Wire colors for dual-rail power supplies?

[agdr]

I'm curious what wire colors folks like to use with dual rail power supplies, such as +/-15Vdc.

For house wiring (in the US) the line/phase (hot) is black, neutral is white, and earth ground is green or bare.

For single-rail electronics red is positive and black/ground is negative.

So then, for dual-rail electronics:

• Positive rail = ?
• Negative rail = ?
• Circuit ground (between the two supplies) = ?
• Chassis ground, if different from circuit ground = ?

I've typically used red for the positive, black for the negative, white or yellow for the circuit ground, and green for the chassis ground if the need arises. I'm especially curious what color folks use for the circuit ground here. 🙂

What brought up the question? I'm getting ready to order a bunch of wire. 🙂

 

[yngvejos]

I use red for positive, yellow/green, white or black for 0 and blue for negative.
For house wiring in Norway the three phases are brown, white and black while neutral is blue.

 

[agdr]

Thanks for the reply! Good point about the building wiring colors varying with country. I've just edited the post. Here is a nifty table with the colors for all the countries:

Wiring Color Codes Infographic : Color Codes - Electronics Textbook

 

[wwenze]

I like following ATX. So +5V is red, +12V is yellow, and -12V is blue. 0V is black.

 

[tomchr]

RED = Positive
BLACK = Ground
BLUE = Negative

That's my scheme. In DC systems, red is commonly used for positive and black for ground. I just added the blue to it.

Chassis ground is yellow with a green stripe.

Tom

 

[DF96]

I would use red for positive, black for negative, and probably green for ground. Any secondary positive would be orange or possibly yellow, secondary negative would be grey or possibly white.

As you will have gathered by now, there is no strong consensus except red means positive.

 

[Sangram]

If I was buying wire off a spool it would be red/black/yellow (or white, blue or green for negative).

Sometimes though you strip a few strands off a ribbon cable. then I use the VIBGYOR system, the middle wire is ground and whichever wire colour has shorter wavelength (of reflected light) becomes the positive. Hence I'll end up with funny combos like brown/black/purple or similar.

 

[DUG]

+ red
common black
- blue

I use same for test points on PCB's.

 

[nigelwright7557]

I always use UK mains wire which is brown, blue and green.
I use brown for B+.
I use blue for B-.
I use green for zero volts.

 

[agdr]

Hey a big thanks to everyone for the comments! Gives me a lot to consider. 🙂 Definitely a lot of variation in standards around the world.

tomchr - you have a good point there, I hadn't thought about that. With red as V+ and black as 0V/ground, the "positive half" colors of the dual-rail supply would match up with single-rail colors.

 

[glennb]

Electrons don't care about wire color. I use black for everything. I am very careful about checking the wiring before powering on! I prefer a subdued appearance of amplifier internals rather than a rainbow display.

 

[DF96]

Lots of people appear on here with non-working circuits which have been carefully checked by them; using the same wire colour everywhere makes remote diagnosis much harder. The "rainbow display" is an important part of making a circuit easy to debug and faultfind.

 

[gadut]

I currently use AC cable NYYHY made by local company, it will refer to below colour:
L : Brown
N : Blue
E : Yellow/green stripe

This will also match with transformer primary cable colour which has Brown and Blue colour.

While for DC, below scheme can be used ( red and black seems commonly use)
+ : Red
- : Black
G : Yellow

which ever colour shceme that you use, just remember not to mix them

 

[DualTriode]

This is a practical interesting question!

I was scratching my head over it yesterday. The battery terminals are red for positive black for negative. For test driving a op-amp headphone amplifier I put two 12 volt gell cells in series. For negative 12 volts I connected to the black terminal of the first battery with black insulated wire. For positive 12 volts I used red insulated wire to connect to to the red terminal of the second battery. I used yellow insulated wire to connect to to the common in the center of all of that.

So red is positive 12 volts, black is negative 12 volts and yellow is common.

Your millage may vary.

DT

 

[AndrewT]

I currently use AC cable NYYHY made by local company, it will refer to below colour:
L : Brown
N : Blue
E : Yellow/green stripe

This will also match with transformer primary cable colour which has Brown and Blue colour.

While for DC, below scheme can be used ( red and black seems commonly use)
+ : Red
- : Black
G : Yellow

which ever colour shceme that you use, just remember not to mix them

This is a practical interesting question!

I was scratching my head over it yesterday. The battery terminals are red for positive black for negative. For test driving a op-amp headphone amplifier I put two 12 volt gell cells in series. For negative 12 volts I connected to the black terminal of the first battery with black insulated wire. For positive 12 volts I used red insulated wire to connect to to the red terminal of the second battery. I used yellow insulated wire to connect to to the common in the center of all of that.

So red is positive 12 volts, black is negative 12 volts and yellow is common.

Your millage may vary.

DT

Mains wiring is Brown, Blue, Green/Yellow
Low voltage DC wiring is Red, Yellow, Black.
No confusion.
Instantly recognisable which (mains ,or low voltage) one is looking at.

 

[MorrisMorris]

Thanks for the information. Carefully it studying)

 

[MAAC0]

Many commercial amps follow this rule
Red +V
Black Circuit Ground
Yellow -V
Striped green /yellow Chassis ground