Toroidal Electromagnet

mak toroidal shape coil made from wire of any magnetic material or silicon steel, it will work as a coil and core both.direction of magnetic filed will be around the coil.

It can work even with normal coper wire but strength of filed is much low in that case.

Hi Rakesh (I hope that is your first name!! Sorry if its not.),

as English is not your first language, (or your keyboard is giving you problems!), although I can easily (mostly anyway!) understand your misspelt words, but other people who are CR4 members, and like you do not have English as a first language, might get problems.

So please be so kind as to use the built in spell checker to make sure that even if the grammar is not good, at least the words are correctly spelled....it makes your input far more attractive too....

If its any consolation, I use it to check my spelling as well, even though I was born in the UK....my spelling is far from perfect!! I am not alone either....

You can be taken more seriously when you take this simple easy step.

If you need any further help in this area, please be so kind as to ask me, or any other member for help, its not a problem.......

Thank you Andy,

Thanks for your kind support, I shell make my best effort to improve on my write-up in future.

You are welcome to send any suggestion to my inbox.

Regards,

I tried wrapping a coil of magnetic wire around a steel core and hooked it up to a dc power source but the ring could not attract anything. But if I left a large space open that part attracted metal objects. Any ideas???

You can think of the iron ring as a magnetic circuit, and iron presents a low resistance to magnetic flux. The air gap presents a high resistance to magnetic flux. The amount of energy stored in the magnetic field is lowest when the field is inside the iron. Any piece of iron in the vicinity of the air gap is attracted because the field concentrates inside that piece of iron, reducing the energy of the field. The reduction of energy in the field is converted to a force attracting the piece of iron.

Stephen,

I can't see how this can work. The reason Toroids are used in transformers is to maximise the efficiency of the Electromagnetic field by containing it within the toroid.

The only possible way I can see it working is something along these lines.

Someone with more knowledge than me may have other options or just laugh at this one.

Either way, I learn something.

Regards,
Sapper.

I must admit that I haven't fully understood what you are trying to achieve, but would the following be easier? It would give a North say on the left and a south pole on the right, depending upon the polarity of the applied DC.

The more turns, the stronger the magnet. The higher the voltage = higher current = stronger magnet.

Please be aware that a ring, magentized at right angles to what I have shown (like a normal toroidal transformer) the lines of force will mostly remain in the ring - which is what is wanted and why toroidal transformers radiate very little magnetism and are remarkably efficient at the same time.....all good qualities for a transformer, but not if you want to pick things up with a magnet.

A normal "Horse shoe" magnet is basically a toroidal ring with a cut out to "expose" the magnetic field......

What I have written here is I feel magnetically correct, but whether it is any help for you in your "Quest" I cannot say.....i need to understand your wishes better.....

I forgot my sketch, sorry, here it is!!

I know it can be done because in my other thread emc_c said to leave space in between the coils. This worked to a certain extent. The field was not strong at all. I am now wondering if criss-crossing two wires to make a criss-cross coil and connecting them together or if wrapping it with magnetic tape then the magnetic wire coil hooked up to the dc power supply, or if coiling a good number of windings on two sides of the ring and leaving the other two sides clear would make the field I want? Which was shown in my other thread by emc_c picture. I tried emc_c's idea of leaving space between the windings and I hooked it up to a 12 v 3amp dc power supply and it did not attract any metal objects. I am using a steel ring washer as my core. Any ideas as to what I did wrong with emc_c's idea or any ideas on how to create a toroid with an external magnetic field? I do not know what core is used or what magnetic wire was used in emc_c's idea. I am using a steel core and magnetic wire from Radio Shack, the magnetic wire that comes in a pack of three and three different colors, green, red, and clear. Do I need to change any of this to make emc_c's idea or any other idea as to how to make a toroid with an external magnetic field that looks like and is as strong as a bar magnet's field and that attracts metal objects?

