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printed inductors

Discussion in 'Electronic Basics' started by Tom Del Rosso, May 14, 2013.

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  1. When an inductor is printed on a PCB in the shape of a 'square wave' or
    square zigzag, each time it zags the trace doubles back on itself. Doesn't
    this cancel the magnetic field to an extent? How much does the coil
    structure matter to a coiled inductor, or would the straight wire have the
    same inductance?
     
  2. brent

    brent Guest

    perhaps it is a high frequency inductor which is more like a
    distributed transmission line inductor?
     
  3. Phil Allison

    Phil Allison Guest

    "Tim Wescott"

    ** Tim has no idea just how stupid he is.


    ..... Phil
     
  4. We make spiral coils on PCB to 'shim' magnetic fields.
    I'm not sure what you mean by zig-zagging back... maybe a picture?

    Re: a coil versus a length of wire. You get more inductance from the
    coil. I think if you have a fixed length of wire and wanted to make
    the largest inductance then you'd wind it as one big single turn
    coil. (hopefully someone will correct me if that is wrong.)

    George H.
     
  5. Baron

    Baron Guest

    George Herold Inscribed thus:
    I suspect the OP is refering to the meander lines on a pcb used to match
    signal timing over varying trace lengths.
     
  6. I should have said that this definitely is an inductor. It's a choke
    connected to the power trace on a 4GHz board.
     
  7. Yeah just DC coils.
    OK thanks... (of course I have to go and check it now... grumble)

    George H.
     
  8. Hard to tune... I bet. This has just 4 coils, one each for the X, Y
    and Z gradient and then a Z^2 gradient. (Z is the diectron of the
    static field.)
    OK I'll have to check... gotta run

    George H
     
  9. Optimal coil length is a bit less than the coil radius.
    http://www.qsl.net/zl1an/Downloads/Inductance_Problem.pdf

    A Brooks coil is pretty close to optimal.
     
  10. amdx

    amdx Guest

  11. You mean for a given length of wire? Doesn't seem useful, since you can use
    a different length.
     
  12. Sure. But if you need to produce some 100,000 coils, wirelength may become
    an important parameter.

    petrus bitbyter
     
  13. What about a toroid? (I always want to put to r's in torroid)
    Or do you get more B field by spraying it everywhere?


    George H.
    (I love SED, say something stupid and learn something new, thanks)
     
  14. Tim Williams

    Tim Williams Guest

    You get more B by focusing it into a smaller space, but that doesn't
    usually give you more inductance -- it takes a lot of work to make B,
    because B is energy density (in fact, e ~ B^2).

    Dunno about the length required for an air-core toroid. Should be easy to
    find from the thin, infinite-turns toroid formulas though.

    Tim
     
  15. Yeah, I get to integrate the B field over all space so letting it
    spread out is a win. (In other ways toroids seem like a nice inductor
    shape.)

    George H.
     
  16. Phil Allison

    Phil Allison Guest

    "Spehro Pefhany"
    ** You have just linked a page from a Kiwi radio ham ??

    WTF ??

    The wanker does NOT even mention that his question is restricted to single
    layer coils.

    With any number of layers permitted, the solution is more like a sphere with
    a hollow centre.

    Coils made for loudspeaker crossovers were sometimes wound like a ball of
    wool in a "beehive" shape for maximum utilisation of the wire used.



    ..... Phil
     
  17. Robert Baer

    Robert Baer Guest

    The only geometries i saw were spiral in nature on one side (shaped
    either circular or square); inner end of spiral to via withstraight exit
    to outside of area.
     
  18. josephkk

    josephkk Guest

    That is not an inductor, that is a delay line (transmission line type).

    ?-)
     
  19. josephkk

    josephkk Guest

    At 4GHz it is not so clear. If you really want to know the tools are
    expensive (in part to really encourage you to buy platform enough). Like
    serious 3D EM solvers. Ask Dr. Hobbs.

    ?-)
     
  20. josephkk

    josephkk Guest

    Not always. The relationship between A (area enclosed) l (length of coil
    transverse to its axis) and n (number of turns) is not that clean. Crank
    the formulas and see for your self where the first and second order terms
    are.
     
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