For one printer I put a button in octoprint to toggle USB port power on the raspberry pi and powered the ramps/Arduino from the pi instead of the 12v printer PSU. Then I could turn off most of the printer right from the web interface.
I simplified a bit. But it’s easy to bork the cable in the process, and it’s also possible the cable didn’t follow standard wire coloring.
Here’s the step by step process for anybody who wants to do this but doesn’t know for sure what to do.
You will need a razor blade or wire stripper and a wire cutter, as well as a roll of electrical tape.
Also it should go without saying, but unplug both ends of the damn cable before you start. And if you’re using a blade, please be careful not to cut your finger open. Paying $800 for stitches in your finger hurts, defeats the purpose of being a cheapass and modding a cable to save a few bucks, and gets blood everywhere.
Verify that the usb cable is a CHARGE AND SYNC cable. A charge only cable will not work.
With your razor blade, make an incision into the usb cable about 6 inches from either end. Don’t cut too deep. Only go deep enough to cut the outer jacket. The cut should be slightly longer than your tape is wide. If you have a wire stripper, strip about a 3/4 inch section of the cable about 6 inches from either end.
If using a blade, cut around the jacket at both ends of your incision and peel off the jacket between your cuts. You should have about 3/4 inch of unwrapped cable.
If there’s a wire mesh wrapping the inside of the cable, cut SOME of the mesh, being careful to ensure that the mesh is still connected on both ends. If there’s a foil wrapper, find the seam and peel it back to expose the inner wires. You can cut the foil if necessary, but do not remove it entirely. Ensure that SOME of the foil and/or mesh is still attached at BOTH sides of the exposed section.
The inner wires should now be exposed. There should be 4 wires - red black white and green. There might also be a 5th wire with no insulation at all, but this won’t be in all cables. It’s okay if it’s missing. However, if you don’t see ALL of those 4 colors or see different colors STOP. Tape the cable back up and get a different one. If you only see TWO wires, you have a charge only cable and it won’t work. Tape it back up.
Clip the red wire TWICE, about an 1/8th inch apart. There should be a gap in the wire now if you line the ends up. DO NOT cut anything else inside the cable. The black white and green wires MUST remain intact for the cable to function.
Bend the red wires up and out of the jacket. Close up the foil and/or mesh and wrap ONLY the exposed portion of the cable with ONE layer of electrical tape, leaving the red wires sticking up on either side of the tape. It’s okay if some metal is exposed on either side of the tape, but the red wires should be able to lay down on it without the ends touching anything metal.
Lay the ends of the red wires down so that the ends are laying on the tape. The metal inside the red wire should NOT contact anything else that’s metal in the cable.
Wrap the whole opened section of the cable with electrical tape to an inch or two on both sides of the open section.
Plug it in and give it a try. You should have data-only usb cable that doesn’t deliver power now. Mark or label the cable in some way so that you don’t lose your mind trying to figure out why this damn usb cable doesn’t charge your phone when you pull it out of a box of random shit 5 years from now.
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