Thanks for the help.

here is a link to the idea emc_c had:

http://cr4.globalspec.com/comment/351134/Re-Magnetizing-a-Steel-Ring

A coil by its current path will generate an axial magnetic field, stronger in the coil since magnetic lines / surface unit are denser and weaker out side since magnetic lines spread radially.

Either you do what I explained or you place a series of short coils "radially" and you obtain a series of magnetic loops with field vector in radial direction. The bigger space between coils goes in the same direction but is not as strong for the different reasons how a magnetic field builds up.

It is impossible to produce a uniform radial field in an annular shape (toroid), but it is possible to create individual magnetic poles. You might take a look at the eight-pole magnet here:

http://www.shinetsu-rare-earth-magnet.jp/e/circuit/radial.html - sorry, link no longer available

If you want to create a multi-pole electromagnet in this configuration, you can use the wound stator of a polyphase AC motor as a model.

would wrapping magnetic tape around the ring and then coil the magnetic wire around the ring with spaces in between the coils create the field like emc_c's picture shows??? thanks.

Please do not misunderstand me the question is: do you want to obtain a radial flux from the ring or do you only want to follow a recommendation?

If you read all comments you find same indications. If you apply a "majority voting" you have the answer.

The magnetic field generated by a current in a conductor is a circular one with the center on the conductor. If you consider 2 parallel conductors (as in a coil since the turns are parallel to each other) between two turns the two magnetic fields have CONTRARY directions so that a deduction occurs this is the reason two parallel conductors attract each other. Make a sketch take a book where the basics of magnetics are described and think it over.

Hi Steph,

The type of core you need is like a speaker core structure without the permanent magnet i.e, a cup with a center pole sticking up in the middle about same hight as the cup's edge.

Don't forget to pay attention to the crossection areas between the poles as they should be maintained evenly!

The coil inside wound around the center pole and it should be slightly shorter than the lenght of the poles. You can also put a dust washer (made from non-magnetic material) slips tightly over the center pole and inside the ring pole.

Naturally, your magnetic field is between the center pole and the ring pole and you will have a little scatter outward as well but not that much.

You should use a soft iron (low carbon) as a pole material to reduce magnetic remanence.

Take a hollow cylinder and wrap the windings around it

Would you be more specific what you're after?

Is it a ring shaped magnet (like a speaker magnet) or a toroid magnet?

They are not the same in any way you know, and least of all the way the windings are applied on them.

I broke one of my old speaker to get the magnet out of it but I could not cut it or change it in any way since it is ceramic. I just want a ring shaped electromagnet with an external magnetic field, which is a field outside of the core. When you wind magnet wire around a ring core the magnetic field is restriced inside the coils so it will not attract any metal object which means there isnt any external magnetic field like ampre's law predicts. I want the external magnetic field. Would criss crossing the magnet wire as I coil it or wrapping magnet tape around the ring then winding magnetic wire around the ring, or wind magnet wire so there are gaps in between each coil ( which I tried but it would not attract anything like a magnet should) or winding two coils of magnet wire around the ring attaching them together or winding two coils or one coil so there are two big spaces between the coils create the field I want?? Refer to emc_c post, linked in one of my replies, to see the field I am trying to duplicate.

Thanks for all of the help.

I showed you a sketch, in a previous post of how to wire it for N at one end and S at the other......was that not what you wanted?

Your way of explaining what you want is as strange as the magnet you wanna create.

First of all the term "toroid" is not even correct to use here because, as I gather, you want a ring-shaped one with open ends, and not a closed shaped electromagnet, like the toroid, however, dimensions would be important to be able to help you better.

Criss-cross winding is only recd if you not using a former to support the coil with and your wire's thin.

What size ring magnet you're after both in diameter & length?

Further what do you mean - "When you wind magnet wire around a ring core the magnetic field is restricted inside the coils" - not experiencing the it in the center of the ring?

You definitely won't, especially if your coil isn't powerful enough to be able to match the strength of a speaker magnet!

