User friendly interconnects between proto-boards? - Page 1
Forum section: electronics / general

author: e100
author_rank: Frequent Contributor
timestamp: August 05, 2024, 08:45:43 am
content: I'm building a bunch of modules on individual 70 x 90mm 0.1 inch proto-boards that need to connect to each other and survive being disconnected and reconnected several times a day as I tinker with each one. The number of conductors varies between 3 and 10 depending on the board.Regular IDC cables aren't really designed for this type of usage and I have doubts about the reliability of ribbon cables that are subject to repeated handling.Screw terminals are slow and damage the conductor. Individual 2mm plugs and sockets take forever to solder.Is there something better out there for doing this specific kind of job that will work with a standard 0.1 inch proto board?

author: SMTech
author_rank: Frequent Contributor
timestamp: August 05, 2024, 09:55:17 am
content: I don't see the issue with ribbon if you sensibly use connectors with cable restraining clips and treat everything with due care and attention. That said do you need the cable at all, can you not use IDC male/female and forgo the cable between?

author: nali
author_rank: Frequent Contributor
timestamp: August 05, 2024, 10:07:27 am
content: You can get ribbon cable headers with ejector lugs if you're worried about pulling on the cableOr maybe pluggable terminal blocks?I used to use Molex KK when messing with perfboard, they're pretty easy to crimp and remove or change wires.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 05, 2024, 10:58:02 am
content: I had a look at a few datasheets of ribbon cable IDC connectors. Some go as low as 30 mating cycles. In a datasheet from Wurth, three "performance" levels are mentioned with 50, 250 and 500 mating cycles.A datasheet from 3M also suggested such a short number of cycles, but the pdf was ill formatted and it was unclear what the info actually meant. See page 4 on:https://multimedia.3m.com/mws/media/787866O/3mtm-idc-ribbon-cable-socket-891-series.pdfBut what this all means?The manufacturer is pretty sure your connector will survive this amount of cycles. It does not mean that it would fail a few cycles lager. or even 10x or 100x cycles later.The stress relief brackets over the cable help to reduce stress in the IDC connection to the wires.The ejector lugs on the male sockets also reduce stress on the cables.If you want robust connectors that survive a high amount of mating cycles, they become expensive really quickly. IDC cables with their plugs are easily replaceable if / when they wear out, but for the sockets soldered into a PCB it's not so easy. Oxidation probably is not a big issue, as the constant wiping will probably remove it. But it also wears out the (gold?) plating. A trick that is sometimes used is to use extension connectors. This way, you can disconnect an extension connector from a PCB and put a new one in if it wears out.Maybe using USB-C connectors is an option. Apparently these are rated for 10.000 mating cycles but that probably does not hold true if you buy the cheapest you can find.

author: ledtester
author_rank: Super Contributor
timestamp: August 05, 2024, 12:25:38 pm
content: Maybe "pluggable terminal blocks", eg:https://www.aliexpress.us/item/3256804030840641.htmlThey consist of two pieces -- a screw terminal block and a board receptacle that accepts the terminal block.

author: e100
author_rank: Frequent Contributor
timestamp: August 05, 2024, 01:15:40 pm
content: Quote from: Doctorandus_P on August 05, 2024, 10:58:02 amGood idea.Quote from: Doctorandus_P on August 05, 2024, 10:58:02 amGood point, USB-C breakout boards are readily available.I also found breakout boards for HDMI "type A" connectors which are basically a double sized USB connector which means they also have double the contact spacing of 1mm vs the 0.5mm found in USB-C.FPC ribbon cables and breakout boards also look interesting.

author: e100
author_rank: Frequent Contributor
timestamp: August 05, 2024, 01:43:26 pm
content: Quote from: ledtester on August 05, 2024, 12:25:38 pmThe picture definiely shows 2.54 as the spacing. I've never seen them that small, however Sparkfun also has them, so they must be OK. The screw heads must be tiny.

author: tggzzz
author_rank: Super Contributor
timestamp: August 05, 2024, 01:55:26 pm
content: Quote from: e100 on August 05, 2024, 01:15:40 pmPlus, with care, the connectors and cables ought to have reasonable impedance characteristics. While that's not necessary for audio, it is beneficial for modern digital signals and general RF signals.

author: e100
author_rank: Frequent Contributor
timestamp: August 05, 2024, 02:41:48 pm
content: Quote from: tggzzz on August 05, 2024, 01:55:26 pmIndeed things were looking good until I watched this video where they tested a bunch of HDMI cables and 16% failed either because of missing conductors or signal integrity, or both. Luckily all my signals are sub MHz but missing conductors is something I'll have to check for.

author: Smokey
author_rank: Super Contributor
timestamp: August 05, 2024, 04:00:59 pm
content: D-Subs. Love me some D-Subs.Solder cup or crimp. Either way.

author: tszaboo
author_rank: Super Contributor
timestamp: August 05, 2024, 04:38:47 pm
content: Quote from: Doctorandus_P on August 05, 2024, 10:58:02 amYes it's not like after 30 cycles it just stops conducting. I had this in production. There was this connector rated maybe 30 cycles, so I made it replaceable on the testing equipment. Made a few connectors, put it on the shelf ready to replace the production tester, then promptly forgot about it. The production people run thousands of boards through it and it was still working. I had to sweep out metal shaving and dust out it and it was still doing it's job good enough to test the DUT.

