Magnetism / Electromagnet Levitation question

[stevanlieberman]

TL;DR Summary

Can one support one magnet so it does not move hanging below an electromagnetic strip say a foot away from the strip so it does not fall and is there a formula for this?

I can make one magnet ‘leap’ up to another magnet and I can push one magnet away with another magnet but can’t figure out how to do both at the same time so the first magnet can essentially be suspended in mid air with the controlling magnet being above. Any thoughts are appreciated. Thanks

 

[hutchphd]

Earnshaw's theorem proved conclusively that it is not possible to levitate stably using only static, macroscopic, paramagnetic fields

 

[DaveE]

It's unstable, like a pencil standing on it's point. The more the magnet falls, the less lifting force there is. You can do it with position sensing and feedback control of the field strength.

You can do the reverse with repulsion from magnets below opposing gravity, which can be passive. You'll need multiple magnets or a complex structure to keep the magnet in the center.

Like these:
https://www.maglev.net/best-maglev-toys-and-gadgets

 

[DaveE]

It's unstable, like a pencil standing on it's point. The more the magnet falls, the less lifting force there is. You can do it with position sensing and feedback control of the field strength.

You also do the reverse with repulsion from magnets below opposing gravity, which can be passive. You'll need multiple magnets or a complex structure to keep the magnet in the center.

Like these:
https://www.maglev.net/best-maglev-toys-and-gadgets

Wait. Now I'm not so sure. Magnetic levitation is more complicated than I thought. For example, you need some force to keep the levitated magnet from rolling over.

Perhaps an experiment tonight...

 

[stevanlieberman]

It says “ levitation A magnet or properly assembled array of magnets can be stably levitated against gravity when gyroscopically stabilized by spinning it in a toroidal field created by a base ring of magnet(s)”

But all of the devices cited do it from the bottom up. I am wondering if it can be done with the gyroscopic device is above the thing being levitated?

 

[stevanlieberman]

Oh they have one from above. How are they moving the electricity into the bulb? Thanks

 

[DaveE]

Oh they have one from above. How are they moving the electricity into the bulb? Thanks

The same way your phone charges wirelessly. You don't have to have wires to transfer energy with electromagnetism. If you did your radio wouldn't work.

 

[Tom.G]

http://www.google.com/search?hl=en&source=hp&biw=&bih=&q=levitating+globe+magnetic

Many years ago, I built one with an electromagnet above a globe of the Moon (about 6 inches diameter). You could start the Moon spinning and with no friction it would keep going.

The fun part was I put a noise-maker circuit inside the Moon globe connected to a tilt sensor. During a demonstration, I would invite someone to take the Moon out and then replace it. Not knowing what to do, they would often freeze when the noise-maker started!

I used a beam of light and a large (1.25 inches, 3.2cm. square) photocell to sense the vertical position of the globe. The electromagnet was wound with five pounds of 14 gauge (AWG) wire (about 400ft., 120m.).

The control circuit was a full wave bridge rectifier with phase control, fed from the wall power outlet (same approach as a lamp dimmer, but they feed AC to the lamp). Feeding DC to the electromagnet allowed a much higher current, and stronger field, than AC would have.

Have Fun!
Tom

 

[stevanlieberman]

I would have loved to have seen that. My goal is to create a light fixture that has what looks like spinning balls of light hanging a foot from the ceiling and every 5 feet across a 30 foot room. It sounds like your moo globe did everything I am trying to do. Did you ever write down the design? Thanks

 

[Tom.G]

@stevanlieberman

I think I still have the main parts around here somewhere.

But you must realize that the position sensing is a light shining on a photocell and the suspended globe blocks part of the the light to the photocell. That means you will have posts hanging from the ceiling for each suspended item. (or a significant alignment problem if the lights and sensors are on walls 15 feet away)

Also the spacing between the electromagnet and the globe was around 6 inches (15cm), and the electromagnet ran too hot for continuous operation. Of course a globe that weighed less or was closer to the electromagnet would decrease the current and the temperature rise.

How are you planning to get power to the lamps?

Still Interested?
Are you comfortable and experienced working with powerline voltages?

Cheers,
Tom

 

[artis]

You can have a levitating object with permanent fields you just need the object to be spinning like the spinning top so that the gyro effect balances the unstable magnetic positioning.
Since this has no friction I'm sure a small induction type stator coil could be used to make the object spin continually or something like that , maybe even air blowing on the object