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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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    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.
     
  2. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    So the first question would be how much power can you put through the old coils before they overheat.
    Do they heat up when run off you 24 volt battery bank?
    Can you measure the current?
     
  3. BroncoDave

    BroncoDave Member

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    By "current" do you mean volts or amps? Yes, I can measure both once I get it together. I have to get the 300' of 12 AWG wire and one more coil and cut the middle leg off my core piece.
     
  4. dave

    Dave New Member

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  5. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Current in Amps is a series measurement. Voltage is a parallel measurement.

    Your ammeter will usually insert a small resistance, measure and scale appropriately.

    Current through and voltage across the device works, but you need two meters. When the ammeter is removed, both the voltage and current will change.

    Try a boat store: e.g. http://www.easternmarine.com/100-spool-4-way-16-18-gauge-bonded-trailer-wire-49955 This is 4 conductor trailer wire (4 wires in a ribbon configuration), but you can always parallel two together. I have some trailer wire and it is stiff, but not solid.

    I used some flat Romex like stranded cable from a local boat store that I could buy by the foot.

    You may have to splice it.

    4pyros
    He essentially has a water-cooled electromagnet which is good.
     
  6. BroncoDave

    BroncoDave Member

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    Ok, thanks for the tip. I can get a 200' roll of 18 or 20 guage speaker wire at Home Depot pretty cheap. Yes, it will be water-cooled for the first 25' of the trip back up then turned off 'til it gets back to the bottom. About 15 sec. for the trip down and about 45 - 60 sec. to winch it back to the top.
     
  7. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Actually you might make out better leaving it alone or cutting off one 'arm'. That's because the closer the open ends are to each other the better they will pick things up. Reluctance increases with magnetic path length, so there is less with a shorter overall magnetic path length.
    Dont forget that you can experiment too. Try picking something up with one side (center and one arm) then something across all three legs. If you can find something shaped properly that only contacts the outer two legs you can also try picking up with that configuration. Maybe find something that contacts those two legs only then attach a weight for the experiment test.
    In each test, try to find the weight that can be picked up without just falling. That could mean adding smaller weights one by one until it lets go.
    If you can add say 20 weights before falling with one configuration and only 15 weights with another config, then the first configuration is better, as long as all the weights are all the same weight each. If they are not the same then you must add them in the same order for each test, so if you number them say 1 through 20 you must use 1 first, 2 second, etc., for every test.
     
  8. BroncoDave

    BroncoDave Member

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    Ok, so I will have to make a new core since the middle leg is twice as wide as the outer legs. No problem. I have enough mild steel to do that. The coils should be tight around the legs of the core with as little as possible protruding and the two legs as close together as possible. Correct?
     
  9. alec_t

    alec_t Well-Known Member Most Helpful Member

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  10. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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  11. crutschow

    crutschow Well-Known Member Most Helpful Member

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    If you lost a magnet in the well, can't you just drop a piece of iron on your cable into the well. The magnet should stick to the metal, allowing you to retrieve it. Or is the magnet not strong enough to support the 6 pound weight still attached to it?
     
  12. shortbus=

    shortbus= Well-Known Member

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    Tried to stay out of this thread. The lifting type or for that matter a 'magnetic chuck' for holding steel to a surface grinder are made the same way. And the microwave oven transformer with a coil in the middle is the same basic thing. The center leg of the "E" (or M as the op described it) is one pole. The outside legs make the second pole. When the object to be picked up is across the center and at least one of outside legs the electromagnet is complete.

    Don't know why Matt thinks a single, straight electromagnet is more powerful? :) Using both poles of a magnet makes a more powerful one, not twice as powerful as a single pole but close to it.
     
  13. BroncoDave

    BroncoDave Member

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    Mag & Weight.jpg This is the magnet & weight that's at the bottom of my well. They are not connected. The cable goes through the weight and connects to an eye bolt on the magnet. The weight just sits on top of the magnet cover. I have no clue how they got disconnected from the cable or what position they are in. I only know that I have to get them out before I can continue deepening my well. The magnet is not very strong or heavy, but I will need the electromagnet to be VERY strong to pull the 6 lb. weight up. The well casing is 8" steel pipe. To keep the electromagnet from sticking to the casing it will be inside a short piece of 7" PVC pipe.
     
