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Cat 5 wire question

Discussion in 'Electronic Design' started by amdx, Nov 15, 2011.

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  1. amdx

    amdx Guest

    I have a freezer monitoring system that uses Cat5 cable.
    It uses Maxim's 1 wire system.
    Over the years the insulation of the Cat5 cable has cracked
    because of movement of the wire at the low temperature of
    the freezers, -20F.

    I'm going to start replacing leads to the sensors, each sensor
    uses only two wires, most of the leads to the sensors are less than
    10ft. I'm not sure how important it is to follow tight Cat5 spec's.
    I want a two conductor Cat5 spec'ed cable that is low temperature
    Any ideas,
  2. amdx

    amdx Guest

    What is MOW?
  3. Rich Grise

    Rich Grise Guest

    Two pieces of #24 teflon-insulated wire, twisted to about 4-6 TPI?

    Solid doesn't like to flex, but stranded gets weak points at the ends
    where it's tinned. I have no idea about any heatshrink that doesn't
    get stiff to brittle in the cold, so good luck on that - maybe a glop
    of silicone RTV?

    Good Luck!
  4. Rich Grise

    Rich Grise Guest

    Microwave Oven Wire? ;-)

    But in answer to the wire question - I've given my best answer - use
    teflon-insulated hookup wire twisted into pairs; the hard part will be
    the termination, albeit I guess proper crimp terminals are good for
    stranded, and don't really care about temperature.

  5. Glen Walpert

    Glen Walpert Guest

    Insulation or jacket? it is pretty rare for the insulation to fail if
    the jacket is intact.
    Direct burial CAT5e cable with a polyethylene jacket should be pretty
    good for low temp service. Good plenum rated cable would be a lot better
    than cheap PVC jacketed cable too - if your problem is PVC jacket failure
    then upgrading to Belden plenum rated might be all you need.

    Maxim 1-wire sensors do not need CAT5 cables, why not use an industrial
    cable designed for low temp service?

  6. Mark Datter

    Mark Datter Guest

    I'd bet that a simple pair of 24Ga Teflon insulated wire would do.
    Hell, you can buy "STP" (shielded twisted pair) that comes with a Teflon
    sheath on it. run four lengths, if you actually need a full cat 5 feed.
    Feed only one for the apparent need seen here.

    Or, just twist together that 24Ga pair to or beyond the appropriate
    twist level, and feed that bare pair. No need for all the others or any
    sheathing. Teflon can handle far colder than your freezer.
  7. Mark Datter

    Mark Datter Guest

    "Maxim One Wire"?
  8. Mark Datter

    Mark Datter Guest

    Silver plated is what you want. The most common call out. Tin plated
    under Teflon is a pain in the ass to actually "tin" in use. But certain
    types of terminations do not need, nor should they have tinned wire ends.
    DUH! Then you do NOT tin it, dimwit! One doesn't invite embrittlement.
    Kynar. Also High Voltage heat shrinks actually perform well at lower
    temps because they are so thick.
    I don't think the problem was mentioned as being AT a termination
  9. Mark Datter

    Mark Datter Guest

    Teflon sheathed "STP" (shielded twisted pair). It is just over an
    eighth inch in diameter for 24 Ga, IIRC. Military uses it for long cable
    run pairs all the time.

    Third entry down on the list table:

  10. amdx

    amdx Guest

    Thanks guys,
    Sounds like the impedance characteristic is not as important as I
    thought. Although, I'm glad that most of the system and splitters are
    Cat5. I'll throw some different speaker wires that I have in the
    freezer, the ones that don't crack will get a 1 Wire system test.
    If it all fails, I'll check the Gore DXN2309.

    P.S. The latest 1 Wire thrill ride.
    My computer died, I put a new computer together. When I went to plug the
    RS232 1 wire adapter in, I found the new mobo doesn't have an RS232
    connector. So I ordered a new USB 1 Wire adapter. When I got that, I
    then found my temperature monitoring software doesn't support the new
    USB 1 Wire adapter. I then ordered a USB to RS232 converter. That has
    got the system working fine.
    One other problem, my alarms where telling me most of the freezers
    were over the low temperature setting. I read my temps in Fahrenheit and
    the alarms are set in Centigrade, once I made the conversion to
    Centigrade and set the alarms to the proper temperature it works.
    I posted a screenshot in ABSE, looks best in a viewer.
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