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Offline msknight

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Buying wire
« on: June 10, 2021, 02:51:39 pm »
This is going to sound a bit bonkers, but... hey, this is the beginners section :-)

Previously, I have used wire I've stripped from various things for projects and stuff. No problem. I've got kynar wire for tracks, etc. but the majority of my hobby work has either been old car loudspeaker wire that I've got hanging around, or else I've stripped old cables and had no idea about what it's rated at. I find myself in the position where I'm building a game controller (yes, a joystick!) and I want to connect the LED's together, but I want to use something that I know is properly rated, not unnecessarily thick, and doesn't look like I've done a thoughtless scrap job on it.

The question is.... how do I go about buying wire?

I've done searches by voltage, trying to buy by amperage, and I'm getting flooded with search results which are not what I'm looking for. So... here I am.

I'm in the UK, so I'm presuming I'm buying by mm thickness rather than gauge? And is that by the included jacket or do I add a few mm to account for that as well?

Case in question this time is wiring joystick button LED's together. Only a few, 5V, total load will be around 100mA. I want something not too chunky as there's going to be a lot of wire in close proximity, but thick enough to do the job.

Or as I'm planning to buy a small reel for future use, perhaps something a little more highly rated?

Hoping for some education on buying wire before I lose more hair by trawling through e-bay.
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Offline msknight

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Re: Buying wire
« Reply #1 on: June 10, 2021, 03:14:24 pm »
OK - to add a little to this...

I'm thinking of buying 10m of multi-colour 28 AWG ribbon cable and separating it into single strands which should... I believe... be 4 amps per strand ... but they say that it drops to about 1 amp, but I'm guessing that it's when its used as a ribbon cable and the problem is heat dissipation of the cables in close proximity.

Am I in the right ballpark? Am I understanding this right?
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Offline mindcrime

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Re: Buying wire
« Reply #2 on: June 10, 2021, 03:23:19 pm »
I'm in the UK, so I'm presuming I'm buying by mm thickness rather than gauge?

Not necessarily. AIUI, the UK have their own "wire gauge" standard, which is similar to, but not exactly like, AWG (American Wire Gauge). So you might encounter that as well. And depending on what sites you're searching, it's entirely possible that you'll still encounter wire denoted using AWG. Of course you can probably choose to explicitly search only by mm diameter if you want, but I'd guess casual searches will turn up a mixture of different denotations. Not a big deal though, as finding conversion charts is pretty easy.


Quote
Only a few, 5V, total load will be around 100mA. I want something not too chunky as there's going to be a lot of wire in close proximity, but thick enough to do the job.

If you know the current load you'll be dealing with, you can explicitly work out the required wire size. There are charts you can search up that show the current carrying capacity of various wire sizes. Or conversely, you can look up the resistance per unit of length for a given wire size and work it all out from there using Ohm's Law (assuming you know the expected voltage). The goal ultimately is to find the minimum required wire diameter / gauge.

Once you know that, you do have a few other choices to deal with, like insulation. But at 5V, any insulation is almost certainly going to be way more than sufficient. This starts to become more of an issue when you start messing with higher voltages and need to be very explicit that your wire is sufficiently insulated to deal with the voltage it's tasked to carry. Other than voltage rating, another factor to consider with insulation is its temperature resistance, and how supple it is. I doubt you're going to be pushing any temperature boundaries in this controller, so that's probably not a big issue. Just note the suggested max temp for your wire and double check that you don't be exposing the wire to anything above that. 

Silicone insulation is usually a very good combination of suppleness, voltage rating, and temperature capacity (which is why it's so often used for high quality test leads) but it's usually more expensive than some of the cheaper plastic insulating materials.

Also: note that in the above paragraph(s), I glossed over any reference to wire material. That's because, while various wire materials are available, I don't think there's any reason at all for you to consider anything other than copper wire for your application. But if for some crazy reason you did want to consider, say, aluminum wire (don't though), the charts I mentioned can be found where the wire material is one of the factors. But just use copper, really.

Stranded vs. solid core wire is another choice you'll need to make. Solid core usually has a little less resistance at a given size, and can sometimes be easier to connect to things without crimping or soldering on an explicit connector component of some sort. But stranded wire tends to be more supple and easier to work with. For an application like you're describing you could probably get by with either.

« Last Edit: June 10, 2021, 03:27:32 pm by mindcrime »
 
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Offline TimFox

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Re: Buying wire
« Reply #3 on: June 10, 2021, 03:32:14 pm »


The question is.... how do I go about buying wire?

