module (internal'ish) connector: small IDC or FFC - Page 1
Forum section: electronics / beginners

author: Saimoun
author_rank: Frequent Contributor
timestamp: November 08, 2022, 02:58:54 pm
content: HiMy product has a module interface which the end users will be able to connect to. It's only 4 pins and I was thinking using a simple IDC connector on the board, but there are no 1.27mm IDC connectors with few pins it seems (or at least they are not common)? The only I could find was 6 pins 2.54mm, which would be ok but it's just so big and takes so much space on the boardFFC seems like it could be a solution?The concept for the end users is:1/ open the product's enclosure2/ attach the module to the enclosure3/ connect the module to the module's interface (4 pins only like I said)4/ close the enclosureWhat would you recommend?ThanksSimon

author: pcprogrammer
author_rank: Super Contributor
timestamp: November 08, 2022, 03:08:04 pm
content: What about JST XH connectors? Are these also to big?https://www.jst.co.uk/productSeries.php?pid=136

author: Saimoun
author_rank: Frequent Contributor
timestamp: November 08, 2022, 03:12:21 pm
content: These also look great, I just did not know how to call them. But are they available in a smaller pitch, or at least in 2x2?Also are they common enough, i.e. I won't struggle when I have to find a cable for it?Thanks

author: pcprogrammer
author_rank: Super Contributor
timestamp: November 08, 2022, 03:22:54 pm
content: Don't know if they have these in a 2x2 configuration, but the 1x4 is easily obtainable.https://nl.aliexpress.com/wholesale?catId=0&initiative_id=SB_20221108072205&SearchText=jst+xh+4+pin&spm=a2g0o.home.1000002.0

author: pcprogrammer
author_rank: Super Contributor
timestamp: November 08, 2022, 03:26:25 pm
content: You can check on the JST website on what types they have. For instance thesehttps://www.jst.co.uk/productSeries.php?pid=16413&cat=30

author: Saimoun
author_rank: Frequent Contributor
timestamp: November 09, 2022, 11:15:50 am
content: Thanks Peter this is nice, but it's still so big. I mean I was thinking I could put a simple 4 pins 1.27mm male header, my only problem is it does not hold very well (hence my idea of using IDC which clips in place).

author: pcprogrammer
author_rank: Super Contributor
timestamp: November 09, 2022, 11:43:19 am
content: Hi Simon, since you need this to connect to the end users parts I doubt if FFC/FPC is usable. These are somewhat dedicated flat cable connectors that don't allow a connection with simple wires, unless you use some intermediate board like thishttps://nl.aliexpress.com/item/4000902737228.htmlApart from JST is my knowledge of small connectors exhausted

author: Saimoun
author_rank: Frequent Contributor
timestamp: November 09, 2022, 11:49:08 am
content: Thanks Peter - you're right FFC/FPC definitely sounds like the wrong choice.I actually found what looks like a JST with a smaller pitch, 1.25mm (I've seen many with this size so I guess the standard for JST is 1.25mm and not 1.27mm). They are not official JST but the same concept:https://lcsc.com/product-detail/Wire-To-Board-Wire-To-Wire-Connector_CAX-1-25-4A_C722600.htmlI found many 1.25mm cables that look like they could fit - for ex these ones from amazon:https://www.amazon.com/Connector-Wire%EF%BC%8CMicro-1-25MM-Female-Cables/dp/B07GQZXHYQThey come with the connector, so the question is whether this connector is a standard like the IDC and pretty much any connector would fit or whether I need to be very careful to match connector / cable?Thanks

author: pcprogrammer
author_rank: Super Contributor
timestamp: November 09, 2022, 12:36:07 pm
content: I guess you do have to match them, but it might be JST SH type connector. Found this on hobbyking:https://hobbyking.com/en_us/jst-sh-1-25mm-4-pin-female-connector-10pc.htmlThe female pins look very similar to the XH ones but must be smaller. For doing the crimping your self you need the correct pliers to do so.On the JST site I found GH for this:https://www.jst.co.uk/productSeries.php?pid=11517

