Tips for super reliable BNC and D-SUB connectors - Page 1
Forum section: electronics / projects

author: brainchild
author_rank: Newbie
timestamp: January 09, 2018, 03:51:39 pm
content: I'm working on a patch panel for a research facility which will have a bunch of connectors of various types. Currently I'm trying to find good BNC and D-SUB connectors. There are plenty of options, but it's hard to find really suitable ones and so I'm hoping to get some tips here. Since these are for a facility that has a planned life span of 30+ years the connectors need to be extremely reliable and be able to handle tens of thousands of connect/disconnect cycles. Most connectors I've looked at are missing information about cycle lifespan and the few that does have the info specify 500-1000 which is nowhere near enough.So, does anyone here have experience with really reliable female BNC and D-SUB connectors for panel mounting that you can recommend?

author: edpalmer42
author_rank: Super Contributor
timestamp: January 09, 2018, 04:14:43 pm
content: Use 'connector savers' which are nothing more than male-female adapters. They stay permanently attached to the important connector. When they wear out, replace them in two minutes and carry on. The important connector only sees one cycle while the connector saver sees hundreds.Ed

author: ajb
author_rank: Super Contributor
timestamp: January 09, 2018, 05:01:14 pm
content: For cable-to-cable type patch panels you can even use the bulkhead feed-throughs as your sacrificial elements. You'd have to pull the panel at least partly off to replace them, but no worries about any connector savers getting removed and lost.If the patch panel is PCB-based or something, then use connector savers or design it to use sacrificial connector boards, or maybe use bulkhead feed-throughs and internal patch cables for the high-cycle connectors. Definitely don't put heavily abused external connectors directly on expensive/hard to replace PCBs if you can avoid it!

author: brainchild
author_rank: Newbie
timestamp: January 11, 2018, 02:37:31 pm
content: Connector savers is a good idea in principle, but unfortunately it won't work for us. The facility will have a constant stream of new guest researchers using the systems, so the connector savers will no doubt be mistakenly removed or get lost and new users won't know (or care) that there's supposed to be a connector saver on all connectors.The idea with panel mounted adapters is good in principle, but it means two more connection points for each cable which would mean two more points of potential failure. And even though it means it's easier to replace connectors it still means that the connectors will wear out and cause erroneous readings. Considering the cost of running this facility a bad connection could be very costly and we need to keep that to a minimum. Sure, you could set up a schedule to replace the connectors every 5 years or so, but the longer between replacements the better.So thank you for your tips, but currently I'm still looking at using regular, but reliable connectors. And I still haven't found any suitable so if you have more suggestions or tips they would be greatly appreciated.

author: Gribo
author_rank: Frequent Contributor
timestamp: January 11, 2018, 04:09:26 pm
content: Get higher spec connectors. There are several manufacturers out there that make mil spec DSUB connectors with very high mating cycle counts.One such manufacturer is ITT Cannon. 20$ per DSub, ouch..

author: tooki
author_rank: Super Contributor
timestamp: January 11, 2018, 05:23:40 pm
content: Quote from: Gribo on January 11, 2018, 04:09:26 pmI was looking at their website, and the mil-spec D-SUBs, even ones costing hundreds (!) had 500 mating cycles. Can you show an example of such connectors with truly high mating cycle ratings?

author: Gribo
author_rank: Frequent Contributor
timestamp: January 11, 2018, 06:37:00 pm
content: The TTI mating cycle spec is way too conservative. I had equipment using their DSub connectors with newbie techs plugging and unplugging all day long for more than 10 years, without any issue with the panel connectors. The cable side connectors were using cheap connectors and were being replaced on an annual basis. A PC with a parallel port that was part of the same system had to be replaced because the motherboard DSub connector was too flaky after a similar abuse.

author: edpalmer42
author_rank: Super Contributor
timestamp: January 11, 2018, 06:48:35 pm
content: What frequency range are we talking about? Maybe a different connector family would be more appropriate. For that matter, isanyRF connector family rated for thousands of connections? I've never looked into that.Ed

author: glarsson
author_rank: Frequent Contributor
timestamp: January 11, 2018, 07:07:47 pm
content: Even if a connector with a large number of mating cycles in the specification can be found, the question then is if that number is valid when the connector is mated with guest connectors of unknown quality?