I'm in the UK, so I'm presuming I'm buying by mm thickness rather than gauge? And is that by the included jacket or do I add a few mm to account for that as well?


Once, as an American doing an installation in the UK, the local guy asked if “4 mil” wire were adequate, and I thought he meant 4 mm diameter.  In fact, he meant 4 mm2, which is quite different.  I believe that wire in the UK is specified by the wire cross-section area (not including insulation).  The old British SWG was similar but not equal to the contemporary US AWG.
 
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Offline Zero999

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Re: Buying wire
« Reply #4 on: June 10, 2021, 04:23:57 pm »


The question is.... how do I go about buying wire?

I'm in the UK, so I'm presuming I'm buying by mm thickness rather than gauge? And is that by the included jacket or do I add a few mm to account for that as well?


Once, as an American doing an installation in the UK, the local guy asked if “4 mil” wire were adequate, and I thought he meant 4 mm diameter.  In fact, he meant 4 mm2, which is quite different.  I believe that wire in the UK is specified by the wire cross-section area (not including insulation).  The old British SWG was similar but not equal to the contemporary US AWG.
We use IEC 60228, which defines standard sizes by cross-sectional area. Unfortunately it only starts at 0.5mm2, so for smaller sizes AWG and occasionally SWG, or a rounded cross-sectional area close to either, is used insread. It would be nice if the IEC would go smaller, but I suppose there's less motivation to, as they're more concerned with big, hazardous electrical installations and equipment, rather than small stuff.

https://en.wikipedia.org/wiki/IEC_60228
 

Offline tooki

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Re: Buying wire
« Reply #5 on: June 10, 2021, 05:24:32 pm »


The question is.... how do I go about buying wire?

I'm in the UK, so I'm presuming I'm buying by mm thickness rather than gauge? And is that by the included jacket or do I add a few mm to account for that as well?


Once, as an American doing an installation in the UK, the local guy asked if “4 mil” wire were adequate, and I thought he meant 4 mm diameter.  In fact, he meant 4 mm2, which is quite different.  I believe that wire in the UK is specified by the wire cross-section area (not including insulation).  The old British SWG was similar but not equal to the contemporary US AWG.
We use IEC 60228, which defines standard sizes by cross-sectional area. Unfortunately it only starts at 0.5mm2, so for smaller sizes AWG and occasionally SWG, or a rounded cross-sectional area close to either, is used insread. It would be nice if the IEC would go smaller, but I suppose there's less motivation to, as they're more concerned with big, hazardous electrical installations and equipment, rather than small stuff.

https://en.wikipedia.org/wiki/IEC_60228
That doesn’t mean that thinner wires aren’t available in metric cross sectional area. I use 0.25mm2 stranded wire all the time.
 

Offline tooki

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Re: Buying wire
« Reply #6 on: June 10, 2021, 05:29:35 pm »
This is going to sound a bit bonkers, but... hey, this is the beginners section :-)

Previously, I have used wire I've stripped from various things for projects and stuff. No problem. I've got kynar wire for tracks, etc. but the majority of my hobby work has either been old car loudspeaker wire that I've got hanging around, or else I've stripped old cables and had no idea about what it's rated at. I find myself in the position where I'm building a game controller (yes, a joystick!) and I want to connect the LED's together, but I want to use something that I know is properly rated, not unnecessarily thick, and doesn't look like I've done a thoughtless scrap job on it.

The question is.... how do I go about buying wire?

I've done searches by voltage, trying to buy by amperage, and I'm getting flooded with search results which are not what I'm looking for. So... here I am.

I'm in the UK, so I'm presuming I'm buying by mm thickness rather than gauge? And is that by the included jacket or do I add a few mm to account for that as well?

Case in question this time is wiring joystick button LED's together. Only a few, 5V, total load will be around 100mA. I want something not too chunky as there's going to be a lot of wire in close proximity, but thick enough to do the job.

Or as I'm planning to buy a small reel for future use, perhaps something a little more highly rated?

Hoping for some education on buying wire before I lose more hair by trawling through e-bay.
I think many of your questions (like how it’s measured) would be answered by studying the datasheets for various kinds of wire and cable.

100mA is nothing. You can use practically anything you want. The longer the run, the thicker it should be, but at this current, avoiding hair-thin magnet wire is sufficient.
 
