Collection of questions - wire terminations, best practice - Page 1
Forum section: electronics / beginners

author: de_light
author_rank: Regular Contributor
timestamp: July 24, 2024, 08:54:25 am
content: Been tinkering with electronics at a hobbylist level for about eighteen months now. Revisiting some of my initial products and trying to bring some of my wiring up to standard. As I'm getting more involved, I want to do things the 'right way' - meeting some basic standards so at least I have a yardstick to compare my work to. Could anyone help with these questions?1. What is the best way to terminate wire from an IEC lug connected to mains? I have a screw-in IEC socket into a project box. I read somewhere on this forum that it is acceptable to 'hook-in' the wire to provide mechanical support and then solder on. I assume something like an insulated spade connector wouldn't be appropriate because it may come loose with mechanical stress or say movement of the device?2. Said IEC connector may be attached with metal screws to the plastic Jiffy box housing. These screws could become conductive if a fault condition arises, so I assume it is best practice to earth the screws?3. Does anyone have a clear explanation for the differences between identifying class 2, 5 and 6 cable? If I use extension cord cable, I assume that is 'flex' cable and would be class 5?4. I have also read it is best practice to use crimped ferrules on stranded wire when placed under a screw terminal. In this case, is it:a. ever used with mains power outlets (e.g. flush-fit ones on said project box) or is it acceptable to twist, trim and fold in half?b. Would you ever use a ferrule on stranded wire before say using it for an Anderson powerpole 30A connector? I have always just placed twisted wire in an Anderson connector and crimped it with the appropriate tool, but wondered whether using a ferrule first is a better way to prevent loose strands or an imperfect crimp?Thanks in advance.

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 24, 2024, 09:59:18 am
content: You´re entering a world of pain if you ask for mains security related topics in a global forum - because:- Codes are different all over the world- On most places you´re not allowed to tinker with these things unless you did a qualification that mostly teaches your questionsAs long as you don't want to get a qualified electrician the only advice I can give is: Be curious, check out things that professionals have done and try to understand why. Then your questions will be more specific and may be better to be discussed.

author: tooki
author_rank: Super Contributor
timestamp: July 28, 2024, 12:33:40 pm
content: Quote from: Phil1977 on July 24, 2024, 09:59:18 amFYI, you mean “safety”, not “security”.In terms of primary meaning, security = resistance to attacks, safety = resistance to accidents.(I know, in German they’re both “Sicherheit”, but in English they aren’t interchangeable. And before anyone thinks they’re being clever by chiming in to say there are edge cases, and additional uses like “job security”: I know that, so no need to “correct” me. I’m just talking about the main two meanings, which are constantly mixed up by German speakers.)Quote from: Phil1977 on July 24, 2024, 09:59:18 amBut rarely thaaaaaaat different, with regards to what’s allowed inside a device. Generally speaking, if you follow what is allowed in both USA and Europe, you’re good to go anywher, for a hobbyist device. It’d be a different matter if it were a product for sale.Quote from: Phil1977 on July 24, 2024, 09:59:18 amIs that really true, though? OP isn’t asking about modifying the mains wiring of their house, but about mains-powered devices. I’m not aware of any rule outright barring hobbyists from building and using mains-powered devices for their own use in Germany and Switzerland, for example, even though both of them disallow non-electricians from working on the mains wiring of their house. In many places, like North America, it’s perfectly legal to do your own home electrical repairs too.And don’t forget that much of the world is third-world countries where there are few applicable rules at all, and/or the rules aren’t enforced.