author: Saimoun
author_rank: Frequent Contributor
timestamp: November 09, 2022, 02:10:34 pm
content: Thanks again Peter, but now I'm wondering if this is the right choice, especially since these JST conenctors are designed for more or less permanent installations, while I still want my users to be able to connect and disconnect. I'm worried that with a JST connector they will need a lot of force to disconnect the cable.I think the best solution is simple pin headers, unless someone has a better idea. I've had this idea of making the connector being able to be plugged in either way by doubling the pins (8 pins instead of 4), the same way the USB-C plug does:Something like:Code:5V IO1 IO2 GNDGND IO2 IO1 5V(2x4 pins).The other concern about a simple header is how well it will hold but I think once it is installed the cable holds pretty well?

author: pcprogrammer
author_rank: Super Contributor
timestamp: November 09, 2022, 02:46:35 pm
content: A problem with these type of connectors is that they tend to loosen quickly. Like for instance the dupont pins that you can use with the male 2.54mm headers are not that great for often connecting and disconnecting, at least that is my experience.Also the JST XH connectors are not that reliable after many connect disconnect cycles. Found this out with the battery connector of the FNIRSI-1013DAfter many disconnects during the reverse engineering it is a bit wonky now.If your product connects to something external it might be better to look into some more robust connector with a fixed orientation like a DIN plug, or a mini DIN plug as used for PS2 for instance.

author: Saimoun
author_rank: Frequent Contributor
timestamp: November 09, 2022, 03:33:58 pm
content: Yes I agree. My experience though is that the part that gets loose is the plastic part, hence the idea of using male connectors on the board with a female cable end. I.e. if the plastic part (the female cable end) gets loose then it's easy to change the cable.Just to give a bit of background: my product basically has a module interface, and I will make a few modules which the end-users can attach and connect to the product. That should not create many plug/unplug. The problem is the module interface is open source and any user can create their own module - which is where they might do a little more of plugging/unplugging. But I'm also thinking the users that will make their own module will know a thing or two about electronics and will know what to do if the connection gets loose.I'll investigate other plugs see if something makes sense

author: tooki
author_rank: Super Contributor
timestamp: November 09, 2022, 10:48:15 pm
content: Quote from: pcprogrammer on November 09, 2022, 02:46:35 pmThe standard cheap Chinese DuPont connectors do indeed loosen dramatically after just a few insertions.Theoriginalpin header connector, the Amphenol Mini-PV, is rated for 1000 insertion cycles. (According to Amphenol, “PV” stands for “perpetual virgin” precisely because of the high insertion cycles.) The downside is that they cost about 100 times as much as the Chinese DuPonts. For example, I paid $14 for a roll of 1000 Chinese DuPont contacts. 1000 hand-crimpable Mini-PV contacts cost $145 from Digi-Key. (The reeled Mini-PV are a pain to use by hand because they are joined end-to-end and thus need to be cut off, very precisely, on both ends. You can’t just flex them off the carrier like most contacts. And even so, 1000pcs of reeled Mini-PV wouldstillcost $75.)With that said, I’ve completely switched to genuine Mini-PV for test leads, where a few hundred insertions are absolutely to be expected, so even if it cost me zero time (and wire) to replace the contact every three insertions, it’d still be cheaper to use the real thing. And the real Mini-PV comes in three insertion force levels, and the highest force ones (intended for connectors with just a few pins) hold really well, so much better than the Chinese DuPonts could ever hope to on their first insertion!But for internal wiring that’s just to assemble and then leave alone, the Chinese DuPont contacts are fine.Somewhere in between are things like JST XH and Molex KK, whose curled-back spring contacts don’t loosen anywhere near as much as the single-bend Chinese DuPont contacts. (But they’re not as robust as Mini-PV, which uses a separate beryllium copper leaf spring inside the brass body.) Some, like KK, are available in both brass, which deforms easily, and phosphor bronze, which is more resilient. Genuine JST XH contacts are phosphor bronze (brass by special order), but clones may be brass, you often don’t know. Chinese DuPont contacts are brass.There are other 2.54mm pin headers connectors that are better than the Chinese DuPonts, but not as good as Mini-PV, like Molex C-Grid and SL, and Amphenol Dubox, which is rated for 200 cycles.

