Basic info on best magnet type for art project needed

[ErwinRedl]

Heya!

I'd like to use 16 electromagnets arranged in a 4x4 grid under a perfectly leveled glass plate to move around a steel ball on the surface of the plate. By turning the 16 magnets ON and OFF in different sequences the ball would roll around in different patterns.

I bought an 11 lbs holding electromagnet lift solenoid from Amazon and used a 1/2 inch E52100 steel ball for a first test. Unfortunately the magnet wasn't strong enough to move the ball even when the ball was just 1/2 inch off horizontally from the magnet.

Looking through different options on Amazon I found different types of electromagnets: a sucked electric lifting magnet electromagnet, a electric lifting magnet electromagnet, the holding electromagnet lift solenoid, etc. Are those basically all the same or are there some essential differences? If there are differences which one would be the best for my application? I also will increase the lifting force, of course.

Are there more suitable balls than the E52100 that are somewhat affordable?

Thank you for your help in advance!

Erwin

 

[IRstuff]

You expect the ball to ROLL? There's nothing described here that will accomplish that. The ball is going to want to slide, not roll.

TTFN
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[ErwinRedl]

Balls actually LOVE to roll! Never seen a sliding ball unless on a slippery surface...
Just tried out the attracting the ball from a very close distance to the magnet. And yes, of course the ball rolls...

Erwin

 

[dgallup]

You are not coupling your magnetic field to your balls efficiently.

How thick is your glass plate? It needs to be as thin as possible

How big are these solenoids? I think you probably need a bigger diameter ball so some of it is hanging over your solenoid pole.

Is there any kind or magnetic return path? The field strength will be much stronger if you can reduce the total reluctance of the magnetic circuit.

Magnets in general hate big gaps, they are very non-linear.

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[asimpson]

Holding electromagnets are usually made for holding flat ferrous matals against their face. Lihe these.

http://www.adamsmagnetic.com/magnetic_assemblies/assem_electromagnets.php

They have a very short range as the field is directed up the outside face and down the centre core. This makes them very strong at holding a coves the face.

The would not attract well distant objects and the ball would tend to go towards the ouside rather than the centre.

You may be better off with just bare solenoid coils without the steel of ferrite core to direct magnetic field:

http://www.marcospecialties.com/pinball-parts/AE-23-800-09

Should be available from electronics or hobbyist.

Wont be as strong but the friction of the rolling on glass should be minimal and there will be a tendency to attract to centre of coil.

The cores direct and enhance the field. Cores in a grid may be magnetised by coils beside them even though they are off and offer a point of attraction to steel ball. Perhaps a slim ferrite just under glass at the centre of coil would help attract ball more accurately.

Magnetic fields weaken hugely with distance. You would have to be sure coil is strong enough to get ball rolling from one grid to next.

I can only suggest trial and error

 

[asimpson]

Not as easy as it first appears:

http://www.youtube.com/watch?v=AhS_2gU1qW0

 

[asimpson]

this one looks good:

http://www.youtube.com/watch?v=5fpp5iCPzd8

 

[MagBen]

This forum is pretty quiet recently, so I try to make some noise.
dgallup summarized the basis well. just to supplement:
1. ball loves to roll when its gravity is the main force to make it move. It will slide when there exists a strong magnetic force, asimpson's last video shows that.
2. lifting electromagnets are normally not ideal for this application, since they confine the flux to themselves, and can hardly attract a ball at a long distance. A solenoid with a flat core would be better for a wide open flux pattern to attract a long distance ball, however, the protruding part of core should not be too long to form a return path with the nearest protruded cores, the flux again is confined to nearby area. Bare solenoid air coil is better in this perspective, but will weaken the field strength
3. A plain low carbon steel ball would be a little better than E52100

 

[MagBen]

air coils with a whole slim steel sheet (the same size as glass) under the glass sounds good to me.