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12V pulse to serial port

Discussion in 'Electronic Basics' started by Mickael, Aug 10, 2004.

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  1. Mickael

    Mickael Guest

    I need to read a 12v pulse from a serial port, Can I connect that 12V
    pulse directly to the serial cable (Receive pin) and get information
    from there?
  2. Lord Garth

    Lord Garth Guest

    The input to an RS232 serial port is supposed to swing between +12V
    and -12V. A signal between +3 and -3 is undefined.

    You can use a 1488 or one of the Maxim ICs to create the correct
    bipolar signal from your source.

    You can also use a 4050 hex buffer for level shifting. Its inputs can
    withstand a 12 volt input when its supply is 5 volts. The output would
    then be capable of being read by the parallel port rather than the serial

    See here:
  3. Dbowey

    Dbowey Guest

    arriane posted:
    Probably, yes, but.....

    The direct connections between two "RS232" equipments with the Send Data of
    each connected to the Recive Data of the other is called a "Null Modem."

    I am aware of two different "RS232" specs, however.

    One, is the RS232 recommended standard (thus the RS prefix), and its interface
    is at +and - 12V. This has always been accepted as a Standard.

    The other is the ANSI/EIA 232, which IS an industry Standard, and its interface
    is at + and - 5V.

    I've mixed the two occasionally with trouble free results, but I usually use a
    pull-down resistor on the Receive Data pins to drop the voltage a bit.

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