help with making inductor

Discussion in 'The Projects Forum' started by KMK, Nov 8, 2010.

  1. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    Hi everyone,
    I'm trying to make an inductor & wanted to know if the thin enamled coil from an old tubelight coil would work for that.
     
  2. Artikbot

    Member

    Nov 7, 2010
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    As long as the enamel coat is not damaged, it will.

    Just make sure you choose the adequate type of core ;)
     
  3. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    Hey Artikbot
    thansk for that information..thewire does seemm altight, but im some places the emanel doses seem ot be scratched.. will it still work ?
     
  4. Artikbot

    Member

    Nov 7, 2010
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    If your multimeter is accurate enough (down to the milliohm level), you can do some testing:

    Measure the resistance of the extended wire (or at least, touching itself as less times as possible).
    Now wind the inductor and re-test it again. If the values are identical/very very similar (it won't be identical due to the testing leads possessing resistance), the wire isn't damaged. If the values differ by quite a lot... Then the wire is shorted sowewhere, therefore useless.

    But that it works for the test doesn't mean it will work forever, as heat will expand (and contract when cooled down) the wire causing creeping on the enamel coat (if it's old it's very susceptible to creeping) and it will eventually fall off.

    You can buy small 2-3m wire bags for about 3 USD... Not really worth to recycle wire from old parts.

    Although I've had very good luck salvaging 15+ years old heavy gauge wire out of old toroidal transformers ;)
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    The really old magnet wire had either a lacquer or shellac coating. It cracks with age.
    Later stuff usually has a synthetic coating which is a bit more flexible.

    Whether it'll work for you or not depends on what you're winding it on, and how you wind it. If you're winding it on an insulating type of form (say, the body of a Bic pen) and there is a little space between each wind, and you spray on some acrylic enamel to hold it in place and provide new insulation or cover each layer with tape, you can likely get away with it. But, if you're winding it on an uninsulated conductive core, and/or winding it tight (no space between windings), your results will vary considerably.
     
  6. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    thanka for that info.. i did crate an inductor by winding it aroung an iron nail.. before winding, the resistance was abt 4 ohms... after winding, it cane to abt 6.. does that tell u anything...? also is there ant way to check if the inductor is working or not..?


    thanks
     
  7. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    What value of inductor are you trying to make? What's it for?
     
  8. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    i dont know tha value.. but im just trying to get the hang of making an inductor fo some projects/experiments mentioned here..so was trying it out..
    also when winding multiple layers of same coil.. do all the layers go in same direction(on a horizontally held conductor) EG from left to right.. or alternately.. ?
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    A nail makes for a very poor inductor core, as there are horrific losses due to eddy currents, saturation, etc. Basically, it's the wrong material for the job.

    Ferrite cores are good for fairly low frequency inductors and broadband transformers.

    Iron powder cores are used for higher frequencies.

    You can also wind air coils, if the value of inductance required is low, and/or you don't mind winding on a lot of turns.

    Wheeler's Formula is pretty decent for making single-layer air coils; it's off by a few percent, but you can get pretty close with it.

    For multi-layer air coils, you need a more complex formula. There are lots of websites that provide online calculators for such inductors.

    If you want to use toroids, perform a Google search on "mini Ring Core Calculator" - it is a great set of freeware tools that will be of great assistance in helping you to wind toroidal inductors, and contains data on a few manufacturer's toroidal cores.
     
  10. Markd77

    Senior Member

    Sep 7, 2009
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    It doesen't make any difference.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    That's OK; experiment away. Nails work moderately well for electromagnets, if you wind enough turns on them. You can also make a rudimentary motor using nails and a piece of dowel rod.

    With n-layer coils, direction of wind can become a factor if you have multiple inductors on a board; they will interact with each other. Placing inductors 90° from each other tends to minimize the interactions.

    If you're winding multilayer coils, you don't have a lot of choice but to wind back and fourth. Some RF inductors are wound in what almost appears to be a herringbone weave pattern; that is to minimize the parasitic capacitance.
     
  12. wayneh

    Expert

    Sep 9, 2010
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    Right, as long as the windings themselves go around the core in the same direction, like on a fishing reel. Back and forth doesn't matter.
     
  13. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    Thnaks for all the help everyone.
    i have made an iductor.. but can any one tell me hot to check if it works ?
     
  14. wayneh

    Expert

    Sep 9, 2010
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    First make sure you don't send too much current thru it and burn it up. There are guidelines for max current versus wire gauge and coil depth.

    Once you're OK with that, send an appropriately small DC current thru it and see if it behaves as a magnet. If yes, you've got an inductor. No field means you have a wire break somewhere, and it's not an inductor. Of course an ohms meter is another test.

    Why did you wind it in the first place, what are you trying to do?
     
  15. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Without an LCR meter or an oscilloscope, it is nearly impossible to get the exact value of an inductor.

    There are some 555 timer setups that one can use for search for the inductors resonance with a capacitor, but the accuracy isn't too great, and requires a bit of math. Actually, the oscilloscope method requires a bit of math, as well, in addition to a signal generator.

    If you are only trying to make an electromagnet (nail or bolt for the core), then hooking it up to a battery will let you know if it is working, as it will be a magnet.
     
  16. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    i was just checking if i can make an inductor.. then plan to try & make the FM transmitter mentioned in the projrcts section..
    but how was i supposed to make it without winding it ..?
    and it looks like its not working as the nailsdosent seem to get magnetised.. dosent even pull a small nut..
     
  17. Wendy

    Moderator

    Mar 24, 2008
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  18. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    If there are only a few turns, the magnet will not be very strong.

    You mentioned you are working on the receiver, use a Web Calculator to get you into the ballpark range of what you need for value.

    Any coil of wire is an inductor, in fact a straight wire is an inductor at a high enough frequency, so they are easy to make. The problem really comes when trying to NOT have a parasitic inductance in high speed logic circuits (hundreds of Mhz)
     
  19. Markd77

    Senior Member

    Sep 7, 2009
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    If you have a compass try putting the coil near it and see if it makes the needle swing - not too close at first, to avoid demagnetising the compass.
    Failing that, a small magnet hanging on a fine thread.
     
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