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Offline james_s

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Re: Buying wire
« Reply #7 on: June 10, 2021, 05:38:59 pm »
I think most of the questions have been answered, but I will add one thing, don't buy ribbon cable and separate the strands, it's a pain to do, especially with cheaper ribbon cable that tends to have really stiff insulation and crappy thin conductors. Also the insulation is usually made out of stuff that melts really easily and shrivels up if you try to solder the wire. Buy spools of individual hookup wire, or go look at recyclers and thrift stores for old computer cables, like the kind with DB25 connectors on them. I have a few of those I cut up years ago and have been using the individual wires ever since, they have a bundle of wires in 25 different colors and at least in the cables I used it's pretty good stuff.
 
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Offline msknight

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Re: Buying wire
« Reply #8 on: June 10, 2021, 09:13:21 pm »
Thanks All,

I've gone for some 10m bundles of hookup wire at 20awg in a variety of colours. Copper tinned.

I think the key thing I needed was, "hookup wire," and that got me the hits I needed on ebay. It also helped that some of the listings showed the various thicknesses of AWG, so that I could, "see," the numbers. Good job they did, as I'd have thought the higher the number, the thicker the cable. I was wrong there!

The table says that this cable has a maximum rating of 2.6A, so I could have easily gone thinner, but I don't have much luck working with wires that are too thin. I break them too easily.

Thanks again for the help.
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Offline mindcrime

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Re: Buying wire
« Reply #9 on: June 10, 2021, 09:27:59 pm »

The table says that this cable has a maximum rating of 2.6A, so I could have easily gone thinner, but I don't have much luck working with wires that are too thin. I break them too easily.


Nothing wrong with that. The goal isn't always to optimize for "thinnest wire possible". Those "other" factors like "eas of use" certainly factor in, especially for a hobbyist.  Also, sometimes it's good to pick something a little bit "middle of the road" so you can use the same wire in many projects, instead of having to buy 372 different roles of wire. Sure, your collection will probably grow over time as you encounter specific needs, but 20 AWG is a fairly good general purpose wire for many things.

 

Offline james_s

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Re: Buying wire
« Reply #10 on: June 11, 2021, 04:13:42 am »
The table says that this cable has a maximum rating of 2.6A, so I could have easily gone thinner, but I don't have much luck working with wires that are too thin. I break them too easily.

That means the wire won't melt the insulation carrying 2.6A, you'd never want to actually load it up that high. The thinner the wire the higher the resistance, and resistance causes a voltage drop which is wasted power and may cause something to malfunction. A few feet of wire carrying the maximum rated current could drop a volt or more.
 

Offline tooki

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Re: Buying wire
« Reply #11 on: June 11, 2021, 05:28:51 am »
Thanks All,

I've gone for some 10m bundles of hookup wire at 20awg in a variety of colours. Copper tinned.

I think the key thing I needed was, "hookup wire," and that got me the hits I needed on ebay. It also helped that some of the listings showed the various thicknesses of AWG, so that I could, "see," the numbers. Good job they did, as I'd have thought the higher the number, the thicker the cable. I was wrong there!

The table says that this cable has a maximum rating of 2.6A, so I could have easily gone thinner, but I don't have much luck working with wires that are too thin. I break them too easily.

Thanks again for the help.
What table are you using? 20AWG can carry way more than 2.6A.

For LEDs, 20AWG is too thick — the LED legs may not do well with the weight of that wire, such that vibration could break them off if you don’t support the wire completely.

I like 24AWG (0.22mm2)–0.25mm2 for things like that, provided heat shrunk tube is used and the wire is not hanging free.

The table says that this cable has a maximum rating of 2.6A, so I could have easily gone thinner, but I don't have much luck working with wires that are too thin. I break them too easily.

That means the wire won't melt the insulation carrying 2.6A, you'd never want to actually load it up that high. The thinner the wire the higher the resistance, and resistance causes a voltage drop which is wasted power and may cause something to malfunction. A few feet of wire carrying the maximum rated current could drop a volt or more.
20AWG copper wire has a resistance of 33.3mOhm/m. To drop a volt across 1m, you’d have to be running 30A through it (3-6x a typical current rating for that gauge), at which point it would be dissipating 30W.
 

Offline msknight

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Re: Buying wire
« Reply #12 on: June 11, 2021, 05:52:32 am »
I'm using the table provided by the seller.

The LED's are in gaming push buttons, so the presentation to the outside world is in 7mm tags.

