H-bridge for levitation

Discussion in 'The Projects Forum' started by csy, Feb 8, 2010.

  1. csy

    Thread Starter New Member

    Feb 8, 2010
    hi..im doing my project on levitation too.
    may i know actually how is the Hbridge(LM18201) function in this system?
    is it just changing the direction of current that will cause the polarity of electromagnet to change?or any other function?
    thanks ^^
  2. bertus


    Apr 5, 2008
    Greetings! And welcome to AAC!

    I've moved your post into its own thread, where it will draw more responses:
    Please refrain from "hijacking" existing threads with tangent or off-topic questions. You can create new threads for new questions using the "New Thread" button on the upper left of the page.

  3. JDT

    Well-Known Member

    Feb 12, 2009
    When you say "Magnetic Levitation System" is your object just a lump of iron suspended in the magnetic field? Or is your object itself a magnet?

    What I'm trying to say here is: Attraction or repulsion?

    What distance away from the solenoid poles are you hoping it will be?

    Either way, do not need an H bridge because the current in your solenoid does not need to reverse. Magnetic bearings on rotating machines usually have 4 solenoids all attracting, at 90deg spacing. The shaft is laminated iron, not itself magnetic.

    The distance sensor needs to be able to produce an analog output v. distance. Optical sensors are generally make/break types (unless you have an expensive laser reflective type). Capacitive or inductive sensors can be used. These generally use an oscillator where the frequency changes with distance. A hall-effect device can be used with a separate permanent magnetic circuit. This will measure the strength of the magnetic field as the air gap changes.

    BTW The current in the solenoid is usually controlled by PWM, so the transistor does not dissipate very much power. Because the solenoid is inductive, use a free-wheeling diode to maintain the solenoid current when the transistor is off. The proportional controlling system uses a PID system to obtain stability. Could be some interesting maths here!
    Last edited: Feb 8, 2010
  4. BMorse

    AAC Fanatic!

    Sep 26, 2009

    Take a look at this, I believe this is what the op is building....
    View attachment LMD18201T Maglev.pdf
  5. csy

    Thread Starter New Member

    Feb 8, 2010
    The object is a magnetic disc on top of a ping pong.i need to use a potentiometer to adjust the ball position. ball going up or down is depends on me..
    is it related to the attraction/repulsion force? or just the intensity of the electromagnetic field?

    thanks for sharing..