RJ11 crimp contacts for 22AWG stranded cable?  - Page 1
Forum section: electronics / projects

author: Lomax
author_rank: Frequent Contributor
timestamp: September 06, 2017, 09:46:19 pm
content: Having gotthe cable I ordered, one of the first things I wanted to do was to make up a good ~6m cable for my 1-Wire AAG/Dallas weather station. Annoyingly, it has RJ11 sockets (I hate RJ11), and I had been making do in the lab with a piece of flat telephone cable I had lying around. I've got plenty of RJ11 crimp contacts, so I've tried to crimp one on to one end of the new cable, but after three careful attempts, where I've spent a lot of time trying to make sure all strands from each wire go in the right place, I've ended up with three crimps where two pins have been shorted out.Ok, so maybe the RJ11 crimp contacts I have are not intended for stranded wire - and certainly not for 22AWG wire - but I figured it was worth a shot. On the third attempt, I checked under the microscope with plenty of light before crimping, and it definitely looked like all wire strands were in the right slot, but post crimp the angry beep from my meter says otherwise.TL;DR: I need to fit an RJ11 plug onto a 22AWG stranded cable - preferably by crimping - which connectors should I get?

author: Ian.M
author_rank: Super Contributor
timestamp: September 06, 2017, 09:56:35 pm
content: Normally RJ series crimp plugs have insulation piercing contacts so you shouldn't strip the wire. *MOST* RJ crimp plugs aren't recommended for solid core anyway so its just a matter of finding one that accepts 22AWG wire - the top end of the normal size range.N.B do you really want real RJ11: 6P2C, center contacts missing, or do you actually want 6P4C or a fully populated 6P6C modular plug?

author: Benta
author_rank: Super Contributor
timestamp: September 06, 2017, 10:20:02 pm
content: RJ-11 is not a crimp connector, it's insulation-piercing. Cut the cable, stick it in and use the special "comb" type pressure pliers. Done.It really doesn't get any easier.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 06, 2017, 10:21:10 pm
content: Quote from: Ian.M on September 06, 2017, 09:56:35 pmHmm, yeah, I appreciate that (not stripping the wire), but the plugs I have won't take 22AWG "unstripped". I thought maybe there would be a wall between each contact, but on closer inspection of one of my failed crimps I can see that this is exactly the problem; the naked strands have been squashed and spread out by the contact, making a connection with the strands from the wire next door. So much for spending ages making sure all strands were in the right channel.Quote from: Ian.M on September 06, 2017, 09:56:35 pm6P4C, though I don't know if that matters - they're the same size, no? Thecrimping die I useis marked 6/6 6/4/ 6/2...

author: Lomax
author_rank: Frequent Contributor
timestamp: September 06, 2017, 10:24:17 pm
content: Quote from: Benta on September 06, 2017, 10:20:02 pmThanks. I'm probably using the wrong terminology here, but the plugs I have are "single use" and require pressing action from a shaped die ("comb" shaped as you say) - to me that's a lot like a "crimp" thing. "Insulation piercing" isn't too snappy - is there a better term? Also, even with the correct cable (flat and flimsy "telephone" type cable) I still think you'd need to separate the (non-stripped) wires; I can clearly see four circular channels leading from the body of the housing into the "pressure tool application zone" - I can't imagine that the flat cable would be able to enter far enough without removing some of the outer sheath first.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 06, 2017, 10:30:51 pm
content: 22AWG is way too big for an RJ11.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 06, 2017, 10:33:38 pm
content: Quote from: mikeselectricstuff on September 06, 2017, 10:30:51 pm"Way too big"? Looks more like "just a tiny little bit too big" to me!

author: Benta
author_rank: Super Contributor
timestamp: September 06, 2017, 10:41:49 pm
content: Quote from: Lomax on September 06, 2017, 10:24:17 pmNo, you donotneed to separate the wires when inserting unstripped flat cable into an RJ-11 connector.Cut at a right angle, stick it in and press the tool. That's it!Too bad that you find the technical term "unsnappy", but its correct. You have:Insulation piercing connectors: RJ-11, RJ-45 etc.Insulation displacement connectors (aka IDC), where small "forks" cut through the insulation on each side of a wire and cold welds to the internal strands.Aaaand crimp, which is circumferential pressure from the outside onto either stranded or solid wire. Can be a U-form crimp or a ferrule.Snappy enough?

author: Lomax
author_rank: Frequent Contributor
timestamp: September 06, 2017, 10:43:16 pm
content: Quote from: Benta on September 06, 2017, 10:41:49 pmI guess. I'm all for using the correct terminology, so thanks for correcting me - I learned something new today!

author: Lomax
author_rank: Frequent Contributor
timestamp: September 06, 2017, 10:54:34 pm
content: Quote from: Benta on September 06, 2017, 10:41:49 pmIs that how this (manufacturer supplied) cable was made?I do not understand why I can clearly see the blue and brown wires, unless the white sheath was partially removed before the "insulation piercing process" was performed.

author: The Soulman
author_rank: Super Contributor
timestamp: September 06, 2017, 11:37:05 pm
content: Ah, that is double insulated cable, you must strip back the(outer)insulation but not strip back the(inner)insulation before inserting.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 06, 2017, 11:41:46 pm
content: Quote from: The Soulman on September 06, 2017, 11:37:05 pmI have never seen any other kind of cable used in a "consumer" RJ11 cable. Got any examples?