author: tooki
author_rank: Super Contributor
timestamp: July 28, 2024, 02:05:03 pm
content: Quote from: de_light on July 24, 2024, 08:54:25 am”IEC lug” is a bit of an unclear description, since the mating side of the connector is what conforms to an IEC standard, not the termination on the inside.IEC connectors most commonly have one of several terminations (and I’m sure others exist too):- solder lugs- spade terminals (Faston)- screw terminals- PCB pins- insulation-displacement terminalsI’m assuming your question is whether you can solder to Faston spades: yes, you can. You solder the same as to a solder lug: Strip the wire, pretin it, form a hook using round-nose pliers, and then solder it in.But I’m not sure why you assume Faston connectors are no good; they’re widely used for this, which is why IEC connectors with those spades are common. The only caveat I’d give, and it’s an important one, is that the terminals must be properly crimped. This means the correct tool of decent quality, used with a good quality terminal paired with the correct size of wire. So no tool or terminals from AliExpress or Amazon.Note that crimped connections are generally more reliable with regards to mechanical stress and vibration than soldered connections.Quote from: de_light on July 24, 2024, 08:54:25 amThat’s one solution. You could, for example, instead put heat-shrink tubing over the screws and nuts inside. Or use nylon screws. Or use a snap-in jack instead.Quote from: de_light on July 24, 2024, 08:54:25 amThe word “identifying” here is throwing me off a bit.If you’re asking what the classes fundamentally mean, it’s simple:Class 1 is solid wireClass 2 is “rigid stranded” wire (containing two subgroups, “stranded” and “multi-stranded”, see the table linked below)Both of those are typically used in fixed installations only.Class 5 is “fine stranded” wire, the most common type of stranded wire, commonly used for both fixed and portable/moving applications. This is what typical flex cable is.Class 6 is “extra-fine stranded” wire, which uses extra-fine stranding to give higher flexibility. Used only where this flexibility is needed and justifies the higher cost. Unlike classes 2 and 5, class 6 has a much wider range of possible conductor stranding. (For example, a 0.5mm2 class 2 wire is 7 strands, class 5 is 16-19 strands, but class 6 is anywhere from 28 to 256 strands.) For things like test leads, you really need to look at the stranding more than the class.If you’re asking how to identify a wire’s stranding class (as in, forensic investigation), you cut it open, count the number of individual conductor strands and measure their size, then compare to a decent table (likethis onefrom Kabeltronik) to see what it matches.If you’re asking how to identify a cable when choosing one to purchase, any decent vendor will state it on their datasheet. Either explicitly as a conductor class, or implicitly by listing the conductor stranding.The big exceptions can be cables that comply with the harmonized cable codes, since a given cable code defines what kind of stranding it uses. See e.g.https://www.tme.com/us/en-us/news/library-articles/page/41461/designation-of-cables-according-to-harmonised-standards/Common power cord flex is H05VV-F, which is:H = harmonized05 = 300/500V (i.e. 300V single-phase, 500V three-phase)V = PVC conductor insulationV = PVC jacketF = fine wire for cables (class 5)Quote from: de_light on July 24, 2024, 08:54:25 amAbsolutely. In many places this is required by code. But even where it isn’t, it’s highly recommended. Not only does it eliminate dangers (like stray strands shorting to adjacent terminals), it also makes using the screw terminals much easier.Quote from: de_light on July 24, 2024, 08:54:25 amAbsolutely.Quote from: de_light on July 24, 2024, 08:54:25 amIn many places, no, that would not be allowed. But as I said, regardless of whether it’s allowed or not, I strongly urge you to use ferrules.FYI: Under no circumstances should you tin the stranded wire with solder before inserting it into a screw terminal. Solder cold-flows under pressure, so even if tightened firmly initially, it will loosen with time.Quote from: de_light on July 24, 2024, 08:54:25 amNo, you would not normally do this. There’s no real advantage over just cleanly inserting the wire into the crimp contact. And adding another 3 layers of dissimilar metals (the ferrule base metal plus the plating on both inside and outside surfaces) certainly introduces more variability into the process.The only exception, sorta, is if you need to “bulk up” an undersize wire to fit into a larger crimp contact. I have done this before, but only for signal lines which carry practically no current. (I did it recently for insulated crimp forks, to get 0.25mm2 (24AWG) wire into forks intended for 0.5mm2 wire, because I do not have a crimp tool for 0.25mm insulated terminals. But it is just for the 24V input signal to solid state relays, so only around 20mA.)I would also only ever consider doing this on a closed-barrel crimp. DO NOT use a ferrule on an open-barrel crimp, since the two conductor crimp “wings” are supposed to grab onto half of the strands each and grip them. (For the same reason, don’t twist the wire tightly before inserting.)Note also that you aren’t really supposed to twist the wire before crimping. That reduces the reliability, apparently. Moreover, a tighter twist increases the diameter. With ferrules, and especially with extra-fine stranded wire, it’s possible to twist enough that it won’t fit into the correct size ferrule, which might lead one to go up a ferrule size. High-reliability wiring standards (like NASA and military) expressly prohibit twisting the strands, other than to carefully restore the wire’s original strand lay, if it gets disturbed during stripping.If you have trouble with wire being difficult to insert, practice and improve your wire handling techniques: learn to be gentler, and use tools that are gentler. For example, using cable shears to cut wire preserves the stranding lay much better than diagonal cutters. Diagonal cutters crush the wire rather than slice through it as shears do.If you’re getting “imperfect crimps”, and you’re sure your technique is sound (= correct contact size for the wire in use, with the correct tool, using the correct jaw opening for the combination of wire and contact size), then you need a better crimp tool. My experience with crimp tools is that cheap ones (from AliExpress/ebay/amazon) do not produce consistent crimps, due to poor manufacturing tolerances, poor design, and the lack of a contact locator (a positioner that holds the contact in the correct place) and lack of a wire or insulation stop (a thing that ensures the wire is inserted correctly, by providing and end stop that either the strands or insulation run into, depending on the design). In contrast, a proper tool will produce one perfect crimp after another. (Last week, I crimped 100 contacts each of Molex Micro-Fit and Amphenol Ecomate, using the correct official tools, and did not have even one imperfect crimp.)

