What's the easiest 2 wire cable ?

Discussion in 'General Electronics Chat' started by Roger at CCCC, Jan 30, 2010.

  1. Roger at CCCC

    Thread Starter Member

    Jun 8, 2009
    17
    0
    Simple question, I think:

    I want to buy/make a simple cable so that I can use a DS18B20 1-wire thermometer at a distance of 20 or 30 feet or maybe even up to 100 feet. It only needs two wires but probably needs to be polarized (is that the right word?) to make sure that ground and signal are connected properly at each end. There are so many choices of connectors and wires that I’m not sure what’s simplest and easiest. So this is the question: what is the simplest, cheapest, and easiest way to make/buy a two wire cable with end connectors with a length of between 20 and 100 feet? Thanks for any suggestions.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    What are you connecting the 1-wire device to?

    hgmjr
     
  3. Roger at CCCC

    Thread Starter Member

    Jun 8, 2009
    17
    0
    The 1-wire device is connected to an Arduino microcomputer. Actually, I think I have answered my own question. I have a lot of old telephone wire and jacks. I have discovered that it works just fine for long cables with one problem. Telephone jacks, for reasons that I do not understand, reverse polarity so that the red wire on one jack is actually connected to the green wire at the jack at the other end of the cable. If I reverse the wires inside the jack, then everything works just fine. So this is a different question than what I first asked. Now I would like to find a way to modify the telephone jack so that it doesn't matter which wire is signal or ground in the incoming cable. I tried connecting some diodes in a bridge rectifier arrangement but that didn't seem to work, although I don't know why. So I'm battling ignorance at several levels. But my goal is still to find a simple cheap and foolproof way to run a long two wire cable. Anyway, thanks for your comments.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    You will find that the longer cable runs will require you to allow longer setup and hold times for the signals you use to read and write the 1-wire device. This is due to the additional capacitance that is introduced by the longer cable length.

    hgmjr
     
  5. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    Cat 5 internet wire or phone wire is easily available and pretty cheap, look at Home
    Depot or similar. Both have more conductors than you need.
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    For sensor apps like that I often use 2-wire microphone cable. It usually has red and white wires as a twisted pair, and foil and stranded earth shield.

    Its cheap, commonly available, and stands up to flexing and general punishment pretty well.
     
  7. Roger at CCCC

    Thread Starter Member

    Jun 8, 2009
    17
    0
    Thanks, RB, I hadn't thought of microphone wire.
     
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