Arduino Forum

Community => Bar Sport => Topic started by: ardly on Feb 16, 2020, 11:12 pm

Title: How does magnetically suspended globe work
Post by: ardly on Feb 16, 2020, 11:12 pm
I have a globe which floats supended in the air by magnetism beneath an arm, how does it work?

The arm contains a permanent magnet because with power to the device off the globe will stick to the arm. With the power off it is impossible to get the globe to float beneath the arm.

With the power on you can carefully position the globe beneath the arm, releasing it when you feel no upwards force, and it will float there.

If you turn the power off while the globe is floating it will drop.
Title: Re: How does magnetically suspended globe work
Post by: MAS3 on Feb 17, 2020, 01:09 am
Hi.

I think this has been explained a lot already.
Enter magnetic levitation (https://duckduckgo.com/?q=magnetic+levitation&t=h_&ia=web) in your favourite search engine, and lots of links to sites trying to explain this will appear.
Title: Re: How does magnetically suspended globe work
Post by: ardly on Feb 18, 2020, 06:28 pm
Hi.

I think this has been explained a lot already.
Enter magnetic levitation (https://duckduckgo.com/?q=magnetic+levitation&t=h_&ia=web) in your favourite search engine, and lots of links to sites trying to explain this will appear.
You are right I was being a bit lazy, but I thought people in the Bar might have some interesting takes on the problem.

After your post I did do a search and there are lots of sites "trying" to explain how to do it. Most try to balance one magnet above another one.  My globe is metalic and it hangs below a permanent magnet.

There was one blog with an 8 minute video where the person seemed to know what he was doing, though he was trying to suspend a magnet below an electromagnet (not quite what my globe does). He came up with a circuit, made a PCB with a Hall Effect sensor and an electromagnet and almost solved it. His magnet however oscillated a lot would not float and he gave up!

It is quite easy to suspend my globe and once suspended there are no perceptible oscillations, it just hangs there.

I guess the permanent magnet supports most of the weight of the globe and an electromagnet is then used for fine balance, probably with a Hall Effect sensor determining if the globe is rising or falling. I imagine it uses a discrete circuit for control but I am still unclear how this is achieved with no discernible movement.
Title: Re: How does magnetically suspended globe work
Post by: Johan_Ha on Feb 18, 2020, 09:44 pm
PID control?
Title: Re: How does magnetically suspended globe work
Post by: GoForSmoke on Feb 19, 2020, 05:24 pm
Perhaps when power is on the electric field of the globe is boosted just enough for the magnet to hold.

Intuition tells me there should be a way to make the globe spin (charged object in magnetic field) but maybe it would whirl as well.