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Simultaneous IR Object Detection and IR Control?

Discussion in 'Electronic Basics' started by redbrickhat, Feb 26, 2006.

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  1. redbrickhat

    redbrickhat Guest

    I am planning to build a robot that uses a Sharp GP2D120 for IR object
    I would also like to control it using a VCR remote control and the Sony
    IR protocol.

    Is there any way of doing this without the IR signal from the remote
    control causing the GP2D120 to think it's detected an object?

    Any feedback will be appreciated.

    Thank you.
  2. Dennis

    Dennis Guest

    Decode all the characters on the Sony remote. Find a unique character that's
    not on the remote. Transmit the unique character from your IR LED (used to
    detect objects)with some time between the character being sent and when
    receiving and decoding characters use that character as an object detected
    condition. You will still need to deal with receiving the remote and
    detecting the object at the same time but this will allow the receiver to
    identify the signal being detected as an object or a command.

    Hope this helps,

  3. Guest

    It sounds like the distance detector is a canned solution that you
    can't change, which may limit your ability to solve problems.

    One thing you could do is simply sanity filter the output - if the
    distance reading jumps, take another. Don't believe anything that
    doesn't read the same (+/- error) twice. Harder if you have it
    spinning to scan the room...

    If you were designing both IR systems from scratch, using different
    modulation frequencies would help. It's possible they are already
    different - have you tried and verified a problem? When the IR
    transmitter and receiver are adjacent, it's easy to use synchronous
    detection (turn on the source, read, turn off the source, read,
    subtract) to get noise immunity - the module may already do that. When
    the source is something else, you are limited to filtering based on
    frequency (or much more complicated, pseudorandom code) and checking
    the data for validity with a checksum, etc.

    Would polarizing filters work with IR?

    Have you tested to verify there's actuall a problem?
  4. Bob Monsen

    Bob Monsen Guest

    You should be able to shield the GP2D120 from the IR remote control,
    although reflection could be a problem. I wonder if the hood could
    be made from something that wouldn't reflect IR? However, I'm also
    guessing they are modulated on different frequencies, so you might be
    trying to solve a problem that does not exist.

    If you simply can't make this happen, for whatever reason, try the
    TLP434/RLP434 Easylink Wireless modules. They use RF at 434MHz. They
    should work reliably, although they will cost more and take more power.

    Bob Monsen

    My life is a simple thing that would interest no one. It is a known
    fact that I was born and that is all that is necessary.
    Albert Einstein (1879 - 1955)
  5. Rich Grise

    Rich Grise Guest

    Just modulate them at different frequencies, like they do with radio
    stations. :)

    Good Luck!
  6. This shouldn't cause much of a problem -- The Sharp detectors use a
    modulated signal of ab0ut 1 khz with a 10% duty cycle. The remote
    control detector/demodulators use a signal of around 38-42 khz. In
    general, this won't cause a problem -- one of my robots uses the sharp
    detectors as auxiliary obstacle detectors and can also be controlled via
    VCR remotes -- I've not noticed any issues in practice.

    Hope that helps -- tAfkaks

    (Replies: cleanse my address of the Mark of the Beast!)

    Teleoperate a roving mobile robot from the web:

    Coauthor with Dennis Clark of "Building Robot Drive Trains".
    Buy several copies today!
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