The lion kingdom started toying with levitators in 2006, with just levitating a hard drive magnet.

Although the circuit board has been reworked, it's manely the same board that was fabricated in Jan 2006.

The electromagnet is manely unchanged from when it was wound in Feb 2006.

Its original purpose was to clean contact lenses.  Helas, it took going through the ordeal to realize it didn't work.  The contact lenses needed a more aggressive shaking & heating.  The electromagnet couldn't switch fast enough to provide very aggressive shaking.

Since then, it has been used for temporary artwork.

A microcontroller pulses the electromagnet.  Between the pulses, it reads 2 hall effect sensors flanking the electromagnet to determine the object height.  2 hall effect sensors connected to a voltage divider give an average reading which is more accurate than a single hall effect sensor.

It uses a BJT instead of a MOSFET because BJTs were more resistant to back EMF.  It only pulls.  If the object gets too close to the magnet, it has no way to repell it.  Fortunately, it never gets too high in normal use.  A full H bridge for bidirectional magnetism would drop the voltage too much & be overly complicated for a case that never happens.

WISHLIST:

The magnet gets too hot, even with a cooling fan.  It needs a shroud to redirect more cooling air around it.  A lighter model made of PETG is needed.  The PLA model is heavy because it's more fragile.  

A way to automatically rotate the model & light it is needed.  Currently, it always points toward magnetic north.

Stoppers inside the model to align the magnet.  Division line inside a ring line.  Better tabs for farstening it.