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Wire gauge for electromagnet?

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by BroncoDave, Apr 30, 2014.

  1. BroncoDave

    BroncoDave Member

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    Hello all. I'm new here looking for help with a little problem. I am trying to remove alot of metal from the bottom of my water well. I have been using a permanent magnet and have removed a 5 gallon bucket full so far. The magnet and the 6lb. steel weight got unhooked from my cable and are sitting at the bottom of my well 115' down. I made an electromagnet out of a transformer from a microwave oven and sealed it with plasti-dip. With a 9 volt transistor battery it will lift 25 lbs. When I hook up 2-12v car batteries in parallel and enough small single strand wire to reach the bottom of my well, it wont even lift 1lb. Could someone tell me what gauge wire I should use?
    Thanks in advance for any help.
     
  2. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I don't know what your current is so it is hard to have a good answer.
    A 9V transistor battery can not make much current.
    If a car battery, maybe two batteries, can not lift much metal than the current must be low because of the 125' x2 of wire.
    Are you using telephone wire now?

    Use LARGER wire. How much larger, I don't know.
    I would use extension cord wire.
     
  3. BroncoDave

    BroncoDave Member

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    The wire is about 2x the size of telephone wire and the batteries are 1-12v car battery and 2-6v deep cycle RV batteries. The 6v batteries are in series ran parallel with the 12v battery. All batteries are fully charged and good. Will try larger wire and see what happens. Was also wonderjng if 2 more coils would help any. Right now I have one coil on the center leg of the "M" shaped part of the microwave transformer. Could I put coils on the other two legs?
     
  4. dave

    Dave New Member

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  5. alec_t

    alec_t Well-Known Member Most Helpful Member

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    As a guide, assuming the present wire + magnet + battery setup can lift 1 lb and you need to lift 10 lb, then you need to increase the cross-sectional area of the wire by a factor of 10, i.e. increase the diameter of the wire by a factor of >3.
     
  6. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    22 AWG wire has resistance of about 16 ohms per 1000 feet, so that's 4 ohms for 250 feet which is close to what you have.
    16 AWG wire has one-quarter that resistance, so that's about 1 ohm for 250 feet, which would probably do it.

    It would help if you knew or could measure the resistance of your coil, then we could choose the wire more carefully.
    You could of course try it on something above ground first before you use it in the well.

    Just one question: What do you do if you loose that one in the well too :)
    Try a grappling hook and rope.

    With all that metal down there, is there perchance any lead down there too?
     
  7. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I think you have batteries in series and parallel.
    Series batteries will boost the voltage which you need to over come resistance in the wire.
    Parallel batteries, can increase current draw, in you case it is not helping.
    >If the current was very high like when starting a car, parallel will help.
    >Your current is very low because of the resistance in the wire.
    It is not a good idea to parallel or series unlike batteries.
    >If you don't let any of the batteries get discharged! You could series all your batteries to get 24 volts. This will double the current but that will only get 2 pounds of magnet.

    I agree you need 10x the current so you need 3x the wire diameter. (copper not insulation) {square root of 10}
     
  8. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    If you are using the transformer core as the electromagnet you will not have much luck. It is designed so that the magnetic flux follows the shape and does not go outside of the core much, if at all. You really need to use a straight piece, or perhaps a 'U' so that you have either a bar magnet or a horseshoe magnet. Just using the shell-type core as the magnet will not pick up much, if anything.
     
  9. BroncoDave

    BroncoDave Member

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    Ok, so I will use 16 or 14 gauge wire. The coil is on the middle leg of the "M" and only magnetizes that leg. Would it help if I put two more coils on the other two legs?
    The reason the other magnet and weight came off the cable is that I was using a carabeener to attach them to the cable. I am now using a threaded reusable chain link. No lead in the well. Just chromium 6. Did I mention I live in Hinkley, Ca? The town that made Erin Brockavich famous. The battery setup is what it is. I have to use what I have or can pick up for free. My budget for this is zero. The purpose of this whole project is to deepen the well. To do so, I first need to reach the bottom of the well by removing all the rusty flakes of old well casing that have fallen to the bottom. The well was originally drilled to 120' and is now 115'. That means I still have 5'x8" of rusty metal flakes to remove.
     
  10. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Just checking, is this what your electromagnet looks like?

    magnet.png
     
  11. BroncoDave

    BroncoDave Member

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  12. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    It couldn't hurt to have coils on the other two "legs", but really you would be better off with a bar or U shaped magnet.
     
  13. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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  14. alec_t

    alec_t Well-Known Member Most Helpful Member

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    To take advantage of having 3 coils rather than 1 you'd have to bump up the driving voltage for series-connected coils or else increase the wire thickness yet again for parallel-connected coils.
     
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  15. BroncoDave

    BroncoDave Member

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    Ok, so I will use 12 or 10 gauge wire and add two coils in series and run all 3 batteries in series. That will give me 24v. Thanks to all for the help. I will let you know how it works.
     
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  16. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If you use multiple coils you will, of course, have to get the magnetic polarities correct for the three limbs of the core.
     
  17. BroncoDave

    BroncoDave Member

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    Splain please.
     
  18. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    You need to make sure the wire is wound in the correct direction so that one coil does not cancel another out. Again, using an "M" shaped core really is not going to work very well for this.
     
  19. BroncoDave

    BroncoDave Member

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    Would it be better if I cut the middle leg off and put a coil on each of the two remaining legs? And power them in series with 24v and 150' x 2 of 10 AWG wire?
     
  20. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    I would recommend cutting the middle leg off, definitely. You can either wind a coil around each of the legs (just make sure they're wound in the same direction) or wind a single, large coil around the center. 10 AWG is quite thick, I'm not sure if it will be able to provide a very powerful magnetic field, but at least it should be able to handle the current. Figuring out how well it would work requires a fair amount of math that I am not very interested in doing at the moment :p Either way you'll need to watch the insulation, you don't want the windings shorting against each other or the core.
     
  21. BroncoDave

    BroncoDave Member

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    I have to dip the whole thing in Plasti-Dip to seal it for under water use. The coils are pre wound. They are the big ones off the microwave transformers.
     
    Last edited: May 1, 2014

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