author: BillyO
author_rank: Super Contributor
timestamp: July 28, 2024, 02:06:08 pm
content: Quote from: tooki on July 28, 2024, 12:33:40 pmWho made you the language police?You are wrong. Security refers to protective measures against dangers and threats of all kinds, not just resistance to attacks. In this respect his usage is fine.From the Merriman-Webster dictionary.Quote

author: tooki
author_rank: Super Contributor
timestamp: July 28, 2024, 04:51:13 pm
content: Quote from: BillyO on July 28, 2024, 02:06:08 pmLMAO at you literally proving the reason why I put in the disclaimer. I amnotwrong: remember that I said only theprimarymeaning and that there are some edge cases and overlap. My definition does distill the essence of the two main meanings, or rather, the keydifferencein their meaning where they don’t overlap.And in this case, it is electrical safety that is the concern, not security.But what do I know? I’m merely a native speaker, former professional technical writer, and son of an English teacher.Well that and the fact that my statement is easy to verify.Here’s a guide specifically for Germans, even, by Germany’s primary safety organization:https://www.tuev-nord.de/explore/en/explains/whats-the-difference-between-safety-and-security/More discussion:https://forum.wordreference.com/threads/whats-the-difference-between-safety-and-security.1203758/https://learningenglish.voanews.com/a/differences-between-security-and-safety-/5791194.htmlhttps://www.italki.com/en/post/question-383289https://testbook.com/key-differences/difference-between-safety-and-securityhttps://english.stackexchange.com/questions/58630/what-is-the-correct-use-of-safety-and-securityhttps://www.theguardian.com/notesandqueries/query/0,,-202834,00.htmlAnd the point is not to police, but to educate. There’s a difference. It’s why I said “FYI”, indicating that it’s just an additional comment. And who made you the anti-education police, eh?

author: SmallCog
author_rank: Frequent Contributor
timestamp: July 29, 2024, 03:33:05 am
content: Probably nothing in them about IEC sockets, but if you're looking for a "what's a good way to do this" type information have a look at the NASA Workmanship StandardsThey go into a lot of detail about different types of wire terminations, soldering, etc and are a handy free resource to refer to.https://archive.org/details/nasa-workmanship-standards/mode/2up