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Ideas on a simple project please - rotating small dalek!

Discussion in 'Electronic Basics' started by [email protected], Jun 12, 2007.

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  1. Guest

    Hi all,

    I have somehow promised to make, what I'm sure for others is, a very
    simple project - but I have never done anything like this and would
    really appreciate some suggestions on the best way to do so.

    A highly controllable rotating display 'table', about 8 inches in
    diameter, capable of holding a toy dalek (12" height, weighting
    1Kg?). Must be able to smoothly rotate the dalek at least 180
    degrees, although more is fine. I'm looking for a gentle, controlled
    rotation. The user should be able to rotate the table clockwise and/or
    anti-clockwise in small steps at will. The rotation speed not very
    important - maybe 180 degrees between 5 and 20 seconds?

    (The idea is to hide the table and make it look like the dalek is
    looking/following a person.)

    Low voltage - 6V, 9V or 12V battery.
    The control unit must be remote from the table, up to 5 meters away,
    cable connection.
    On the control unit, a method of rotating the table clockwise or
    anti-clockwise. Also a stop position.
    Somewhere a master on/off switch.

    Very happy to buy a Lego / Meccano / self assembly kit, if this has
    every thing I need. Alternatively where should I go to get the motor
    and a speed controller? Or do I need gear cogs? Or maybe what I need
    is name of a good book to start with!

    Any help/pointers gratefully received.

  2. I suggest a servo unit intended to control the flight
    surfaces of model airplanes. They are made in many sizes,
    have smooth, proportional response, include the reduction
    gears to provide relatively high torque, have the right
    voltage requirements and move fast enough for this.
  3. default

    default Guest

    Model servos work over a range of about 270 degrees and are reasonably
    priced compared to DIY. Tower Hobbies will probably have the best
    prices. They are on the 'net.

    You need a circuit to actuate it. They take pulse position modulation
    to set the position. For that a "servo tester" would work for you.

    Simple servo tester schematic

    You may also want to consider a "thrust bearing" to bear the load of
    the table and contents - the servo isn't optimized for a load directly
    on it's shaft - for that you need something like a lazy susan bearing
    to support the weight of the table.
  4. BobG

    BobG Guest

    The RC servo will work like an Owl's head if the guy walks around it
    in a circle. Better to have a little micromo gearhead motor with an
    encoder on the back of it... run a couple of wires from the 5v dc
    motor and the encoder to a little microcontroller. (I'm a programmer.
    All the problems I solve have a microcontroller in the solution). Add
    Passive Infrared Sensors in the eyeballs and the darn thing will track
    anything hot autonomously.
  5. default

    default Guest

    Good idea.

    He expressed the idea that he's not too into electronics and wanted it
    simple. Learning a pic may be outside the scope of the project.

    I made a remote positioner from a pair of stepper motors. One stepper
    generates the signal and the other follows the first. An quad op amp
    takes the signal one motor generates, and turns it into a square wave
    drives for a few Darlington power transistors. Turn the knob on the
    generator and the slave follows it. I used a pair of cheap surplus
    bipolar steppers of the same type, but could have also used ones with
    different step angles for more or less fine control of the driven
    motor. Really worked well for a remote antenna tuner.
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