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Re: [rsa] commutator questions

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  • Peter A. Bonucci
    douglas, I don t know your application, but if I needed to get video from one place to another, I would consider an RF or optical link. A photo transmitter
    Message 1 of 9 , Aug 31, 2003
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      douglas,

      I don't know your application, but if I needed to get video from one
      place to another, I would consider an RF or optical link.

      A photo transmitter might shoot down the axle and be received at the
      other end. An RF link could radiate into the room and be received
      anywhere on the other half. It is non-contact, so friction and contact
      noise won't be a problem.

      Price, weight, size, power consumption, and acceptable complexity will
      probably be your major trade-offs. It seems to me that an optical link
      could probably be done for the smallest weight and size, but that may
      not be the trade-off you are looking for.

      Peter A. Bonucci

      douglas irving repetto wrote:
      > david said:
      >
      >>Most guys build their own...
      >
      >
      > That's what my friend has been doing (machining his own), but he's
      > having real trouble with wear and noise in his signals. These are art
      > installations that are on for very long periods of time. He has been
      > experimenting with various materials and designs, but can't come up
      > with anything that's consistently quiet and durable. Any advice or
      > pointers to info?
      >
      > thanks,
      > douglas
      >
      >
      >
      >
      >
      >
      >>At 17:34 30-08-03 -0400, you wrote:
      >>
      >>
      >>
      >>>hi,
      >>>
      >>>
      >>>a friend of mine is working on a bunch of projects that involve
      >>>rotating cameras. he's been having trouble finding a reliable
      >>>commutator design. can anyone point me to some online or book-based
      >>>info on commutator design?
      >>>
      >>>(by "commutator" i mean a device that allows you to feed
      >>>power/signals to a rotating part, as opposed to a device that turns a
      >>>motor's output from AC to DC. is "commutator" the correct word for
      >>>this?)
      >>>
      >>>thanks,
      >>
      >> >douglas
      >>
      >> >
      >
      >
    • Terry Slocum
      Douglas, It depends a lot on what type of signal you are trying to put through it. To control the motors on a crane model I made, I used a piece of copper clad
      Message 2 of 9 , Sep 2, 2003
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        Douglas,

        It depends a lot on what type of signal you are trying to put through it. To control the motors on a crane model I made, I used a piece of copper clad circuit board material and etched some rings in it. I used spring loaded brass brushes. It seemed to work fine.

        If you are trying to pass video, or worse yet modulated video you will have a huge signal loss as soon as the signal leaves the sheilded environment of the cable. Whatever material you use for the "commutator",it will act as an antenna and radiate most of the signal into space. You might try putting a small transmitter in the camera head. Or use something to modulate the video feed onto a low frequence (60hZ) carrier. Some of the low end TV distribution systems work this way. There is also a system for model railroading that lets you put a video camera on the train and transmit video through the wheels to the track.

        Terry

        --- In sfrsa@yahoogroups.com, douglas irving repetto <douglas@m...> wrote:
        >
        > david said:
        > >Most guys build their own...
        >
        > That's what my friend has been doing (machining his own), but he's
        > having real trouble with wear and noise in his signals. These are art
        > installations that are on for very long periods of time. He has been
        > experimenting with various materials and designs, but can't come up
        > with anything that's consistently quiet and durable. Any advice or
        > pointers to info?
        >
        > thanks,
        > douglas
        >
        >
        >
        >
        >
        > >At 17:34 30-08-03 -0400, you wrote:
        > >
        > >
        > >>hi,
        > >>
        > >>
        > >>a friend of mine is working on a bunch of projects that involve
        > >>rotating cameras. he's been having trouble finding a reliable
        > >>commutator design. can anyone point me to some online or book-based
        > >>info on commutator design?
        > >>
        > >>(by "commutator" i mean a device that allows you to feed
        > >>power/signals to a rotating part, as opposed to a device that turns a
        > >>motor's output from AC to DC. is "commutator" the correct word for
        > >>this?)
        > >>
        > >>thanks,
        > > >douglas
        > >>
        > > >
        >
        > --
        > ................................................http://artbots.org
        > .....douglas.....irving.........................http://dorkbot.org
        > .................................http://shoko.calarts.edu/musicdsp
        > .......... repetto..............http://music.columbia.edu/organism
        > ................................http://music.columbia.edu/~douglas
      • douglas irving repetto
        a while ago i asked for some advice on commutator designs for a friend of mine. he s just found what looks like a really good (albeit pre-made) solution:
        Message 3 of 9 , Sep 9, 2003
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          a while ago i asked for some advice on commutator designs for a
          friend of mine. he's just found what looks like a really good (albeit
          pre-made) solution:

          http://www.mercotac.com/index.html


          i'm not sure what the price on these is.



          douglas





          --
          ................................................http://artbots.org
          .....douglas.....irving.........................http://dorkbot.org
          .................................http://shoko.calarts.edu/musicdsp
          .......... repetto..............http://music.columbia.edu/organism
          ................................http://music.columbia.edu/~douglas
        • Al Margolis(TX)
          McMaster-Carr has some. Search for rotating electrical connectors at http://www.mcmaster.com. -- Al Margolis, founder www.hobbyengineering.com The WEB s
          Message 4 of 9 , Sep 9, 2003
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            McMaster-Carr has some. Search for "rotating electrical connectors" at
            http://www.mcmaster.com

            -- Al Margolis, founder
            www.hobbyengineering.com
            The WEB's newest source for robotics supplies and information

            -----Original Message-----
            From: douglas irving repetto [mailto:douglas@...]
            Sent: Tuesday, September 09, 2003 1:52 PM
            To: sfrsa@yahoogroups.com
            Subject: Re: [rsa] commutator questions



            a while ago i asked for some advice on commutator designs for a
            friend of mine. he's just found what looks like a really good (albeit
            pre-made) solution:

            http://www.mercotac.com/index.html


            i'm not sure what the price on these is.



            douglas





            --
            ................................................http://artbots.org
            .....douglas.....irving.........................http://dorkbot.org
            .................................http://shoko.calarts.edu/musicdsp
            .......... repetto..............http://music.columbia.edu/organism
            ................................http://music.columbia.edu/~douglas


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