"No-crimp" connector idea - Page 1
Forum section: electronics / projects

author: ElectronicSupersonic
author_rank: Regular Contributor
timestamp: September 15, 2019, 05:39:11 am
content: While working on a project (one of many which most probably never be finished), I had to design an easy to assemble connector (like IDC type connectors). Here is what I came up with.Since my goal was to design something which wouldn't require expensive crimping tools, the usual crimp style was not an option. Instead omega shaped contacts are used. Where wire is inserted in to an "eyelet" and affixed in place by the spring action of the contact. Thus special tools are not needed.Same idea could be used for both round (3.5mm headphone jack style) and the usual rectangular connectors. Bellow are attached screenshots of both types. Note that these are only to illustrate the idea - not the actual working solutions.

author: Dubbie
author_rank: Unknown
timestamp: September 15, 2019, 05:44:33 am
content: You should make some and see if they work.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 15, 2019, 06:42:25 am
content: Hmmm...Heh, I can see where you're going with these. It's nice thinking, but it's missing something.Have you held a piece of stranded wire in your life? How the heck are you going to coax every single strand into a just-perfectly-sized space? (If you have a solution for that, I would honestly like to see it. Every so often I find myself wrestling very fine strands (might be welding cable, might be litz cable) into a crimp lug. Such a PITA when they're tight fitting!)Even if it's solid core wire, how are you going to have adequate retention force, while also being able to push the thing in?For the phono jack: how are you going to insert the wires, or tension the springs, while also stretching the spring over the connector body?For the square pin connector: the square pin spreads the terminal frame apart, loosening the wire, doesn't it?Tim

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 15, 2019, 07:29:52 am
content: For solid wire something like that is used on electrical outlets.

author: ElectronicSupersonic
author_rank: Regular Contributor
timestamp: September 15, 2019, 07:45:21 am
content: QuoteThe pin is held in place by the housing. Housing has a groove intended to press-fit both the wire (sleeve) and the contact. Thus contact, then inserted, is "squished" by the housing and accordingly provides retention. Since housing is tight, pin insertion shouldn't cause problems, there is simply no place to spread inside the housing.QuoteWell pre-cut wires would be inserted first (in the correct location leaving striped ends not inserted), then rings are to be mounted then strands go.QuoteWires are to be press-fit in to the housing, thus a good amount of retention should be present. That is housing is designed to provide retention via tight fit of grooves where wires would go.

author: tautech
author_rank: Super Contributor
timestamp: September 15, 2019, 08:15:44 am
content: Quote from: T3sl4co1l on September 15, 2019, 06:42:25 amYep, we've all been tested on that one !There's a simple trick for fine stranded cables and insertion into crimp lugs, ferrules and the like.Pull off ~6"or more of insulation tape and spin/twist it loosely into a soft round rope shape and bind the strands not too firmly together starting from the insulation sheath nearly to the tip of the strands and then back towards the insulation a couple of turns. Keep finished end taught.Insert exposed strand tip into lug and press not too firmly home.The tape rope slides down the strands and will bunch up at the end of the sheath between it and the lug.Unwrap tape rope then press cable fully home..... done !Done properly you'll never miss inserting even a single strand.This tape rope can be used again and again.Thanks to my sparky mate Wayne for that one.

author: Yansi
author_rank: Super Contributor
timestamp: September 15, 2019, 09:09:49 am
content: ...and then you reinvent the spring terminals (WAGO).

author: Gyro
author_rank: Super Contributor
timestamp: September 15, 2019, 09:12:16 am
content: Maybe I'm just not getting it, but I don't understand what stops individual strands from squeezing out into the open side of the 'omega' when compressed? That would spoil the 'perfect fit'. Wire diameters will be subtly different between types too.A connection really needs to be 'gas tight' for long term reliability, I'm not sure how/if this achieves that.

author: 2N3055
author_rank: Super Contributor
timestamp: September 15, 2019, 10:18:23 am
content: Quote from: Yansi on September 15, 2019, 09:09:49 amThis. Spring based terminals are old news.

author: FreddieChopin
author_rank: Regular Contributor
timestamp: September 15, 2019, 10:25:10 am
content: Quote from: Yansi on September 15, 2019, 09:09:49 amWago connectors are horrible because they are prone to rust, have pretty high contact resistance and when overloaded they melt. I worked on many building sites in Poland and everywhere I worked it was forbidden to use wago because when installation is overloaded with electric oven, kettle or arc welder it can start a fire. Instead we use proven screw terminals that can whitstand high overloads.In my parents house there is aluminim electric instaltion done by my grandfather, it is soldered instead of any terminals and it works without issues since 1950s and I'll bet it will work great 30-40 years into the future. We don't do much soldered electric installation nowdays unless client is willing to pay more for it because it takes time.

