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I would like to build my own .100 (2.54mm) cables to mate with standard single and double row headers, but the 'rectangular connectors' section of distributors websites is huge. Which ones do you recommend? Can you recommend an IDC system that works with discrete wires (not ribbon cables)?

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well, almost all of them that aren't specifically designed for ribbon cable or other specific cable types will work fine with discrete wires.

Most of the easy to use ones aren't true IDC connectors as jeanne mentioned, and generally speaking the crimping tools are really expensive for small scale work ($150 for the tool, which is really just a pair of pliers in the right shape is normal). You can hack crimp them and solder carefully and be fine.

TBH any of the rectangular connectors in the correct shape/spacing are fine. Look for the ones that best match your wire and look easy to crimp without the proper tool.

As far as i can tell in the production world its more or less a battle of who can provide the best automated tools for assembly as it is which shroud/crimp is 'better'.

The twisted wire bundle things works OK as long as the signals on the wire don't have integrity issues. If they do, do not try it.

I ran into very much the same problem in the past when having to connect 2 pcb's together with relatively high frequency signals (multiple channels of ~3mhz I2S). We ended up using the very thin plastic style ribbon cable (FFC or Flat Flexible Cable), the stuff you see on LCD screens or inside cell phones.

I don't honestly to this day know a good supplier for small quantities of this stuff. I just asked our factory in china when they normally used and they sent over a bunch of connectors and cables for me to test and match the impedance of ( i think it was 3M's FFC series but not sure).

Worked great but I had a hell of a time attempting to find that stuff myself without it costing a fortune, like $5 for a 3inch cable, but like $0.40 from the factory. If you can find it cost effectively, it really makes life easier for good controlled impedance interconnects.

If you do find FFC parts for a reasonable price in low quantity let me know how :)

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  • \$\begingroup\$ If your twisted wire bundle has integrity issues, then you're doing it wrong. Twist together your differential and power lines separately, and then twist the whole bundle. You can buy twisted unshielded pair (for good reason), or you can make it yourself! \$\endgroup\$ – Kevin Vermeer Jul 15 '10 at 17:41
  • \$\begingroup\$ @reemrevnivek what you've described is still not safe, twisting 2 wires together does not make it acceptable as a way to transmit any signal, diff or single ended. The nature of the wire core, the insulation, space between cores and number of turns per unit length all effect the characteristic impedance of the line. My point in the answer was that if a line requires that you take transmission line effects into account (be concerned about signal integrity) you should completely avoid this type of connection. Even transmitting 400khz I2C through something like this can be unreliable. \$\endgroup\$ – Mark Jul 15 '10 at 19:09
  • \$\begingroup\$ @Mark, it seems to me this is done all the time with CAT5 cable. There are 4 pairs of wires which are twisted at different rates, then bundled together in a sleeve. Being that the question doesn't say as much, I'm not sure that crosstalk and impedance mismatch are even issues. If there are problems with radiating, simply use a small-diameter coax for interconnecting the sensitive lines. \$\endgroup\$ – Jesse Jul 17 '10 at 13:59
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    \$\begingroup\$ @jesse the twisted pairs in a CAT5 cable are twisted at different rates on purpose. The reason is to avoid the same conductors being next to each other too often. Having the conductors next to each other often can introduce transients into one wire of a pair more than the other defeating some of the effectively of differential signals. You'll also find that higher rated CAT cable, such as CAT 5e and CAT 6 have higher minimum twist rates as this one of the steps taken to increase their frequency rating. I said in my answer this only needs to be addressed for signals with integrity issues. \$\endgroup\$ – Mark Jul 18 '10 at 3:44
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We've used ITW PANCON "MAS-CON" series connectors. (single row, available in 0.1" or 0.156" spacing) They work pretty nicely, the crimper tool isn't very expensive.

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It's not exactly what you asked for, but check out EMSL's article on Twisted Wire Bundles.

alt text

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  • \$\begingroup\$ Yup, we have twisted wire bundles all over the place at work.... I think that article overestimated the necessity of having another person hold the wire. With the drill in one hand, and the other end of the wire in the other, you can easily get 5 foot cables. \$\endgroup\$ – Kevin Vermeer Jul 15 '10 at 1:01
  • \$\begingroup\$ The solution here is a bench-mounted vice! Make arbitrarily long twisted cable bundles... \$\endgroup\$ – Connor Wolf Jul 15 '10 at 7:03
  • \$\begingroup\$ sometimes the 'other person' can even be a re-purposed metal coat-hanger slung over a door knob. \$\endgroup\$ – JustJeff Jul 15 '10 at 14:57
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They aren't IDC, since you do have to strip the wires, but we use these pins and these shells or similar, depending on the number of positions required.

We have the correct crimping tool, which is something like this (but that may not come with the right die for those specific pins).

It's expensive, but then it's actually a bit more complicated than a regular pair of pliers. For one thing, it ratchets. When you put the pin in it and start to ratchet it closed, the die will line up and hold the pin while you insert the wire, so you don't feel like you need three hands. And unlike ordinary large automotive/appliance type crimp connectors, it doesn't just crush a tube in which you've inserted the wire. Rather, the die bends the tabs of the connector around and into the stripped wire, and bends the other tabs around the insulation. And it has an adjustable stop, so it will crimp each pin the same regardless of how hard you squeeze it.

But that's for production work. For hobbyist use, you could roughly crimp these with small pliers, then carefully solder them.

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  • \$\begingroup\$ What's the correct crimping tool? \$\endgroup\$ – blalor Jul 15 '10 at 12:36
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    \$\begingroup\$ Please edit to change "these pins" to mention a specific series. Otherwise readers have to follow the links in question to figure out what they are. \$\endgroup\$ – Jason S Jul 15 '10 at 14:41
  • \$\begingroup\$ I like that style of 'square socket pin locks into housing' connector. Of course they are very common. With care the pins can be taken out and rearranged to reconfigure and recycle [a connecter that came from an old computer]. \$\endgroup\$ – joeforker Jul 15 '10 at 15:36
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Why do you want to mate to [EDIT] standard, straight, unpolarized, non-locking [/EDIT] .1" headers? I'd strongly suggest going with something that's locking and polarized. The AMP-Latch and mini-JST series both fit the bill [EDIT] and have a 0.1" pitch. [/EDIT] Mini-JST needs a crimper, AMP-Latch has both crimping options and IDC (designed for ribbon cable, it will work with discrete wires but I don't think you'll find anything marketed as such). Remember that you can use .098" connectors as well, don't limit yourself to 0.1" for the 2/1000ths of an inch.

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  • \$\begingroup\$ Because my board has .1" holes of course. \$\endgroup\$ – joeforker Jul 15 '10 at 14:24
  • \$\begingroup\$ Because everything else that you work with uses industry standard connectors. \$\endgroup\$ – Jeanne Pindar Jul 15 '10 at 14:43
  • \$\begingroup\$ @Joeforker - Both of the connectors I listed have a .1" pitch. \$\endgroup\$ – Kevin Vermeer Jul 15 '10 at 17:37
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    \$\begingroup\$ @reemrevnivik 0.1" headers are used constantly, in many industries, in many production products for cable attachment. For instance there are about a dozen such headers sitting on the motherboard the computer i'm typing on for everything from thermal measurement, to fan control, to speaker output, buttons, leds, etc. \$\endgroup\$ – Mark Jul 15 '10 at 19:12
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    \$\begingroup\$ Up until a couple years ago, PATA/IDE drives in everybody's desktop PC were connected with 40-pin 0.1" connectors. \$\endgroup\$ – davr Jul 21 '10 at 15:45

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