I want to hook up something to a usb-c cable, only for power. See it as lighting a LED with usb-c. However, once I cut the wire, I was surprised. I found a twisted pair (green, white) a yellow wire (I assume controller wire) a black one (I assume ground) and three red wires (which I assumed were for power). With a multi meter I then hooked up the wires (black to ground and red, one by one, for power) and looked for which of the red wires outputted power, but none of them did. Can someone explain why not, or what I am doing wrong? I can't seem to figure out the way the wire should work.

Image of the stripped cable

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    \$\begingroup\$ I would have a look at: en.wikipedia.org/wiki/USB-C and match the connector's pins to the wires using the continuity test of my multimeter. \$\endgroup\$ Jun 12 '17 at 15:21
  • \$\begingroup\$ I did take a look at that page already, but I fail to get any further with it. I do know that the yellow wire does give an output that looks like data, but that's all I get from the wires when I hook it up to the oscilloscope, so yeah... I'm stuck... \$\endgroup\$
    – Bram
    Jun 12 '17 at 15:31
  • \$\begingroup\$ You may want to find another source of ground on the system, and measure voltages of potential supply wires against that. Then using that as your positive, try to find the ground wire (or power down the system and test continuity to your test ground). There's definitely nothing that says that the wire colors inside a low-end consumer cable are going to match any standard, what we hope is that the cable connects the proper pins on each connector, though pay little enough and sometimes even that ends up wrong. \$\endgroup\$ Jun 12 '17 at 15:38
  • \$\begingroup\$ The only way to determine what a cable's pinout is, is to find a diagram or table of the pin out and ohm out each pin to identify it. en.wikipedia.org/wiki/USB-C \$\endgroup\$
    – Voltage Spike
    Jun 12 '17 at 16:18
  • \$\begingroup\$ I've updated the post with a picture. I tried different grounds, including the exterior/protective layer which looks like it's made from tinfoil and metal. I still do not get anything. In regards to determining it: why would I need to know that? \$\endgroup\$
    – Bram
    Jun 12 '17 at 16:29

A USB Type C receptacle — what you would be plugging your modified cable into — is prohibited from supplying power until certain conditions are met.

This is necessary to prevent damage from two devices supplying power being connected to each other with a C to C cable.

You can use a regular USB A male cable with an A to C adapter, which has the necessary pulldown resistor to be recognized and enable Vbus, or you can add that resistor between CC and GND to your cable, but that will require you to test which wire goes to which pin which may be hard without more test equipment.

Of course, as has always been the case, it is incorrect to draw more than 100 mA from a USB port without negotiating for more power or detecting a battery-charger type port.


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