Board to board wire connectors advice - Page 1
Forum section: electronics / beginners

author: Infraviolet
author_rank: Super Contributor
timestamp: March 11, 2023, 07:29:14 pm
content: What do people tend to use for board-to-board wiring? Especially in circumstances where the different boards can move relative to each othr (like parts at ends of robotic limbs, or like wired hand held controllers for otherwise static devices).I learnt a long time ago never to trust soldered wires for this, single core would break internally after cycles of bending, and be annoyingly springy before that. Multi-core would break very quickly at the space between the solder and the insulation, absolutely ****ing nightmare.I've used pre-made crimped cable assemblies and appropriate header types, but these are annoyingly expensive.I've found Molex Picoblades particularly useful, but the cost for the cable assemblies is very nasty (it's a ****ing piece of wire and some crimped ends and plastic housings, how can it cost >£7), £0.5 per header I don't mind, but the cables are clearly overpriced. And they're a single source part too, if Molex discontinues the series I won't be able to get any more.I haven't really found a particular 2.54mm pitch type for regular use.Ideally I'm after, in a style for 2.54mm pitch and in another for a pitch in the 1.2/1.25/1.27/1.28 mm range, some sort of cable and header family which:1. Is cheap, for pre-made cables as well as headers, and made by more than one manufacturer2. Has through hole headers available (I use SMD a lot, but never for things like cables where forces can get exerted) (I looked in to FFC cables but they don't seem to ever have through hole headers for low conductorcount varieties)3. Available for conductor counts of 4, 6 and 8, 6 being the most important4. Has a single row of pins on the headers5. Has compact connectors and headers, nothing huge, nothing like big molded wire ends on miniature D cables6. Is available in side-entry format7. Has some amount of "locking", whether that is an actual clasp or just the friction fit of things like Picoblades, not totally loose to pull away the way dupont leads on header pins are8. Will not fit together reversed, connector shape enforces correct insertion orientation9. Carrying capacity of >=50mA per conductor for any 1.2xmm options, >=500mA per conductor for any 2.54mm solutionsI looked at some JST, because I think there are quite a few clones made of those connector types, but for those I couldn't find evidence of through hole 1.2xmm headers existing, and got a bit lost trying to consider 2.54mm options.What have people found works?Or otherwise what workarounds have people been using to navigate between the impossibility of reliably using directly soldered wires (and inconvenience for disassembly), and the nasty prices of cable asemblies?Thank you

author: rdl
author_rank: Super Contributor
timestamp: March 12, 2023, 04:47:18 am
content: I don't know of anything that will meet all those requirements. I use Molex SL a lot and they can cover many of them. The problem there is you'd need a proper crimping tool. If you haven't already, read through this thread. Maybe it'll give you some better ideas.https://www.eevblog.com/forum/reviews/affordable-crimp-tools-for-small-connectors-(dupont-etc-)/

author: Jwillis
author_rank: Super Contributor
timestamp: March 12, 2023, 04:54:50 am
content: Depends how many wires there are. Ribbon cable like that use for Parallel ATA (PATA)in a desk top computer or Flexible Flat Cables (FFC) like inside a printer.For cables that require constant bending I try to use fine stranded silicone cables. You can get silicone ribbon cable as well. But any fine stranded wire would work.I try to avoid soldering to the board only but rather use a cable to board anchor as well. This can be a wire to board connector or looping the cable through an anchor holes on the board. In a pinch, hot glue has worked . That way your insulation is also anchored to the board and not just the solder joint.Removable connectors should be something that will lock together like DIN connectors or similar idea that also anchor the insulation.JST have many Types of connector, each used for different applications. SM (2.5mm Pitch), RCY (2.5mm Pitch), SHD (1mm Pitch), GH (1.25mm Pitch), ZH (1.5mm Pitch), PA (2mm Pitch), PH (2mm Pitch), XA (2.5mm Pitch), XH (2.5mm Pitch), EH (2.5mm Pitch), RE (2.54mm Pitch), VH (3.96mm Pitch) neither of which is compatible with each other.There are literally thousands of connectors for specific applications, voltage and current requirements. But mainly you want the insulation on the wire to be secured to the connector to relieve strain on the wire.

