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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.

John U
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  • Red and black for positive and ground are common, but certainly not a universal standard for something like benchtop use. Any color for a negative supply will be even less standard. Use what you have around, although it would be good to keep away from red, black, and green. – Olin Lathrop Feb 18 '14 at 20:34
  • Id have gone red, white and blue with white an indistinct and colorless 0v. Hang what other folk do. LOL – Andy aka Feb 18 '14 at 20:40
  • Black is colorless too. – Spehro Pefhany Feb 18 '14 at 20:41
  • I guess I brought this upon myself, ask a pedantic question, get pedantic comments... :D – John U Feb 18 '14 at 20:48
  • No standard **BUT** | NOT yellow - to be seen as highest V+. | NOT Orange = ambiguous. | Blue is a good choice. – Russell McMahon Feb 19 '14 at 03:14

1 Answers1

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

enter image description here

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.

felixphew
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Spehro Pefhany
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