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I have a USB type A to type B cable, I took it from a printer. Now, I want to utilize this USB cable to make a 5V breadboard power supply. I will cut the cable and connect power lines to breadboard's power rails. But, I can't be sure if it is guaranteed to have cables for power transmission or not. I mean, I don't want to ruin the cable if it cannot be used to transmit power.

So, I am sure (well, almost) that there are data lines in the cable, because it was used to transfer data between computer and printer. However, printer had its own power plug. Thus, I am not sure whether this cable has a power line or just data lines.

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    \$\begingroup\$ All USB cables have power lines. \$\endgroup\$
    – DKNguyen
    Apr 29, 2020 at 14:17
  • \$\begingroup\$ @DKNguyen ok, thank you. \$\endgroup\$
    – muyustan
    Apr 29, 2020 at 14:18
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    \$\begingroup\$ no, they do not ... i am 99% certain that at least one cable exists that does not have all of the wires ... think about it, someone somewhere has manufactured a cheap cable \$\endgroup\$
    – jsotola
    Apr 29, 2020 at 14:19
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    \$\begingroup\$ Some dirt-cheap charging cables have only the power line (which is not USB-compliant). \$\endgroup\$
    – DurandA
    Apr 29, 2020 at 14:21

2 Answers 2

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If the USB connector on the cable is stamped/embossed with the USB logotype, then it has all four wires connected.

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  • \$\begingroup\$ I just realized that looking into the connectors and counting the goldish parts could give information about cable count.... \$\endgroup\$
    – muyustan
    Apr 29, 2020 at 14:21
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    \$\begingroup\$ @muyustan No, the connector will surely have all the pins, but the cable may still lack one wire. \$\endgroup\$
    – pipe
    Apr 29, 2020 at 14:23
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    \$\begingroup\$ well, I just realized something and it turned out to be wrong.......... \$\endgroup\$
    – muyustan
    Apr 29, 2020 at 14:24
  • \$\begingroup\$ Anecdote: We have seen all kinds of craziness when dicing up 'standard' cables. Certainly not all USB cables have the same gauge wire - at least that's typically in the datasheet. Historically, the greatest offender for conductor unpredictability from manufacturer-to-manufacturer were cable assemblies with D-shaped, 9-pin connectors ("DB9's"). \$\endgroup\$
    – Chris Knudsen
    Apr 29, 2020 at 20:19
  • \$\begingroup\$ @ChrisKnudsen My boss has an anecdote where they ordered a large number of bog standard USB cables from a company in china, but turns out a lot of them failed. They manufactured X-ray machines so they X-rayed some cables and some of them had wires that didn't reach the connector etc. The manufacturer shrugged and just said that if you wanted them all to work you should have specified that in the order. \$\endgroup\$
    – pipe
    Apr 29, 2020 at 21:00
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A USB-compliant device must sense VBUS voltage level regardless whether they use their local power or not, see details here. Therefore every standard USB cable does have the VBUS and Ground wires.

An exception is a special USB 3.0 cable used/defined for Windows Debugger over USB port, it has Type-A to Type-A plugs on both ends (non-standard for USB), usually of orange color, and no VBUS connection.

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  • \$\begingroup\$ That's the information I was looking for but didn't find. When I did not found anything about VBUS I had to assume that a device could pull-up to its own power. \$\endgroup\$
    – pipe
    Apr 30, 2020 at 7:32
  • \$\begingroup\$ USB-A/male to USB-A/male cables are part of the USB standard but they are uncommon. Part of the standard is to not have the Vbus and D+/D- lines connected. This is one exception where Vbus is not part of the handshake process. \$\endgroup\$
    – MacGuffin
    Oct 18, 2022 at 5:01

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