Can anyone help me to understand wire gauge? - Page 1
Forum section: electronics / beginners

author: LektroiD
author_rank: Frequent Contributor
timestamp: July 04, 2018, 12:13:43 pm
content: I've been confused by this for years, and unfortunately there's barely any youtube tutorials that seem to explain it. It's a real mystery...How do I find the correct thickness of wire for my projects? In the old days I would go into my local Tandy store and see the physical thickness of the wire available and buy what looked right for whatever application I was using it in. But now everything is online, and even with photos, it's hard to tell the thickness without having it in your hand. I know there is AWG, SWG, but the last ones I bought seem to relate to nothing, it just says 7/0.2 ...What AWG is this???this for exampleI would like to buy some wire a few gauges thicker than my 7/0.2 as the 7/0.2 wire I have does not look ideal to run 12V at 2A. At the same time, I don't want to buy something too thick that won't fit into my power connectors

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 04, 2018, 12:28:55 pm
content: The linked data sheet...https://www.rapidonline.com/pdf/01-0400e.pdfsuggests you can squeeze 2A through it.https://www.canford.co.uk/Technical/Article/MetricAWGWireSizeEquivalentsfor your 7/0.2 has a row for .22mm2 CSA....7 strands... 0.2mm diameter... CSA=7xPI*(0.2/2)^2 = .22mm2 CSA

author: Zero999
author_rank: Super Contributor
timestamp: July 04, 2018, 12:32:14 pm
content: Here's a table showing the diameter and cross-sectional area vs AWG. It also lists the ampacity, but this isn't easy to calculate. It depends on the maximum allowable voltage drop, temperature rise and how well thermally insulated the cable is.https://en.wikipedia.org/wiki/American_wire_gauge

author: C
author_rank: Super Contributor
timestamp: July 04, 2018, 12:32:43 pm
content: You need to think of wire as a resistor.There is a specification that states the resistance per length.As wire gets larger the resistance is lower.What the wire is made out of makes a difference in the resistance.You are selecting wire size so that you do not have too much voltage drop & not create to much heat.For example a longer extension cord should be larger wire to keep from having more voltage drop at the load's current.Then for stranded wire, you have a specification for how many strands are used. The more strands the more flexible the wire, the more flexing it can stand before failure.

author: goldfinger
author_rank: Regular Contributor
timestamp: July 04, 2018, 12:37:32 pm
content: See at link the translation table between AWG, imperial and metric.https://www.google.com.au/amp/s/www.engineeringtoolbox.com/amp/awg-wire-gauge-d_731.htmlAt 12v 2A a AWG of 16-18 is more than enough for any reasonable length that isn’t a huge current so you don’t need more than that.Sent from my iPhone using Tapatalk

author: Cnoob
author_rank: Regular Contributor
timestamp: July 04, 2018, 12:48:32 pm
content: standard hook up wires sizes are 7/0.2 (1.5A), 16/0.2 (3.0A), 24/0.2(4.5A) and 32/0.2(6.0A) at 85C.First number is number of strands, second is diameter of each strand. Cross sectional area is number of strands times diameter of each strand divided by 2 pie: (16*0.2)/2*3.14.I have include a link to a wire chart but you can also look up Wikipedia for AWG and have tables show metric equivalents.https://www.canford.co.uk/Technical/Article/MetricAWGWireSizeEquivalentsI hope this is of some help.

author: ArthurDent
author_rank: Super Contributor
timestamp: July 04, 2018, 02:07:55 pm
content: This link will give you more info than you need but it does have everything. It lists larger AWG sizes on the top part of the chart and smaller AWG/metric on the lower part. The chart column you'd be interested in for choosing wire size for a needed current handling capacity is 'chassis wiring'.The way I see you using the chart is, say you want to choose wire for 3.5A, you look down the chassis wiring column to 3.5A then read over to the left hand column to see AWG 24 is what you need. If you want to figure what stranding wire to use you can figure that, if you use 7 strand wire, you divide 3.5A by 7 and each strand would need to be able to carry about 0.5A and using the chart, AWG 32 will handle 0.53A so 7/32 stranded wire in AWG will work.If you're calculating this metrically, then for 7 strand wire go to the lower part of the chart and see that right below 32 AWG there is metric 2.0 (equal to 0.2MM from the 'conductor diameter mm' column) that is rated 0.51A so 7/0.2 is the metric stranded wire size you would need for 3.5A.http://www.powerstream.com/Wire_Size.htm

author: Cerebus
author_rank: Super Contributor
timestamp: July 04, 2018, 03:59:10 pm
content: Quote from: Cnoob on July 04, 2018, 12:48:32 pmApple or cherry pie? Your maths is, how can I put this nicely, not exactly quite right in the sense that it's completely wrong.The area of a circle is ∏r2, not ∏d/2. So the cross sectional area is in fact the number of strands times pi times the radius squared of an individual strand. e.g in the case of 16/0.2mm, cross sectional area = 16 * 3.14159 * 0.12~ 0.5mm2.

