Standard wiring colours 12V DC circuit - Page 1
Forum section: electronics / beginners

author: Unordung
author_rank: Contributor
timestamp: February 23, 2021, 10:09:40 am
content: Hi guys a nice simple question.In Australia is there a IEEE standard that you can point me too that dictates that wiring for a 12V DC system should have specific colors,such as positive = red negative = blackI know this is the common practice but is this a written standard? If so where can I find it?

author: Gyro
author_rank: Super Contributor
timestamp: February 23, 2021, 10:18:13 am
content: No, I think that this is just a convention forsomeDC wiring (of whatever voltage). For example, automotive wiring normally uses different colours (I think Brown is at least one manufacturer's convention for +12V).Another example is that many countries have used Red for Line and Black for Neutral on AC mains in the past - before the more common Brown and Blue these days.I don't think you will find a universal written standard. It's more of a handed down habit.

author: Psi
author_rank: Super Contributor
timestamp: February 23, 2021, 10:22:48 am
content: Personally, when I wire things I stick to computer ATX colors. Just for simplicity.12v =yellow5V = red3.3V = orangeground = black.

author: Ian.M
author_rank: Super Contributor
timestamp: February 23, 2021, 10:44:18 am
content: XKCD #927https://www.electricaltechnology.org/2020/07/electrical-wiring-color-codes-nec-iec.htmlIts a real mess and if your product has an international market that includes North America, and uses both mains and low voltage wiring, you are totally screwed as there are no simple single color options for low voltage wiring that don't risk confusion with mains wiring colors to NEC or harmonized EU/international IEC code.When there's no risk of confusion with AC wiring colours, its not uncommon to use its 'hotter' colors (e.g. red, orange, yellow) for positive rails and 'cooler' colors (e.g. blue) for negative, with black as 0V, or it may be green (or white or grey in N.A.) for ground as 0V and black's actually the negative rail.

author: Gyro
author_rank: Super Contributor
timestamp: February 23, 2021, 12:32:56 pm
content: Just following up on my 'handed down habit' theme. I wouldn't be surprised if the Red Black differentiation was originally down to which were the easiest or cheapest colours in which to manufacture vulcanised rubber insulation at the end of the 19th/early 20th century, with Green being the other one. They would have been dull colours anyway, nothing like today's shades.Red and Green of course the absolute worse for the most common form of colour blindness.

author: wizard69
author_rank: Super Contributor
timestamp: February 23, 2021, 01:17:09 pm
content: Black as DC negative is pretty common but there are also other practices in place. For example in the USA it is common in machine tool practice to make the 24 VDC negative Blue with a white strip while positive is solid Blue. Boating for example has its own practices though a variant of black is often DC negative.In a nut shell you need to know what is current practice in the niche your product is expected to operating in. There may be some national or international standards to consider also.

author: CaptDon
author_rank: Super Contributor
timestamp: February 23, 2021, 02:27:22 pm
content: It always amazed me that in the U.S. house wiring for 120vac that black was the hot wire. We are so used to it being low or return in everything else. I once heard a saying "Green is ground the world around", and usually it is although often it includes a yellow stripe which frees up solid green for other uses. I often encounter dual supplies like +/- 5vdc or +/-12 vdc and I wire them with Green as the return. Red is the plus, black is the minus. If you want to see a real mess check out analog audio wiring going in trenches between studios!!! We spent a full week documenting the remaining unused single purpose wiring that was clogging the trenches and were able to remove about 1/3 of the total wiring in the trenches!!

author: penfold
author_rank: Frequent Contributor
timestamp: February 23, 2021, 04:14:58 pm
content: Its very application dependent, if its just general equipment wiring in a "product" then no; I know there are some IEC standards for control panel wiring, but this can be easily overruled by customer "house styles" depending on industries etc

author: Terry Bites
author_rank: Super Contributor
timestamp: February 23, 2021, 11:05:46 pm
content: Its realy not a defined thing, but a common sense thing. Do what is familiar and common place, then document it all properly as well. In the lab everyone uses Red for + Black for - and green (green yellow) for common and ground. If you have more than a single supply you're free to make up your own code.https://www.electricalclassroom.com/electrical-wiring-colour-codes/