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Very short range bidirectional RF link.

Discussion in 'Electronic Design' started by moby, Nov 27, 2005.

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  1. moby

    moby Guest

    I need to be able to transmit analog data (1..100khz) over a very short
    range (max 2 metres)
    reliably and without wires. IR is not a possibility as there are times
    when the stations will not be able to "see" each other. Latency must be
    much less than 1ms, hence digitising and bluetooth (with its 40..50ms
    latency) is out. Several pairs of units may be being used in close
    proximity hence single frequency "garage door opener" style devices are
    out. Of course it has to run on 3 volts, almost no current and be no
    bigger than a quarter. Any chips or modules suitable ?.
  2. Phil Allison

    Phil Allison Guest

    "moby" <

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  3. John - KD5YI

    John - KD5YI Guest

    A method:

    Achieving it within the other constraints (no current, size of quarter, etc)
    will depend on your abilities.

  4. Bob Monsen

    Bob Monsen Guest

    Check out the laipac tech RF ASK modules. You can either encode the
    data yourself, or use them in conjunction with the Holtek HT12E and
    HT12D encoder and decoder chips, which will do it for you, and also allow
    8 bit addressing of devices.

    They are not tranceivers, so you'll need both a transmitter and a receiver
    for each station, and some kind of simple protocol for preventing garbled
    data (eg, checksums, packet headers, sequence numbers, retransmission,
    etc, etc.)

    They have pretty good range, and don't require anything fancy for antennas
    (1/4 wavelength wire works well. 1/2 wavelength dipole would probably
    work better, although I suspect they are impedance matched for the wire
    antenna. They are 433MHz).

    If you are looking for chip level solutions, try Chipcon. They have
    various tranceivers on a chip that would work for you. Their Zigbee
    chips may be what you want. They will do more of the high-level work for

    Microchip also has a transmitter on a PIC + external receiver chip
    solution (see rfPIC on the microchip site).

    Bob Monsen

    What good your beautiful proof on (the transcendence of) PI. Why
    investigate such problems, given that irrational numbers do not even exist?
    - Leopold Kronecker
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