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How to make a RS-232 Activity LED circuit?

Discussion in 'Electronic Basics' started by Bob Business, Sep 14, 2003.

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  1. Bob Business

    Bob Business Guest

    I have a project that uses a 2 wire connection via RS-232 / DB9 serial
    to program it, but nothing is happening, so I thought I could use a
    circuit that connects and displays activity via 2 dual color LEDs.
    Since I am a programmer by trade, I have no idea how to do this, so I
    was wondering if anyone had any plans or ideas. Note that RS does
    carry a product like this for $15, but it is DB25, and has lights for
    7 data lines. I only need 2.
  2. Bob,

    Take a red and a green LED and connect them antiparallel. Then a serie
    resistor of let's say 2k2. Connect this combination between GND and the
    signal line you want to observe. Keep in mind that this LEDs eat energy. So
    if you use them on a line that's meant to power a small circuit, a mouse for
    instance, there may not be enough current left to power this circuit.

  3. the Wiz

    the Wiz Guest

    The minimum RS232 connection is usually 3 wires transmit, receive, and ground.

    More about me:
    VB3/VB6/NSBasic Palm/C/ PowerBasic source code:
    Drivers for Pablo graphics tablet and JamCam cameras:
    johnecarter atat mindspring dotdot com. Fix the obvious to reply by email.
  4. Jim Large

    Jim Large Guest

    You are assuming that the O.P. wants two-way
    communications. I used to have a micrcontroller
    board from Circuit Cellar that had "one and a
    half" serial ports. One was the console port
    (three wires), and the "half" was for a printer.
    It only had a Tx signal and ground. There was
    no Rx.

    -- Jim L.
  5. CFoley1064

    CFoley1064 Guest

    I used to have a micrcontroller
    Ah, yes. The BCC-52 board, based on the 8052AH-BASIC (no longer made by Intel,
    of course). They should've put 41 pins on 'em. Other than that, a lovely,
    versatile 8-bit SBC, especially good for beginners. Micromint now has the MCU
    made by a 3rd party. The board is especially useful if the customer wants to
    be able to understand what the SBC is doing, and may want to tweak it in the
    future. As long as you burn in _your_ program on the EPROM (you can do that
    from the board, too), they can play to their heart's content, and just cycle
    power to go back to the original program they paid for. KISS. They still sell
    'em at

    Good luck
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