Inductor Help

Discussion in 'The Projects Forum' started by eswara1997, Jan 25, 2015.

  1. eswara1997

    Thread Starter Member

    Dec 14, 2013
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    Hello,

    I am currently working on a theremin project. This one exactly:

    http://interface.khm.de/index.php/lab/interfaces-advanced/theremin-as-a-capacitive-sensing-device/

    There is a schematic and breadbaord diagram if you scrolld down. The author has also mentioned this: "Care must be taken in the choice of the parts L1 and C1. C1 must be a ceramic capacitor NP0 type (zero temperature coefficient) and L1 a high Q inductor suitable for high frequency such as a Neosid 00612299 but for the first test a standard 10uH Choke will do also the job."

    I ordered this item:
    http://www.mouser.com/ProductDetail/Kemet/SU16VD-40010/?qs=%2fha2pyFaduioQQvSwxPrBQYRxCMxaM8Q4eXENqjGH0g%3d

    Datasheet:
    http://www.mouser.com/ds/2/212/KEM_LF0021_SU16VD-417258.pdf

    So my first question is this, will this inductor be applicable for this circuit. Can it work. The datasheet doesn't help me much.

    My second question is, how the heck do i put this on a breadboard. It has 4 pins and im not completely sure how it works. Any help will be appreciated.
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
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  3. eswara1997

    Thread Starter Member

    Dec 14, 2013
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    so is that a high Q high frequency inductor?

    The one that i purchased, what is it for. Can i use it on a breadboard at all? It seems to fit.

    Lastly, what exactly is q, and how does this inductor work in an LC oscillator. Sorta new to LCs, i have only worked with RCs before.
     
  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The one you purchased is a common mode choke - two isolated inductors sharing a single core such that one type of signal is greatly attenuated while another type is passed through. Its construction is similar to a specialized transformer. These are used as part of a noise filter noise for AC power lines, such as in the input stage of a switching power supply.

    ak
     
    Last edited: Jan 25, 2015
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Q factor[edit]
    An ideal inductor would have no resistance or energy losses. However, real inductors have winding resistance from the metal wire forming the coils. Since the winding resistance appears as a resistance in series with the inductor, it is often called the series resistance. The inductor's series resistance converts electric current through the coils into heat, thus causing a loss of inductive quality. The quality factor (or Q) of an inductor is the ratio of its inductive reactance to its resistance at a given frequency, and is a measure of its efficiency. The higher the Q factor of the inductor, the closer it approaches the behavior of an ideal, lossless, inductor. High Q inductors are used with capacitors to make resonant circuits in radio transmitters and receivers. The higher the Q is, the narrower the bandwidth of the resonant circuit.
    The Q factor of an inductor can be found through the following formula, where L is the inductance, R is the inductor's effective series resistance, ω is the radian operating frequency, and the product ωL is the inductive reactance:
    [​IMG]
     
  6. eswara1997

    Thread Starter Member

    Dec 14, 2013
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    so what is a "high" Q value. Is there some trend or some sort of threshold. What value should it be approaching basically?
     
  7. ronv

    AAC Fanatic!

    Nov 12, 2008
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    In your case it is not Q so much as it is self resonant frequency. The capacitor and inductor make a resonant circuit at 4.1 Mhz. So you want an inductor with a resonant frequency well above this so it doesn't change that frequency. Maybe 10 X higher would be a good target. The one you have has the resonant peak at 5 or 6 Mhz.
    Q = 10 might be considered low, 100 high.
     
    eswara1997 likes this.
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