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Offline james_s

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Re: Buying wire
« Reply #13 on: June 11, 2021, 06:30:05 am »
20awg should work well for those, typically you crimp terminals onto the wire and they slide on to the terminals on the buttons. Much smaller than that and it gets hard to get reliable crimps with typical terminals.

Regarding that ampacity chart, those numbers look more like what would be used for runs of wires through walls where the total run length for a complete circuit could be 100 feet or more. There are different guidelines for chassis wiring which it sounds like this would count as. Either way mechanical robustness is going to be a greater consideration than current in this application.
« Last Edit: June 11, 2021, 06:32:00 am by james_s »
 

Offline msknight

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Re: Buying wire
« Reply #14 on: June 11, 2021, 06:46:59 am »
The LED's will be cabled in parallel so it will be soldered rather than crimped, I've measured a draw of about 7mA each and the controller board can supply 400mA on the 5v supply pin, so I'll easily be able to light 7 LEDs this way and have juice left over.

The "button" also has to go back to the same ground as the LEDs, so there'll be a short wire running from the top spade connector to the ground connector on each switch also, another reason to solder rather than crimp. Three cables to each LED ground spade.

I know this will mean de-soldering for maintenance, but I've weighed this up in my head and I'm using arcade quality parts shoehorned into a small stick case (I know, snake oil is a thing, but only time will tell) so maintenance work should be relatively low. Like you say, mechanical robustness is a consideration, given how I play games :-)
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Offline Zero999

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Re: Buying wire
« Reply #15 on: June 11, 2021, 07:55:11 am »


The question is.... how do I go about buying wire?

I'm in the UK, so I'm presuming I'm buying by mm thickness rather than gauge? And is that by the included jacket or do I add a few mm to account for that as well?


Once, as an American doing an installation in the UK, the local guy asked if “4 mil” wire were adequate, and I thought he meant 4 mm diameter.  In fact, he meant 4 mm2, which is quite different.  I believe that wire in the UK is specified by the wire cross-section area (not including insulation).  The old British SWG was similar but not equal to the contemporary US AWG.
We use IEC 60228, which defines standard sizes by cross-sectional area. Unfortunately it only starts at 0.5mm2, so for smaller sizes AWG and occasionally SWG, or a rounded cross-sectional area close to either, is used insread. It would be nice if the IEC would go smaller, but I suppose there's less motivation to, as they're more concerned with big, hazardous electrical installations and equipment, rather than small stuff.

https://en.wikipedia.org/wiki/IEC_60228
That doesn’t mean that thinner wires aren’t available in metric cross sectional area. I use 0.25mm2 stranded wire all the time.
Are you sure it isn't 24 SWG? Most of the metric sizes for small wire, are rounded SWG, or AWG.
 

Offline tooki

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Re: Buying wire
« Reply #16 on: June 12, 2021, 12:30:03 pm »
If they are SWG or AWG sizes in disguise, the European manufacturers aren’t saying. What is clear is that they’re specifying them in metric. (And some American wire manufacturers like Alpha also make wires in those sizes and refer to them as “metric”.)

https://www.kabeltronik.de/en/electronics-industry/hook-up-wires-stranded/art/hook-up-wire-stranded-pvc-liyv/

Helukabel (the brand I’m currently using the most) seems to be having website problems right now so I can’t get to the catalog, but attached is the datasheet for the stranded hookup wire.
 

Offline Zero999

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Re: Buying wire
« Reply #17 on: June 12, 2021, 01:54:53 pm »
If they are SWG or AWG sizes in disguise, the European manufacturers aren’t saying. What is clear is that they’re specifying them in metric. (And some American wire manufacturers like Alpha also make wires in those sizes and refer to them as “metric”.)
That's what I believe is happening: in Europe the wire will more likely to be specified in metric, even though it's really AWG. There's little point in using different tooling to make say 22AWG and 0.33mm2, when they could just make one size, which is within the tolerance band of them both.
 

Offline tkamiya

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Re: Buying wire
« Reply #18 on: June 12, 2021, 11:34:43 pm »
For most of my project, current and voltage are low enough that just about any wire would do.  An exception to this will be around power supplies.  I usually end up deciding on mechanical property rather than electrical.  My usual is AWG 24 gauge stranded.  For little more current, next step up for me is 20 gauge and up.  I was unfamiliar with AWG so I bought small length from Amazon sellers until I found one I liked.  I really don't know what this insulation material is, but mine were advertised as silicone wire.  Pretty well heat tolerant and very flexible.  I like them.

