Proximity induction circuit and circular magnetic accelerator

Discussion in 'The Projects Forum' started by jmhead, Jul 2, 2007.

  1. jmhead

    Thread Starter New Member

    Jul 2, 2007
    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. beenthere

    Retired Moderator

    Apr 20, 2004
    My guess is that you might need to learn some more electronics so you can start with a better idea of how your circuit is going to operate.

    It is going to take better timing and current control to accelerate the balls than sensing an approach and dumping the full charge of a cap through a coil. If the ball passes through the coil during that discharge, the magnetic field will act to slow it down - perhaps bringing the ball to a stop.

    I would suggest pairs of Hall effect or optical sensors. The first turns on current through the coil to start accelerating the ball, and the second stops current just as the ball gets to the coil.

    Further, I would want to use IGBT's to switch current through the coils.

    Some things that need to be worked out: What is the mass of the balls, what is the size of the coils, and what current through the coils will give you the acceleration you wish? Have you tried any of this experimentally?

    This could be a pretty slick project. If you get it running, it might be possible to start it with several balls on a table top, and hang it vertically once the balls are running. With cylinder magnets, the coils can have current switched to both pull and push the magnets. Stay with it.
  3. jmhead

    Thread Starter New Member

    Jul 2, 2007
    Thanks for the suggestions!
    I probably am going to have to do some preliminary learning projects to do this well. I have tried and know some things that won't work in relation to the electro-magnets, in addition to other research.
    I plan to have the coils around the tube at intervals (the steel ball will serve as the core), but first I'll experiment with linear.
    I want the steel ball to reach high velocities without having to dump lots of energy into the system at once using more gradual acceleration.
    Your information gave me some starting points. I'll have to build some experimental circuits to learn more about switching high voltages and proximity sensing.
    Eventually I want to computerize this with a programmable chip etc. and write a program to maximize the timing efficiency.

    Thanks for your help!
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
    Won't it be difficult to use Hall effect sensors to detect a ball in an area with intensely pulsating magnetic fields? Perhaps optical sensors would be more appropriate.
  5. jmhead

    Thread Starter New Member

    Jul 2, 2007
    Yes, Someone else pointed that out to me as well. I will be exploring optical sensing methods, as inductive methods would be swamped by the propulsion coils' magnetic fields. I hadn't thought of that before it was brought to my attention, but it makes a lot of sense. Otherwise the sensors would be going off on me willy nilly!
  6. mrmeval

    Distinguished Member

    Jun 30, 2006
    There are optically triggered ones. Magnetic is tough because of the exceptionally high field. It tends to swamp out detectors. Now there was one where the builder used parasitic coils to read ... something. And with that they were able to deduce where the ball was. IIRC they were talking exceptionally fast analysis circuits and some pretty sophisticated high speed high energy firing circuits.

    This is just an example of some hobby ones. I used to have some better links...
  7. jmhead

    Thread Starter New Member

    Jul 2, 2007
    Thanks, I will definitely be looking into some coil gun concepts...
    The idea is to gradually introduce energy into the system, rather than dumping it in all at once etc.

    For anyone interested, here is my 3d rendering of my pre-prototype idea:'Circular%20Accelerator%20Project'