variable dc power supply, powering large gage wire not working?

Discussion in 'General Electronics Chat' started by ElectromagnetNewbee, Sep 4, 2014.

  1. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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    So, I hook a 20 amp variable DC power supply to an 8 gage copper coil. and the volts on the power supply goes down to 0? If I hook an 24 gage copper coil to the power supply it all works fine, I can adjust the volts and current ok?

    what does this mean?
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Is the powersupply currentlimited / protected?
    The 8 Gauge wire may have a to low resistance, so that the powersupply goes into protection.

    Bertus
     
  3. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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    Even when I hookup a 12 gage, 80 feet electromagnet copper coil the volts all drop down to 0? why is this. the smaller gage wire works fine? why?
     
  4. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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    its model HY3020E made in china. its says 'regulated' power supply? not sure. also i dont have it grounded? could that be the issue?
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The higher the gauge number, the higher the resistance.

    Bertus
     
  6. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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  7. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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    so how do i fix this? how do i get it to work? can i add resistance to the line somehow? how do i do that?
     
  8. alfacliff

    Well-Known Member

    Dec 13, 2013
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    it takes a lot of large wire to have enough resitance to equal 20 amps draw. 8 guage wire runs .628 ohms per 1000 ft. current equals voltage devided by resistance if you set tyhe supply for 10 volts and used 1000 feet, the current would be about 16 amps. any less wire and the current would be more.
     
  9. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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    ok, so... how how would i add restistance to the line so the volts dont drop? can i use a metal bar and put it in the curcuit? i just want to power these large electromagnetic coils? what is the best way to do this? is it easiest just to buy a flippen battery to power it?

    how do i stop it from going into protection mode? i dont want it to do that?
     
  10. wayneh

    Expert

    Sep 9, 2010
    12,155
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    You need more power, it's as simple as that. A battery is an option but offers poor regulation and no safety features. A beefier power supply would provide those features but will be expensive.

    I fear you will soon turn your wire coil into a fuse and release the smoke, as well as molten copper. This is not sounding like a safe project for someone with your experience level.

    What are you really trying to do with your coil?
     
  11. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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    i just found out about ohms law, a bit late. it sounds like i need to add a resistor to the line and i can make it work correct? All I am trying to do with a coil is experiment with magnets and electromagnets, I just want to create magnatism!
     
  12. inwo

    Well-Known Member

    Nov 7, 2013
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    A resistor will just waste power.
    Choose a wire size that has the resistance you need.

    Look in a wire table for ohms per foot.

    Shoot for size and length to equal about 1 ohm.

    That will give you the same amps as voltage setting.

    And power (heat) will = current or voltage squared.
    Or amps times volts.
     
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  13. wayneh

    Expert

    Sep 9, 2010
    12,155
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    Then by all means start smaller. A couple hundred turns of, say, 22 gauge wire will give you a strong magnet without drawing a huge current and a potentially dangerous amount of power. If you are just now learning Ohm's law, then it is worth noting that the strength of an electromagnet depends on amp-turns. So you can add more current (expensive) or you can add more turns (relatively cheap).

    The core and configuration you use also has a huge effect. Magnetic field lines resemble electricity in that they require a return path. Making sure that the return path is "conductive" increases the field strength where you want it. Magnetic permeability is a measure of how good a material is at "conducting" the magnetic field lines. So for instance a coil wound around an iron nail in a "C" shape will focus the field lines within the gap. The iron has a high permeability whereas the air in the gap has a low permeability.
     
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  14. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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    In this case, i dont care if it wastes power. I just need it to work with what I have for right now. a 30 volt, 20 amp variable dc power supply. what size of resister do i need to make it power this 8 gage coil?
     
  15. wayneh

    Expert

    Sep 9, 2010
    12,155
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    I would use a lightbulb as your "resistor". It is made to dissipate heat and will give you visual indication that your circuit is complete. Just be sure the bulb is rated to the full voltage being supplied because your coil will have only a little voltage drop across it.
     
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  16. ElectromagnetNewbee

    Thread Starter Member

    Jul 13, 2014
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    The lightbulb as a resistor option is exactly what I will do! wow! :) ill be soo happy if this works!
     
  17. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    thank god for built in power supply protection schemes..
    "protecting lives for years and counting"
     
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  18. tcmtech

    Well-Known Member

    Nov 4, 2013
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    You may also want to do some reading on 'Ampere Turns' and how they relate to the strength of a electromagnetic field.

    Big wire doesn't automatically mean big magnetic field.
     
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  19. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I don't think your 8gauge coils are intended for DC operation. Do you have a photo, a model number or a description of the device from where you pulled these coils?
     
  20. MrAl

    Well-Known Member

    Jun 17, 2014
    2,440
    492
    Hi,

    Yes the Mastech power supplies all have internal short circuit detection and protection. If the resistance is too low they turn the power down automatically. Mine does the same thing. If you add a certain resistance to the circuit it wont do that, like 0.1 or maybe 0.5 ohms.

    Also, the potentiometers are very cheap junk and get noisy after a while. After that the fine adjustment makes the voltage jump up and down as you try to adjust it. Best bet there is probably to change out the pots with some decent quality pots.
     
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