author: nanofrog
author_rank: Super Contributor
timestamp: September 07, 2017, 12:03:03 am
content: As mentioned, only the outer jacket has to be removed. The insulation on the individual conductors is left on/un-stripped.Your die will make nice crimps this way and you'll avoid shorts.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 07, 2017, 12:34:48 am
content: Quote from: nanofrog on September 07, 2017, 12:03:03 amI was referring to this statement:Quote from: Benta on September 06, 2017, 10:41:49 pm

author: Lomax
author_rank: Frequent Contributor
timestamp: September 07, 2017, 01:33:01 am
content: Never mind, it is done. Behold, a round cable with 22 AWG members, "isolation pierced" into an RJ11 plug - with reliable connections and no shorts:

author: DBecker
author_rank: Frequent Contributor
timestamp: September 07, 2017, 04:01:18 am
content: There should be a strip guide on your crimp tool, or an integrated stripper that cuts back the sheath the proper distance.When properly crimped, the strain relief should latch while grabbing onto the sheath.There are many slight variations to the connectors to handle different wire sizes, insulation thicknesses, and round vs flat. The contacts may be bifurcated to straddle solid conductors, inline to make maximum contact with stranded conductors, or slightly offset to handle both. These are important when you care about production-scale reliability, but aren't usually thought about too much when doing field crimps.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 07, 2017, 01:18:54 pm
content: Quote from: DBecker on September 07, 2017, 04:01:18 amThere isn't (it's acrimp tool with exchangeable dies, not a dedicated modular "isolation piercing" tool). Quite simple to hold up the cable next to the contact to see how far it needs to be stripped though.Quote from: DBecker on September 07, 2017, 04:01:18 amYeah.Quote from: DBecker on September 07, 2017, 04:01:18 amExactly. This is why I asked this question. I have spent quite some time searching for RJ11 contacts for stranded 22 AWG wire, but you'd be surprised how rarely 1) whether the contact is intended for stranded or solid cable and 2) what maximum gauge cable the contact will accept is displayed in the catalogues. Typically they are only listed as RJ11 plugs, with the only differentiator being the number of contacts that are populated (6/6 6/4 6/2). I thought that this being the EEVBlog forum there would be loads of people here who have faced the same issue, but apparently not.Quote from: DBecker on September 07, 2017, 04:01:18 amPretty important when the cable members are too thick to fit in the channels too.

author: Ian.M
author_rank: Super Contributor
timestamp: September 07, 2017, 02:48:41 pm
content: Just make sure the individual wire ends are butted right up against the end wall of the channels under the contacts, and the jacket buts against where the channels start, double check the wire order, and make sure that any strain releafs, cable ID sleeves etc. are in place *BEFORE* crimping.On the issue of wire gauge - the AWG tells you next to nothing about the insulation diameter (except that it must be >X), so unless you stick to manufacturers who provide detailed dimensioned drawings of their connectors, you will either have to test samples or reach out to them and enquire about the maximum wire diameter. If its not specified you can *ASS*U*ME* that modular connector plugs up to 6 ways are compatible with 'silver satin' phone wire (to BT spec. CW1311) and not much else and that 8P8C 'RJ45' plugs are compatible with Cat5 Ethernet patch cord.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 07, 2017, 03:20:40 pm
content: Quote from: Ian.M on September 07, 2017, 02:48:41 pmGood point. I have looked at quite a few datasheets, but far from all include this measurement. It's a pain basically. What I did was I took a 1.1mm PCB drill and put it in a pin vice, and carefully widened the channels by hand. Tedious, but it worked, and I only needed one cable terminated like this. I then back-filled the RJ11 housing with epoxy, which I let set overnight, and I believe I now have a very reliable termination. Seems a bit crazy to use RJ11on a weather instrument, which of course is meant to be outdoors in every kind of weather, but it seems to be the most popular connector in 1-Wire networks. Personally, I hate them.

author: Ian.M
author_rank: Super Contributor
timestamp: September 07, 2017, 03:30:31 pm
content: Yes. They aren't really fit for harsh environments, unless used as part of a plug with an O ring seal and a screw-down retaining ring. I'd be concerned about corrosion between the contact and the wire strands - however there's not a lot you can do about that if you want to pot the back of the plug, as a smear of electrical grade grease on the wires to seal the contact, if it even touches the sides on the way in could prevent the epoxy adhering. Make sure you've got at least a foot of slack so you can cut it back and reterminate if it gives you trouble in the future.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 07, 2017, 03:51:29 pm
content: Quote from: Ian.M on September 07, 2017, 03:30:31 pmThis ^

author: Ian.M
author_rank: Super Contributor
timestamp: September 07, 2017, 04:18:46 pm
content: Maybe immerse the end in reasonably hot melted Vaseline, pull a vacuum on it to get air bubbles out, then blot off as much as you can before it cools. That should get penetration into any voids moisture could creep into without cable jacket damage. Pulling a vacuum on it is going to be a PITA, but its amazing what you can do with a block of Plasticine to make a temporary seal.

author: nanofrog
author_rank: Super Contributor
timestamp: September 07, 2017, 04:36:45 pm
content: Quote from: Ian.M on September 07, 2017, 04:18:46 pmGreat tip.Looks like handy stuff to keep around, and it's inexpensive.