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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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    Yep. I hear you. Just for the halibut I hooked the whole thing to my 2000 Isuzu Rodeo with the engine running and put a pintle hitch in a 5 gallon bucket of water and it picked it up and lifted it up out of the bucket with no problem. I jiggled it around in the air and it fell off the magnet. Come to find out the only REALLY good batteries in the bunch are one of the 6v deep cycle RV batteries and the one in my Rodeo. How difficult and or expensive would it be to build or buy a power supply with an output of say 24v or 48v and about 200-600 amps? And sleep is over rated.
     
  2. tvtech

    tvtech Well-Known Member Most Helpful Member

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    Hey Bronco

    A 24V or 48V PSU at around 200-600 Amps will not happen. Better to buy a SLA battery charger and a few new batteries when you are in Electromagnet mode. Use them (the charged batteries) until the job is done.

    Man, I am tired now. I will make more sense Tomorrow. Sleep on it.

    All the best,
    tvtech
     
  3. BroncoDave

    BroncoDave Member

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    I knew you were going to say that. Can't sleep yet. Gotta go to school now. Gonna try to barrow battery charger from the school. The Auto Tech instructors are friends of mine. Go to bed.
     
  4. dave

    Dave New Member

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  5. ramuna

    ramuna Member

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    I'm sorry Bronco, I had/ & have no intention of dissing you as a "working class bum". Despite what tvtech says about me knowing squat, and by implication, himself being an expert down-the-well-metal- fisher, I honestly think that your chances of success with this idea are exceptionally small. Think about it, the inner bore of the well is 8". The PVC tube section you're using as magnet support is 7" with (its hard to see clearly from the images you uploaded) the bolthead and nut on the outside of this tube. So you have a 1/2" clearance between the well casing & PVC tube which is whittled down to almost nothing where the bolthead and nut protrude. The contraption just has to incline a tiny bit off vertical for it to jam inside the casing. Even if you, by some miracle, manage to lower it vertically down to the bottom of the well, and it picks up a heavy lump of steel, the weight of the steel will more likely than not, kink the PVC tube to one side (and that'll jam it).

    The key to making this idea work is to have enough clearance to make the contraption jam-proof, even with it lifting stuff from the bottom. The next idea you should use, is to have a quickblow fuse rated for the current that the magnet draws, between the magnet power-supply and the magnet. That way, if things screw up again with the wires, all you lose is the cheapo fuse. Check your wires for integrity (ie no shorts) after your previous mishap BEFORE you reconnect the magnet power supply.

    MrAl's point, which you found hard to follow (and so did I, sorry MrAl !) was for you to wind the electromagnet coil around the centre-leg of the magnet, instead of what you have at present (on the 'spine' of the E-section, judging from the photographs). That will give you the strongest magnetic field. The centre leg will be the North pole and side-legs be Souths or the other way around, depending on the directions of winding and current flow.

    And get some sleep ! A tired brain is useless for anything ! Good luck!
     
  6. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Using the third wire in parallel with one of the others would reduce the overall wire resistance by 25%, which might help get more current through the coil, but if one or more of the batteries is knackered that's probably where your volts are getting dropped.
    Do you know (from the microwave power rating) what maximum current the coil can withstand?
    Edit: If the coil (apart from its connections) is exposed to well water you have a water-cooled magnet which could be run at a somewhat higher current than the rated max ;)
     
  7. BroncoDave

    BroncoDave Member

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    Please try and keep up with my tired brain. I'll say it again, Please read and understand all posts before wasting your time typing. I said earlier that the first time I dropped it in that it got jammed up near the bottom. I removed the 7" PVC and am no longer using the winch because of that. I am now lowering and raising it with just the power wires by hand. One HELL of a workout I might add. Anyone want to come help? I'm doing this ALL by myself. No power equipment of any kind. Just manually operated contraptions that I built from scratch. Including the hand cranked winch.

