charging via bluetooth

Discussion in 'Wireless & RF Design' started by vishnu.mec, Dec 10, 2011.

  1. vishnu.mec

    Thread Starter New Member

    Aug 6, 2010
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    hai all..!
    can anyone please tell me if it's possible to transfer energy through bluetooth?
    i mean a bluetooth device will be plugged to the power supply and there will be a field around it. so if we place a mobile phone in that range, it can be charged.
    we only lack the conversion techniques..
    so what do you guys think??
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,421
    3,355
    No. There is not enough RF energy transmitted to be of any use for the purpose you intended.
     
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  3. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    An emerging technology is power harvesting. Ambient RF energy can be used for that. But this is still a field of research.

    A common cellphone will probably consume too much energy while it's on. Even if turned off it would take a considerable amount of time to charge this relatively big battery. Wireless cellphone chargers exist and could even be incorporated into an existing phone if space is available. They use, however, inductive coupling.

    Then there is the fact that a BT adapter is not designed to do this, meaning it will not transmit continuously a carrier so it would be quite inefficient.

    Google Energy harvesting.
    Have a look at this example from Powercast.

    If you want to experiment try the LTC3108, a power management IC supposedly capable of stepping up voltages from 20mV. (use the SSOP not the DFN package, the DFN is difficult to solder)

    Finding and configuring an antenna for this purpose/frequency would be quite challenging.
     
    Last edited: Dec 10, 2011
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  4. vishnu.mec

    Thread Starter New Member

    Aug 6, 2010
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    so v just have to increase the number of transmitting devices, right?
     
  5. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    I guess first you have to estimate how much RF energy you can obtain from a BT device.
    Then you also need to verify how you want to transform the RF energy captured to charge your battery.

    Since you will need to modify your cell phone anyway why not go a much simpler way?

    Make a wireless charger using low frequency (125kHz) and inductive coupling.
     
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  6. @android

    Member

    Dec 15, 2011
    178
    9
    No. conversion technique is not the point of consideration. First tell me how can you provide enough current to charge battery with wireless field?? Basically they are all voltage waveforms and after interacting with the antenna(of course Farraday's law!!); they induce very very small amount of current which we need to amplify for further use. SO???
     
  7. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Well, it is absolutely possible to charge a battery with an alternating (electro)magnetic field.

    RFID tags are powered like this, depending on frequency this can be via RF energy for up to a few meters for UHF tags or via inductive coupling at low frequency. This means there would also be energy available to charge a battery.

    Google:
    Energy harvesting

    Wireless charging

    The question was about BT which I believe to be much too weak to do anything useful. The selfdischarge of a battery is probably higher than what you could get from BT. Just an assumption, I have no proof for that.
     
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