Electronic – Red for +ve, black for 0v, …which colour for -ve rail

colour-codingstandardwiring

I'm bodging together a bench PSU from an old server PSU, about to order a mixed bag of terminal posts for the front panel but then tripped over the problem that I'm not sure what's the correct or most common colour to use for the -ve rail on a split-rail supply.

Obviously there's red for +ve, black for 0v, green for earth… but what for the -ve rail?

Commonly available terminal colours are yellow and blue, and I'm aware that blue is used in -48v telecomms supplies (either as 0v or -48v depending which side of the EU standard you are, headdesk), so it's the front runner at the moment… unless you guys know different?

I thought I'd check here before I make a hideous faux-pas.

Best Answer

Personally, I would use a "cold" color for the negative such as blue or maybe purple.

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One "standard" I can think of that's not incompatible with red=positive and black=0V is the standard PC power supply color code:

enter image description here For more info on wiring colour codes see this wikipedia article.

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