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Help in witricity

  1. Oct 26, 2009 #1
    we want to build a witricity circuit. will you please suggest us a circuit and components.Frequency 15MHz.Distance of separation of coils 75cm. Efficiency 45%.Load 220/60W.230v,50Hz supply..Thanks in advance
  2. jcsd
  3. Oct 26, 2009 #2


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    Staff: Mentor

    It is illegal to operate this circuit in most countries, unless you are inside of a well shielded room. Quiz Question -- Why is it illegal?

    What is the application?
  4. Oct 26, 2009 #3


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    I would expect that they would specify a maximum diameter for the coils. If you can choose, probably coils about a metre in diameter would work OK. Maybe 5 turns of thick copper wire wound with at least one wire diameter separation between wires. But that is just a guess.

    Also, if they don't specify otherwise, you could have the transmitting coil in the middle of two receive coils 1.5 M apart. This would avoid losing half the signal being transmitted away from one coil.

    If you are using a low impedance signal source, the transmit coil needs to be series tuned. That is the coil and a tuning capacitor are placed in series.
    You could try series tuning the receive coil(s) too.

    And keep it legal. Low power (like from a signal generator, not a transmitter) and in a well shielded location. Probably a basement would be OK if it is below ground level in all directions.
  5. Oct 26, 2009 #4
    Class E!!!
  6. Oct 26, 2009 #5
    WWVH? OR? Im not quite sure
    Did I get it?
  7. Oct 27, 2009 #6


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    Transmitting without a licence is illegal in most countries because spectrum space is valuable and government control is used to ensure it is used in a manner that does not interfere with other users.

    So, it does not have to interfere with anything to be illegal.

    It is illegal because it is against the law to transmit without a licence except in a few specified spectrum allocations and then only with approved equipment at approved power levels.

    Penalties in most countries are severe and may include prison time.

    Because nearly all electronic equipment radiates some interference, maximum levels of radiation that do not require a licence are published and it is possible to stay below those levels for low powered experiments.

    Radio Amateurs ("Hams") have the enviable privilege of being able to do experiments like this one and do them at high power. Antenna study is fascinating.
  8. Oct 27, 2009 #7
    What about tesla coils? SMPS? arc welders? There are plenty of sources of RF emissions that, although may not cause harmful interferance, are certaintly powerful (I think the welder in my garage is rated at 4.6Kw) The only restrictions I have read are those which limit the radiation on frequencies which may be harmful, like high power CB radio interfering with TV transmissions etc. Websters defines "transmitter" as "an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal. Does this make every tesla coiler, welder, or experimenter working with SMPS a criminal? This seems a bit counter-intuitive as the way radio was discovered in the first place was by experimenters manufacturing and using their own equipment.
  9. Oct 27, 2009 #8


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    Potentially, all of those things are illegal.

    As your quote says "an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal"

    The antenna bit is important. If there is a length of wire or other metal which approaches being a half wavelength long at the frequency of the interference attached to the device, it will become quite a good radiator.
    This can be mains wiring and the radiation might be harmonics of the original signal.
    If you had something like that and someone complained, you could find someone knocking on your front door.

    Accidental interference like that would just get you a "don't do it again", but transmitting to your mate across town on some random frequency would see you end up in court.

    The reason this project raised alarm signals was that the frequency was 15 MHz and there was no limit on the size of the antenna or radiated power. On a good day, you could transmit right around the world with an unrestricted setup like that.
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