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suitable motor for small motorized platform?

Discussion in 'Electronic Design' started by Bill Proms, May 9, 2013.

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  1. Bill Proms

    Bill Proms Guest

    I have a small platform that has a pocket videocamera attached to it.
    Since I have the camera and platform in a remote location, I need to be
    able to move the camera slightly in two dirctions: toward and away from
    an external lens (the lens is not attached and focus is done by moving
    the camera toward or away from the lens) and also slightly in
    perpendicular directions to and fro (because some objects are not
    centered in the lens and the camera can move slightly to compensate).

    I first tried making two small stacked platforms on top of modified
    drawer sliders with strings attached. The idea was to pull a string to
    move the camera in either of the directions above, but there is too much
    stress needed to get the camera to move and I must find a better way.

    Then the idea has occurred to attach a nut to the bottom of each
    platform and then use a threaded rod with a motor attached to the rod to
    move the platform in either direction. Since the camera needs to be
    able to move slowly in any of the directions and go forward and reverse,
    I'm not sure what type of motor would be suitable. I have some 3 Volt
    DC hobby motors, but I think these are way too fast for the job plus I
    doubt they reverse direction with polarity change. Can someone suggest
    a suitable motor, preferably something surplus? BTW, the threaded rod
    wouldn't need to be anything larger than 1/4" diameter or so.

    Thanks,
    Bill
     
  2. mpm

    mpm Guest

    Perhaps you can adapt something like this: (?)
    Link: http://reallyrightstuff.com/Product...0&eq=&desc=B150-B:-Macro-focusing-rail&key=it
     
  3. Martin Brown

    Martin Brown Guest

    Gearing the motor speed down is sensible anyway.
    That makes me wonder just how big and heavy your "small" camera platform
    is and what load it has to move around.

    You might be able to do what you want with fairly standard radio control
    servo motors combined with an optical feedback. Otherwise look at the
    platforms for 3D printer beds for inspiration...
     
  4. You can find 4096 steps-per-revolution steppers on eBay for a few
    dollars shipped (internal gear reduction). 5mm diameter flatted
    shafts. I'm using them to build a 'barn door' DSLR mount to photograph
    the night sky. The 4096 is based on half-steps, BTW. You can also find
    proper couplers which allows some lack of axial alignment, or just use
    a bit of rubber hose.



    Best regards,
    Spehro Pefhany
     
  5. Jasen Betts

    Jasen Betts Guest

    It sounds like you want motors with gearboxes, AKA gearmotors.
    most small DC brushmotors reverse with reversed polarity many that
    don't can easily be modified to reverse
     
  6. Any permanent magnet DC motor should reverse with reverse polarity
    input. Small DC motors tend strongly to be PM type.
     
  7. Bill Proms

    Bill Proms Guest

    Thanks to all for the responses so far. You certainly have given me
    plenty of ideas. To give you an idea of what I have now, take a look at
    this:

    http://goo.gl/N1Qqq

    I don't have this. I fashioned something out of wood and used drawer
    sliders, cut way down, for each slid-able axis. If I want to move in
    either x-x or y-y, I just pull the appropriate string attached to the
    ends. This isn't working out too well though as there's too much
    friction in the system, plus I designed it on the fly without actually
    planning anything out.

    What I did today was actually purchase that device at the link above.
    If you look at the picture, it uses a geared sprocket with geared rails
    for each axis for smooth manual motion as the sprocket is turned. I'm
    wondering if I could mount a small motor alongside of each sprocket,
    couple over the motor and sprocket with a rubber band to act as a belt
    and move each axis by powering the motor. When I converted a small
    telescope I have from manual to electric focus, that's exactly what was
    done.... small motor alongside the manual focus and a belt placed over
    the motor and focuser.

    I'm not sure though what speed or type of motor I would need. A motor
    like on the telescope would be ideal, but I don't have the specs for it.
    Appreciate any ideas here.

    Bill
     
  8. Guest

    something like this? https://www.sparkfun.com/products/8912


    -Lasse
     
  9. Guest

    Take a look at Marlin P. Jones & Assoc Inc., www.mpja.com. They have a
    selection of steppers & dc motors & geared dc motors. The latter range
    down to 12v/6.8 rpm.

    Hul

     
  10. I'm guessing you want a fairly low speed output. We get 1 RPM timing
    motors from
    Herbach and Rademan

    http://www.herbach.com/

    But I don't think they reverse.
    Can you measure how much torque you need? That will help in picking a
    motor.

    George H.
     
  11. josephkk

    josephkk Guest

    I recommend you start from an inexpensive plastic X-Y stage. Then add a
    couple of stepper motors with appropriate reduction drives. You may be
    able to find all of this surplus (a better X-Y stage will be a big plus).

    ?-)
     
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