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Connecting to the real world

Discussion in 'Electronic Design' started by John Devereux, Mar 31, 2005.

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  1. Hi,

    I have a PCB with 0.1 inch dual row headers, inside a sealed metal
    box. I need to connect the Real World to it. We usually avoid using
    external connectors, but in this case we need to make the whole box
    "unpluggable" and do not want the end user going inside the box.

    Does anybody know of any "waterproof" (IP67) connectors suitable for
    terminating ribbon cables (4-12 ways)?

    Ideally I would like to use insulation displacement style terminations
    at the bulkhead connectors, but I can't seem to find any.

    We have tried various circular connectors with "solder bucket" pins;
    they are very fiddly and time consuming to wire up. Also the ribbon
    cable wires tend to drop off since they are very thin! Then the others
    drop off while you are fixing the first one etc...

    What do people use for this?

    Thanks,
     
  2. PeteS

    PeteS Guest

    As you have found, most IP67 connectors are not IDC. Two big names I
    can suggest you look at are Bulgin and Binder. They have a wide variety
    of IP67 rated connectors with varying styles.

    If IP67 is a must, you are probably not going to get an IDC style
    connector, simply because to get that rating, there has to be a
    compression seal all the way around the connector, and IDC connectors
    only have fit compression at the ends, not all the way around.

    You can get IDC (for D style connectors, for instance) if you can live
    with IP44 or thereabouts, but I don't recall seeing anything above
    that.

    I (occasionally) design IP67 stuff, and connectors are always my single
    biggest concern (to say nothing of cost).

    Cheers
    PeteS
     
  3. Greg Neff

    Greg Neff Guest

    Not ribbon cables. If you want to use a standard ribbon cable style
    header on your board, then try Tyco AMP 102387 (MOD IV) series
    housings. These accept wires with crimp socket contacts. The other
    ends of the wires can then be crimped to any contact suitable for your
    waterproof connector.

    ================================

    Greg Neff
    VP Engineering
    *Microsym* Computers Inc.
     
  4. Alan Turner

    Alan Turner Guest

    Perhaps you could use a microcontroller to multiplex the signal(s) onto a
    serial link with fewer leads to connect. I suppose an optical coupling
    would be ideal if you want to make it waterproof.

    Regards,
    Alan
     
  5. Thanks, but we are already using a serial link. But we also need to
    provide other signals for power, and for customers that cannot use the
    serial link.
     
  6. Mark Jones

    Mark Jones Guest


    Try Permatex blue RTV engine sealant from your local car parts store. This
    stuff will withstand almost anything. Use a wide bead area if user disassembly
    is a concern.
     
  7. Use an ITT Cannon - TNM IP67 circular connector.
    The QM range of pcb-mount pins will fit the TNM.
    So have a small pcb at the rear of the connector,
    converting the round pin layout into a 0.1" IDC
    header. 1:1 IDC cable from there to the main pcb.

    In the RS cat: 265-9705 chassis plug, and 349-8854
    gold-plated pcb TNM contacts.
     
  8. Thanks Tony!

    Actually I had already considered something like that with the
    connectors we tried... glad idea not completely barmy.
    I just got the new catalogue the other day. The contacts appear to be
    discontinued! Possibly I can get elsewhere though.


    Thanks,
     
  9. Rich Grise

    Rich Grise Guest

    Look at automotive connectors. They can get hefty, but they're quite
    water- and dirt-resistant.

    Good Luck!
    Rich
     
  10. Getting the pins lined up exactly right before
    soldering is liable to be the bum-biter though.

    I suspect it will need slightly oversize holes
    in the pcb, assemble the plug, plug it into a
    socket, *then* solder the pcb on.
     
  11. Ahhh... Practice, Practice - you also need heat-shrink on all the wires ....
    ;)

    The semi-mil circular connectors are the only ones that will last with dirt
    and moisture around - you *can* get types with crimp-pins but splitting
    ribbon-cable and crimping the ends is IMO at best a Hobby-Thing (in larger
    series, I would consider it Cowboy ;-).

    One solution, i have seen, was to use a flexible mylar "pcb" with a layout
    matching the connector, solder the connector into that and connect the other
    end via some kind of header. But that costs..

    Maybe your best option is simply to have someone specializing in wire
    harnesses produce a quality connector assembly for you. With a little
    flexibility in connecting the other end - i.e. you might need to loose the
    ribbon - it is probably not expensive either compared to endless D.I.Y
    efforts.
     
  12. "Frithiof Andreas Jensen"
    Yes, doing that too... of course that takes even more time, and makes
    it harder to inspect / fault find.
    Agreed :). (Actually we are just supplying the PCB, it is my customer
    that is "packaging" it).
    Yes. It looks like the easiest option is to accept losing the
    convenience of the ribbon cable (as suggested) and just use individual
    wires. You can get crimp housings that go onto the PCBs dual row 0.1
    inch headers, instead of the IDC ribbon. The thicker wires that these
    will accept should solve most of the problems. Still surprised you
    can't get an IDC "military" style circular connector though.
     
  13. Of Course - I have forgotten that; Those are very widely used - so the
    tools/people who can do them are available.
    That's the Millitary for ya: "If it was good enuff for General McArthur then
    it's damn fine stuff, son" ;-) ....

    And it takes many approvals from many V.I.P's to get different components
    authorized - maybe the manufacturers do not see the point in trying to push
    a new standard, after all: Soldering this stuff up is routinely billed at
    "cost + x%" in millitary contracts, so it is only a lead-time problem for
    everybody (except for the Tax-payer, but maybe he/she works at Raytheon
    anyway).
     
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