    This is the configuration I have been using all along until last night.
    Mag.jpg



    This is the configuration I changed it to last night.
    Mag 2.jpg
     
  8. BroncoDave

    BroncoDave Member

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    I hadn't thought of using the third wire before. Thanks for the tip 4pyros. From what I have experienced and discovered so far is that no matter how many volts I put into this thing, at the coil the voltage is always 4-5 volts. It's the Amp's that make the differance. The good 12v battery in my Rodeo by itself with the engine running at idle it was drawing 14- 15 amp's. With the multiple batteries ran in series puting out 35v it was only drawing 4-5 amp's. On account of the bad batteries would be my guess. I was able to barrow a good charger that puts out 200 jump start amp's at 12v. Getting ready to hook that up and see what happens now. Will let you all know in a few.
     
  9. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Why did you change the configuration?
     
  10. BroncoDave

    BroncoDave Member

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    With the first setup only the center leg had any real magnetism. The outer legs only had any power when an object could contact the center leg as well as one or both of the outer legs. The new setup powers the two outer legs giving me two magnetic legs rather than one. Time for some humor. My favorite joke in the whole world is a visual one. You guys ready for this? I saw this at a gas station one night and it made my imagination run wild. Here it is. "TWO BLONDES IN A SMART CAR" Now let your imagination do the rest.
     
  11. ramuna

    ramuna Member

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    "Please try and keep up with my tired brain. I'll say it again, Please read and understand all posts before wasting your time typing."

    An excellent idea. I just did, and learnt somethings new:

    Post #30 contained an obvious and easy to implement suggestion, which you neither answered nor commented upon.

    Post #32 said that the fallen magnet's diameter is 8" AND that the well casing is a steel pipe with inner diameter of 8". At least one of those measurements is wrong don't you think ?

    "I said earlier that the first time I dropped it in that it got jammed up near the bottom."

    Post #64 said that the jamming occurred due to cables twisting. I find that hard to visualise. Even if the cables twisted, the more likely explanation for the jam is the size of the contraption in relation to the diameter of the casing.

    "I removed the 7" PVC and am no longer using the winch because of that."

    Post #32 said that the PVC tube was to prevent the magnet sticking to the steel well casing. How will you prevent it now that the PVC has been taken off ?

    "I am now lowering and raising it with just the power wires by hand."

    Post #64 said that the power wires were soldered on and got yanked off....not a very reassuring test of their weight-lifting strength is it ? Don't you think there may be a good chance of you repeating your earlier mistake and dropping the new electromagnet down the well to join its mates down below ?

    I'm sorry Bronco, I know you're under a lot of stress & are trying your best but I repeat my earlier statement: The key to getting this to work is to prevent jamming ie. clearance, non-magnetic shrouding etc. Getting the magnet which is at the bottom of the well, out again, given that its diameter is close to that of the steel well casing and that it will stick to the casing, is beyond my ability to advise upon.



     
  12. BroncoDave

    BroncoDave Member

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    O.M.F.G. You read everything but did not understand everything. Try to keep up with my tired brain again. An unanswered post speaks as loud and clear as an answered one. Sometimes even louder. That suggestion will NOT work. If you understand all the info I have given on my situation you would know why. The wire and cable twisting caused the 7" PVC to get cocked in the casing and jam. I didn't think I had to go that far into the details for anyone understandn that. My bad. The magnetic part of the magnet is facing Straight down and not to the side. It can't get close enough to the casing to stick. Do I really need to go this deep in detail about everything or can you read between the lines yet?

    Where does it say 8"?



    Mag & Weight.jpg

    Can you see the 1/4" thick bracket welded to the top of the core? Think I can atatch the wires to that in a way that will support the weight and not put tention on the conections at the coil? I didn't have to worry about it before with the winch cable atatched to it. Have you ever tried to do anything like this with noone to help you, all by yourself? It's EASILY a 2 or 3 man job.

    Photo-0120.jpg
    Well this wasted another couple hours. Oh well. I didn't really need to sleep anyway. All this and not a single comment about my joke? Tuff crowd.
     
    Last edited: May 9, 2014
  13. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi there,

    No need to be sorry, i understand that these things can sound very confusing when all you have is text available to get the point across. I probably should have included a drawing, but a drawing like that takes about a half hour or more to make because it has to detail the windings and core and all that, and preferably in 3d.
    It's so, so easy to understand when the person you are telling is right in front of you and you have a core in hand and start winding turns around the core (or coil form more usually). That way you can explain that the way the turns go onto the core and the direction of the current affects the magnetic path flux direction.
    It's actually simpler to explain using the flux direction, but not everyone is familiar with the way flux 'appears' from coils and current flow, and the resulting direction of theoretical 'flow'.