Most of ribbon cables are not heat tolerant as they are never meant to be soldered.  I wouldn't suggest it.
 

Offline tooki

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Re: Buying wire
« Reply #19 on: June 13, 2021, 08:49:06 am »
If they are SWG or AWG sizes in disguise, the European manufacturers aren’t saying. What is clear is that they’re specifying them in metric. (And some American wire manufacturers like Alpha also make wires in those sizes and refer to them as “metric”.)
That's what I believe is happening: in Europe the wire will more likely to be specified in metric, even though it's really AWG. There's little point in using different tooling to make say 22AWG and 0.33mm2, when they could just make one size, which is within the tolerance band of them both.
Well, the small metric sizes seem to more closely align with SWG than AWG. But it’s also possible that over the years, the European manufacturers have switched over to actual metric. It’s been a long time, and production equipment doesn’t last forever. Not to mention the metric pride on the continent...

Regardless, I’m not sure what your actual point was: my statement was that you can buy small wires in metric, and you can. 0.25mm2 and 0.1mm2 are, IMHO, likely to be just that. 0.14mm2 and 0.08mm2 probably are SWG-derived.
 

Offline wizard69

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Re: Buying wire
« Reply #20 on: June 13, 2021, 01:42:03 pm »
Having a selection of hook up wire in the lab is a good thing, however you mentioned joystick and that has me wondering.    The questions is this: is the joystick mounted to a chassis or is it mobile, that is on a long tether?    As has been noted the currents are really low here so in the case of a chassis mount joystick you will be fine with hook up wire.

If on the other hand you will have the joystick tethered and exposed to a lot of movement, say a game application, you will want a more durable cable designed to be flexed a lot.   Hook up wire (bottom basement wire anyways) will not hold up to constant flexing and movement.   In the case of a cable assembly that is expected to be moved around a lot, you will want wire and insulation designed to hold up to that sort of activity.

On a side note do understand what has already been mentioned here, there are multiple issues with choosing the best wire to implement a project in.    There is a max current draw associated with every wire diameter and insulation combination and frankly you almost never want to hit max values.   that is one aspect of wire selection, the other is voltage drop which may make a difference.   I know others have already brought this up but standard copper wire is effectively a low ohm resistor.   Sometimes controlling this resistance is the most important part of the selection process if you want to avoid voltage drop across the wire.    In other words sometimes you need to implement a larger wire simply to lower voltage drop.

Thanks All,

I've gone for some 10m bundles of hookup wire at 20awg in a variety of colours. Copper tinned.

I think the key thing I needed was, "hookup wire," and that got me the hits I needed on ebay. It also helped that some of the listings showed the various thicknesses of AWG, so that I could, "see," the numbers. Good job they did, as I'd have thought the higher the number, the thicker the cable. I was wrong there!
Life these days is all about finding the right search terms.    However sometimes you are better off staying away form E-Bay and going to a distributor like DIgiKey or maybe Farnel in the UK.   Even if you don't buy from such dealers their search mechanisms will show you a larger variety of wire and you can easily narrow down stuff using parametric search.
Quote
The table says that this cable has a maximum rating of 2.6A, so I could have easily gone thinner, but I don't have much luck working with wires that are too thin. I break them too easily.

Thanks again for the help.

Yes you hit upon another issue; sometimes the ability to work with the wire is the most important element in a purchase.   You can buy hook up wire with all sorts of insulation some of which you wouldn't want to strip regularly.   This also highlights that tools make a difference, buy yourself a nice pair of wire strippers which can make your life much easier.   Proper wire strippers (there are many forms) can save you from waste and frustration.
 

Offline msknight

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Re: Buying wire
« Reply #21 on: June 13, 2021, 02:26:19 pm »
Good points.

The joystick is a small case in which I've mounted decent arcade buttons. It just about handles the depth. Once I've worked out the cabling, there will probably be four slim buttons, two in each side, and some small square buttons on the top for select, etc. I was going to use the DaemonBite Mini, but it's out of stock and the maker hasn't responded to my query, so I'm going with the open source version instead - https://github.com/MickGyver/DaemonBite-Arcade-Encoder - it lacks some of the advanced features of his closed source version, but hey ho. The ProMicro was with me one day after ordering, and programming it turned out to be very easy.

