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Thread: wiring rs232 cables..

  1. #1
    Constant Bitrate
    Join Date
    Nov 2004
    South West

    wiring rs232 cables..

    hi guys, i have to make up a cable to extend my touchscreen controler. i have the plugs and some 4pair rs232 cable. i have the diagram and it says pin 5 to pin 5 is rs232 ground. i am only using 7 pins so should i use a normal conductor for pin 5 or use the drain wire from the cable shield? if i use a conductor wire should i connect the drain wire to the shells of the plugs and if so how? (cant seem to get the solder to stick) thanks!

  2. #2
    Constant Bitrate
    Join Date
    Jul 2002
    Here's my 2 cents worth.

    For the signal ground I think its best not to use the cable shield - just one of the wires in your cable.

    I don't think I've had any shielded RS-232 cables and using the shield probably isn't that important unless you're in really electrically noisy environments. RS-232 voltage swings are pretty large by comparison to most electronics these days and the frequencies (baud rates) are pretty low too so I think its pretty robust.

    If you do connect the shield, its best to just connect it on one end to avoid ground loop problems. Keep in mind that there are an awful lot of plastic RS-232 connectors out there, and I don't think there is any guarantee a metal connector or the mounting screws are grounded to anything anyway. You might have to connect a jumper wire to a good ground point for your shield to do any good.

  3. #3
    Maximum Bitrate kiltjim's Avatar
    Join Date
    Feb 2004
    PA, USA
    I wouldn't use the shield as the ground. I would use a seperate wire for the ground, this should avoid some noise in the connection. It might cause your mouse to jump around, not much, but enough to irritate you later on.
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  4. #4
    Maximum Bitrate Change's Avatar
    Join Date
    Aug 2004
    Another thing you can do for really long cable runs is use cat5, and for each twisted pair use one conductor for signal and one for ground. Doubt the touchscreen controller is using all the control lines of your serial port, probably just TxD and RxD.

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