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Proximity induction circuit and circular magnetic accelerator

Discussion in 'Electronic Design' started by jhead, Jul 3, 2007.

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  1. jhead

    jhead Guest

    I am wanting to build a circular magnetic accelerator using a
    proximity induction sensor to discharge the capacitors, that will
    activate the electro-magnet coils just before the ball bearing reaches
    the coil.

    My question is this what kind of circuit will I need to build to use
    an induction sensor to trip a "switch" and send power to the coil
    nearest the steel ball (there will be an array of coils around the
    plastic tube)?

    I would rather not use a relay, as there would be moving parts, and
    the switch would have to work quite rapidly once things got going.

    I'm thinking that I may have to have several banks of capacitors as
    there may not be enough time between discharges to charge the
    capacitors array back up.

    And what concepts should I further explore to make this work?
     
  2. whit3rd

    whit3rd Guest

    Presumably you are pulsing magnets; you have to both turn them
    ON when the ball is approaching and OFF when the ball is about
    to depart. The problem is solved in some particle accelerators,
    by modeling the acceleration of the particle and setting
    accurate time delays to the multiple acceleration stages.
    Since the acceleration is intended to be one unit per stage, your
    times will be in reciprocal of the order of a quadratic series (1/M**2
    for M = N, N+1, ...N+P).

    The full capacity of your accelerator is reached when the ON/OFF
    cycle is too slow for the fast-moving ball.
    If you're pulsing magnets in the vicinity, DON'T use an induction
    sensor.
    The pickup-noise problem is... severe.
     
  3. The circuits similar to what you are looking for are used for the
    magnetizing of permanent magnets and/or surge testing of equipment.
    Typically, they use powerful thyristors or IGBTs. Those devices are
    quite expensive.
    The relay contacts will be welded together by the surge current, unless
    this is a special relay designed for this kind of operation.


    Vladimir Vassilevsky

    DSP and Mixed Signal Design Consultant

    http://www.abvolt.com
     
  4. default

    default Guest

    Search for "coil gun" on the Internet. The idea is to put a piece of
    steel in a plastic tube energize a series of magnets to propel the
    steel out the end and into a target.

    Depending on how many joules you need to switch it can be
    inexpensively done with SCR's (thyristors) or IGBT's if they cycle
    time needs to be very short (small loop).

    http://www.coilgun.info/home.htm a place to start
     
  5. neon

    neon

    1,325
    0
    Oct 21, 2006
    you will ned a LM555 generator whereby the design allow frequency canges and a ripple counter to run all your coils. coils like capacitors store energy s you will reach a limit somewhere whereby it will just resonatebasicaly stop time and distance is the criteria.
     
  6. jhead

    jhead Guest

    Thanks for the suggestions. I will be exploring optical sensing
    methods, as any induction sensors would be swamped, as was basicly
    pointed out.
     
  7. MooseFET

    MooseFET Guest

    You also need to look at how you do your switching. Ideally, the coil
    current will be snapped on just before the ball gets to the coil and
    off just as it passes the middle of it. A sharp turn off, will
    actually repel the ball out of the coil.

    Ideally, the energy from the coil ends up back in the storage
    capacitors. This will save on the heating of the system.
     
  8. jhead

    jhead Guest

    For anyone interested, here is my 3d rendering of my pre-prototype
    idea:
    http://jmhead.com/content.php?page='Circular Accelerator Project'
     
  9. For a steel ball, there will be two completely different
    effects taking place that can exert force on the ball. At
    low frequencies, where the magnetic field has time to wait
    for the surface eddy currents to die down, so the magnetic
    field can pass through the ball, there will be forces caused
    by the permeability of the steel. Those forces always act
    in the direction that will increase the total magnetic flux.
    The other and higher speed effect is the reaction between
    the applied magnetic field and the magnetic field created by
    the induced current, circulating in the surface of the
    conductive ball (eddy currents). Since eddy currents
    inhibit changes in the flux already passing through the
    ball, this force can act as an attraction or a repulsion,
    depending on the polarity of the external field, compared to
    the one produced by the eddy currents. This effect is a lot
    more complicated to describe in a few words, but, for high
    speed rail machines, is the dominant effect available to
    produce force, unless the moving body is relative non
    conductive.
     
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