What's the best way to split cable inside a project box? - Page 1
Forum section: electronics / projects

author: seb1982
author_rank: Regular Contributor
timestamp: March 23, 2013, 07:40:29 pm
content: Hi!I'm building a project which involves wiring 3 transformers in parallel to a single mains cable (all, obviously, well within the capabilities of a standard wall socket!). I need to split the Live and Neutral wires three ways, but I can't seem to find any dedicated hardware to do this.Other than wire up a standard terminal block with jumper wires to link the main wire to two other "outputs" to run wires from (which doesn't seem particularly safe or elegant), I can't see anything specifically designed for this. Is there a search term that I should be using? I've been looking for hours on the Farnell and RS websites!If any of you know any good, safe methods, I'd be ever so grateful to hear them!Thanks

author: Ghydda
author_rank: Regular Contributor
timestamp: March 23, 2013, 08:19:16 pm
content: No I believe the terminal block is about as good a solution as you'll likely to get.Regarding the safeness of the solution I see no problems what so ever as long as you have not stripped the cable of the isolation past the terminal block and no loose core points in any other direction than into the terminal block.I usually use a ferrule terminal to ensure no cores are going awol.You can also join several wires into a single ferrule terminal by using an oversize ferrule or using those twin-types meant for daisy chaining wires between ferrules.

author: hlavac
author_rank: Frequent Contributor
timestamp: March 23, 2013, 08:26:48 pm
content: Just solder the wires together, put a thick wrap of insulation tape over it, then heat shrink over all that... to make it easy make two wires come out on each side of the joint.

author: ddavidebor
author_rank: Super Contributor
timestamp: March 23, 2013, 11:09:46 pm
content: If you can, why not use a piece of pcb board? Directly soldered or with screw connector

author: mamalala
author_rank: Unknown
timestamp: March 23, 2013, 11:24:37 pm
content: Quote from: hlavac on March 23, 2013, 08:26:48 pmBut that only applies if one does not use any screw-terminals for that. it even does not apply if the solder-such-way-wires end up in any kind of screw terminal block. The problem is that the tin and lead in the solder is much softer than the material that the contacing materials in such a terminal are made of. This means that the solderd wire strands with squeeze and soften over time, leading to bad contatcs, leading to increaes contact resistance, etc. In short: it's a safety hazard.Its's better to use one of these:http://csimg.shopwahl.de/srv/DE/0001603117518/T/340x340/C/FFFFFF/url/klauke-adernendha-1-4-lse.jpg(dunno the name in english, please let me know!) on each stranded wire seperately, and then clamp the whole bundle together into another screw-terminaly or the likes.Of course, if everything is purely soldered connections, then it does not matter. Note that "stranded" is a relative term iused here: you should never, ever, tin any wire that is supposed to end up in a screw-terminal (or the like), no matter if the wire is really a stranded one or a single-core type. As soon as you applied solder/tin to it, no screwing aroundGreetings,Chris

author: Monkeh
author_rank: Super Contributor
timestamp: March 24, 2013, 01:11:54 am
content: Quote from: seb1982 on March 23, 2013, 07:40:29 pmWhat about it seems unsafe? Ponder how your entire house is wired, how industrial machinery is wired, and so on. ps. you can put multiple wires under a single screw.Personally, I tend to daisy chain across.Quote from: mamalala on March 23, 2013, 11:24:37 pmUh, he was saying to join wires with solder. Not to tin them before putting them in a screw terminal.. You can screw down an untinned end of a wire with the other end soldered. And what you suggested are called bootlace ferrules.

author: mamalala
author_rank: Unknown
timestamp: March 24, 2013, 01:40:42 am
content: Quote from: Monkeh on March 24, 2013, 01:11:54 amSure, just was mentioning it...Thanks for letting me know how those things are called in english!Greetings,Chris

author: Monkeh
author_rank: Super Contributor
timestamp: March 24, 2013, 01:48:02 am
content: Quote from: mamalala on March 24, 2013, 01:40:42 amOn the flipside, there's nothing wrong with tinned wires in constant-force contacts (.. not normally called that on this scale, think cage clamp/spring), although the only reason to is to get a stranded wire into a contact without a lever or button for release (it's better than a ferrule because you can get the solder up inside the insulation so you can push it properly).

author: SeanB
author_rank: Super Contributor
timestamp: March 24, 2013, 06:03:24 am
content: Quote from: mamalala on March 23, 2013, 11:24:37 pmBootlace ferrule.Anyway, the easiest is a crimp connector, those white ones so common in equipment to join wires. Strip all the wires, twist together and place inside then crimp. Those are available in a few sizes and ratings, and are mains rated.

author: ddavidebor
author_rank: Super Contributor
timestamp: March 24, 2013, 09:59:47 am
content: And look nice too! You can use different color and sizes.Funky cables!

author: Niklas
author_rank: Frequent Contributor
timestamp: March 24, 2013, 10:50:08 am
content: Electricians use something like this to connect loose wire ends in building installations:http://uk.rs-online.com/web/p/screw-terminals/2509517885/http://se.farnell.com/thomas-betts/pt66m/wire-joint-18-12-awg-nylon-red/dp/1905217Strip the insulation about 1-1.5 cm, stick the copper wires inside the joint and twist. Works with both single core wires and multicore wires.Another alternative could be this connector:http://se.farnell.com/multicomp/pc254x-cl/connector-push-in-4way-yellow/dp/2113916Strip the insulation and just push the exposed copper into the connector. To release a cable, twist and pull.

author: M. András
author_rank: Super Contributor
timestamp: March 24, 2013, 11:36:43 am
content: nah the last one is for solidcore wire only, or with ferrules

author: Monkeh
author_rank: Super Contributor
timestamp: March 24, 2013, 04:39:49 pm
content: Quote from: Niklas on March 24, 2013, 10:50:08 amThese are actually crimps.QuotePlease no. Just.. no.

author: Monkeh
author_rank: Super Contributor
timestamp: March 24, 2013, 10:06:18 pm
content: There's no need to fuse each transformer.

author: seb1982
author_rank: Regular Contributor
timestamp: March 25, 2013, 12:39:39 am
content: Thanks for the replies, everyone. Looks like it's going to be a good old terminal block, then! Well, they've never let me down in the past, so I don't suppose they'll start now!Ah, you must have been reading my mind, Monkeh! I've been pondering the fusing issue this afternoon!It's going to be a bench power supply, and I was going to fuse the primary side of each transformer with a suitably-rated time lag fuse, and shove a self-resetting poly on each secondary side as belt and braces.Do you reckon that's overkill for the job at hand? One transformer is 2x30v 250VA, another transformer is 2x15v 70VA and the third is 1x15v 15VA. I'd be interested to hear anyone's thoughts on fusing.

author: Monkeh
author_rank: Super Contributor
timestamp: March 25, 2013, 12:43:19 am
content: You can fuse the whole lot with a 3A time delay fuse. Additional fusing shouldn't really be needed. Protecting the secondaries with a PTC isn't a bad idea, though.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: March 25, 2013, 10:28:02 am
content: Quote from: Niklas on March 24, 2013, 10:50:08 amI don't know about elsewhere but not any UK electrician who know what they're doing.Terminal block and bootlace ferrules.

author: skipjackrc4
author_rank: Regular Contributor
timestamp: March 25, 2013, 10:59:18 pm
content: Ugghh. I hate wire nuts. We see them everywhere, though.