Inductor value doubt!

Discussion in 'Wireless & RF Design' started by aj_silverthunder, Nov 8, 2009.

  1. aj_silverthunder

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    guys what will be the inductance of a solenoid inductor if : 1)5 turns 2)4mm internal diameter 3)5mm length of the wire!please help me guys!
     
  2. bertus

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    Last edited: Nov 8, 2009
  3. aj_silverthunder

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    but please tell me the value of that inductor!
     
  4. SgtWookie

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    Google "inductor calculator"
     
  5. BMorse

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  6. thatoneguy

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  7. SgtWookie

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    Actually, a critical element has not been provided; that's the size of the wire used.

    If AWG 21 wire is used, inductance will be about 122nH
    If AWG 30 wire is used, inductance will be about 102nH
    If AWG 40 wire is used, inductance will be about 99nH.
     
  8. aj_silverthunder

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    guys u told the inductance will be 57.9nH ,but can i use #18 copper wire to make that inductor!
     
  9. KL7AJ

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    Naturally, that formula only works if the diameter of the wire is less than the center-to-center turns spacing. :) (In a similar vein, I learned the hard way that certain antenna modeling programs "puke" if you try to have two elements occupy the same space....silly me!) :rolleyes:


    Hmmm....I'll have to consult my wire gauge to diameter conversion chart to see if I can answer the lad's question directly. Please stand by.


    Eric
     
  10. aj_silverthunder

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    i am really thankful for r interest!thank u very much!
     
  11. KL7AJ

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    No problem...I've been winding coils since I was 8. By the way, if it turns out to be mechanically impossible to wind a given coil with that particular gauge wire, you can always twiddle the diameter or the length, or number of turns, as long as the end product is the same. There IS a magic optimized proportion for a coil...that is, the diameter/length/turns ratio that gives you the MOST inductance for a given length of wire. This will also result in the highest Q possible for a solenoid. I forgot the name of this type coil, but there are on-line cackle-ators for that as well.

    Eric
     
  12. SgtWookie

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    Hmm,

    Bertus came up with very different results than I did; his was around 57uH, but by my calculations it would be in the 100uH range, depending on inductor wire size.

    AWG 21 is about the limit for wire diameter, if you wish to keep the coil within the length constraint specified (5mm).
     
  13. aj_silverthunder

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    wht if i use AWG 18 to make that inductor,what would be it inductance
     
  14. thatoneguy

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    The coil length would be over 5mm, so it couldn't be made with 18 Gauge wire.

    --ETA: 18ga wire, solid, with insulation is 1.2mm Diameter, 5 of them next to each other would be 6mm long.


    Smallest, using 20 Gauge insulated wire, 100% fill


    Coil length: 5 mm
    Avg. coil diameter: 4.9 mm
    Winding thickness: 900 µm

    Wire length: 82 mm
    Resistance: 2.2 mohm (copper wire at 20°C))

    5 Turns, 5mm long, 4mm inside diameter.
    Inductans: 71.34 nH
    Using a different gauge wire will change the calculation GREATLY when working with these small values.
     
    Last edited: Nov 10, 2009
  15. bertus

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    Hello,

    I used the formula from the page I gave before:


    Greetings,
    Bertus
     
  16. aj_silverthunder

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    is it better to use insulated copper wire to make LC circuit or a non-insulated one!
     
  17. thatoneguy

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    It must be insulated for this size, preferably "magnet wire", which has an enamel coating rather than the plastic sheath.

    Using a thicker insulation will change the length of the coil, and therefore the inductance. This is the reason that the calculations above do not match, or are given as a range. My estimate assumes the wires are wound next to each other, with insulation touching (100% fill factor).

    If the coils may be in contact with each other, or any other items in the circuit, insulated wire should be used.

    Some high power transmitters have non-insulated inductors, but those are kept from being easily accessed or touched.
     
  18. aj_silverthunder

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    should i leave gap in between the woundings to make solenoid inductor like this: "http://www.flickr.com/photos/aj_silverthunder/4098212631/ "
    or should i not leave any gap between them..
     
  19. thatoneguy

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    If you are using wire larger than 22gauge, there won't be any room to wind the coil within the dimensions you specified.
     
  20. KL7AJ

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    This depends on the frequency. If it's a UHF circuit, you will be better off with fat, uninsulated conductors...as long as the spacing between turns is sufficient to hold off the voltage.


    Eric
     
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