Case to Case Connections

Question

I'm looking for ideas for connecting encased devices. So PCB -> Panel <-air gap-> Panel -> PCB. Better: Free end (for crimping connector) -> Panel <-air gap-> Panel -> Free end (for crimping connector). I'm just looking to transfer signals and low-current, low-voltage power in a cheap way. Although PCB edge-mounted connectors are an available option, I can't use these.

An example solution would be an IDC connector with flat cable: flexible with a variety of potential contacts and easily obtained with pre-made cables. It's easy to find PCB mounts and male/female connectors but a panel mount socket (or plug) seems non-existent.

An alternative would be d-sub connectors. Again, variety of potential contacts, easy to solder up, but quite large. Easy to find male/female connectors as well as panel mount. Cheap as chips, but quite large.

I've come across pluggable terminal blocks but these are expensive.

The hardest element to find seems to be the panel mount socket (except for d-sub) but I'm not sure that I'm searching with the right keywords. It's even harder to find a panel mount socket that is not expensive. I'd settle for d-sub but thought I'd throw this out there for ideas.

jw0752 · Answer

You could check out : http://www.tag-connect.com Neil is an expert on connecting things together inexpensively. John

shabaz · Answer

Hi Andrew, 'Modular' (RJ45) could be an option, since circular panel mount sockets are available, and the circular hole is easier to make than rectangular. Wiring them is simple/cheap, provided you're ok with twisted pairs. I've used RJ45 on a few projects, and I like it because I can use standard ready-made network cables. It might be too bulky though if you wanted something smaller. For higher density, maybe 'MDR' connectors? They were used for old SCSI connections, and are available in (say) 20-pin and 30-pin, and the connectors are panel mount usually. Regarding IDC connectors, there are some that are panel mount but they are more rare. This one maybe: https://uk.farnell.com/3m/4620-6000/header-idc-lugged-20way/dp/469166 (It is panel mount but would use ribbon cable, to the PCB, or strip the other end of the ribbon cable and solder to the PCB or whatever).

jc2048 · Answer

Many crimp connector series include panel-mounting housings. As an example, this link is a Molex Mini-Fit Jr plug housing which will clip into a panel. https://www.molex.com/molex/products/part-detail/crimp_housings/0039012066 They're intended more for wiring harnesses to internal bulkhead panels in industrial and consumer equipment, but if you're not too fussy about looks and just want something that's functional they might do you. The specialised crimp tool is very expensive, but the crimps are large enough that you can solder the wires to them as an alternative, or if you're careful just use a pair of pliers. TE Connectivity also have a huge range of different parts.

Andrew J · Answer

I've been thinking about right-angled headers to go with some of the Moiex KK connectors I have, on a separate PCB as Shabaz suggests above. I struggle to see how those lugs support the panel connector from both sides as I can't envisage the panel 'sandwich' effect to stop them falling through from one side.

dougw · Answer

How many pins do you need? How much weight or force will the connection need to support? How often does the connection need to be disconnected? Are there any other mechanical connections between panels? Is there motion or vibration involved? Do the connectors need to lock together? How big are the PCBs? PCB-mount connectors that are also bulkhead mounted exist but are over-constrained mechanically - if the pcb is screwed to the chassis and the connector is fastened to the panel, it can put stress on the solder joints. (So tight tolerances will need to be maintained) If the panel-to-panel connector is the only connection between modules, the connector may need to withstand high forces. Many connectors only have one side panel mounted to avoid this because they are not strong enough to support more than the weight of a cable. There are many through-hole board-to-board connectors that need cutouts in the panels to go between modules, but they don't usually have panel fasteners. The DB connectors you mentioned can do it all, but have limited strength, and it is tough to get them screwed together in the confined gap between panels. Many circular bulkhead connectors can be mounted to PCBs although most are vertically oriented on the PCB. Also usually pretty expensive. The bottom line is that what you want is not commonly available because the connectors would need to be so strong, they would be very expensive. There are many possible solutions to accommodate specific applications where some of the normal requirements are not needed, but more information is needed to tailor a solution.

jw0752 · Answer

Hi andrew, Another technique that I like to use when I am searching for a component is to get out one of my parts supply house catalogs from a few years ago. I will then go page by page through the section related to my need and look at the pictures. Very often I can find what I am looking for. The searches on the internet do not lend themselves to this type of browsing. John

Andrew J · Answer

Interesting and useful points Doug. I seem to have narrowed it down to 15 pins across 3 connectors, for convenience - 2 on the back, 1 on the front. But I could go 10, 5, 5, 5, 15. There's no vibration, shearing force or weight beyond perhaps a cable with connectors on each end as they will be linking bench top cases together. So I might connect the rear two to two connectors on another case, ditto the front one to another case. I don't want them permanently connected to each other, nor to open the case to connect/disconnect them. It's all hobbyist stuff in any case so there are no standards to conform to. But also, the question was as much about working out what is out there because it seemed to be a bit of a desert and I may have been using the wrong search terms - your pointers make me think that what I'm finding is what I'm finding!!

genebren · Answer

Andrew, I like to use connectors that have nice pre-made cables available for them, like USB and HDMI. While these cables may have limited connections, they are plentiful and relatively inexpensive. One of the approaches that I have used when going from device to device to shift over to a serial bus (UART, I2C, SPI) and multiplex the data onto a minimum set of pins. This definitely works for digital signals, but may be more problematic when it comes to power and analog signals. Another useful approach that I have used with analog/power are IDC connectors from AMP ( https://www.newark.com/w/c/connectors/idc-connectors?product-range=mta-100-series ). These come in different pitches and connector counts. They are easy to use, with push on wires and can be used with ribbon cables for very neat cables. Best of all they can be used with standard headers, or special locking headers. Good luck! Gene

shabaz · Answer

Hi Andrew,

I know what you mean, and sometimes it may be easier to just place all connectors on one side of the board, so it fits any enclosure, but often it's not ideal/feasible to put them all on one side.

Another option could be to have a snap-off portion of PCB, where (say) it could have vertical DIL header and screw holes on the PCB so that the snap-off portion is screwed onto the enclosure. and then have flat flex (for example) to connect to the main board. For really low cost non-critical applications, the flat flex could just be soldered without connectors.

This is also ideal for all sorts of connectors that are PCB-mount, and saves on wire assembly time etc.

In this example (at right angles in this case however) I needed three connectors, but the main PCB wasn't designed for that, so I created a small separate custom PCB with the three connectors on it, and inside the enclosure there are JST cables going from here to the boards that require each of the connections.

Andrew J · Answer

That's something I've been thinking of and trying to determine if I could do it with the connectors I have - related to Jon's answer below actually. Or even with a bunch of IDC connectors.

shabaz · Answer

I see.. Personally I think RJ45 is cleaner than D-Sub (for 8 or fewer connections) since the cables are ready-made and popular (can even get 25cm cables for short interconnects) whereas with D-Sub at least to me it's confusing if they are null modem or otherwise. Yes, these were photos found via google, on aliexpress.. it's getting crazy finding parts in stock these days.. and it was nice to see a photo with cable on the end. If it's a non-critical application then they should be good enough from Aliexpress I guess.