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Power BLough-R

by Brian Lough

The simplest way of stripping 5V from a USB cable. Useful for 3D printers used with Octoprint.

Designed by Brian Lough, this is a a pass through device for USB Type A connectors that doesn't connect the 5V line. it has a Male connector and one end and a Female connector at the other.

How is that useful?

Well basically it is simple, non-intrusive way of solving a problem that 3D-printers connected to Octoprint machines have, their screen stays on, even when their PSU is off because they are still receiving 5V via USB.

The new version of the PCB now breaks out the pins from the female USB connector, this is useful for adding 5V back into a USB device that is power hungry (such as an external hard drive), especially if using an extension cable.

How does it work?

Plug the Power BLough-R directly into a USB port of the computer running Octoprint and plug the printer's USB cable into the Power BLough-R. Your Octoprint machine will be able to communicate with your printer as normal once your printer's PSU is on.

Is this the only way to solve this problem?

There are other solutions to this problem, some people have taken to cutting traces on boards, others have modified the USB cable (either by cutting the 5V line or placing tape over the connector), but this is a nice, non intrusive way to achieve the goal.


Printer Compatibility

The Power BLoughR works with most printers, but there are some exceptions. Some printers, such as the Prusa MK3, already separate the printers 5v from the USB 5v. When you use the Power BLoughR with these printers, nothing powers the USB to serial chip, so it will not appear in the port drop down in Octoprint. A good general test to know if you need the Power BLoughR or not is, with the printer off, plug in the USB. If the screen turns on, the Power BLoughR should work for you.


  • Is there a switch? No, Brian wanted to make this as simple as possible. Standard cheap switches can probably handle standard USB current, but he was also concerned about people using these with phone chargers.
  • How do you pronounce the name? Power Blocker, Brian's second name is pronounced "lock" (we don't expect anyone to guess that!)
  • Isn't this just the same as cutting the 5V line of the USB cable? This is exactly like that, but no cables were harmed in this solution!