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Short Distance Wireless Power System

  1. Jun 13, 2009 #1

    I am working on building a wireless power system, I have looked into it a bit and the best if not only way seems to be a resonant air core transformer.

    My primary coil/circuitry can really be infinite in dimension, but my secondary coil needs to be no more than 2 inches in diameter but could be equally as thick.

    I am only looking to transfer power about 1-2 inches as well, basically through a table.

    My draw out of the transformer is going to be 14 V, to be used in another circuit to power some LEDs etc.

    I will update you on my progress, but any links, formulae, or other help would be much appreciated.


  2. jcsd
  3. Jun 14, 2009 #2


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    Science Advisor

    If you can choose your frequency and drive impedance, a low impedance link below the table loosely coupled to a parallel tuned circuit above the table seems possible.

    It will be quite inefficient but given enough drive power, you might be able to get enough out.

    It would be a case of empirical design, though..... ie build it and see what happens. :)
    The link below the table could have a series capacitor to tune out any reactance.

    Just for you, I tried winding 10 turns of wire on a 2 inch former and another 12 turns of wire about 2 inches away.
    With about 100 pF total across the 12 turn secondary, it resonated at about 15 MHz. This seemed to be about the best arrangement. The voltage across the tuned circuit was then about 1/3rd of that across the primary. Pretty inefficient coupling, but maybe good enough.
    You would need to develop about 60 volts peak to peak across such a primary to be able to run LEDs off the secondary. I haven't done this, so I can't be sure.

    You could try putting variable capacitance in series with the primary to get a voltage step-up if your signal source is low impedance.

    Adding ferrite as a core only helped if the ferrite went through both coils, so this would not be possible in your case.

    Fascinating project, though.
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