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Making an electromagnet...

Discussion in 'Hobby Electronics' started by DD, Feb 26, 2007.

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  1. DD

    DD Guest

    I have promised to make an electro magnet/solenoid for my grandson. Even
    though I used to make them when I was a kid, I am blowed if I can now
    get one to work effectively. Currently I have egg on my face! I took
    some wire from a transformer which is about 0.5mm dia and I am using a
    ferrite core.
    I have no idea what the wire gauge should be, nor the number of turns or
    the required current to give a magnet that will lift more than a couple
    of paper clips!
    Can anyone help me?

    DD
     
  2. Bruce Varley

    Bruce Varley Guest

    You're better off with a closed magnetic path if you can find something
    magnetic with the correct shape, ie. U shaped with flag parallel ends, the
    coil wound round the middle, and picking up something that closes the gap
    like an iron plate or bar. A wide cross section and not-too-long arrangement
    will work better.

    Since you're not interested in the finer points of magnetic behaviour, you
    may find ordinary iron or steel works better than ferrite.

    For something around the size of your fist, maybe a couple of hundred turns
    of #20 or #22 enamelled wire, a 12 volt DC supply and a bit of resistance to
    keep the current from getting too high and burning out your coil. #20 is
    good for a couple of amps IIRC. Google will give you resistance / metre for
    various wire sizes.
     
  3. Phil Allison

    Phil Allison Guest

    "DD"

    ** Err - what shape is the core.

    Not ring shaped I hope.


    ** Forget ferrite - it has a low magnetic filed strength.

    Try using a 1/2 inch dia, 6 inch long, mild steel bolt with about 250
    turns on it.

    Even a 1.5 volt D cell should do the trick with that.





    ....... Phil
     
  4. Mark Harriss

    Mark Harriss Guest


    Mild steel will work much better than ferrite but magnetically soft iron
    or silicon steel would work better: if you could salvage the E cores
    from a plugpack transformer and run power to the low voltage secondary
    you should have something fairly usable to begin with.
     
  5. Lionel

    Lionel Guest

    Try about a hundred turns of wire around a roofing nail & power it
    with a 'D' size battery. That's how the demo was usually done when I
    was a schoolkid.
     
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