    Last edited: May 9, 2014
  14. MrAl

    MrAl Well-Known Member Most Helpful Member

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    You can also turn the electromagnet OFF when it descends, then when it is coming up it may slide ok.
     
  15. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    I mentioned a straight electromagnet before I really understood what the OP was saying. I originally thought he was using the entire core! :eek: If that was the case, a straight electromagnet WOULD have worked better! :p

    As mentioned several times before though, if the OP does stick with the E part of the core, with multiple windings, he will need to be absolutely sure that the windings are wound the right way around.

    Matt
     
    • Thanks Thanks x 1
  16. BroncoDave

    BroncoDave Member

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    Ok, so I cut all three legs so they came past the coil 1/4" and ran 100' of 16 AWG extension cord from the three batteries (hooked up in series for 24v) to the single coil on the middle leg of my shortened "m" core. I don't know how much it will lift, but when I atatch it to something that is too heavy for me to lift, (like my air compressor). I can't detatch it even with my biggest prybar. I think it is strong enough to do what I need it to. Thanks for all your help guys.
     
  17. alec_t

    alec_t Well-Known Member Most Helpful Member

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    That's an understatement. Just be careful you don't haul up the well casing too :)
     
  18. tvtech

    tvtech Well-Known Member Most Helpful Member

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    ^^^^LOL Alec :D

    BroncoDave has built an Electromagnet of note!!

    Regards,
    tvtech
     
  19. BroncoDave

    BroncoDave Member

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    A couple of them. I made a smaller one with the transformer from a 500w microwave just to experament with and I discovered that if submerging an electromagnet in water has any effect on it's performance, it's not enough to be noticable. The bigger magnet is from a 1000w microwave. I'm gonna have alot of fun with these things messin with people after this well work is done. Thanks loads guys.
     
    • Like Like x 1
  20. tvtech

    tvtech Well-Known Member Most Helpful Member

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    And you know what Dave...just for being an absolute sport and fun person to deal with I am going to give you your first "like" here.

    It does not mean much but it also tells others that you are genuine :)

    All the best,
    tvtech
     
  21. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Wow this sounds like a real electromagnet alright.

    Just to note, as Matt mentioned the winding of the coils could make a difference in the overall strength. It depends on how you intend to use the magnet, but most likely you'll use the entire face front which means you want the magnetic excitation in the center leg opposite to the two outer legs. In other words, if you hold the core up so you can view it as a big "E" then if the lower leg mag direction is left, then the upper leg mag direction should also be left, and the center mag direction to the right.

    This means you could wind the lower arm with the wire starting at the right side and winding up and then back over the lower leg until you reach the main body of the "E", and the upper arm the same way, but the center arm would be wound starting at the main body of the "E" and winding the same way but progressing toward the end of the center leg (so from left to right instead of right to left).

    The nice thing though is that the way you wind the windings is not as important as the magnetic flux direction itself. This makes winding the thing easier if you use three coils.
    With this method, winding all three windings in exactly the same direction starting at the same point on each of the three legs (start at the main body or at the end of each leg). Looking at the "E" from the front face where the "I" is normally mounted this would look like all three coils were wound in the very same way in the same direction and starting and ending the same on each leg.
    The trick then is to simply call the 'start' of the two outer legs on one end of the coil, and call the 'start' of the center leg winding the opposite end of the coil so that the current flows in the opposite direction in the center leg when you connect the power.

    The other thing though is that when you wind onto the outer two legs you use up the window area for both sides. That means you can fit less turns on the center leg now. It is probably stronger with three coils even though we cant use as big a center coil, but i've never tried this and base this on the reluctance with consideration of the proximity to the work piece.

    It sounds like you already have this working good enough so you probably dont have to change anything now anyway.
     

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