0
\$\begingroup\$

Hall-effect magnetic levitation kits are available (cheaply) and require manual assembly. You put electromagnets in the center and you have some board which controls the stability via a Hall sensor. Next you surround it with regular (neodymium) magnets so the “top” floating platform doesn’t flip sideways.

How Hall sensors work is a mystery to me, but my main goal to try to stack 2 or more of the “bottom” platforms vertically. Can it be done? It’s OK if there is a wire running from the lower to the upper platform.

Ultimately, I am trying to create a levitating (wobbling) scarecrow, with three layers by putting a coverall dress with head and arms on top of these platforms.

This video shows the basic design.

enter image description here Image from the same source as the video link.

\$\endgroup\$
14
  • 2
    \$\begingroup\$ 'Can it be done?' is too vague a question to ask. The answer is usually yes, if you can handle sufficient power (read cooling!) to create the levitation fields for the lowest stack, which will be supporting the weight of the stacks above. Such a stack would have the levels increase in size downwards exponentially, as they had to hold all the stages above. There are easier ways to make a wobbling scarecrow. Making one stage is usually enough for most experimenters, and a vital first step for you to complete before contemplating two or three levels. \$\endgroup\$
    – Neil_UK
    Commented Feb 4, 2023 at 15:37
  • \$\begingroup\$ Thanks. Can the same be done on the Moon, without connecting wire, since electricity can jump the distance of magnetic field in Vacuum? This what it’s really for herox.com/ExpOnMoon \$\endgroup\$
    – estinamir
    Commented Feb 4, 2023 at 15:49
  • 1
    \$\begingroup\$ Vacuum is an insulator - current doesn't flow through it. What will levitating a wobbly scarecrow in vacuum on the Moon prove or demonstrate about physics? \$\endgroup\$
    – JRE
    Commented Feb 4, 2023 at 15:53
  • 1
    \$\begingroup\$ The power needed is a function of the weight to be levitated. How much will the lower gravity of the Moon matter? It should reduce the required power somewhat - I don't know by how much. It will also change the requirements on the control circuit - possibly to the point that it can't control the levitator any more. It seems to me that you'd have to redesign the control circuit and the levitator coils to account for the lower weight. \$\endgroup\$
    – JRE
    Commented Feb 4, 2023 at 16:09
  • 1
    \$\begingroup\$ Read the answers to that question. Vacuum doesn't conduct electricity. You can make electricity flow in a vacuum tube by providing free electrons. You heat a filament made of a special metal, and the electrons spread out and can be made to flow from one electrode to another. Doing that intentionally in an open vacuum is going to be very difficult. \$\endgroup\$
    – JRE
    Commented Feb 4, 2023 at 16:34

1 Answer 1

1
\$\begingroup\$

Theoretically yes, sure, at least to the extent that you're not exceeding the lifting capability of any of the devices (presumably you're mostly limited by the bottom one, or you'll need to make ones that get ever smaller as they progress upward).

Practically oh, my, that's going to be a challenge.

First, yes, you can have wires connecting the floating bits -- why not? It may be a good idea to have some sort of a cage that restrains how much they can move, so that in the event of power loss or other failure the bits don't jump around and either break themselves or get lost. You'll want to source really flexible wire, and if your first try lives long enough to break from wire fatigue, you'll want to get some wire that's made for continuous flexing (it's out there). Buy that wire new, or harvest it out of some device that already has it, like a printer.

Second, you'll need to make sure that your base has enough raw lifting power to lift the higher-up bits.

Third, and the biggest part of the challenge, is that the various bits will interact. Getting the first part working, where you're just floating a magnet in the air with a dead load on it, will be a challenge. Then you'll need to replace that dead load with a load that's not only live, but is responsive to how it's base pushes on it.

Think about this -- if you hold that floating apple gizmo in your hand, and lift your hand suddenly, it'll push back, but it'll do so after a bit of a delay. That's the load that the base will see when you put the second layer onto your assembly.

I can almost guarantee that if you just design two independent levitators, get them tuned up, then try floating the second stage on the first, that the assembly will be dynamically unstable. This effort will either take a whole lot of messing around to work right, or it'll take some advanced control techniques (I'd start by modeling the whole mess in state-space), or possibly both.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.