author: Monkeh
author_rank: Super Contributor
timestamp: September 15, 2019, 10:59:08 am
content: Quote from: FreddieChopin on September 15, 2019, 10:25:10 amJust like anything else with steel in it, like your screw terminals..Quote[citation needed]QuoteJust like everything else with plastic housings, like your screw terminals..QuotePerhaps Poland should investigate the concept of a circuit breaker.QuoteProven to be cheap, awkward, and easily misused, yes.QuoteSoldered.. aluminium. Not impossible, also not likely, and of course surely won't melt under overload

author: Yansi
author_rank: Super Contributor
timestamp: September 15, 2019, 11:06:18 am
content: Quote from: FreddieChopin on September 15, 2019, 10:25:10 amIf something is overloaded, then probably the overloaded components is not at fault, more likely You who put it there incorrectly in the first place.Spring terminals are currently the go-to in the industry and there are no problems with their reliability. In fact, they have better reliability, than screw-type terminals. Even installation errors like forgotten screw that was not tightened properly are quite eliminated.Soldered what?! O_o

author: FreddieChopin
author_rank: Regular Contributor
timestamp: September 15, 2019, 01:44:32 pm
content: Quote from: Yansi on September 15, 2019, 11:06:18 amAt work we use YDYp 3x1.5mm cable to wire outlets. Sometimes B16 breaker wont trip with something heavy connected (like dishwasher or kettle) but WAGO will burnwhile screw connectors are fineIt's simple math - more connection area -> less I^2R losses -> less heat.

author: Monkeh
author_rank: Super Contributor
timestamp: September 15, 2019, 01:49:09 pm
content: Quote from: FreddieChopin on September 15, 2019, 01:44:32 pmDishwasher or kettle? You mean a sub-10A load, on a 16A breaker, using a connector generally rated around 32A? Bullshit.Having watched real Wago connectors take a 3xIn overload for several minutes, I don't believe you.

author: langwadt
author_rank: Super Contributor
timestamp: September 15, 2019, 01:54:20 pm
content: looks like it would basically be like a incorrectly done crimp

author: Yansi
author_rank: Super Contributor
timestamp: September 15, 2019, 02:08:23 pm
content: Quote from: FreddieChopin on September 15, 2019, 01:44:32 pmIf you do that, you should get slapped. On a 16 Amp circuit, 2.5 mm2wires shall be used.YDYp is good at best as a light fixture wiring.

author: Monkeh
author_rank: Super Contributor
timestamp: September 15, 2019, 02:09:52 pm
content: Quote from: Yansi on September 15, 2019, 02:08:23 pmErr, that's going to depend on your regulations, so that's a high horse you can abandon rapidly. 1.5mm² is adequate for 16A in many cases.

author: Addicted2AnalogTek
author_rank: Frequent Contributor
timestamp: September 15, 2019, 02:35:49 pm
content: Quote from: Alex Eisenhut on September 15, 2019, 07:29:52 amSome info regarding these connections on receptacles and switches:According to US NEC (National Electric Code), using these push-in connections are not permissible. I've encountered many of these where "do-it-yourselfers" or maintenance people have swapped a receptacle (typically on GFCIs) and installed the new device this way. This type of connection is notoriously unreliable and many times, regardless of the screw being tightened, the wire slips out when removing the device. The only accepted method is to loop the wire around the screw terminal, pinch the end and the conductor together (so that it holds regardless of whether the screw is tight) then snug the screw and tighten a half turn.

author: madires
author_rank: Super Contributor
timestamp: September 15, 2019, 03:01:57 pm
content: Quote from: FreddieChopin on September 15, 2019, 10:25:10 amGenuine Wago or Wago style copies/counterfeits?