author: Veketti
author_rank: Regular Contributor
timestamp: March 12, 2023, 07:25:06 am
content: Well, I don't have extensive experience nor pro in this matter, but I've used Molex mini-spox and still use, but to be honest JST-HX from Aliexpress seems to do the job as well. Actually the connectors do hold tighter than Mini-Spox. Then I've switched to flexible silicon wires, which are breeze to route and handle. They just stay where you put them and not cause any bending forces. Only downside is the crimping. Need to be extra careful that the wire holds after crimping. Maybe it's due to the extra thin strands. Buying these silicon wires locally is not viable cost wise so again Aliexpress is your friend with a fraction of price.

author: rdl
author_rank: Super Contributor
timestamp: March 12, 2023, 10:05:58 pm
content: Another type that might be worth looking into is IDC connectors. The kind that use normal ribbon cable, like what was used on floppy drives and older HDDs. They're all double row though. I think you can get them as small as 4x4, If you can work around that, they do a pretty good job and require no special tool to crimp. They're basically a right-angle style connector so you have to plan ahead a bit.

author: tooki
author_rank: Super Contributor
timestamp: March 14, 2023, 11:22:15 pm
content: I really like 1.27mm pitch box headers. They exist in both SMD and THT, and the IDC females crimp on easily with a small vice or parallel-jaw pliers. They are, however, only available in dual-row.

author: MathWizard
author_rank: Super Contributor
timestamp: March 15, 2023, 08:55:39 pm
content: I bought a recommended crimper, but I haven't bought the plastic bits yet, or small gauge wire or metal bits.I have some old PCB's with headers, and some random wire cables, from printers/etc. I never had a hotair gun years ago, so I barely salvaged any headers/wire combos.

author: Infraviolet
author_rank: Super Contributor
timestamp: March 16, 2023, 09:50:44 pm
content: tooki, could you give some links to examples of both the board connectors and the mating cable connectors? Are thesea standard type, or lots of different incompatible single-manufacturer options? Aren't the IDC connectors that one mounts on to ribbon cables often really bulky, like several cm in two of their dimensions, maybe I'm misinterpreting the type you are trying to describe. Pictures would be helpful.Thanks

author: tooki
author_rank: Super Contributor
timestamp: March 17, 2023, 08:05:46 am
content: They’re exactly like normal box headers and IDC connectors, but in miniature: smaller headers, smaller connectors, thinner, narrower ribbon cable.They’re not proprietary, I’ve had no trouble whatsoever mixing various brands from Digi-Key and no-name from aliexpress.The official ESP32 debugger board, the ESP-PROG, is a great example because it has both its UART and JTAG ports in both 0.1”/2.54mm and 0.05”/1.27mm headers side by side, so you can see a direct size comparison. See attached pic.

author: EPAIII
author_rank: Super Contributor
timestamp: March 17, 2023, 08:19:45 am
content: The first thing about connections between boards is what kind of signal are they passing. A 5 Amp, DC power supply connection needs one thing and a 1 Ghz serial digital or RF signal needs another.When I have had multi-board projects to knit together the first thing I try to use is 0.05" ribbon cable with ID (insulation displacement) connectors. I used dual row headers, not single row ones. They are just far more common and easy to source. And PCB traces can be routed between the pins of one row to bring all of them out one side. The ID connectors make the construction of the interconnect cables so easy and quick and you can use either inexpensive tools or just a bench vise.And for connections outside of the box or chassis, there are ID style, D sub-miniature connectors. Again, quick and easy to apply.ID connectors on ribbon cables have saved me days of work on some projects.Once I have as many of the connections as possible going through the ribbon cables, then I look at the remaining ones to see what their requirements may be.As for movement, you need to look into the subject of strain relief and cable management. Almost any type of cable can be damaged if it is not installed properly. The first rule is stranded wire, not solid. Some connectors have built in strain relief and devices to limit the radius of bends. And you can use improvised means, such as flexible tubing over the wires. The ID connectors for ribbon cable have strain relief additions that also help to control the flexing. I have never had such a cable, with the strain relief pieces installed, break due to flexing. But care should be taken in the installation and routing of the cables when a lot of bending is anticipated.

author: Infraviolet
author_rank: Super Contributor
timestamp: March 19, 2023, 07:25:22 pm
content: Thanks, the 1.27mm pitch IDCs look worth more investigation now I see what you mean by them.

author: tooki
author_rank: Super Contributor
timestamp: March 19, 2023, 09:17:29 pm
content: Quote from: Infraviolet on March 19, 2023, 07:25:22 pmI think they’re delightful little buggers. I’ve used them in two projects so far and have been really happy with them.