witricity help regarding amplifiers

Discussion in 'The Projects Forum' started by mohit204, Nov 7, 2009.

  1. mohit204

    Thread Starter New Member

    Nov 7, 2009
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    hey,
    I am doing a project in witricity,where i plan to light a 60W 220v bulb by transmitting power wirelessly.
    Since the concept works at higher frequencies than normal,i chose to build a Colpitts oscilltor circuit giving an output of 1MHZ.
    My problem is that i am not able to design a proper amplifier circuit,to amplify the output from my the oscillator(which is very less) ,so that i can feed it to the primary coils of my model

    Any help please would be appreciated
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    1Mhz is firmly in the realm of RF, which will attract the attention of whatever athorities who are in charge of the RF spectrum in your area. How are you planning on dealing with this? A 60W (more actually, there will be losses) signal in the middle of the AM band ain't nothing to sneeze at.
     
  3. mohit204

    Thread Starter New Member

    Nov 7, 2009
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    well,my model is a part of a college project wherein we are allowed frequencies up to 15 mHZ.So the frequency is not a problem for me

    My problem is how do i generate sufficient power in my primary coil to transfer it to the secondary.The output of the oscillator will be in a a few mV.I guess amplification of the oscillator signal is a means,bu which kind of amplifiers to use seems to be bothering me
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Amplifiers are actually easy, something like a class C would work fine, but even universities are not exempt from emissions rules. By definition you want to broadcast power.

    The may be an exception for 13.5Mhz, you need to research it a bit. This freq has been set aside for industrial applications.

    Again, frequency isn't the only issue. By international law there are strict controls on emissions, since the RF spectrum is extremely limited and respects no boundries. The fines are substantial, and it is easy to trace down to location.

    What you are interested in is standard practice for Ham radio types. You can use directional antennas and couple it pretty tightly.

    Speaking of Hams, they are the ones most likely to both help you if you respect the airwaves, and turn you in if you don't, and we are everywhere, even in India.
     
    Last edited: Nov 8, 2009
  5. wolfkeeper

    New Member

    Nov 8, 2009
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    Actually, by definition he *doesn't* want to broadcast power.

    This witricity stuff works like induction hobs; it's near field, magnetic stuff, not far field radiation.

    You do still get far field radiation, but that's a *loss* and is undesirable; and the more of it there is, the less well the energy transfer has worked and will work.

    Check out the wikipedia page:

    http://en.wikipedia.org/wiki/Resonant_energy_transfer

    There's also some quasi-standards on inductive loops around, you need to design your stuff to meet them if possible, or ideally run it in a faraday cage.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    If you want any distance you can not separate the electro from the magnetic. Otherwise, what's the point? A transformer is more efficient.

    Coils are used as antenna's frequently, this is basic physics, and if you generate a powerful magnet field there will be radiated energy as photons on the side.
     
  7. geogaurav

    New Member

    Nov 18, 2009
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    hey mohit...i guess d problem statemnt says that you need to hav a 230v, 50hz input supply....then hw can u use collpit oscilatr for ac input.....i mean, if m not wrong this oscilatr works on dc input....
    also i want to raise same quest to evryone dat what should i use if i have to increse d freq of ac supply...i.e. from 50hz to abt 10 MHz....I again remind u all dat freq isnt a issue here...
     
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