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Thread: com port max voltage

  1. #1
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    com port max voltage

    what is the max voltage you can feed pin 8 of a serial port?
    and do any of you uses any protection to stop spikes from relays when they
    open and close

  2. #2
    Raw Wave Rob Withey's Avatar
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    Quote Originally Posted by vtcom View Post
    what is the max voltage you can feed pin 8 of a serial port?
    See RS232 spec here : http://www.lammertbies.nl/comm/info/RS-232_specs.html
    Quote Originally Posted by vtcom View Post
    and do any of you uses any protection to stop spikes from relays when they
    open and close
    Use a snubber diode across the coil, standard thing to catch the back emf.
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

  3. #3
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    most that link is over my head am i correct to believe it can take 25 volt

  4. #4
    Raw Wave Rob Withey's Avatar
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    Quote Originally Posted by vtcom View Post
    most that link is over my head am i correct to believe it can take 25 volt
    In theory, yes. However in practice it tends to be more like -12 -> +12v and I'd be slightly worried about putting more than that in. In any case I would put a current limiting resistor in series to reduce the chances of any issues.
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

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