author: Simon
author_rank: Unknown
timestamp: September 15, 2019, 03:18:23 pm
content: The problem is contact resistance. The key is to just fing a connector that you can use is many applications and stick with it. This is like standards. There are so many crimp tools because companies want to screw you for the tools. TE are the worse because all tooling is made by "the" tooling subsidiary that are expected to turn a profit. with mass produced off the shelf die sets costing £500-1500 for tiny pins it is daylight robery when I can get a custom die made for heavy duty pins for £1000

author: Zero999
author_rank: Super Contributor
timestamp: September 15, 2019, 03:44:10 pm
content: What voltage is this connector going to be working at?If it can be plugged or unplugged, when live, then the earth connection needs to made first and broken last and there shall be no chance of the earth becoming live.Going from the drawings in the original post, there's no way it'll meet the above requirements.

author: Simon
author_rank: Unknown
timestamp: September 15, 2019, 03:54:51 pm
content: It also relies on a specific wire size to work. i like the idea but in all my experionce of using various connectors i can't see it working.

author: Yansi
author_rank: Super Contributor
timestamp: September 15, 2019, 04:36:27 pm
content: Quote from: Zero999 on September 15, 2019, 03:44:10 pmTell that to a TRS phone jack.//Way to many times I've see 1/4" TRS jacks used for amplifier speaker outputs... stupid design choice//

author: Simon
author_rank: Unknown
timestamp: September 15, 2019, 04:41:41 pm
content: It's about the voltage level and safety regulations on mains plugs. Plenty of connectors are rated for high voltages and disconnect everything at once. My issue with this design is that in practice it will never work because of real life and contact resistance of the wire with the contact.If you want a universal connector that is not a pain in the as use Deutsch/TE DT, DTM or DTP connectors and/or the equivalents from Amphenol sine AT, ATM and ATP. The crimp tool for all 3 sizes of pin and all wire sizes costs £500 and lasts forever. Never mind all of the other shitty TE connectors that have a single die for a single size that costs £500.

author: mikerj
author_rank: Super Contributor
timestamp: September 15, 2019, 04:44:25 pm
content: It seems extremely unlikely this will achieve a reliable gas tight connection. Also what mechanically retains the cable, looks like one good pull would see the cable separated for the connector.

author: Zero999
author_rank: Super Contributor
timestamp: September 15, 2019, 07:32:26 pm
content: Quote from: Simon on September 15, 2019, 04:41:41 pmBut it's not safe to use one of those for the earth, as well as live conductors. Look at any properly mains electrical plug/socket and you'll find the earth connection is always designed to make first and break last.

author: Nominal Animal
author_rank: Super Contributor
timestamp: September 15, 2019, 07:46:40 pm
content: Where I live, outside temperatures can easily vary by about 60°C during the year. This means that screw terminals can fail due to thermal expansion, whereas spring-loaded terminals will keep contacts (due to spring action) regardless of temperature changes. Even indoors you can have 20°C temperature swings, especially if you leave your house at maintenance temperatures (around 10°C) for a winter month, due to a well-earned holiday somewhere warmer.Because of this, I trust (locally sourced from reputable sources) Wago-style connectors way more than screw terminals. So do all the local electrichickens I've talked to.

author: ebastler
author_rank: Super Contributor
timestamp: September 15, 2019, 07:59:55 pm
content: Quote from: ElectronicSupersonic on September 15, 2019, 05:39:11 amHow much spring travel do you expect those "omega contacts" to have? Your renderings look like the inner diameter of the eyelet which receives the wire is pretty much fixed. How would these contacts clamp wires of slightly varying diameter? (Or worse, multi-stranded wire twisted in slightly different ways, and with some room for the strands to move relative to each other?)

author: Simon
author_rank: Unknown
timestamp: September 15, 2019, 08:28:23 pm
content: Quote from: Zero999 on September 15, 2019, 07:32:26 pmThey are not meant for such a use. They are equipment interconnection connectors that will only be mated or unmated when the equipment is powered off.

author: tooki
author_rank: Super Contributor
timestamp: September 16, 2019, 03:40:12 am
content: Quote from: tautech on September 15, 2019, 08:15:44 amCould you maybe make a video of this? I'm having trouble visualizing what you mean, but it sounds useful!

author: tautech
author_rank: Super Contributor
timestamp: September 16, 2019, 04:13:18 am
content: Quote from: tooki on September 16, 2019, 03:40:12 amWorking with Wayne here tomorrow I think so I'll try to grab it with my phone.Added the word twist for hopefully more clarity. ^^^While it took a few minutes to write to get good meaning it takes but seconds to accomplish.

