Accessibility for a 3-wire connection?

[grandaspanna]

I'm building a small hobby device that will require 3 wires for the user to connect (plug-in) to their existing equipment. Because there isn't a standard connector to cover this, they will be separate wires with a 1-pin connector. I need them to be able to distinguish between the three wires. Labels will be awkward from a build perspective and also bulky considering the size. I've experimented with heatshrink bands, but that's also fiddly.

I'm considering two other options:

• Slightly different lengths for each wire
• Different colours for each wire

The first seems plausible, but I'm worried about the second one being appropriate for someone with a visual accessibility need. I could use black and white for two of them, but what's a colour that would be generally considered different enough from those?

Is there standard or agreed conventions on this?

[jpanhalt]

Colored or numbered wires are the usual way.  Aircraft and commercial wiring is often numbered.

As for color, "colorblind" people are not color blnd per se.  They do perfectly well with most colors.  I have even known pathologists and surgeons who were "colorblind."

I would be leery of selling any product that required an "ordinary" person to connect wires in a certain order. That's why user manuals for consumer goods are mostly safety garbage.

[grandaspanna]

Thanks. I was hoping there might be some standards or specific recommendations for maximal differentiation.

I was looking for something official and the closest I've found so far is this: https://esv.vic.gov.au/wp-content/uploads/2020/08/Guidelines_Colour_vision_deficiency_Jun2020.pdf

This gives me an idea that black/white/yellow should be ok.

The target users aren't casual consumers and will have some basic electrical knowledge, including soldering skills. However, I am keen to make it as simple as possible and accessible.

[mariush]

Black is usually for ground, red is often used for power/voltage.

white / green is used for data , see for example usb

You can also get wires with a stripe of a different color, see for example all kinds of combinations : https://www.digikey.com/short/7f9rt0d1

[Berni]

Black, white and a bright color.

Color blind people tend to have trouble telling apart certain colors, but they still see color saturation just fine. So anything like red, yellow, green etc.. will work for the third one.

There  rare color blind people that basically see black and white but its very very rare. The thing to avoid is having something like a yellow and green cable, those tend to be the hardest for the most common kind of colorblind people to tell apart. They simply see the two colors as the same color.

[ajb]

Good on you for thinking about this sort of thing 

Red-green color blindness is by far the most common type, so avoiding anything that requires distinguishing between reds/oranges/yellows/greens will go a long way towards helping avoid issues for people with color vision problems.  You could also do black, white, and then some color with a stripe, as long as the color is dark enough all three should be easily distinguishable only by contrast.

How thick are the wires?  There are slide-on labeling bands that might be a good alternative to heatshrink, but not sure what sizes are available.

[grandaspanna]

I've so far experimented with 28AWG ribbon cable and 26AWG single-strand. Overall lengths will be about 10cm.

I love using this stuff: https://www.adafruit.com/product/1881

It's 26AWG and is labelled as silicone insulated. It's flexible, easy to solder. I wish I could buy it in larger quantities :-)

Anyway, thanks for the ideas. I was able to track down someone with a red/green deficiency and they called out yellow as having a good contrast to the black and white. That's what I'll start with.