Also, how many coils are you talking about here, one or more placed on this ring of yours?

Last attempt to suggest you a solution.

You can use the construction on the right which offers the radial magnetic flows as you wish but ATTENTION if coil No1 is used the magnetic fields have the directions indicated by arrows (or the other way around depending on current direction in the coil). In a ring magnet as on the left sketch the arrows have on both sides same direction. You can use one or two coils as you wish. The limit is set by saturation of middle cylinder.

In several comments the speaker magnet was mentioned. I used such magnets BUT they are NOT radially magnetized rings, usually they have a ring magnet AXIALLY magnetized and obtain, as in my sketch, the radial magnetic field with polar pieces.

May I suggest that when you get a solution proposal from which ever participant look also in an other source since many of us participate also where they do not master the problem enough and give oppinions not counsels. One of the participants wrote that for important questions the answers have to be considered with especially great care and not blindly followed.

Geeeeeehhh!!! In my modest opinion this guy is attempting to building a -Flying Saucer- I guess! Thinks about it! Good Idea after all pal'.... Now the trick will be how to make those magnetical waves counteract each other in order to make the thing levitate. Fun stuff! This thing migth be make by having the internal magnetical waves figth each other to create an strong magnetics turbulences that lift that Puppy-Up.

I believe this will be made out by funneling such magnetics propulsion waves down like a turbo jet turbine but in this case of course this will be like an invisible stream force of waves existing the electromagnetic engine full force up up in the air. Then once upthere the apparatus will keep on generating it's own power by solar power cells to supply the electromagnetical engine constantly 24/7. Awesone, congratulations in such invention and don't forget an strong communication system to stay in touch as well.

StarTrek Time,

MC

It seems you are looking for a tube with N at one end and S at the other. The diagram from Andy in Germany is what you need. The tube should be of a non-magnetic material. If you wind your coil over a steel core the core will channel the magnetic field. Use instead a tube of aluminium, brass or plastic. Use closely packed parallel turns on the coil as the force varies as amps x turns.

See the thread about solenoids which is closely related to this thread http://cr4.globalspec.com/thread/34808#comment362788

Chas

StephenD420,

Welcome to the confusing world of three dimensional field design. Your first task to craft a specific magnetic field geometry is to specify the geometry you wish to generate. Using a washer like toroid core permits two types of magnetic field geometry, literally one that resides solely inside the core (the one you apparently don't want) and one that the north and south poles reside on the flat surfaces of the washer. Remember also that the lines of flux create a closed loop from one pole to another.

Now to produce a field with a solenoid you apply the right hand rule. Stick your right thumb out like you were trying to hitch a ride. The direction of your thumb is the direction of the magnetic field you wish to produce. Your curled fingers point the direction that a current must flow to produce a magnetic field inside a solenoid in that direction. A simple examination will show that your solenoid's magnetic field will be larger inside the coil than outside. You should now notice that your choice of a toroid magnet forces your wires to wrap around the smallest dimension of your toroid. If you stretch your washer into a pipe (yes, I know they are both toroids) then you can get many more turns wrapped along the pipe's length, for when the right hand rule is followed for each wire in the loop the field of each wire segment will add toward a larger field. If you attempt to add a solenoid inside the toroid to "get more turns in," then you must remember that the field outside the solenoid will be opposite the field inside the solenoid. So the current inside the toroid should rotate opposite the current outside the toroid.

I hope this helps you.

Looks like we have hade some difficulty understanding what you need. You have received some good suggestions of magnetic fields "outside the toroid" which provide axial flux lines with poles the the top and bottom (posts 3,5,12,14,22) and some which provide radial flux lines with poles on the inside and outside (posts 6,19). If neither of these suit your needs, you need to provide a sketch of what you need. Remember that the attractive forces will be in the same direction as the flux lines. Help us help you.

Take a look at this Google for images of toroidal flux and see if that helps.