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reccomendations for flexible 24 AWG cable?

Discussion in 'Electronic Design' started by Michael Noone, Jan 9, 2006.

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  1. Hi - I need to run 5 24AWG wires to a circuit board that is moving in two
    different dimensions. In the future I hope to switch to flex cable for this
    job, but right now I'm going to have to stick with normal stranded wire.
    I'm hoping for as long of life as possible on these cables, knowing full
    well that they will wear out after some time and need to be replaced. I
    could either run 5 individual wires or one 5 or more conductor cable. I'm
    not sure which would offer the better results. So - my question is this:

    What will give me the best results in terms of flexibility and longevity?
    I'm wondering both about using 1 cable or 5 individual wires and particular
    types/brands/models of cable. I don't think price will be a concern - but
    just in case I should mention that my budget is that I want to be able to
    buy 5' or so of cable for under $50. Most of what I've been looking at is
    in 100' spools for around $30 or so.

    Any suggestions? I'm hoping for something that I can pick up at Digi-Key or
    Mouser.

    Thanks in advance for your help,

    -Mike
     
  2. Pooh Bear

    Pooh Bear Guest

    If they stock it, you're best off with 'test lead' style wire. Multiple very
    small strands that are less troubled by regular flexing and a soft compliant
    insulation ( maybe silicone based ). To be honest I don't know if this is
    regularly available in such a small gauge as 24 but worth trying.

    Graham
     
  3. Looking at Digi-Key they have some 22AWG test lead wire, such as W2722B-
    100-ND (see http://dkc3.digikey.com/PDF/T061/1489.pdf). My worry is that
    I'm using Molex 50212-8100 crimp terminals
    (http://www.molex.com/customer.html?supplierPN=502128100) which are rated
    for 24-30AWG in a 2mm pitch Molex 35507-0500 crimp housing
    (http://www.molex.com/customer.html?supplierPN=355070500)

    These cables will be put together by hand in low quantities. Though with
    normal wire I think I might be able to fudge the rated size for the cable a
    bit more - in this case I'm noticing that the outer diameter of the cable
    is 2.54mm, while the Molex crimp housing is 2mm pitch. Probabaly more than
    can be fudged. Mouser seems to also have 22AWG test leads but nothing
    finer.

    Though it does make me remember soething from a while back - I put together
    a breakout cable for an industrial power supply with a fairly fine pitched
    connector using test lead wire. To get the insulation inside the crimp I
    ended up shaving off some of the outer insulation. Maybe that would be a
    solution for this?

    Thanks,

    -Mike
     
  4. Pooh Bear

    Pooh Bear Guest

    Yup. That's the stuff.
    OK, the o/d seems to be a problem. The cable is 'too big' !
    Tricky.

    I've seen tiny flex that used silicone insulation that had a smaller o/d. May
    be worth searching elsewhere.

    Graham
     
  5. I was just scanning multi conductor cable in the Newark Inone catalog,
    Friday, and came across a version by Belden called "FleXnake" that
    they sell by the foot. You may want to strip the outer sheath off if
    the cable is too large. But the insulation is very flexible and the
    wire is highly stranded. They make a 5 conductor, unpaired,
    unshielded version. Unfortunately, even though this is a registered
    trademark, the keyword "FleXnake" does not bring up any results on
    Newark's search engine. But several pages in the catalog are devoted
    to the multi conductor, multi pair, shielded and non shielded
    variations both on rolls and by the foot. I think the price was about
    a dollar per conductor foot.
     
  6. It looks like the industrial high flex control cable made by Belden is
    trademarked, "Infinity". The FleXnake kind may be just audio cable.

    It is supposedly rated for 9 million of some kind of flex cycles.
    Here is a data sheet for the 9 conductor version, 20 ga, .02"
    conductor insulation thickness.
    http://bwccat.belden.com/ecat/pdf/7105A.pdf
    The Newark part number for the by the foot version is 16F9470.
     
  7. Richard H.

    Richard H. Guest

    Michael,

    How about Cat5 Ethernet patch cable? It's 24AWG, fairly robust, 8
    conductor, easily had for <$10. Rough measurements from a couple samples:

    Cable OD: 0.210"; conductor OD: 0.036" (7x 0.0043" strands)
    Cable OD: 0.200"; conductor OD: 0.032" (7x 0.0033" strands)

    Cable flexibility varies, so you're better off buying where you can
    check it in person. E.g., the first one listed is more pliable and
    loosely jacketed; it's made by Berk-Tek. The individual strands are not
    as pliable as probe wire.

    It's pretty rare to see an Ethernet patch cable fail under regular use
    even in dynamic environments (highly mobile / shared use), excepting
    RJ-45 connector tabs and physical abuse. But, they don't see truly
    high-volume movement, and the connector is crimped to the cable jacket
    for strain relief.

    Do you have options for strain relief, such as fastening the cable to
    the PCB? Or maybe hot-gluing the back-end of the connector to relieve
    strain on the individual conductors at the edge of the crimp? That's
    where I'd be most concerned about a failure.

    Cheers,
    Richard
     
  8. The infinity series looks like a good fit. Belden part number 7200A is a 6
    conductor (3x2 twisted pairs) 24AWG shielded cable - looks just about
    perfect. Now I have to find a distributor - which is proving to be rather
    challenging! Waiting on a couple companies to call me back.

    -Mike
     
  9. Hi Richard - Ethernet cable was originally my plan, especially since
    originally I thought I needed 8 conductors. Problem is at least all the
    ethernet cable I have is fairly stiff, even the stranded stuff. I use
    some fairly high end patch cable at work, and even that is decidedly
    stiffer than I'd like. Ideally I'd like this cable to be like a wet
    noodle. But if the Belden cable John reccomended doesn't pan out I
    probabaly will end up with patch cable.

    -Mike
     
  10. Rich Grise

    Rich Grise Guest

    How about that telephone-cord style stuff, but 6-conductor? (or 8, you
    can leave a few open or maybe have a couple of spare grounds or
    whatever). The "ethernet" cables I've seen all have solid wire, which
    would fail in a matter of weeks in a flex setting.

    Or even two ordinary telephone cords?

    Good Luck!
    Rich
     
  11. JeffM

    JeffM Guest

    How about that telephone-cord style stuff, but 6-conductor?
    Have you ever tried to work with "tinsel wire"
    outside its specified connectors? Not fun.
     
  12. I vaguely remember trying to work with one of those big crystal
    earbuds wot had flimsy flesh-colored (insert standard inclusiveness
    disclaimer) twisted tinsel wires.


    Best regards,
    Spehro Pefhany
     
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