Degaussing coil construction

Discussion in 'The Projects Forum' started by Karenzee, Apr 23, 2015.

  1. Karenzee

    Thread Starter New Member

    Mar 6, 2015
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    Hi,

    i would like to build a rather large degaussing coil, but i've seen different designs and i don't know what would be the best and easier to make.

    What is the best material to wind the wire on? (i see mention of copper and aluminum)

    My grandfather had one many years ago (he said it was hula-hoop sized) for clockwork repair, i look for something similar.


    Thank you in advance!
     
  2. #12

    Expert

    Nov 30, 2010
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    "Best" and "easiest" are two different things. You use anything handy as a form to wind the wire on. Most degaussing coils are made of copper wire. I'll bet Google can find many different sizes for you.
     
  3. Karenzee

    Thread Starter New Member

    Mar 6, 2015
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    Hi #12,

    you are right, from what i've read best is soft iron or copper tubes if possible but aluminum is also included. But if that's not that important that's good!

    I did already searched on various sites but i thought that maybe for a larger size i should consider some things in particular.


    I know that small portable degaussing coil also exists, could ccfl inverter work for that purpose?


    Thank you!
     
  4. KJ6EAD

    Senior Member

    Apr 30, 2011
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    I've always just taken one off an old CRT TV or game monitor. Could one from a very large CRT such as 37" suffice?
     
  5. #12

    Expert

    Nov 30, 2010
    16,284
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    You can degauss anything from the tip of a screwdriver to the Starship Enterprise. Do you want us to guess what you are trying to degauss? Only then would I know if a ccfl inverter would work.
     
    Last edited: Apr 23, 2015
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,545
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    I had one at one time that was made by just winding a coil of 14g enameld copper 14" in dia ~1" to 1 1/4" across. Motor winding tape used and then shellac-ed.
    For TV degausing purposes.
    You have to remember to turn it perpendicular to the screen before turning off.
    Max.
     
    Last edited: Apr 23, 2015
  7. DickCappels

    Moderator

    Aug 21, 2008
    2,653
    632
    Take note that the coils in most of the old color TV's and monitors have a thermistor in series with in to limit the current as well as to taper off the current so as to demagnetize CRT. Please take note that they should not be used without a current limiting means such as the thermistor, a light bulb, or a capacitor. Otherwise the current would be and remain very high.

    [​IMG]

    If you are not going to be demagnetizing CRTs or some other large assembly, then you would be probably better off with a degaussing wand. Wands can also be used with color CRTs but it takes a lot more work to get decent purity with a wand.
    [​IMG]
    Which is an inductor with an iron core. As far as I know the impedance of the coil limits the current. Note the push-button on the wand -the ones I've seen tend to get very warm very quickly.

    Copper vs Aluminum: Aluminum was sometimes used because it is a little cheaper than copper but for building a one-off, it would probably not be worth the hassle of making proper electrical connections to aluminum.
     
    #12 likes this.
  8. Karenzee

    Thread Starter New Member

    Mar 6, 2015
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    Hi!

    the degaussing coil is for clockwork (swiss & east european), that my grandfather is repairing, as well being in use in his toolshop.

    About the thermistor, what should i look for (i've seen PTC crt models and the small very high temperature silicium resistors)


    About the ccfl i just want to make a portable degaussing coil (under a plate for watches and tools), one is rated 680vac -1A and the 900vac - 2A



    Thank you all for your answers!
     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Ive not seen such high voltage in anything small and portable. Those voltages are as high or higher than most large industrial machines use. Are you SURE about the values you listed?
     
    Metalmann likes this.
  10. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    please consider getting power from an ordinary electrical outlet. 120 or 240 VAC, using a standard power cord.
     
  11. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    using 28 gage wire on a 24" diameter circle. 320 turns would give you 2000 ft of wire. At 65 ohms per 1000 ft. the coil would be about 130 ohms. With 120 VAC it would draw around 1 amp of current and dissipate 130 watts in heat. used at 25% duty cycle heat would not be a problem. Also, when the wire warms up from 20 C to 50 C the resistance would increase from 130 ohms to about 145 ohms, so current use would decrease 5 to 7%
     
  12. Karenzee

    Thread Starter New Member

    Mar 6, 2015
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    Hi Kermit2,




    The larger coil is for my grandfather and will be a standard degaussing coil powered via the electrical outlet, i was just wonderering for myself if i could use one thoses small inverter to make a portable degaussing coil.




    You're right about the values! what i saw was dc booster HV modules.


    I've found 12v and 24v ccfl's but never tested the output current (still probably less than 1A) so this is not a good option.


    Any ideas how to power a portable degaussing coil?


    Thanks!
     
  13. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    a small 12 volt battery and one of those mobile inverters sold for use in cars should do it. the small batteries could be recharged through an accesory outlet in your vehicle. 7 and 10 amp hour 12 volt sealed LA units cost about 20-25 bucks, maybe a little more for a 400-500W inverter unit.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You need AC, a DC current will do the opposite you are attempting to do.
    Max.
     
  15. Karenzee

    Thread Starter New Member

    Mar 6, 2015
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    Kermit2,

    I should've thought of that! thanks! i'll look if i have that here, if not that not too expensive.


    MaxHeadRoom,

    I know, i just looked in a box (not the right one) where i thought i placed ccfl's but instead there was a few hv dc modules in it
     
  16. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    i believe a mobile type inverter supplies 120 VAC when powered by a 12 volt battery. right?
     
  17. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the thermistor and bolometer used in tv's are not necessary if you just turn on the current, and then pull the coil away from and rotate the coil before turning it off again. far enough away that it dosnt re magnetise things.
    a copper or aluminum form would not owrk, it would act as a shorted turn to the coil use non conductive coil form. some builders stores have 12 inch cardboard tubes used for forms for concrete, not very expensive and can be cut to a lot of forms.
     
  18. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I needed to deGauss some cross-bracing Moly tubes in my airplane that had been magnetized by welding. I used one of these:

    [​IMG]

    The problem is to get the decaying AC field to finish the deGaussing process (just opening the switch suddenly can leave the metal objects magnetized) so I used one of these:

    [​IMG]

    I still have that bulk tape eraser here somewhere. You could make one by removing the side bar laminations off an old line-powered power transformer.
     
  19. Karenzee

    Thread Starter New Member

    Mar 6, 2015
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    Kermit2,

    I found a small one rated for 10 to 15vdc to 120vac - 200watt, that should work.

    MikeML,

    Seems ideal! how long were you keeping it turned on?
     
  20. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    slowly. Slowly increasing distance from the coil works the same way as the variac unit.
     
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