How to make inductor coils?

  1. I am looking forward to a small project. For this i need some inductor coils. I searched through the local shops, but i could find any inductor coil. According to what i know inductor coils are made by making loops using wires. http://www.instructables.com/id/Making-a-Simple-Induction-Coil/
    Is it possible to make any inductor coil like that?

    These are the coils that i need
    .12 uH coil
    .15uH
    .68 uH coil
    .82 uH coil

    For the .15uH there is a description like this.
    "Air wound; 1.5 turns
    on 3/8 form
    #26 insulated wire"

    I would also appreciate if you could explain these in a simple manner because i dont know a lot about electronics.
     
  2. jcsd
  3. vk6kro

    vk6kro 4,058
    Science Advisor

    Inductors like those would usually be used at very high frequencies. What are you trying to make?

    You could use a 3/8th inch drill bit and wind the coil on the shaft of it. You would then slide the coil off the drill bit and use it like that.
    Once wound, it will hold its shape to some extent, although #26 wire is quite thin.so you would have to support it at each end.
     
  4. What you explained is how to make the .15uH coil, right?

    What about the others? Is it possible to make them too?
     
  5. vk6kro

    vk6kro 4,058
    Science Advisor

    Yes, maybe.

    There are formulae for calculating these dimensions, however with very small coils like these, you really need a tester to measure the final result.
    This is because, slight variations in the wire diameter, coil diameter, coil length and turns spacing can all have an effect on the final inductance.

    One formula for calculating inductance given the coil dimensions is Wheeler's formula. I won't quote this, but you can look it up.

    Here is an Internet coil calculator.
    http://www.crystalradio.net/cal/indcal2.shtml
    You would have to check the result, though.
    If there is a variable capacitor in parallel with the coil, you can usually adjust this for resonance, even if the coil is slightly inaccurate.

    There are manufacturers of coils:
    http://www.murata.com/products/catalog/pdf/o05e.pdf

    There are meters that can measure such small coils:
    http://electronics-diy.com/lc_meter.php
     
  6. NascentOxygen

    Staff: Mentor

    You should indicate what this project is. I suspect that the inductor values may be critical to the success of the project.
    While you can wind coils yourself and to any value, expect the final coil's inductance to differ from what you designed for by a factor of anything up to about x3 or x1/3, so for critical values they will have to be modified or tweaked to get the value closer to the desired value. The "connecting wire" that you join to these inductors may contribute more inductance than the coils themselves. Construction techniques can be very important.

    What is the circuit you hope to construct?
     
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