    Probably the simplest in text alone is to say that if the strength gets weaker with any one coil energized with current in a given direction, then reverse the direction of current in that coil (by reversing the two coil leads). If the magnetic 'pull' gets stronger when the extra coil is connected, then it must be connected with the right polarity.

    I think he's still using only one coil though so this is still a secondary point.
     
  14. BroncoDave

    BroncoDave Member

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    I'm disapointed in you MrAl. You didn't see the drawings that took me a half hour to make?

    I changed it from this,
    Mag.jpg


    To this. The red represents the coils.

    Mag 2.jpg
     
  15. BroncoDave

    BroncoDave Member

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    About the battery charger I barrowed. It has a problem that I need some help with. The 4 wires from the transformer that go to an aluminum heat sink for the positive cable are hooked to these round things that are pressed into the aluminum. Not sure what they are but they have these numbers on them (DT , B7504A , 0652). They are burnt to the point that they fell apart. I have this old RV power converter with a built in battery charger with similar parts but different numbers (1N3492 , 8119) and the Motorola "M" symbol above the numbers. My question is, are they compatible?
     
  16. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    The B7504A is a 75 amp press in diode.
    The 1N3492 is a 35 amp press in diode.

    You should use one with a 75 amp rating or better.

    If you do a google search on the part numbers you will find the data sheets.

    You could possibly use two of the 1N3492's in parallel but you should change both of the B7504A's with 1N3492 pairs to keep the voltage drops the same.
     
  17. BroncoDave

    BroncoDave Member

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    Cool. Thanks 4pyros. Now all I gotta do is find 2 more 1N3492. There are 2 empty holes in the aluminum plate for them.
     
  18. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    I few notes;
    If you have to buy anything I would up the current rating if its not too big a difference in price.
    The two 1N3492 will only give you 70 amps when relay you need 75 amps or more.
    The fact that the 75 amp diode's burned up means they were probably under rated to begin with.

    Two diodes in parallel will give you a slightly higher voltage by about .3 volts which should be fine for ordinary battery charging but if its a smart charger then it may throw off the control circuitry and you would be better off using single diodes as designed.
     
  19. alec_t

    alec_t Well-Known Member Most Helpful Member

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    I'm probably missing something, but can the coil really take >70 Amps without letting out the magic smoke?
     
  20. BroncoDave

    BroncoDave Member

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    I'm hoping it can take 200 amps. That's the highest setting on the charger. It's not a smart charger. I didn't see any blondes in it.
     
  21. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi again Bronco,

    Well i have to apologize for that oversight, what happened was i was pressed for time and had to quickly look over a number of threads both here and in another forum. But had i seen it previously, i would have complemented you and i'll get to that next where i'll have to complement you now :)

    As you probably know by now, the window area in a core is pretty much as important as anything else about the core, like material type, center leg cross sectional area, etc. If you fill the window up with winding turns, you've reached a certain limit of the core where you just cant add any more turns, period, and that is a severe limit.

    That brings us to your 'old' configuration with one coil versus your 'new' config with two coils on the outer two legs.

    The old config had one coil, and turns from that coil simultaneously fill up BOTH windows as each turn is added. The new config though is different in that each turn of an outer winding only fills up ONE window. That means you can fit twice as many turns on the core because you have two windows.
    The drawback is that the area of each outer leg is only half of the inner leg, so it would saturate more easily. But given the large coincidental air gap, it is very doubtful if this core could ever saturate unless you get extremely unlucky and happen to have to pick up some material that is made for transformers (that is, has a relatively low reluctance). In that case the core may saturate, but that is probably going to be very rare, and also the mating surface of this unlucky metal would have to be near perfectly flat to match that of the core metal itself.

    So lots of applause and hats off to your new configuration, and if you care to you can do some careful testing to see how much stronger it is with the two windings instead of the one single in the center. This of course assumes that each outer leg has the same number of turns as the inner core had before the change in config. If they have half the number of turns as the center leg had, there's not much difference.
    Also, the strength may be a little more than twice with the two windings because the total reluctance will be slightly less.

    Hey do i get a prize for the 100th post in this thread? :)
     
    Last edited: May 9, 2014

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