Large Magnetic Levitator

2021-12-28

[public] 319K views, 10.0K likes, dislikes audio only

Update 7/21/2022: STL files for the levitator have been uploaded

https://www.thingiverse.com/thing:5438518

In this video I'm going to show how to build a attractive-type

("hanging") magnetic levitator. This is the easiest type of

levitator to build, because the electromagnet only operates with

one polarity, and only requires a single sensor and transistor

to operate. A repulsion-type levitator requires sensors for X

and Y position, and 4 coils with their own individual H-bridge

drivers.

The electromagnet is built from a 2" x 6" solid steel cylinder

as a core, and 600 turns of 16-gauge wire. The longest distance

I've managed to attract a large N52 magnet was about 9 inches

using 20 amps of current, but the coil heats up very fast with

that much current.

In this video, the magnets shown are hovering just outside the

region where the ferromagnetic attraction to the core would

overcome gravity, so the levitator takes very little power.

Levitating a 3-lb steel wrench only consumed ~5W, and a 30mm N52

magnet by itself consumes about 1W levitating a distance of

about 2" below the electromagnet.

The limiting factor in the levitation distance is the resolution

of the hall-effect sensor, which has an output of 20 mV/mT. Once

a 30mm N52 magnet goes beyond ~2 inches from the sensor, the

output is too small to be distinguished against the idle voltage

of the sensor. Changing to a more sensitive hall effect sensor

would increase the levitation range dramatically, but also

consume exponentially more power.

There is no microcontroller driving the electromagnet. The coil

is energized by a MOSFET that has its gate connected to the

output of an LM324 acting as a comparator. One input to the

LM324 is the hall effect sensor output, and the other input is a

reference voltage set by a potentiometer. I've found that it's

neccesary to make slight adjustments to the reference voltage

when changing to different magnets / loads on a particular

magnet.

Some of the key components used in this build:

-EQ733L Hall Effect Sensor

-LM324 Op-Amp

-IRF7545 MOSFET

-LM7805 5V linear regulator

-6.6 mF / 1 mH input filter

Some other figures:

-12-18V input voltage

-50-500 mA of current draw @ 12V depending on the load

-9.5 mH / 1.3 Ohm electromagnet (600 turns of 16 AWG)

-Magnets used in this video are 30x5 N52 magnets stacked

together and 2x 40x20 N52 magnets stacked together

Music used:

Serge Pavkin - Fractal

Serge Pavkin - Tech Research

Serge Pavkin - Intergalactic

Alexander Nakarada - Space Ambience