RJ45 feedthrough good to 50 bar pressure? - Page 1
Forum section: electronics / projects

author: JBeale
author_rank: Frequent Contributor
timestamp: March 07, 2017, 10:28:38 pm
content: Just out of curiosity. Is there such a thing as a RJ45 jack (or similar) bulkhead feedthrough that can withstand 50 atmospheres (750 psi) of pressure differential without leaking? If it helps, this would be for 100M ethernet so I only need 4 conductors, not 8. My online searches haven't turned up much but maybe I don't know the right terminology.I've seen references to people using automotive spark plugs as individual pressure feedthroughs, which is a neat idea, but then the whole thing would be too large and anyway I don't know how well it would work for ethernet signal integrity.

author: LaserSteve
author_rank: Super Contributor
timestamp: March 07, 2017, 10:31:59 pm
content: Try:http://bfy.tw/AUwZSubconn at 450 Bar, etc...Steve

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 07, 2017, 10:40:36 pm
content: Like, off the shelf?!Will an RJ45 housing even remain solid (i.e., not turn to goo) under that pressure? (I know, it will, at least if it's room temperature air, but I don't have a clue what you'd be doing, mixing that much air with Ethernet...)I can't imagine why such a thing would exist. Maybe, say, it's water tight also, and used on submersibles? Something in drilling? An obscure industry process control? Custom lab equipment?For sure, if nothing else, you can build one from standard parts and a hermetic feedthrough, but even then it won't be cheap. (Or you can probably find a company who'll make you a few, but I can't see that happening for under $10k NRE + tooling.)Putting RJ45 aside -- hermetic pressure seals aren't terribly uncommon AFAIK. Spark plugs are a fine example, but a bit over the top (and inconvenient anyway, as you note). I've seen plates with arrays of glass feedthroughs, still spendy of course, but maybe you can eBay a few if you don't need the quality assurance of new manufactured with a paper trail.As for signal integrity: 100Mb is quite tolerant. The bit times are around ten nanoseconds, so disturbances less than a few nanoseconds (about a meter long) aren't a big deal. Spark plugs would actually be hardly noticed.Edit:Quote from: LaserSteve on March 07, 2017, 10:31:59 pmWell gee, Steve, if you're going to snark, why don't you at least spell it right...QuoteAyyy, that's a good query though. These guys turn up:https://www.macartney.com/what-we-offer/systems-and-products/connectivity/subconn/subconn-ethernet-series/Maybe not precisely what OP is after, but something vaguely similar seems to exist!As for the price tag?Tim

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 07, 2017, 10:44:31 pm
content: There are smaller spark plugs made for the lawn tool and model airplane market. Still would be very bulky, but much smaller than automotive plugs. Look for NGK CM-6.I think the search term you are looking for is "pressure feed throughs"It will give you people like the following.http://www.ametekinterconnect.com/products/hermetichighpressurehightemperatureelectricalbulkheads/gtmsbulkhead

author: JBeale
author_rank: Frequent Contributor
timestamp: March 07, 2017, 10:54:19 pm
content: Basically, a network-connected sensor underwater at 1600 feet. The sensor itself can't be run at that pressure flooded with silicone oil so I need a pressure vessel good to that depth, and hence the feedthrough. And it's just a personal fun project (because why not?), so not a huge budget.I just came across the small model airplane spark plugs likehttp://sparkplugs.morrisonandmarvin.com/10-40.phpwith a 6mm hex, it might actually work ok.It would be a lot cheaper thanhttps://arstechnica.com/science/2014/07/deep-sea-streaming-500-mile-neptune-cabling-brings-internet-to-the-ocean-floor/2/"The hoses are filled with silicon oil, an incompressible fluid, which eliminates the possibility at lower depths that the cable might tear—something Round would prefer, as these cables don't come cheap. A mating pair of copper Ethernet connectors alone can run $25,000, and that cost doubles if the network requires longer fiber optic cables and connectors which are required for instrument platforms and junction boxes in excess of 70m. Some of these satellite sites run tens of miles away. To save money, NEPTUNE uses dry-mate connectors where possible. They're made of titanium, which is preferred at depths beyond 400m, and cost only $2,500 per pair. The tradeoff is they can only be connected on land."

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 07, 2017, 11:07:21 pm
content: Lots to think about here. Spark plugs actually see only brief moments of 50 bar pressure, and don't really have to seal, just leak slowly. They are also not made of sea-water friendly materials. If you have a way of doing a quick test it might work out, but it would be terrible to get your first prototype into place and find that they just don't do the job. There is a reason the specialists are able to charge those extreme prices.

author: CM800
author_rank: Frequent Contributor
timestamp: March 07, 2017, 11:11:15 pm
content: These are what you'd want if you could afford it:http://www.ametekinterconnect.com/products/subseaconnectors-and-feedthrough-penetratorsMaybe give them a call, explain what you're trying to do and see if they have a customer order you could 'bum off' a part or two from on the cheap. Sometimes these companies can be a lot friendlier then they look.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 07, 2017, 11:31:42 pm
content: Forget the RJ45 and look at hardwired feedthroughs.One option may be line bushings designed for explosion-proof enclosures. Not sure if they specify continuous pressure rating.http://atex-enclosure.com/solutions/line-bushings/

author: Ian.M
author_rank: Super Contributor
timestamp: March 08, 2017, 12:09:53 am
content: I doubt it - they seem to be potting the wires in their insulation.You really need a solid pin for each conductor going through a small hole with an insulating seal chemically bonded to both the pin and the hole. You might as well do all eight wires, as extra circuits up the umbilical are always useful - either for power delivery, or low speed backup telemetry.I'd start here:http://www.completehermetics.com/glass-to-metal-seals-and-feedthroughs/or with their competitors.The pressure side of the seal is going to need protecting - probably mount a PCB to the feedthrough pins with a RJ45 jack, then enclose that in an oil filled chamber with bellows to pressurise it to ambient, and a gland to bring in a direct burial rated gel filled CAT5 or CAT6 cableThe fly in the ointment is you are going to either need Ethernet repeaters every 100m up the cable or to use fibre Ethernet. Seehttps://kb.wisc.edu/ns/page.php?id=7829

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 08, 2017, 12:13:04 am
content: Quote from: Ian.M on March 08, 2017, 12:09:53 amPretty sure the insulation is stripped to avoid gas permeating through the strands - may even transition to solid pins - don't know.They are primarily designed for impulse pressure but may be worth looking at some datasheets.

author: LaserSteve
author_rank: Super Contributor
timestamp: March 08, 2017, 07:45:22 pm
content: Perhaps try a fiber optic seal from a company like Accuglas Products and avoid the need for Ethernet Repeaters?https://accuglassproducts.com/home.php?cat=616Steve

author: qwaarjet
author_rank: Regular Contributor
timestamp: March 09, 2017, 07:30:49 am
content: How about PAVE I've used there stuff for vacuum but they have high pressure rated as wellhttp://www.pavetechnologyco.com/design/pdf/3273.html