author: ElectronicSupersonic
author_rank: Regular Contributor
timestamp: September 16, 2019, 05:49:02 am
content: Quote from: Gyro on September 15, 2019, 09:12:16 amMost multi-stranded wires are twisted, thus form sort of single core (especially when twisted some more, at least what's what I do before applying solder to the wire ends). Anyway in IDC connectors (say AVX Series 9176http://datasheets.avx.com/StandardIDC_00-9176.pdf) the slot for wire strands is open from one side (top) and strands going loose through that opening doesn't seem to be an issue. More other since the opening is omega shaped, the open part of it is somewhat narrower, thus to a degree should prevent strands from squeezing out. Another feature that could be done to enhance retention is an waist-like indentation perpendicular to the axis of a wire made in the middle of the contact "barrel".As to wire diameter, connectors are usually rated to a specific AWG range. It can be designed to tight fit the particular range.Quote from: Zero999 on September 15, 2019, 03:44:10 pmThese would be (in theory) used for logic levels and/or 12V DC. Again these is basically just an idea - not something that is to be implemented in the form exactly as shown.Quote from: ebastler on September 15, 2019, 07:59:55 pmAgain, wire diameter somehow it's not an issue in IDC connectors. Say the above mentioned AVX Series 9176 are rated for a range of different AWGs (18-24 in this case). Also a dedicated groove to surround the eyelet can be made in the plastic shell, that would apply an additional pressure enhancing retention.

author: Simon
author_rank: Unknown
timestamp: September 16, 2019, 06:38:37 am
content: You are missing the point. You can't accommodate precisely one wire size. The same gauge in different strands is different diameter. I use Raychem 44 wire a lot and it's always seems smaller than equivalent commercial wire (and is 30% more resistive but is not pure copper). So that won't fit.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 16, 2019, 07:22:20 am
content: A slitted/opened figure-eight shape is probably practical, being an extrusion of the IDC connector spring-and-knife structure. Or put another way, take what you've drawn but open the metal (opposite the open side) into another loop, to grant more spring (compliance range). Vary material thickness to get required clamping force. Possibly it could be used on two or three different wire gauges, rather than exactly one size (stranded or solid only).It'll still need a tool to force the spring apart or punch the wire in.Tim

author: Simon
author_rank: Unknown
timestamp: September 16, 2019, 08:33:37 am
content: The simple fact is that any connector contact/terminal has the wire forced onto it to reduce the resistance of the junction. Simply holding a wire in a sprung part is not enough. I use D38999 connectors, they are not cheap, but the exceed the power handling capability of a mains plug in the same space. But they are not cheap because the design is much more well refined.Horses for courses, but this design is a rather poor horse. If you are interested in connector design there is the wurth book on the very subject:https://simonselectronics.co.uk/product/trilogy-of-connectors/

author: ElectronicSupersonic
author_rank: Regular Contributor
timestamp: September 16, 2019, 08:59:55 am
content: Quote from: T3sl4co1l on September 16, 2019, 07:22:20 amThat's a very good idea! Thanks!Yet another approach would be to make the omega shape more 0 like. Plus add some inward pointed leafs to provide better contact and prevent strands from being pulled out (wire should be oriented accordingly). Like so...

author: Simon
author_rank: Unknown
timestamp: September 16, 2019, 09:01:33 am
content: But this is still all relying on moderate friction?

author: ebastler
author_rank: Super Contributor
timestamp: September 16, 2019, 10:33:04 am
content: Quote from: ElectronicSupersonic on September 16, 2019, 08:59:55 amThe inward-pointed leaf is moving this closer to an IDC connector -- it provides a small clamping area with high local pressure (force per area) for good contact, ideally gas-tight. Now you will need a tool to squeeze the wire in (or worse, multiple wires in one go).But then, why do you need the narrower opening of the Omega shape? If that is needed to stop the wire from slipping out of the eyelet, then you are obviously not holding it tight enough for good contact. So omit the narrow opening, and shape your contact as an steep "groove" with two parallel side walls. That will also accommodate stranded wire bundles of slightly varying thickness, which will fill the groove to varying height, while always being squeezed tightly in the lateral direction.Oh, now you have reinvented the IDC contact geometry.

author: Simon
author_rank: Unknown
timestamp: September 16, 2019, 10:39:29 am
content: Of course contacts need to be manufactured and that will not be cheap. With the cheap connectors you will find a plastic housing is £0.05 but the pins are £0.30 each! It's the metal parts that cost the money.

