No WIFI or ethernet 3b/3b+ after powering on printer

I have 3 printers running octoprint with 3b/3b+ pis. One has given me trouble, I was able to set everything up and connect via wifi but when the 3d printer was powered up the wifi and ethernet no longer work. I've disconnected the printer and restated the pi and still nothing. I've had this happen to 2 pis and I don't know how to fix this.

And the printer board is being powered, right?

Yes, previously (working wifi) the board was powered via usb/pi. Once the printer was powered from the wall that is when the problem happened.

The printer board cannot be powered by the Pi. The printer board has power requirements which are beyond what a serial cable's 5V line can do.

It only allows it to connect not power stepper motors. This behavior is common on all 3 of my printers.

Try this Put tape on the 5V pin - Why and how

This seems like a good solution but I fear some damage was done because the pi is unhooked from the printer and the pi still won't connect.

The original intent for 5V power over USB was:

  • the host computer had a beefy 150W power supply
  • the thumbdrive only sipped a small amount of current

The entire 3D printing industry has completely reversed that original assumption since the Pi sips power and the printer adapter board is like a hungry-hungry hippo. It's crucial to make sure that your Pi isn't sinking power to that adapter board. As suggested, tape can help.

But it's possible that you've fried your Pi from all this.


One thing that confuses me is that it was hooked up for a long time with the printer unpowered so an over draw on the pi would have occurred. Why did the problem arise when the printer was plugged in? Could over current thru the usb cable damage the pi on printer power up.

I could only guess at why. But in theory, it could be from a surge going back into the Pi, from the power draw in the Pi's power regulation circuit to fry from some overload in the USB line... I dunno. You'd have to test it outside of all this to make sure that it's truly fried. It could just be the microSD image for all we know.