author: janoc
author_rank: Super Contributor
timestamp: August 05, 2024, 04:50:33 pm
content: Quote from: e100 on August 05, 2024, 01:15:40 pmPlease, don't do this. At least not with USB. Using USB connectors for anything but USB is an invitation for disaster. Sooner or later someone will plug something in that connector that expects a standard USB device or a charger. If your device isn't USB, doesn't use USB voltage levels, doesn't have the usual pinout, then you can have an expensive mess on your hands.HDMI has the same problem but there it is possibly less likely to cause issues because people associate those only with monitors and TVs and won't be as much tempted to connect their computer output to some random board having it. However, USB is everywhere these days.It is the same reason why using mains plugs and sockets for anything else but mains is a terrible idea. Sooner or later someone will have a brainfart. It could be even you.

author: tooki
author_rank: Super Contributor
timestamp: August 05, 2024, 04:55:24 pm
content: Quote from: SMTech on August 05, 2024, 09:55:17 amUmmm, IDC by definition is a way to terminate cables, so a PCB connector can’t be IDC without cable.Do you just mean box headers?

author: NightMoth
author_rank: Contributor
timestamp: August 05, 2024, 10:59:18 pm
content: HelloYou can use JST XH2.54 cable and socket or JST XH2.54 cable and pin header instead of socket (with pin header instead of socket you dont need to take care about cable header orientation).I used 2...6 wire JST XH connectors for my project with bunch of protoboards which i was assemble/disassemble many times for tuning, and it was easyhttps://www.digikey.com/en/product-highlight/j/jst/xh-series-connectors

author: ledtester
author_rank: Super Contributor
timestamp: August 06, 2024, 12:00:37 am
content: Quote from: e100 on August 05, 2024, 01:43:26 pmYou could also go with 5.08mm spacing to fit protoboards... although sometimes they have thicker pins which would require enlarging the holes.

author: e100
author_rank: Frequent Contributor
timestamp: August 06, 2024, 01:42:52 am
content: Quote from: NightMoth on August 05, 2024, 10:59:18 pmNow I'm confused. Is JST XH2.54 an actual size?The JST web site lists XH as the 2.50mm series and RE as the 2.54mm series.https://www.jst.com/products/crimp-style-connectors-wire-to-board-type/xh-connector/Online sellers are listing XH2.54 connectors so they are either using the genuine JST RE series or else using copies of the XH series with a custom size.

author: NightMoth
author_rank: Contributor
timestamp: August 06, 2024, 02:40:09 am
content: Quote from: e100 on August 06, 2024, 01:42:52 amYes, you are right, it looks like original JST XH series is 2.5mm, but it looks like almost all wendors name similar 2.54mm connector as "JST XH" as well.I'm using "JST XH" with 2.54mm size for 0.1 inch perfboard, and i checked its size in product's specifications on wendor's web store before ordering

author: tooki
author_rank: Super Contributor
timestamp: August 06, 2024, 07:26:22 pm
content: In my experience, the cheap Chinese vendors call it “XH2.54”, but actually ship 2.50mm, which makes sense since they are supposed to mate with real XH.Of course, 2.54 and 2.50mm pitch are so close that for up to about 10 pins, you can fit XH into a 2.54mm PCB footprint or protoboard. The exact number depends on the hole sizes.So don’t take the fact that they fit 2- and 3-pin XH clones into your standard 2.54mm protoboard as any kind of evidence that you have actual 2.54mm connectors. I doubt any XH clones with an actual pin pitch of 2.54mm exist.I’ll also point out that genuine XH are so inexpensive that I don’t bother with the clones anymore. (Except for the wire-mount male version, which JST itself does not manufacture!)

author: kripton2035
author_rank: Super Contributor
timestamp: August 06, 2024, 09:13:41 pm
content: molex micro-fit can be good candidates too.

author: e100
author_rank: Frequent Contributor
timestamp: August 07, 2024, 02:04:50 am
content: Quote from: kripton2035 on August 06, 2024, 09:13:41 pmThose have a 3mm pitch.

author: e100
author_rank: Frequent Contributor
timestamp: August 07, 2024, 02:15:07 am
content: Quote from: tooki on August 06, 2024, 07:26:22 pmI found one vendor selling XH2.54 who provided an engineering drawing showing the pitch as 2.50mm.My first thought was that they had linked to the wrong picture but now I realise they are simply selling 2.50mm connectors under the 2.54 label.

author: NightMoth
author_rank: Contributor
timestamp: August 07, 2024, 06:09:45 am
content: Quote from: tooki on August 06, 2024, 07:26:22 pmMaybe you are right, I failed to measure my "JST XH2.54" with calliper perfectly, but it looks like indeed it closer to 2.5mm than to 2.54mm... anyway difference between 2.5mm and 2.54mm for 10 pins will be negligible.On attached pictures I compared 5pin "JST XH2.54" with 30x 2.54mm pin-header array and distance between pins looks very same. 30x2.54mm pin array fits into 0.1inch perfboard, so 10-pin "JST XH2.54" will fit perfboard without any problem as well.

author: kripton2035
author_rank: Super Contributor
timestamp: August 07, 2024, 06:53:37 am
content: Quote from: e100 on August 07, 2024, 02:04:50 amyes, but easily bend into a perfboard even for a 6 pins connector.

author: thm_w
author_rank: Super Contributor
timestamp: August 07, 2024, 10:58:26 pm
content: If you don't need cabling you can use IDC male and female and have the boards directly connect.If you do need cabling, the IDC will probably be fine, assuming you crimp it correctly or buy premade cabling.Its more of a case of what would you prefer to use.Quote from: NightMoth on August 07, 2024, 06:09:45 amYou can read our last discussion about jst xh here:https://www.eevblog.com/forum/manufacture/what-is-the-real-pitch-of-jst-xh/I have some that measure ~2.53mm, which is technically out of spec for 2.50mm pitch, but arguably not exactly 2.54mm either. But I would say 95% of the time you would get 2.50mm. Or 100% of the time if you order from digikey/lcsc