Ultra Simple Magnetic Levitator

Want to build a magnetic levitator in under two hours? With a total of 7 parts, including the coil, it just cannot get simpler than what [How-ToDo] shows here! It is not only an extremely simple circuit, it also has the advantage of using only discrete components: a MOSFET, hall effect sensor, diode and two resistors, that’s it.

The circuit works by sensing the position of the levitating magnet, using the hall effect sensor , then turns the coil on and off in response via the MOSFET. The magnet moves upwards when the coil is energized and falls down when it is not. This adjustment is made hundreds of times a second, and the result is that the magnets stays floating in mid air.

This is the kind of project that can make a kid get interested in science: it combines easy construction with visually amazing behavior, and can teach you basic concepts (electromagnetism and basic electronics in this case). Excellent for a school project.

For the more advanced enthusiast, more sophisticated levitator design based on an Atmega8 micro-controller will be of interest.

25 thoughts on “Ultra Simple Magnetic Levitator

  1. Quote: “This adjustment is made hundreds of times a second”

    Not really. The adjustment is made dynamically in real time. The physical oscillation you see (up and down) is just like the oscillation of a pendulum. It’s because gravity is a squared relationship of force and mass (as is the proximity to the electromagnet) and the suspended metal has mass so there is also momentum which is a linear relationship between force and mass.

    1. To be pedantic there is no such thing as real-time. As you zoom the space-time continuum you enter the Quantum domain which is no longer a continuous domain but rather a fuzzy discrete domain.

  2. “it just cannot get simpler than what [How-ToDo] shows here!”

    I’ve read it can be done passively. I think the trick is to have the coil as part of a resonant circuit which is run (and I might get this bit wrong) just above the resonant point. I assume this needs to be done with ferrite to prevent eddy repulsions ruining the effect. I don’t know if this has ever been done with mains AC, needing a signal generator and amplifier is a bit of a cheat, but still, passive post AC power supply and might be possible with mains.

    1. There is no resonance in the electronic circuit. The resonance is the result of the different forces of gravity and momentum created by the mass and velocity of the suspended object.

      The electronics is *not* a tuned circuit (or PID) but it does represent the ‘P’ of ‘PID’. The momentum of the physical mass represents the ‘I’ of ‘PID’. The acceleration of gravity is independent of all else so it has no input to anything than can be evaluated as a ‘PID’. To the result is a ‘PID’ without the ‘D’ that can be tuned by altering the gain of the FET and the mass of the suspended object. So what you are left with in math is a simple reciprocal quadratic and if you were to graph it’s movement you see exactly that.

  3. Just wanted to point out thecircuit uses an A3144 Hall effect switch the output is either on or off so Manuels statement that the circuit adjusts its self 100’s of time a second is more accurate than any of the comments so far.

    If it was an analog output hall device than things were be different ….

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