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Electromagnetic force

  1. Oct 14, 2012 #1
    hello i need some help,
    i know very little about EM. i would greatly appreciate any advise u can lend me.

    i need to make an electromagnet but i am wondering how strong air cores can be? will an air core be able to work on and off continuously for hours at a very high rate of speed, it doesnt have to pull up a heavy load the piston it moves is quite light..
    also to put this in prospective its a very small magnet moving a very small piece of metal very fast on/off for hours.. i do have a facility to make coils, i just need some advise on which kind..
     
  2. jcsd
  3. Oct 14, 2012 #2
    Now, I am no expert in magnetics, I just join in. My understanding is the heat generated in a transformer or electromagnet is mostly from the eddy current in the conducting material of the core. If you have an air core, there is no eddy current and there should be no heating up in the air core. Heat is mainly from the power loss due to resistance in the winding.

    Again, I am not an expert.
     
  4. Oct 15, 2012 #3
    thanks, thats good to know.. i dont want heat to become an issue. but im more concerned with power and the ability to work for hours
     
  5. Oct 15, 2012 #4
    Make a coil using the smallest film insulated wire you have.
    Apply a low voltage to the coil. Use a 1 1/2 volt battery.
    If the coil or the battery overheats, you need more turns on your coil or smaller wire. If the magnetic field is too weak and everything is OK temperature wise, use two batteries in series.
    CAUTION: If you break the circuit, there will be a high voltage and you could get shocked.
    If you want more precise instructions, you have to provide details of what you are trying to do.
     
  6. Oct 15, 2012 #5
    very informative.. thank you.

    but my real question is about the strenghts of a solid vs air core electromagnet. i would like to produce the same amount of power as an 8 layer coil (20 -24 gauge copper) 1 1/4" inch tall.. with a solid core.
    can an air core coil make as much power as a solid? i control voltage with an adjustable power supply, so is that all that is required? layers and voltage?

    an air core would reduce weight and thats exactly what i want.

    a strong, light magnet.

    thanks again guys.. all informaton welcome
     
  7. Oct 16, 2012 #6

    NascentOxygen

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    Staff: Mentor

    The magnetic material of your piston becomes the core. What are you using to perform the switching operation? — a manual switch, a relay, or a transistor device?
     
  8. Oct 16, 2012 #7
    im using a manual switch to engage the piston. as soon as the magnet pulls the piston, it is pulled away from an electrical contact point shuting off the magnet. A spring returns the piston and repeats the process.

    I like the part about the piston becoming the core.. that could save space
    also im using a 1.5 amp power supply, it can be adjusted up to 15volts.. output= DC
     
    Last edited: Oct 16, 2012
  9. Oct 16, 2012 #8

    NascentOxygen

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    An electromechanical vibrator. You'll need good quality silver points or they will soon burn away.
     
  10. Oct 16, 2012 #9
    man i was trying to be secretive and u found me out.. hahah. but every time my girl uses it she gets shocked!! haha..

    but seriously thanks. thats good to know.. i figured on using brass or something. ill have to find some silver
    ..
    but wait. im gonna look into the vibrator deal a bit.. haha. they probly do run on a magnet huh?..
     
  11. Oct 16, 2012 #10
    no they dont..

    is there an easy way to tell how long a battery will power a continuous EM? because they make some nice batteries, i just wonder if it could run for up to 8hrs.. 1.5 amps, 3-10 DC volts (give or take.. room to fine tune its speed) output.. I have an DC regulated power supply
     
  12. Oct 17, 2012 #11

    NascentOxygen

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    Perhaps a good source of points for your switching would be the points from an old car's ignition. The points interrupted the current in the ignition coil primary, and cars do routinely run reliably for hours on end. :smile:
     
  13. Oct 17, 2012 #12
    i have thought of that.. they would be perfect if i can make em fit right. but silver contact points are pretty cheap, an ive been looking into that a bit
    i wish i could show u a pic but im trying to not give to much away before my patent..

    if i could make an air coil the same strenght as a solid core id be happy and my machine would be lighter ..

    Its good to be able to bounce ideas off u guys tho
    i really appreciate it.. thanks
     
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