Good quality cable needed


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  1. #1
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    Default Re: Good quality cable needed

    For 150' could the cable be enclosed by a continuous length of black plastic flexible pipe?

    Norm

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  3. #3
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    Default Re: Good quality cable needed

    Hi Norm,

    I need a bending radius on a few inches. The cable will be protected by mesh sleeving to preserve flexibility and add more toughness to it.
    This project of mine is in its infant stage. I’m sorry that I did not take the time to fully explain the requirements but I myself don’t have all the information yet. I’m collecting all the information I can before committing to a final design approach.

    The RS485 half-duplex and maximum 4 wires cable (power + twisted pair) is already decided and can not be changed.

    I found a good (but not ideal) Belden cable 3106Aas a candidate. Its only problem is that does not give me a separate GND wire.

    Dave,
    Your suggested cable seems robust enough.
    I only have one question: can one of the twisted pair be used for power transfer to the slave unit? I was told that the data wires should be twisted and power wires should be normal.

    Thanks for the input.

    Nick

  4. #4
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    Default Re: Good quality cable needed

    Quote Originally Posted by NickMu View Post
    Dave,
    Your suggested cable seems robust enough.
    I only have one question: can one of the twisted pair be used for power transfer to the slave unit? I was told that the data wires should be twisted and power wires should be normal.
    I've never seen a requirement that the power pair be non-twisted and doubt that twisted pair would cause a problem.

    I found it merely by searching Bing using 'rs485 cable power shield waterproof' so your questions would best be addressed to the supplier.

    Since you only need half-duplex, this should cost a bit less.
    http://www.hyperline.com/catalog/cab...sf2-a-pe.shtml
    Last edited by dhouston; - 10th February 2013 at 16:04.

  5. #5
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    Default Re: Good quality cable needed

    I was targeting the same one after you gave me the link.
    I will contact the manufacturer for more information and get back with my findings.

    Thank you again Norm and Dave for your prompt responses.

    Nick

  6. #6
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    Default Re: Good quality cable needed

    I have been sending power along with RS485 for several years on CAT5 (twisted) with no problem at a baud rate of 300 although that may make no difference.

    Norm

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    Default Re: Good quality cable needed

    Any particular reason why you limited your highest baud rate to 300?
    Does it have to do with the power transfer, distance or just you did not need higher baud?
    What kind of current can you safely deliver to the slave? I need 50 – 100 mA.
    I can only guess that you used a diode on each data line and still power from them. If so what is the ratio between signal / no signal timing in your system?
    I need a 20 ms frame within which 10 to 12 bytes will be exchanged between the master and slave with a minimum 5 ms free, on each side, for other tasks. This forces me to use 19200 or higher baud rate.
    Can you share a concept schematic of your setup?

    Thanks again and again.

    Nick

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