I was trying to connect two USB cables together but the one had a blue wire (from the camera) and the other didn't. I Googled about the blue wire and I found out that is used for data transfer. I've included a photo to see what I'm talking about:

USB cable wires

Also the other USB cable had a wire without color and plastic insulation. Is it possible to connect them together and make them work?


2 Answers 2


A standard USB 1.0 and 2.0 cable has the following wires:

  • data: D+ (green) and D- (white)
  • power: +5V (red) and ground (black)
  • shield - the non insulated wire

enter image description here
Image by John Beale.

Ground = subsystem ground, the point which voltage of the connected circuits is considered 0 (e.g. the USB hub ground, the motherboard ground).

Shield = device ground, makes sure there is no potential difference between the two connected devices (e.g. the PC metal case). It ensures screening. Sometimes it is not connected to anything else but the USB connectors. Sometimes is the same as USB ground.

I guess that the blue wire is not used for data, it is the equivalent of the black wire (GND), and the black wire is the shield. Or the blue wire could be the shield.

You can use a continuity tester and check each wire against the USB connector - when you have a connector. When the wires are connected directly to the PCB, you may get an idea about what they are for if you look at the PCB. No one can be sure what the wires do when the manufacturer doesn't follow the standards.

Personally I came across this situation (USB mouse):

  • green and white were the data wires (standard)
  • blue was USB ground
  • orange was +5V
  • no shield
  • \$\begingroup\$ Acording to this: markjohann.hubpages.com/hub/… the blue wire is used for data \$\endgroup\$ May 22, 2014 at 19:21
  • \$\begingroup\$ @MeletisFlevarakis don't know what to say. I got the same wire colors and blue is ground... You'd better open up that camera and look at the PCB. I would say that as long as green and white wire exist, they are used for data... can't be sure though \$\endgroup\$
    – Cornelius
    May 22, 2014 at 19:24
  • \$\begingroup\$ @MeletisFlevarakis look at this answer superuser.com/a/215098. Just like I told you... \$\endgroup\$
    – Cornelius
    May 22, 2014 at 19:33
  • \$\begingroup\$ so basicaly i can use the camera without the blue wire because already i have data cables \$\endgroup\$ May 22, 2014 at 19:49
  • \$\begingroup\$ @MeletisFlevarakis the problem is that you can't know which wire is ground: blue or black? \$\endgroup\$
    – Cornelius
    May 22, 2014 at 19:56

I think I solved it. I had to resolder a new USB cable in here are the pin color correlations of the old cable (I'm in North America so I'll probably end up with a cable reverting to the colors here when I purchase the new cable for this mouse).

This is what I saw on the PCB with the old cabling:

PCB printout wire color
V white
G black
D+ green
D- Orange

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