The fly in the ointment is the GTK spinner which refuses to work with USB hubs... at least, the four small USB hubs I've tried so far, have all failed. I've got two more coming and if it fails with that, then I'll need to run two USB leads out, one for the spinner and one for the ProMicro. If it works, then the positioning of the USB hub in the case will affect where things are placed, and cabled. I might also have to shorten some of the USB cables internally.... but I'm not cutting anything until I'm sure that things will work. However, the main strain external to the case will be one (or possible 2 if I'm unlucky) USB 3m extension cables. So if all goes to plan, I'll be all good. My problem is that things very rarely go to plan.

I am waiting for some crocodile clips to arrive to knock up some test cables, so I can then work out any voltage and amperage implications of what I'm going to do, before I wire things up. The ProMicro is rated to 400mA on its 5v pin, so that should be more than enough to run some LEDs. From what I've done so far, the LED's have a voltage drop of about 2.5v each, so it's all going to have to be done in parallel, but there's enough mA to handle it I think.

Farnell or others have a postage cost for minimum orders. The hook up wire I've ordered from China is less than £30 in total, including delivery... so it's not critical and there'll be plenty for future projects like this. I can't go too far wrong with this project, and then learn a bit more from it in the process. I do find myself looking at the China/West issue and the current threats and conversations and wonder what will happen in terms of trade, tariffs and things like that. So to a point I'm grabbing what I can now.
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Offline Zero999

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Re: Buying wire
« Reply #22 on: June 14, 2021, 12:38:45 pm »
If they are SWG or AWG sizes in disguise, the European manufacturers aren’t saying. What is clear is that they’re specifying them in metric. (And some American wire manufacturers like Alpha also make wires in those sizes and refer to them as “metric”.)
That's what I believe is happening: in Europe the wire will more likely to be specified in metric, even though it's really AWG. There's little point in using different tooling to make say 22AWG and 0.33mm2, when they could just make one size, which is within the tolerance band of them both.
Well, the small metric sizes seem to more closely align with SWG than AWG. But it’s also possible that over the years, the European manufacturers have switched over to actual metric. It’s been a long time, and production equipment doesn’t last forever. Not to mention the metric pride on the continent...

Regardless, I’m not sure what your actual point was: my statement was that you can buy small wires in metric, and you can. 0.25mm2 and 0.1mm2 are, IMHO, likely to be just that. 0.14mm2 and 0.08mm2 probably are SWG-derived.
My point is that, in the absense of a standard set of wire sizes below 0.5mm2, cable manufactures seem to be sticking to AWG, or SWG, even if they specify the crossectional area in metric. I think it would make life easier if smaller sizes could be standardised.
 

Offline TimFox

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Re: Buying wire
« Reply #23 on: June 14, 2021, 01:39:02 pm »
Meanwhile, in the US, we do have a standard set of sizes for copper wire:  AWG.
Exceptions:  there are other gauges for steel wire, etc.  Also, for very large diameter wire we have a quaint unit:  MCM = thousand circular mils.  250 MCM is 0.50 inch (= 500 mils) diameter.  The OP need not worry about such large wires, only used for hundreds of amperes.  Looking this up, I found a rule of thumb that 2 MCM is approximately 1 mm2.
 

Offline Zero999

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Re: Buying wire
« Reply #24 on: June 14, 2021, 02:26:02 pm »
Meanwhile, in the US, we do have a standard set of sizes for copper wire:  AWG.
Exceptions:  there are other gauges for steel wire, etc.  Also, for very large diameter wire we have a quaint unit:  MCM = thousand circular mils.  250 MCM is 0.50 inch (= 500 mils) diameter.  The OP need not worry about such large wires, only used for hundreds of amperes.  Looking this up, I found a rule of thumb that 2 MCM is approximately 1 mm2.
As I said in a previous post we have also have a standard set of wire sizes, which replace the old fashioned SWG. The main benifit of the new system is it makes calculating the resistance easier, because all you need to know is the resistivity of copper and you can plug the numbers into the formula. If it's a solid core cable, the conductor diameter is also easy to calculate. The main downside is sizes below 0.5mm2 haven't been standardised, but it doesn't matter so much.

As the original poster is in the UK, it probably makes more sense for them to use mm2. My go to size is 0.5mm2, because it's the largest size which will fit in the holes on standard strip board. It's also handy to have smaller sizes 0.33mm2 and 0.2mm2

Silicone or PTFE insulation is nice, since it doesn't shrink back, or melt like PVC does, but it's much more expensive.
« Last Edit: June 14, 2021, 02:56:53 pm by Zero999 »
 


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