=item19d3cbb20a
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-07-31 13:43
    I use high end 1/4" stereo 90 degree plug and jacks.
    Look at the German made "Neutrik" electric guitar type.
    The ones that have gold plated brass machined barrel, ring, and tips.
    I have tested these to about 30 amps and work well with only slight temperature rise.

    Duane J
  • ajwardajward Posts: 1,130
    edited 2012-07-31 14:34
    Thanks for all the replies! I first thought of making my own from a 1/2 inch dowel and brass tubing, but there were some things that would be too difficult with just hand tools.

    Ended up getting one of these:
    http://www.ebay.com/itm/260991849118?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_4654wt_1398

    It'll cost less than just the parts for a home made device.

    Amanda
  • ercoerco Posts: 20,261
    edited 2012-07-31 15:01
    Each of those 6 conductors is rated for 2 amps at 220V, so you can transfer a total of:
    6x2x220= 2.64 kilowatts through it' while it's rotating at 250 RPM (4 revs/second)

    So you can make a military or commercial-grade rotating full-power radar antenna installation around this part. Not bad for 8 bucks! I'm jealous I didn't find it, Robert! :)
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-07-31 16:20
    Are there any guesses about how well the ones Amanda ordered would do with signal wires?

    I'd imagine servo signals would be fine but what about really fast(~1MHz) SPI signals?

    I'll probably get a few myself. An ultrasound sensor on a CR servo would be pretty cool.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-07-31 16:28
    I suspect slow signals might be a bigger problem than fast ones, especially if they are edge-sensitive. With a very fast signal, you at least have the benefit of capacitive coupling during the intermittent absence of a galvanic connection. In fact, I would venture to recommend modulating any signals that have to cross the slip ring divide and demodulate them on the other side.

    -Phil
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-07-31 16:30
    There is a web site that shows a variety of slip ring type http://www.slipring.cn

    I would think that the "Through Hole Slip Ring" would be the most useful since you have a motor shaft, etc placed inside the slip ring.

    I found some on ebay - $95 though...
  • W9GFOW9GFO Posts: 4,010
    edited 2012-07-31 18:25
    Although this is not something I have experimented with yet my plan has been to use a simple slip ring (phono plug or similar) for power and ground while serial data is passed via either ir or rf. The theory being that any momentary breaks in contact can be handled by a capacitor and the data would not be affected.
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