Go Down

### Topic: Solenoid Artistic Function - Magnet and Glass Tube (Read 4324 times)previous topic - next topic

#### liuzengqiang

#15
##### Feb 02, 2013, 12:55 am

I did not posted this therefore I never mentioned any dimensions of anything. The author was. If he wants to make the magnet "float" it needs to be about the same diameter to avoid spinning. By the way I wasn't answering to your post. I think I know now why Grumpy is in your name. Maybe a similar word beginning with J will describe you be better.

Mike,

This member is "brainstorming" in another post regarding specific gravity. He is insistent if not self-indulging at the same time. I am not certain he will understand the magnetic force on a magnetic dipole depends not on magnetic induction, but the gradient of it, which is lacking in the center of the solenoid. Varying current is not going to vary this gradient so much. If you are close to the solenoid opening, then you do have this gradient. You can shoot something with a solenoid but the op wants some control.

#### retrolefty

#16
##### Feb 02, 2013, 01:15 amLast Edit: Feb 02, 2013, 01:18 am by retrolefty Reason: 1
Quote
It would be awesome if this magnet had an led on it too.

Then I guess the magnet will also need a battery added to it to power the led?

I've seen some videos of trying to hold a magnet in mid air and be position controlled and it's pretty hard to just hold the magnet in one steady position, but wanting to be able to change it's position vertically it gets very unstable and difficult if not impossible to control. The magnetic forces involved are not linear so the 'tuning' parameters for the PID control loop are virtually impossible to optimize for smooth control.

Not saying it can't be done on some level, but so far many have failed to demonstrate a perfected example. But perhaps you will be successful anyway as sometimes the most likely to succeed are those that don't know what can't be done.

Lefty

#17
##### Feb 02, 2013, 01:30 am

Mike,

This member is "brainstorming" in another post regarding specific gravity. He is insistent if not self-indulging at the same time. I am not certain he will understand the magnetic force on a magnetic dipole depends not on magnetic induction, but the gradient of it, which is lacking in the center of the solenoid. Varying current is not going to vary this gradient so much. If you are close to the solenoid opening, then you do have this gradient. You can shoot something with a solenoid but the op wants some control.

Sorry to tell you; but you keep having it wrong...
The magnet is a real object with physical dimensions. As a cylinder it has height and volume. Its not a plane. That height makes it occupy a real space inside the solenoid and the top and bottom faces of it are not coincident with the solenoid center as will the ideal physical model you are describing. There is gradient from the top to the bottom face. There is also a force called gravity which will be pulling the magnet down and that will keep it off center if no energy is supplied to stabilize it there. On the other hand I never mentioned the center. That's you own creation; but that's Ok the magnet will stay at any position if enough energy is supplied.

#### liuzengqiang

#18
##### Feb 02, 2013, 01:45 am
Lefty,

Even pid would be difficult to change position. The force is not proportional to distance. If you just want to stabilize constant position then it is doable.

#### PeterH

#19
##### Feb 02, 2013, 01:48 am

This does sound like a high energy project b/c I want the magnet to float.

I think you'll find that's quite hard to achieve, and if you're after that sort of thing I suggest you start off by leaving the glass out of the equation and go for a much smaller system.

#### liuzengqiang

#20
##### Feb 02, 2013, 02:09 am
OP, sorry for diverting so much from your topic. If you want this without a wire pulling, you can consider air flow. Using air flowing from below into a pipe that has openings on both end, small openings, you can have a better control of the the height. That is how flow meters work.

#### encryptor

#21
##### Feb 02, 2013, 07:38 pm
thanks for the ideas.  I think suspension of a magnet spinning in one spot would be easier to perform.  I've seen the magnetic barbell that would spin above a concave base.  However back to the idea of making the magnet float.  What if I just have sections of coiled wire and I power the sections on each side of the magnet with a repelling force.  Then I change which sections repel to get the magnet moving.

#### Grumpy_Mike

#22
##### Feb 02, 2013, 07:51 pm
Suspending a magnet is a lot harder than suspending a magnetic piece of metal. This is because the two inverse laws combine to give a fourth law, which is even harder to control.
Side fields will just flip the magnet over.
Look at diamagnetic material, that is material that is repelled by a magnetic field. Bismuth is one such metal, then use the electro magnet to push against gravity, it is a much more stable set up.

Go Up