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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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    Go on, take a guess.
     
  2. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    My guess is they didn't last long.
     
  3. tvtech

    tvtech Well-Known Member Most Helpful Member

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    You lost Mains....so you have not tested them yet....

    Sneaky question = sneaky answer.

    Regards,
    tvtech
     
  4. dave

    Dave New Member

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  5. BroncoDave

    BroncoDave Member

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    Wrong. It works perfectly. It just doesn't put out as much as it says on the front of the charger. It says 2/35/200 and does 2/25/150. The only parts inside are the transformer, 2 mode switches, the diodes and an amp meter.
     
  6. tvtech

    tvtech Well-Known Member Most Helpful Member

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    Now what??

    Answer: Test it to see all is good on the job :)

    Don't blow anything up. Yet.
     
  7. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Good for you
     
  8. BroncoDave

    BroncoDave Member

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    Yep. Only gonna use it intermitently and for short periods at a time to maintain full charge in batteries. Now I get to spend the day lowering my magnet into the well and pulling it back up over and over and over and over by hand. One HELL of a workout. At 115' the wire out weighs the magnet by 10x. And of all the friends I have helped, can you guess how many offered to help me? That's right, NOT ONE.
     
  9. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Before you start in earnest, have you done a ground-level test of the whole caboodle (batteries + wire + magnet) to see how hot the magnet gets in use? That might be a limiting factor.
     
  10. BroncoDave

    BroncoDave Member

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    I sure did. I put a pintle hitch in a 5 gallon bucket of water just for that.
     
  11. BroncoDave

    BroncoDave Member

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    Another delema, the magnet is strong enough to lift the weight, only problem is that the object being lifted must be in contact with at least 2 of the 3 legs. I have ho clue what position the weight is in down there. With the magnet energized I lift it up off the bottom a few inches and set it back down several times trying to feel the weight and I can feel it sticking to something heavy but it just doesn't want to bring it up. I have an idea for a new stronger magnet and I would like your guys opinion. 1 1/2" steel pipe 3' long, 10 AWG solid wire with 1/8" thick insulation 100' long wound around the middle 2' of the pipe. Would this be worth trying?
     
  12. BroncoDave

    BroncoDave Member

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    I just checked the draw on my 3 legged 2 coil magnet and got a reading of 19 amps. That's with 2 - 6v batteries in series and 1 - 12v battery in parallel with the 2 - 6v batteries and the battery charger set on 200 amp boost. I'm thinking that the 200' of 12 AWG is costing me too many amps for a 12v system. I think I need more voltage to push the amps that far.
     
  13. ronv

    ronv Well-Known Member Most Helpful Member

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    Yep, The numbers add up now - at least pretty close. It would seem your coil has a resistance of .2 ohms and the wire .4 ohms. So you are loosing all the juice in the wire instead of the magnet.
    Tell me again about the permanent magnet?
     
  14. BroncoDave

    BroncoDave Member

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    Do you mean the permanent magnet that is at the bottom of the well? If so it looks exactly like the pic below. 6" diameter and about 3/8" thick with a steel cover.

    neo-RB-with-protective-cover.jpg

    I was just out there droppin the e-mag down and pullin it back up and on the third try I had the 6 lb. weight on the mag. and about 20' above the water level it let go and I heard a real big splash as it went back to the bottom. This is getting REAL frustrating. A friend of mine is trying to locate a 24v alternator and some big rig batteries. Until then i'm gonna keep tryin with what I have for now.
     
  15. ChrisP58

    ChrisP58 Well-Known Member

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    Some general information on electromagnets:

    As already mentioned, the magnetic strength is a function of the current in the winding, and the number of turns in the winding. The term is amp-turns. If you double the number of turns, you will have more magnetic strength with the same current. Of course, the DC current through the winding is a function of the applied voltage and the resistance, as per Ohms law.

    The magnetic field, or lines of force, flow between the two open ends of the winding, beginning at the axial face of the winding. If it is an E core, then the magnetic field splits, with half of the force flowing from the center face to each of the two outside faces.

    Note that I said that the magnetic field begins where the winding ends. That means that, if your winding only goes partway up the core, that some of the magnetic field goes right across the unwound length instead of going out from the ends of the core. In other words, if the winding doesn't cover the full length of the core legs, a lot of the magnetic field isn't out where it does you much good. That being said, if you are using prewound bobbins that are shorter than the length of the core legs, it is better to position the coils close to the open ends, than at the the base. That will maximize the force lines from the open end to be out in your 'working' area.

    More info on the working of electomagnets can be found here: http://en.wikipedia.org/wiki/Electromagnet
     
  16. BroncoDave

    BroncoDave Member

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    Yea I got that. There is a thread called "Voltage Multiplier Circuit Design" that I was wondering if this could be applied to my electro magnet?
     
  17. ChrisP58

    ChrisP58 Well-Known Member

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    The voltage multipliers in that thread only work with AC input.
     
  18. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    One big caution here, with that big construction when the 12vdc (or whatever dc you have now) is open circuited, a large voltage can be developed across the two winding ends. This can be a voltage in the thousands of volts and with enough power to cause bad shock.
    A good switch or something should be used to open the circuit, like a big knife switch which you can build yourself.

    When the electromagnet faces come into contact with metal the metal starts to bridge the air gap which exists between the two outer leg faces and the center leg face. This reduces the total reluctance so the magnet should have more strength.
    If the object is not big enough to bridge the gap completely, then some ferrous metal can be used to make the gap smaller. That would allow picking up smaller objects. The metal used to bridge the gap should be transformer metal and oriented the same was as the other metal is, but a piece of steel plate might work too.
    In other words, the magnet may have trouble picking up one piece of steel that does not bridge the gap, but may be able to pick up two such pieces if they are connected end to end because the combined metal will bridge the gap. So making the gap smaller should help, and it could help a lot.

    The coil wire can only handle a certain current level before it starts to get too hot and then it could ruin the insulation and short a turn. If a turn shorts, the coil will be almost useless. This means you have to be careful how much current you apply to the coil and for how long it is applied. Short durations are better.
     
  19. BroncoDave

    BroncoDave Member

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    I have 110 and 220 a/c power right at the well. If the multiplier puts out dc that's what I need. Then I wouldn't need batteries or a battery charger. All I need to do is build the multiplier to put out the amount of power that will do what I need to power my magnet or build a magnet that can handle the power I need to get this job done. Ijust need to figure out what to build and build it. That's where you geniuses come in. The building part I can handle. I can fabricate just about anything. I just need to know what parts to get and what order to put them together in. You guys have gotten me this far. Can you get to the finish line?
     
  20. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    There are several issues here,

    First is that when dealing with mains voltage things get far more dangerous than a large battery-powered electromagnet. High current also means lots of heating, which presents a burn or fire hazard. Furthermore, building a multiplier that can stand that kind of voltage and current may become difficult and expensive. Also keep in mind that when you increase the voltage in a multiplier circuit, the current does not increase. You can't get out more power than you put in, so your current would decrease significantly. Also, even if you could get high enough amps, you would likely trip the breaker serving your outlet.

    There are all sorts of other variables that do not appear to have been taken into consideration. I would keep experimenting with your battery-powered one if I were you.

    Matt
     
  21. BroncoDave

    BroncoDave Member

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    There's got to be something I can build that runs on a/c power to do this. I can't get my hands on the dc parts to put out the voltage and amps I need.
     

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