Getting rid of lightning bolt

What is the problem?

Pi undervoltage symbol showing on dashboard (steady burning). No issues found, but how do I remove the warning symbol.

What did you already try to solve it?

Checked voltage, rebooted Pi

Have you tried running in safe mode?


Did running in safe mode solve the problem?


Complete Logs

octoprint.log, serial.log or output on terminal tab at a minimum, browser error console if UI issue ... no logs, no support! Not log excerpts, complete logs.)

No event log of the incident. Last log found was previous day. This event occurred today.

Additional information about your setup

OctoPrint version, OctoPi version, printer, firmware, browser, operating system, ... as much data as possible

Octoprint Version 1.5.3
OctoPi Version 0.17.0
P1 3B+ Rev 1.3
Printer- Ender 3 with SKR E3 mini v2 running Marlin Bugfix 2.0
Windows 7 using Chrome browser

There is only one way: A proper power supply.
That means: No charger, thick cable, at least 2.5A for a Pi3 and below, and 3A for a Pi 4
And a voltage of 5.2V. Good connectors are mandatory.


Well that's some crap. The first thing I checked was the power supply and wall voltage. The power supply is putting out 4.9V and 3.1A according to my Klein meters. Even with machine variances, it still should be good.

What is a "proper" power supply ? I thought I had one. I'm running the one that came in the kit, and until today, there hasn't been any issues. Running it for 4 months. I didn't check the label to see if it had a listed watts output. I figured it was good to go with the volts and amps checking out.

After thinking about it, I have a spare Buck converter I could use, although I didn't want to rely on the printer's power supply for the Pi because of known voltage variations with tose PSU's.. That's why I set it up with it's own power supply. Is there a maximum amount of amps I can set it at so the fluctuations shouldn't bother it ? Like if I set the Buck converter at 3.5A, will that hurt the 3b+ ??

Where did you measure it? Did you measure it under load?

The Pi does not lie. If, internally it's voltage drops below 4.6v then it will complain, it will throttle to avoid brownouts and it will be unstable.

Best place to measure is across the GPIO pins, since this takes into account the voltage drops from the regulators on the Pi (this is why recommendations are 5.1/5.2v usually).

Max current will not kill the Pi, since current is pulled rather than pushed.


I measured at the micro usb connection on the cable. Which pins would be good to measure from ? Can I just use the fan pins ? I forget what they are, but I have a "always hot" fan running directly over the Pi to keep it cool. shows them. You want between the 5v and ground.

Also, if you have a fan that is likely drawing a lot from the Pi lowering the voltage and causing it more problems.

Thanks for the pinout. I had one on my other laptop before it crashed. I'm using an older laptop until I can get a new HD in my "new" one. The fact I have a fan as an additional load didn't cross my mind until I typed it. I'll recheck it first chance I get, but I'm seriously considering just throwing it on the extra Buck controller. I'll have to see what the fan pulls, and adjust it accordingly. THANKS !!!!!!


Fans only draw 100ma or less. I have fans on all my Pi's and none have caused any excess current draw.

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I had forgotten I had installed a "usb power blocker" a couple of days before this occurred. I installed it to keep power from feeding back into my printer's motherboard. I have masking tape over the power pin on the usb cable, and it had been working fine to prevent the feedback, but figured the "power blocker" would be the more correct way to fix the issue. Anyway, I pulled off the power blocker, and the lightning bolt immediately went away. I'm not sure why it was causing an issue with the Pi, because the Pi isn't getting power from anywhere except its own power supply. I've checked to make sure the masking tape is still doing its job of not letting power back feed to the printer (or let printer power back feed to the Pi), and it seems to still be working. I don't have any lights glowing on the printer's motherboard when the printer is turned off. So I'm at a loss to why the Pi had the issue. Either way, my issue is resolved for now, but I'm going to keep an eye on my masking tape fix to make sure nothing changes. I appreciate the help guys !!!!!

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Remember those power pins on the GPIO? You can power the PI using those. Then a USB data cable with the power leads cut, will connect your PI with your printer without further voltage issues or feedback into the mainboard.

Be careful though doing that, because you skip the power protection/regulation circuits in the Pi, so whatever you plug in there should be a high quality source that you know will not kill the Pi by spiking voltage etc.

Exactly. That's why I have a separate, 110v power source for my Pi. I did not want to chance having voltage issues either from the PSU or the main board. AND why I have isolated (hopefully) any current feedback from the motherboard. That was the reason for trying the "USB current blocker". However, it seems using the "USB current blocker" caused some type of issue with the Pi voltage readings. I still have a print running, but when that print is finished, I plan to power down the printer and make sure that no power is being backfed from the Pi to the printer using my "masking tape on the USB power pin" fix.

Is anybody familiar with the "usb power blocker"? I just wonder if anybody has had issues with it before ?
Power BLough-R - Pi USB Power Blocker - TH3D Studio LLC

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RPi provides two voltages through it's GPIO pins: 5v & 3.3V. I've recently noticed that when I've switched from using the 5V to 3.3V for powering of additional components, i've started to receive occasional "undervoltage" warnings.
Looking at the schematics, XR77004 is responsible for providing the current based on 5v input. I'm guessing that this chip is running into it's current limitation and hence this results in undervoltage on Vcc.

Not using the 3.3V / bypassing with direct usage of 5V resolved the issue in my case.


The TH3D USB power blocker works as advertised.


I'm already connected to the 5v (I think). My fan (a single, 4010 fan) is connected to pins 4 & 6. I just wish I knew what all the other pins were. lol I actually have the pin out diagram, I just mean I have no clue what all the GPIO do.

Maybe...I don't know. What I do know is that I didn't have the problem before I connected, and I haven't had the problem since I disconnected it. And from what I can tell, there doesn't seem to be any power transfer between the main board and the Pi. When the main board is off & Pi is on, there are no lights glowing on the main board. when the main board is on, and the Pi is off, there are no lights glowing on the Pi.

With that power blocker, you introduced one more USB connector, and with that, one more place for contact resistance to occur.
USB connectors are horrible for power supply. I have a USB power bank where just by wiggling on the USB connector plugged into it, the measured outpout voltage jumps wildly between 4.70 and 5.15 V.

Maybe your connectors where in a "4.7 V position" when the issues occured.
Maybe next time you try they are in the "5.15 V position".
Maybe they jump around between those when you accidentially hit them or move the cable a bit. BTDT.

If you want to make sure your Pi is not affected by any power supply issues, do not use any additionally inserted USB connectors between your power supply and your Pi.

It will be a power problem, 4.9 is not high enough.

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