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Should I bother making an electromagnet or just use neodymium for my motor?

  1. Nov 8, 2011 #1
    Okay, so I need to make a DC motor for my physics assie and Im aiming to use an electromagnet to magnetise iron sheets shaped into the shape of a radial magnet. Would this even work? o_O Or would neodymium be better for its size? How large would the electromagnet have to be in order to beat the strength of neodymium?

    Also, can someone tell me how/if electricity pass through the armature? xD I think I wasn't paying attention... :S

    [EDIT: Actually, let me reword that. Do the wires of the poles connect to anything?]

    On second thought, can someone tell me how to wire a DC motor and what materials to use for each part? xD Given that the parts I'll be using are: electromagnet, carbon brushes, magnet wire, bolts, magnetised iron sheets, split-ring commutator (120º splits), axle, variable power supply (2-12V)...thats all I can remember from the top of my head :S

    Oh yeah, does the axle have to be conductive? Thanks, help will be much appreciated :)
     
    Last edited: Nov 8, 2011
  2. jcsd
  3. Nov 8, 2011 #2

    sophiecentaur

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    best to look at an animated sequence of a DC motor working. Google will give you dozens.

    A good permanent magnet will work far better than any electromagnet you or I could possibly wind. Use an iron 'yoke' attached to the magnet to get two poles to sit on either side of your armature coil. (also see the diagrams).

    Your main trouble will be to get a convincing commutator arrangement unless you've been supplied with one.
     
  4. Nov 9, 2011 #3
    Really? Thats a bummer... :S but would a properly wound electromagnet be stronger? For example, an electromagnet with an iron core the size of gluestick and approx 1000 coils (properly wound). Cuz I was planning to wind it like this guy, but probably using a dremel.
    http://www.youtube.com/watch?v=Mjq2jPJ_7bc&list=FLEQSiMdK1O8x9_yX6QK24Vg&index=1&feature=plpp_video

    ..or this that not proper either.... lol

    I really want to use an electromagnet since everyone in my class is using permanent magnets, and we get marks for originality as well. ...or is that just a pipe dream? :S

    As for the commutator, I'm gonna get small copper piping and cut it to length, mark the 120º segments/angles on a piece of paper, centre the copper pipe on the markings, and mark the segment splits on the pipe using a marker. I would then cut it using a dremel equipped with a rotary cutting disk.

    Also, would the thickness of the sheet iron affect the strength of the magnetic field it creates? [STRIKE]I'm[/STRIKE] I was planning to get 1.5mm sheet metal. Would it have to be thicker?

    Oh yeah, does anyone know what everyday devices I can yank a pair of carbon brushes from?
     
    Last edited: Nov 9, 2011
  5. Nov 9, 2011 #4

    sophiecentaur

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    Most / all motors use permanent magnets these days for a good reason. But, for brownie points, a wound field magnet could be good. You will need to be very neat and use the right gauge of wire to fit as much on as poss but still take the current. (Don't ask me, though.)
    AFAIK, most commutators have an even number of segments. Why go for three? Where would the brushes go?
     
    Last edited: Nov 9, 2011
  6. Nov 9, 2011 #5
    Yeah I think I'll just go for the perma mag. Ceebs beating iron into shape now lmao.

    As for the commutator - I thought my textbook said it was better, turned out it was talking about the armature xD. My bad. But heck, this guy did it and his was the best I saw on youtube lol.


    He said: "Don't go with 4 rings, just 3. (You need to match the number of rings with the number of coils, as it's the rings which transfer the current)."

    I think imma stick with 3 rings, and if it doesn't work I'll go down to 2 :) Thanks for responding btw, you're the only one that has so far :D
     
    Last edited by a moderator: Sep 25, 2014
  7. Nov 9, 2011 #6

    sophiecentaur

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    Start with a permanent magnet and wind one later if you have time?
    That 3segment commutator seems to go well.
     
  8. Nov 9, 2011 #7
    Would using them simultaneously work? :D perma mags could be the primary magnetic field at lower voltages, since the electromag wouldn't be as strong. And at higher voltages, the electromag would be able to stand on its own. :D
     
  9. Nov 9, 2011 #8

    sophiecentaur

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    You need to consider the 'magnetic circuit' layout. A strong permanent bar with two iron arms, making a U shape with the armature fitting snugly in between will provide the strongest field you can get.
    Just try winding an electromagnetic like the one in the YouTube movie and compare its lifting power with that of the strongest magnet you can get on line. I don't think there could be any comparison. Also, an electromagnetic will flatten your battery.
     
  10. Nov 9, 2011 #9
    hmm I'm finding it hard to picture that for some reason o_O

    I'm using a power supply not a battery so it's fine :D
     
  11. Nov 10, 2011 #10

    sophiecentaur

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    You won't find a horseshoe shaped modern magnet, which would be ideal if the poles could sit either side of the armature. So you can get the same effect with a short bar magnet and fabricate the horseshoe shape by extending each pole with iron at right angles to the NS line of your magnet. Ideally you would have an iron core for the armature. (See a scalextric or drill motor). This would produce a better field around your armature coils , giving more torque. Iron nails (painted for insulation) would eliminate eddy currents like laminations do.
     
  12. Nov 19, 2013 #11
    The magnet used in the video was the primary winding from the transformer in a microwave
     
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