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electromagnetic controls

Discussion in 'Electronic Basics' started by [email protected], Mar 3, 2007.

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  1. Guest

    Greetings Folks
    New to these groups here, and have not checked out any of the
    archives yet, so please forgive the simple question if the obvious is
    already out there waiting for me... : )
    I would like to scratch build one of those electromagnetic devices
    that will float things under it. Maybe a steel ball bearing. While I
    have an idea of the whats and whyfores, no reason to reinvent the
    wheel if one of you already have the plans...
    I've never seen one, but would it be possible to do this in
    reverse, I mean like having the ball floating above the surface of the
    I've been daydreaming of making a miniture solor system with
    various steel balls sitting on the glass of a smooth running clock
    that would act like those skaters on the glass ice rink music boxes.
    Anyone know how I could speed up one of those clocks??? I've been
    looking for a DC that runs smooth rather then the harsh clicking per
    second, and know they are out there, but not at the cheap stores that
    I've been haunting for the goodies... Any hints on these subjects
    would be appreciated.
    Thanks in advance
  2. The floating-ball gadget needs a feedback loop containing the magnet,
    something to sense the position of the floating ball, and an amplifier to
    drive the magnet. The sensor I remember from the days of Popular
    Electronics was a photocell and lamp, set up so that the position of the
    ball varied the amount of light reaching the cell.

    The usual battery-powered clock has an oscillator, usually a quartz
    crystal digitally divided down to 1 Hz, driving a stepping motor. The
    stepper is used because it doesn't need much power, and because people
    still expect clocks to 'tick'. Line powered analog clocks have
    synchronous motors running at 3600 RPM (on my side of the Atlantic),
    geared down to 1 RPM for the second hand, which gives very smooth motion.
    You can get these motors with various gear ratios from the big supply
    houses. If you need to run the system from DC, you could drive the motor
    with an inverter locked to a precision frequency reference. Clock motors
    draw less than five watts, so the inverter could be just an audio
    amplifier and a transformer, driven by whatever precise 60-Hz source you
    can come up with. I vaguely remember an article by an amateur astronomer
    who built such a device to drive his telescope. Another approach would be
    to control the speed of a high-speed DC motor that has some kind of
    magnetic or optical pulse generator on its shaft. Compare the pulse rate
    from the shaft with a quartz-crystal reference (after suitable processing
    to match the frequencies), then use the difference to vary the voltage
    supplied to the motor. That looks like more trouble than coming up with
    5W at 60 Hz to drive an off-the-shelf synchronous motor.
  3. sez:
    Google "maglev" OR "magnetic levitation". One of the resulting hits took me

    Look in the left margin under "Levitation".
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