author: Docara
author_rank: Regular Contributor
timestamp: July 04, 2018, 04:04:45 pm
content: Hi LektroiD,I notice your in the UK - I'm a UK spark. I will give you some info about cabling in the electrical world that should also apply in the electronic world (in the UK at least)In my experience the only time you will probably come across AWG in anger is with marine or solar cabling or buying cable from abroad. Purchasing overseas isnota good idea because of our VERY high standards pertaining to grades of copper and insulation values of cables which are all covered by the BSI. All cables need to have a BS number. I've been on 1 big installation where we have had to strip out the whole of the cable out because they didn't meet our regs.Now, we use CSA or Cross Sectional Area for our 'units' pertaining to cable size and are in mm squared (mm2 from now on). So Xmm2 cable will give you XMM2 of copper which determines your basic current carrying capacity eg 1mm2 = 13A, 2.5mm2 = 23Amps and 10mm2 =45A for a shower or cooker And the incoming cables to your house will be 16mm2 or more likely 25mm2. So on a house ring circuit the total theoretical current carrying capacity wound be 46A but we would install a 32A breaker. (In the electrical world you then apply 'De-rating Factors' to this cable to take into account fixing methods, temperature and volt drops).Electrically we have fixed sizes of cable 1mm2, 1.5mm2, 2.5mm2, 4mm2, 6mm2 10mm2, 16mm2, 25mm2, 35mm2 50mm2, 70mm2, 95mm2, 120mm2 up to 400mm2 in normal usage. However there are smaller sizes outside these figures eg panel wiring 0.5mm2, 0.75mm2.These can also have the a strand figure instead of CSA for small cable eg automotive which you sometimes see as for example - 7/0.30 meaning there are 7 strands at 0.30mm DIAMETER not CSA so (PI r^2) x strands gives you the CSA of the cableThis sort of sizing system applies across all 'normal' home grown cables you will buy in the UK and most of (f***ing) EuropeAWG - American Wire GaugeI don't know too much about them but what I do know is as follows:-Unless your an American or Canadian they are counter intuitive and confusing to use. The American's, in their wisdom, have decided to have the smallest number reflecting the biggest cables so a cable 000 AWG is bigger than 0 AWG, 3 AWG is smaller than 1 AWG. Their sizes are for diameter in thousanths of an inch so 3 AWG = 0.2294" NOT CSA which we use.The trouble comes when you have a connector which originated in the US and you have to use this tool with that die in this crimper blah blah eg Molex. I have had to do many connections on a board a boat using UK sourced cabling and Molex, Tyco kit and it is painful VERY painful, when you look at the crimper with AWG numbers on it which don't really mean anything to us aarrgghh!In the end I resorted to knocking up a laminated sheet with AWG cable conversions and crimp sizes on it which worked well and carried it with me.Finally, in all honesty if you HAVE to use AWG just hit the internet and use an online conversion tool which gives you a comparable CSA figure. If you use CSA values you can cross reference it to our system very easily, and remember go up a size if in doubt!I have included a link to a site which should help you out, unfortunately it's geared towared power ditribution but you should work it out OK. Towards the buttom is a cable calculator and a little further down is AWG converter.https://www.12voltplanet.co.uk/cable-sizing-selection.htmlHope this helpsMatt

author: ArthurDent
author_rank: Super Contributor
timestamp: July 04, 2018, 05:26:40 pm
content: The link I referenced above will allow you to easily convert from AWG to metric for the sizes you are interested in and to calculate the number of strands and wire size used in stranded wires for point to point wiring which sounded like what you were looking for.If you are planning on using 2-3 wires to make a cable, you have to derate the current rating of a single wire by a factor of 1.75 to 2. The more wires in the cable, or the longer the run, the more you have to derate.You can see from the chart I referenced that a single 12 AWG can handle 41 amps while NEMA code for 12-2 with ground cable used in house wiring in the U.S. (up to about 50 feet) is rated at 20A. Over about 50 feet you have to go to AWG 10 to compensate for losses caused by wire resistance. Ambient temperature can also be a factor in some cases.There is an application where I’m concerned about a microvolt drop across a 6 inch long AWG 24 single wire caused by a 35 ma current and careful grounding and remote current sensing are necessary. Depending what you are trying to accomplish, and your particular needs, these are just guidelines.