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Powerless transceiver ?

  1. Apr 9, 2004 #1


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    Greetings !

    I was wondering if anybody heard of a bluetooth/802.11/
    27 MHz range LAN transceiver (or maybe something like a
    radio transducer) that can operate by using power from
    received transmissions - thus requiring no coupled power source ?

    Also, which of these protocols could allow it technicly in the first
    place - that is, involves continous control signals by the "main"
    control unit or something, thus providing the necessary power
    for the modulated or separate return signal transmission ?

    Finally, if such transceiver circuits exist/are possible - would/do
    they require non-standard improved receiving capability of the units
    with which they communicate due to low transmission power ?

    Thanks. :smile:

    Live long and prosper.
  2. jcsd
  3. Apr 9, 2004 #2


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    That would require some serious power output from the transmitter, very low power consumption on the receiver, close distances, and focused antennas (to keep the power from spreading). And then to transmit data back? From a consumer standard?

    If you're on a network, you're likely using some device that has its own power source. Tapping off that would be easy, especially with USB.

  4. Apr 9, 2004 #3

    Edit: I inadvertently ignored your bluetooth, 24MHz spec when I posted the following, which describes the IR (f>>24Mhz) technology for battery-free reception/transmission already in widespread use.

    If I understand what you're asking, the answer is yes, and they're being used all over the place.

    Those toll tags that let you drive through toll booths without stopping are infrared transmitter/receivers. A transmitter in the toll booth radiates an ir wave with sufficient power to provide the toll tag just enough energy for it to radiate an ir signal that identifies it to the toll booth as you drive by.

    They've been used in agriculture for even longer to identify livestock as they move around and even keep track of how long each one spends at the feed trough etc.

    I think Walmart has a pilot program going to identify and track their stock as it comes into the store and moves from the stock room to the retail shelves, to the cash registers, and out the door. The holygrail of this technology is tags so small and cheap they could be imbedded in every product, making the whole checkout process obsolete! They've got the "small" part nailed, but the tags still cost around 10c (I think). That has to come down closer to a penny for it to be economically viable. It'll happen!
    Last edited: Apr 9, 2004
  5. Apr 9, 2004 #4


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    Greetings !

    O.K. I now about part of that stuff. To clarify
    a bit, I'm reffering more to various computer related
    wireless appliances like keyboards, mice, joysticks
    and stuff like that. I heard about the Microsoft wireless
    keyboards and mice and bluetooth mice as well as similar
    Logitech technology. They all use batteries, but the data
    transfer rates are very low and they are all used in close
    proximity to the computer system with short range wireless

    So, I was intrested to find out weather there are
    technologies out there that can do the same things
    without a power source at all. I suppose it depends a lot
    on the way the protocols work too.

    Thanks. :smile:

    Live long and prosper.
  6. Apr 9, 2004 #5


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    I believe what you're talking about actually RF devices. The tags are commonly called RFIDs. Futhermore, toll devices do not use infrared either; they also use radio.

    - Warren
  7. Apr 10, 2004 #6


    You're right. I was even thinking "RFID" in one part of my brain, but the part that wrote my post translated that into "something....something....intrared device". Maybe I need to get an EEG or something.

    Come to think of it, I need to get a life; it's 4:00 in the morning!

  8. Apr 11, 2004 #7


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    O.K. , if we're into that, how about renaming it to - "multiple
    modulation modes" transponders. And again, would the
    relevant protocols support their operation ? And would
    the current relevant transmitters and receivers (integrated
    into today's computers, for example) be able to pick
    them up at the same short ranges ?

    Thanks. :smile:

    Live long and prosper.
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