Is it Possible to Create a Large but Low-Powered Electromagnet?

[MarcelloP]

Hi to everyone!

I'm currently working on a University project and one of my crazy ideas needs me to get my hands on a pretty strange electromagnet. the measurements are 40cm by 40cm with a height of 3 to 5 cm (doesnt matter a lot) i don't need this magnet to be very powerful (just enough to keep locked on his area pieces of metal of about 20 to 40 grams), but i can't find anythind on the internet, the only electromagnets i can find with this large of an area are way too powerful and expensive, so i started wondering if it's actually phisically doable. Is it?.

thanks a lot for your answers,

Marcello.

 

[Vanadium 50]

Summary:: I need to buy/build a mildly powerful electromagnet of 40cmx40cm with a 3 to 5cm height and I'm wondering if its actually doable.

i started wondering if it's actually phisically doable. Is it?.

Build, no.

You need to define the magnet better. You have specified the size, but not the strength. "keep locked on his area pieces of metal of about 20 to 40 grams" doesn't tell us much. Among other things, some metals won't be picked up by a magnet at all!

To know if you can build it, you need to know the field strength and where the field lines are supposed to go. If you don't know those things, you can't design it.

Buy, maybe.

There may well be magnets out there that do what you want. but if you can't look through a catalog and determine if a given magnet will work or not, you have the exact same problem.

 

[MarcelloP]

Hi thanks for your answer,
the field lines need to be perpendicoular to the large 40x40 area, as for the strenght I'm not really sure, the usecase is to be able to put ferromagnetic discs on the large surface of the electromagnet and lock them in place hard enough to be touched by a hand without moving.
thanks a lot for you time,
Marcello

 

[Baluncore]

Perhaps you could sketch the magnet to show us where the magnetic poles will be and what polarity they will have. We also need to know the thickness of the discs that will be stuck to the magnet, as it determines the pole separation on the magnet.

Why must it be an electromagnet? Permanent magnets can be used for magnetic chucks that can be turned on / off with a lever or knob.
https://www.ebay.com.au/itm/282969231136

 

[Vanadium 50]

the field lines need to be perpendicoular to the large 40x40 area

Exactly perpendicular? Then no...no magnet will do that.

 

[MarcelloP]

Perhaps you could sketch the magnet to show us where the magnetic poles will be and what polarity they will have. We also need to know the thickness of the discs that will be stuck to the magnet, as it determines the pole separation on the magnet.

Why must it be an electromagnet? Permanent magnets can be used for magnetic chucks that can be turned on / off with a lever or knob.
https://www.ebay.com.au/itm/282969231136

I need it to be an electromagnet in order to be able to switch it on and off with a microcontroller, the thickness of the discs is not a design concern so wathever height works best is fine for me,
i'm also attaching a sketch of what i have in mind,
thanks for your answer,
Marcello

 

[MarcelloP]

Exactly perpendicular? Then no...no magnet will do that.

you are right,
not exactly but enough to keep the discs in place,
thanks,
Marcello

 

[Ibix]

I have a travel chess set - the pieces have magnets in their bases and the board is some magnetic sheet. The pieces stick well enough that they don't go flying when your train goes over the points but not so hard that you can't move them. I have the impression you are trying to build something similar, but with the board being the magnet, and possible to turn off and on the stickyness.

I think that the questions you need to answer before we can help is how much vertical force do you need, how much variation in the vertical force is acceptable, and how much lateral force is acceptable. When you have ball park figures for these things you can develop an idea of how much variation in the magnetic field you can tolerate and start thinking about electromagnet design. Until then you don't really understand the constraints on the design.

 

[MarcelloP]

I have a travel chess set - the pieces have magnets in their bases and the board is some magnetic sheet. The pieces stick well enough that they don't go flying when your train goes over the points but not so hard that you can't move them. I have the impression you are trying to build something similar, but with the board being the magnet, and possible to turn off and on the stickyness.

I think that the questions you need to answer before we can help is how much vertical force do you need, how much variation in the vertical force is acceptable, and how much lateral force is acceptable. When you have ball park figures for these things you can develop an idea of how much variation in the magnetic field you can tolerate and start thinking about electromagnet design. Until then you don't really understand the constraints on the design.

yeah I'm trying to build a smart chessboard where i can turn on and off the stickyness, so for the forces i don't really know, i think that as long as they can withstand some light touching and the lateral forces it would be good.
thank you for you reply,
Marcello

 

[Ibix]

Don't know about cost, but might it be easier to have an electromagnet under each square? It positively locks the pieces in squares and you don't need to worry so much about lateral forces.

 

[hutchphd]

So you need 64 electromagnets on an 8x8 array under the chessboard. You would want to address them with 8+8 lines x-y and provide a means for unlatching the piece in play at the moment.

 

[Baluncore]

the thickness of the discs is not a design concern so wathever height works best is fine for me,
i'm also attaching a sketch of what i have in mind,

You need to specify the range of disc diameters and the range of relative disc thickness before a magnet pole pattern can be selected.

Do you need independent control over 64 individual squares or one master control for the whole board?

What is the source of electric energy that keeps the magnet(s) turned on?

 

[berkeman]

yeah I'm trying to build a smart chessboard where i can turn on and off the stickyness, so for the forces i don't really know, i think that as long as they can withstand some light touching and the lateral forces it would be good.
thank you for you reply,
Marcello

Why not just use the traditional design that @Ibix described? I don't see any advantage to electromagnets at each position. You could still put sensing coils at each square to tell when a piece is moved, but so far I don't see a reason to use electrical energy to hold down the pieces.

 

[hutchphd]

One of my first "hobby" projects at the time of the first PC's (I was unemployed unexpectedly) was to build a rotating robot arm with hand to move chess pieces on a standard board. It worked slowly, painfully, and humorously but I learned a lot and spent about $300. And it did in fact work. Also I wrote software that kept track of where everybody was on the board etc. Kept me sane (nearly) and actually taught me an extraordinary amount (this was circa 1985) about small computing and interfacing.
So the sky is the limit here, but the magnets are easy!