mini usb power bleed

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So I have my Pi hooked up to my ender 3. When I am done printing and turn off my printer power supply it still receives power through the mini USB port that's coming from the pi. This is bad because it makes a horribly Noize and isn't enough to fully power the printer. The only thing I can do is unplug the USB cable from the printer and replug it when I am ready to print again. Doing this is one extra step and I would like to just be able to turn on the power supply and start printing.

Any help is much appreciated-printingjunkie

An old post but I bet people still find it looking for alternative to the tape trick. TH3D sells a cheap one. https://www.th3dstudio.com/product/power-blough-r-pi-usb-power-blocker/

printingjunkie, you really don't have to go to the extreme of opening the USB cable and cutting the Red wire. A simpler option is to use a small piece of electrical tape, about 4mm wide and about 20mm long and insert it into the big end USB plug (the one that goes into your Raspberry Pi) to completely cover the metal contact on the right side of the USB plug. I've attached a picture, not my best work but you should get the idea, anyway, this will disconnect the power with no issues and is easier to do.

Instead of just shutting down the power of the pi with the printer (can damage the sd-card) or manipulating the USB-Cable, there is an even simpler solution when using OctoPi with a Raspberry Pi 3B or newer: A small plugin that can just deactivate power-via-usb with a small config-switch. This has the advantage of being completely reversible without modifying any hardware:


Get a small Step-Down-Converter for 24V input and 5V 3A output and use it to get Power for you PI.
Connect the converter with a Y-Cable to the Enders Powersupply and connect the output of the converter to the PI.

When you switch on your printer, the PI gets power as well. When printing is done and you switch of your printer, the PI is off as well ;-)

I do this with my two Ender's and it works perfekt for me.

I designed a small case (see attachment). Use a 3A (1N5408) diode from powersupply to stepdown-converter and an 1000uF capacitor.

Killrob, You run the risk of corrupting your sd card by turning the power off to the pi this way. You should shutdown the pi properly before turning off the powerr to the pi. I have had 3 different issues with pis not being shutdown properly, one sd card corruption from improper shutdown, one the usb driver died and the last one the hdmi port died. As for the usb one and hdmi ones having issues most likely the usb died from to much load and the hdmi was a heat issue. After that i use a proper thermal transfer epoxy to secure the heat sinks. I do recommend that people not run anything off the usb that they are not sure of the ma requirements as to high a load can damage the pi. I have about 10 pi3 and 2 pi3+ running several different systems right now. I run my pi3s for the ender 3 and anet a8 off of seperate power supplys and they are on continually as i can turn the printers on and off from the octoprint pages.

Aanubis that is a good work around.

DavieSprocket, you are right! So why not using the integrated "ShutDown-Function" from OctoPI before pressing the powerbutton?
I have not described the Shutdown. I only pointed out, how you can use the Enders PowerSupply for the PI with 10€ of invest.

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You should keep in mind to explicitely shutdown the Pi before just disconnecting it from power, as otherwise the SD-Card can get damaged easily. Also if you want to use the Pi without the printer already being powered (e.g. slicing, organizing timelapses, ...) this solution isn't feasible neither.

Open the jacket on the usb cable and cut the red wire shrink the cut wire ends and fold them back, tape up the jacket and done. Use the shortest usb cable you can find or shorten one.

I leave my pi on all the time and then turn the power to the power supply on and off manually or with the octoprint plugin enclosure. See morganlowes how to attached, i followed it and it works great. Added bonus once you setup the pi control you can add control of lights external fans.


Octoprint and GPIO Control Tutorial!

If nothing bad will happens when I cut the power, then why do USB cables need power?

On the ender 3 its not needed as the board is powered from the power supply and has its own 5v circuit. Back feeding power from the usb to the ender board can damage the pi usb. I think its pretty bad that most if not all the printer boards do this. They should have a switch or jumper for using the usb to power the board when your updating or changing the firmware only. Under operation there should be no connection to the usb +5vdc power. So the only time you ever need to use the usb power to the board is when your changing or updating firmware.

I have a super cheap ramps1.4 board setup on my a8 and it needs the usb power to power the arduino board logic side, so I have relay on the usb wire to cut the connection so I don't have the usb powering the arduino board, lcd screen when the printers not on.

The skr has power switching pins (psu/usb) that when shunted (aka jumpers) it will either power the controller for for USB and psu. When shunted for psu it only allows the USB to send and receive data. Fully disabling the power portion of the USB. When shunted for USB you get the full 5v and data.

would it be safe to just open the usb jacket and cut the power wire?

because there are devices, which are powered by the USB Plug.
Having the Power is one of the Specs of USB - but, if you don't want to have the Printer electronics be powered, you can just cut the power connector.
There are many connectors, where the Power-Pin is not available, since USB will only be used for Data-Communication.
So I think, it should be safe to do the mentioned step.

Are we sure that it is safe?

Yes, just make sure that you either shrink the cut power wire or tape it so it can not ground out against the usb cable if it has a shielded sheath.

Use a razor knife and very carefully cut a two inch or 50mm slit in along the outer jacket, make sure you do not cut the inner wires will cutting the out jacket. Then lightly pull the wires out and cut the red wire. Tape the wire or shrink then fold back in and tape over the cut point. Its that easy. If you cut the wrong wire then the cable will not work but it will not damage any thing. As your cutting a wire it can not damage any thing as long as you make sure that the cut ends have either shrink or tape on them. Don't do it plugged in as well.

Hi, on my Ender 3 Pro, with red wire cut, now octopi doesnt connect at all. Any thoughts?

Try a different cable, chances are you accidentally clipped another one.

Thank you so much, I will try it.

Easy: use a smart power plug or a power strip with a switch for both the pi and the printer. I have a smart power plug that also monitors power consumption and reports that back to my home automation.

"Alexa, turn off the Pi".... I have the same issue and that was my thought. For now, I just unplug the usb cable.