What’s inside the magnetic levitator?
March 31, 2021 10:49 AM   Subscribe

What is inside this four kilo magnetic levitation device? https://virtualongroup.com/product/levitation-display-4-kg/
posted by varion to Science & Nature (5 answers total)
If it's anything like this, it's an electromagnetic base and a metal disc that floats on top of it.
posted by emelenjr at 11:29 AM on March 31, 2021 [1 favorite]

I found a link to the manual, which says that there's an optical sensor in the base and a reflective dot on the bottom of the floating disc.

There's a warning that "In the event that the power is interrupted, the carrier ring will land on the levitation unit with great force," so it sounds like there are permanent magnets in the base and the carrier ring to keep it centered and an optical sensor and electromagnet to keep the ring at constant height.
posted by ectabo at 11:46 AM on March 31, 2021 [1 favorite]

Basically, magnets in the platform, adjustable magnets in the base, and electronics that track the platform and adjust the magnets in the base to keep it from flying away.

It turns out that you can't use static (unchanging) magnets to make an object hover in space. The situation is inherently unstable, like balancing a broom on the tip of its handle; if you don't do it perfectly, it'll fall over.

But if you track what the platform is doing at all times, and adjust the magnetic field in the base to compensate it, you can nudge it back into position at all times. This is like balancing a broom by its handle on your finger. You can keep it up indefinitely by adjusting the position of your hand; if it starts to more one way, you move your hand so it gets pushed back into place.

So the optical sensor is continually tracking where the platform is, and adjusting the magnetic field to nudge the platform back to center.
posted by Johnny Assay at 11:56 AM on March 31, 2021 [5 favorites]

Response by poster: I am wondering what the permanent magnet layout looks like inside the ring.
I had a hunch it had to be a machine control situation for the electro magnets.
Thanks everyone for helping!
posted by varion at 12:10 PM on March 31, 2021

Best answer: I agree with the comments above. If the insides aren't made by these people, they're probably very similar in design. Here's a reasonably closeup photo of some of the inside.

Exactly how they do the position sensing isn't entirely obvious. My best guess would be that behind the black plastic panel on the base are 4 (or any number more than 3) individual light sensors, perhaps canted a bit outward from each other, and an IR diode emitting light. By comparing the amplitude in each sensor, they can figure out exactly where the reflective dot is in space. To avoid interference from room light, they probably strobe the source at a high frequency and filter for that signal. (The closeup photo of what may be a different product suggests that isn't unlikely.)
posted by eotvos at 12:18 PM on March 31, 2021 [4 favorites]

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