author: tooki
author_rank: Super Contributor
timestamp: November 09, 2022, 10:53:43 pm
content: Quote from: simonlasnier on November 09, 2022, 03:33:58 pmIn most connector types, it’s the female contacts that wear out, not the plastic housing. (In some connectors, like Molex KK, the pin does indeed sandwich between the female contact and the plastic wall of the housing, so housing failure would cause a poor connection. Most connectors aren’t like that, though, and even in those it’s not really a problem, though the single contact area with the pins limits current compared to connectors where the pin touches the female contact on multiple sides.)

author: mariush
author_rank: Super Contributor
timestamp: November 09, 2022, 11:29:52 pm
content: How much space can you afford?Maybe you can use some kind of slot ... because if you want to allow people to make modules, then they wouldn't have to use connectors, but simply design contacts on the edgeI was thinking of repurposing pci-e x1 slots as they're mass produced and relatively cheap :https://www.digikey.com/en/products/detail/amphenol-cs-fci/10018783-10200TLF/1002292... but there's just too many contacts and it would be more costly for people to make pcbs with a notch but it could also be useful to prevent people from inserting it the wrong way and get some reverse voltage (something which could happen unless you key your header.You could the small side for voltage (ex 5v on one side, gnd on the other) and the other side for IO (maybe have 2-4 pins in parallel for one IO , then a pin or two unused / grounded as separation, then another 2-4 pins for the next IO and so on.But there's other connectors with fewer pins. For example this 20 pin connector :https://www.digikey.com/en/products/detail/amphenol-cs-fci/10056847-101LF/5201796It's for 1mm thick boards, but jlcpcb doesn't charge more for thinner boards.

author: Saimoun
author_rank: Frequent Contributor
timestamp: November 10, 2022, 09:03:35 am
content: Thanks tooki for the long explanation, I did not know about the Ampenol original DupontAre you saying that even for the male headers I would be better off using some Amphenol ones like this one?https://www.digikey.com/en/products/detail/amphenol-cs-fci/20021111-00008T1LF/4243326Or does this have nothing to do with the Mini-PV?Quote from: tooki on November 09, 2022, 10:53:43 pmUnderstood. But my point still stands then, better to have the male connectors on the board and the female connectors on the cables as it will be easier to replace the cable if it gets loose.@mariush: thanks, that's actually a really good idea! It will not work with this project as the modules need to be external (for a few reasons). But I can see how a product could have a cool expansion slot a bit like a computer PCI indeed!!

author: tooki
author_rank: Super Contributor
timestamp: November 13, 2022, 08:59:28 am
content: Quote from: simonlasnier on November 10, 2022, 09:03:35 amNah, the headers can be whatever, as long as they’re the standard size (0.64mm) of square pin on the standard 0.1” (2.54mm) pitch. (The one you linked to is the much finer 1.27mm pitch and would not be compatible.)I use mostly cheap headers from aliexpress. Just beware that “gold” headers from AliExpress are sometimes plated in god-knows-what. I threw away an entire batch of those because they were basically impossible to solder. No problems at all with aliexpress standard tin plated headers.I also don’t bother with the Amphenol male mini-PV crimp contacts. The male contacts have no moving parts, so I don’t see how the vastly more expensive Amphenol parts could work any better.P.S. The reason China (and now, us) calls them DuPont connectors is because for a while, DuPont (the chemical company) owned the Mini-PV product before Amphenol bought it. It was originally made by a company called Berg (hence the “Bergcon” headers sold to go along Mini-PV), which was bought by DuPont’s electronics division. Later, DuPont sold that division to Amphenol.But I sometimes worry that the Chinese, at least the AliExpress and eBay vendors, have started using “DuPont” to meananycrimp connector, because you see them put the word on crimp tools that aren’t even distantly compatible with the contacts we are talking about…

author: Saimoun
author_rank: Frequent Contributor
timestamp: November 15, 2022, 01:52:12 pm
content: Ha ha, cool storyAnd thanks for the reply - I'll go with simple headers then and be carefull when choosing the female mating cable