author: ElectronicSupersonic
author_rank: Regular Contributor
timestamp: September 16, 2019, 06:32:42 pm
content: Quote from: Simon on September 16, 2019, 09:01:33 amTo a degree. It's more "the bite" that would provide retention in this instance.Quote from: Simon on September 16, 2019, 10:39:29 amTrue. The price would depend on quantities (i.e. how mass of a production it would be) and many over factors.Quote from: ebastler on September 16, 2019, 10:33:04 amThe "bottle neck" is there for several reasons. One is to assist assembly — while inserting the conductor in to the contact, it spreads the thing apart (slightly) thus guiding it through.Another function would be to affix it in the housing with dedicated protrusions. Plus it can serve as a spring to provide more pressure (provided the right shape of the contact and the housing).Quote from: ebastler on September 16, 2019, 10:33:04 amTo an extent. IDC (as I understand it) solves two issues at once 1) No need to stripe the wire — thus no special tools required 2) No crimping needed (just a press-fit action) — thus again no special tools required. In IDC it's accomplished via blade like geometry that both cuts through the insulation and "bites in" in to the core.With the contacts in question only the second one is true since a wire does need to be striped. Plus there is a larger area that comes in contact with the core (albeit a secondary contact).

author: tooki
author_rank: Super Contributor
timestamp: September 17, 2019, 08:38:29 pm
content: Quote from: ElectronicSupersonic on September 16, 2019, 05:49:02 amNo, only the plastic housing is wider. The contact blades remain parallel.I don't think you really understand the forces at work, namely, that you need REALLY significant forces on a wire to make a reliable connector without solder, which is why crimping is hard to do without the right tool. A proper crimp creates a cold weld; it's not just wires casually hanging out with the contact. That you are even thinking about strands "squeezing out" indicates that you don't understand how wire attachment works. If the wire is loose enough for strands to be able to work loose, then you are orders of magnitude away from the grip forces needed for a reliable connection.Quote from: ElectronicSupersonic on September 16, 2019, 06:32:42 pmYyyeah, no.Quote from: ElectronicSupersonic on September 16, 2019, 06:32:42 pmHuh? How does narrowing it "guide" anything? That makes no sense. There's a reason why the openings to so many things are funnel-shaped.Quote from: ElectronicSupersonic on September 16, 2019, 06:32:42 pmThe force of a bit of springy metal is simply not enough to hold tightly.Quote from: ElectronicSupersonic on September 16, 2019, 06:32:42 pmWhile IDC tooling is simple, it still needs special tools to do reliably. That's why there are IDC crimpers and presses for typical IDC ribbon connectors, and punchdown tools for the punchdown terminals which are omnipresent in telecom, which are also IDC just under a different name.Quote from: ElectronicSupersonic on September 16, 2019, 06:32:42 pmExcept it's probably not as large a contact area as you think. With the insignificant pressures involved, there will be substantial air gaps (meaning not only air in there, but also formation of oxides over time). A proper crimp connection has a much larger contact area, since it squeezes out the air and actually cold welds the metals together!Also, think about this: while the mating surfaces of connector contacts have continued to evolve continuously since, well, forever, the kinds of wire attachment to connector contacts have barely changed at all: we still use soldered, screw terminal, crimped, or IDC, for the most part. The fundamental geometry of each type of wire attachment side haven't changed much, either. (Nor do they vary much in principle between manufacturers, other than minor size changes to force you to buy expensive proprietary tooling.) So why haven't they changed? Could it be because we fairly quickly figured out what does and doesn't work?I don't want to squash your enthusiasm, but this omega idea just doesn't makeanysense to me. On the one hand, it's trying to solve a nonexistent problem. And on the other hand, the design seems to almost deliberately avoid firm pressure on the wire, insofar as it actually widens exactly where the wire needs to be squeezed the hardest. Again, I think there's some kind of fundamental misunderstanding about what the forcesarethat you need to design for.

author: ElectronicSupersonic
author_rank: Regular Contributor
timestamp: September 18, 2019, 03:26:51 am
content: Quote from: tooki on September 17, 2019, 08:38:29 pmIt's quite possible that this design idea is a complete and utter BS since I'm not an engineer (I have a degree in design — not engineering). My intention was merely to share the idea. Whatever comes out of it (if anything) is OK with me.

author: ebastler
author_rank: Super Contributor
timestamp: September 18, 2019, 06:03:02 am
content: Quote from: ElectronicSupersonic on September 18, 2019, 03:26:51 amI'm afraid that would be the wire, coming out of the contact clamp.