author: Gribo
author_rank: Frequent Contributor
timestamp: January 11, 2018, 07:16:08 pm
content: You can use a patch panel as a connector saver. Break out the equipment to an easily repairable/replaceable patch panel. As for the BNCs, I would try to find a suitable quick connect version.

author: massivephoton
author_rank: Contributor
timestamp: January 11, 2018, 07:30:01 pm
content: If the budget allows, take a look at Lemo connectors.Don't know if they have D-Subs, but BNC's are rated for >5000 cycles.https://www.lemo.com/catalog/ROW/UK_English/00and01Coaxial_en.pdf

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 11, 2018, 07:30:36 pm
content: I question whether it is even reasonable to expect to find BNC-like (or any RF connector) and D-SUB-like connectors that would stand up to that kind of (ab)use for "30+ years")? Just plan on testing and replacing flaky connectors every n years as part of ongoing facility maintenance (like waxing the floors or emptying the trash).

author: tggzzz
author_rank: Super Contributor
timestamp: January 11, 2018, 08:35:13 pm
content: For some allocations, patch panels can be replaced by fixed wiring and electronic switching or electromechanical relays. You don't say what is being patched, so I can't judge whether that might be relevant.Over 30 years you are going to have many interesting problems, e.g. oxidation, cables/joints becoming unreliable, a damaged connector buggering the mating half, and many others.I would stay away from anything proprietary (which might not be available in 30 years), and plan on having some form of sacrificial connectors, even if it is just a entire sacrificial front panel.

author: _Wim_
author_rank: Super Contributor
timestamp: January 11, 2018, 09:03:48 pm
content: You could have a look at the Harting "HMC series", these are industrial rugged connectors that are rated for 10.000 mating cyclus. They make industrial Sub-D connectors (not sure if also in the HMC series), BNC I do not think the have...

author: _Wim_
author_rank: Super Contributor
timestamp: January 11, 2018, 09:09:18 pm
content: Webpage for harting HMC series:https://www.harting.com/DE/en-gb/node/192

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 11, 2018, 09:14:07 pm
content: A google search for high duty cycle connectors turns up several options rated for 100k cycles. No D-subs or BNC though in the first couple pages of hits. How wedded are you to those connector styles?

author: SeanB
author_rank: Super Contributor
timestamp: January 12, 2018, 10:32:40 am
content: ITT Cannon specs are pretty conservative. the 500 figure cycle is basically they did 500 cycles and the resistance of the clean, washed dry connector pairs was less than 1 digit on a 5 digit meter changed from the resistance on the first cycle. there are others, but the best bet is to get D connectors that are IDC compatible, and then place a short ribbon cable on them, leading to another D connector of the opposite gender inside, which then mates to the on board ITT connector. that way you only have 2 extra reliable IDC connections, and the stress of inserting and removing the connector is not transmitted to the inside board. For BNC and N connectors use a ITT bulkhead ( preferably the IP68 version, they are a lot more forgiving and have a decent holding method) coupled to a short inside coax lead to the inside connection, which then can be a board mounted socket.No connector is fool proof, I have had to change way too many Socaplex sockets with non replaceable pins, because they either had a pin break off in there or somebody jammed in a bent pin and ruined the internal turned sockets. Those were rated for 100k cycles as well. Another lot had to be changed on a cycle, as they were in a high vibration environment, and the 2mm diameter pins would wear down to nothing from vibration of the mated socket combination. Undo it and more than half the pins would be gold powder in the backshell and some would just be missing half way down.

author: Gribo
author_rank: Frequent Contributor
timestamp: January 12, 2018, 12:58:20 pm
content: Regarding the ITT D connectors, there are two variants for the female contacts, one has 2 'fingers' and the other has a circular cup with internal spring. The circular variant is the more reliable and is much more expansive.

author: cdev
author_rank: Super Contributor
timestamp: January 12, 2018, 01:54:19 pm
content: On my personal opinion scale of durability where some RF connectors are much more durable than others BNCs are among the most durable - under repeated use- friendly connectors.

author: brainchild
author_rank: Newbie
timestamp: January 15, 2018, 10:04:31 am
content: It would be nice to be able to specify any type of connector that is suitable, unfortunately the point of the patch panel is for guest researchers to connect their own equipment, so using non-standard connectors will only mean we need lots of adapter cables instead and we want to avoid that for various practical reasons. We're going to end up with enough adapter cables anyway as it is. Since we don't know exactly what will be connected we will try to cover the basics with D-SUB, BNC, RJ11, RJ45 and banana plugs. We will also use two types of low-voltage Lemo-connectors which is what we are going to use as a standard on our own equipment, but most equipment brought in by the guests will use something else.We don't expect the connectors to actually last for the whole life span of the facility, but the more long-lived they are the better. Replacing them will of course be costly, but nowhere near as expensive as data errors caused by an unreliable connection might be. So reliability is paramount.

author: brainchild
author_rank: Newbie
timestamp: January 15, 2018, 10:23:23 am
content: Quote from: tggzzz on January 11, 2018, 08:35:13 pmI agree, that's one more reason why we're going for BNC, D-SUB and RJ-connectors. We will probably use proprietary Lemo connectors for our own equipment, mainly for the ruggedness and reliability, but we will probably consider buying a big supply of the connectors at the start to make sure we can get hold of replacement parts in the future.The problem is that we don't know exactyl what will be connected. The patch panel is mainly for guest researchers to connect their own equipment through the wall of the instrument cave. We're trying to cover the basics and then use adapters cables for everything else.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 15, 2018, 10:58:04 am
content: Quote from: brainchild on January 15, 2018, 10:23:23 amYou mentioned that using connector savers wouldn't work becaue they are likely to be removed by accident. Have you considered using non-standard connectors and then using the adapter from said non-standard to BNC as your connector saver? This way it is more obvious that this is a connector saver and people won't (accidentaly) steal it, and even when they do, the next person can't not notice it and just plug on their stuff into the connector that has to last ages, since his BNC cable won't mate.In addition, having the savers be on one of those little chains might make it harder to accidentally steal one. And the adapter will always be nearby making it even more obvious they are supposed to use it? I'm talking about this kind of stuff:

author: brainchild
author_rank: Newbie
timestamp: January 15, 2018, 01:12:30 pm
content: The ITT Cannon D*M military grade D-SUB connectors look very promising. As pointed out the specification state only 500 mating cycles, but what SeanB say makes it more reassuring. I will probably buy a bunch of those for our prototype to test out. The question of the BNC connectors still remain though.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 15, 2018, 01:32:20 pm
content: Simply using ordinary bulkhead style female BNC to BNC connectors for a patch panel makes the connectors almost trivial to replace if they are damaged or worn-out. So buy a big box and keep the spares in the back of the cupboard.The physical dimensions of the BNC connector (required for RF impedance and interchange) is not particularly conducive to making a "rugged" version.

author: bitbanger
author_rank: Regular Contributor
timestamp: January 16, 2018, 02:51:14 am
content: Regarding the connector savers: if design permits, I have used these as the 'bulkhead' fitting itself attached from the rear of the panel, with the associated IDC or moulded DB9 connected "behind the scenes". This way they do not get lost and user is none-the-wiser (not to mention it makes panel attachment/removal easier).I have used LEMO and Fischer connectors quite a bit and IMHO some series are NOT user friendly. Even with the polarization, I perpetually have to repair high-pin-count Fichers from the users inserting and rotating to find location... these are NOT something fun to repair in the field!

author: brainchild
author_rank: Newbie
timestamp: January 16, 2018, 09:01:41 am
content: Quote from: bitbanger on January 16, 2018, 02:51:14 amThat is a very good point. I checked the Lemo connectors we're planning on using and they luckily are well designed and the pins won't interact with anything until the plug has been inserted the right way.