Pi under voltage detected

[MichaelOToole]

While testing my Pi , it reports under voltage often...

I'm powering it with a quality supply capable of delivering more than 6 Amps @ 5V (Riden RD6006).

I tested various cables most of which came with other devices and results are a little surprising...

USB Cables Tests:

1. Four 75mm USB-C (with micro adapter), sold as charger cable high current... FAIL
2. Two 500mm USB-C (with micro adapter), sold as charger cable high current... FAIL
3. Several 500mm USB (micro, bog standard cables)... FAIL
4. 1000mm USB (micro, my oldest cable, very old USB)... PASS
5. Two 4000mm braided USB (micro, 2021)... PASS

4 & 5 had no under voltage reports, everything else had...

Where can I get reliable short cables, or perhaps I'll make my own, I have lots of connectors...

 

[Dave32]

I'm powering it with a quality supply capable of delivering more than 6 Amps @ 5V (Riden RD6006).

That would be the problem. The Raspberry Pi officially requires a 5.1V power source.

https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#power-supply

 

[MichaelOToole]

It's a pretty decent power supply, output can be increments of 10mV and current at 1mA increments.
I should have mentioned I power the Pi with 5.10 V already, to allow for any loss in the cable, even so, cables differ (the point I was trying to make)...

 

[Dave32]

Hmmm...
If you want to sidestep the problem entirely, you could power the Pi directly via the pin headers instead of the USB port. That's how current LDO kits are set up to do things - there is a 5V screw terminal block built into one of the PCBs included with the LDO ADXL345 Input Shaper Toolkit.

LDO Input Shaper Toolkit for Klipper

docs.ldomotors.com

LDO V2.4 Kit Wiring Guide (Rev. C)

docs.ldomotors.com

 

[NoGuru]

Oh wow, I didn't know the LDO powered the PI that way. I have the input shaper kit but have not used it.
I don't have the PCB that connects to the Octopus but I think I can make one.

 

[claudermilk]

I power my Pi from the GPIO direct from the Octopus. I built a cable to do that long before LDO came up with their nice little hat PCB. I did have to run to both 5V pins to stop undervolt warnings that started popping up after a while. I actually just got the printer throwing that again the other day--after a couple of years with no problem; a full shutdown and power off then reboot and it's been back to solid ever since. I did re-seat the cable since I was under there poking around to re-flash the Octopus MCU after I clicked the update button (insert Captain America gif here ).

 

[NoGuru]

I power my Pi from the GPIO direct from the Octopus. I built a cable to do that long before LDO came up with their nice little hat PCB. I did have to run to both 5V pins to stop undervolt warnings that started popping up after a while. I actually just got the printer throwing that again the other day--after a couple of years with no problem; a full shutdown and power off then reboot and it's been back to solid ever since. I did re-seat the cable since I was under there poking around to re-flash the Octopus MCU after I clicked the update button (insert Captain America gif here ).

That's funny!
Yeah I was also considering running two points of power, 1 from the 5v PSU and one from the Octopus to see if it helps suppress the warnings. I don't see them often but I don't ever want to see them.

 

[MichaelOToole]

Thanks Dave32, I found the header board, didn't even know it was part of the kit.
I will use it to connect to the MeanWell 5 volts supply with decent cables, that should remove the under-voltage issue.

NoGuru, it's not a good idea to combine two different 5 volt supplies, that may/will cause issues.

 

[Dave32]

I have the input shaper kit but have not used it.

I actually don't care for it either to be honest. The ribbon cable is fiddly, and requires that the printer be tipped up and the electronics bay opened up to connect it, and again to disconnect it when finished. And when mounted to a StealthBurner , even with the ribbon cable disconnected, the connector on the ADXL board will contact the gantry on a V2.4r2 if you move the toolhead to the front left corner, which certainly can't be good for it. So I ended up removing it after doing the tuning... which is less than ideal, as it technically changes the moving mass.

LDO could stand to improve their instructions too - they point to the Klipper docs, but the Klipper docs are universal with instructions for many different hardware types, and it takes some care and intuition to figure out what to actually do for the LDO parts. LDO could instead write up a simple installation checklist, and save a lot of people a lot of time.


I have a USB-connected FYSETC "Portable Input Shaper" on a non-Voron printer that I like a lot better. Their configuration instructions are incorrect (check the Github issues section for the correct info as provided by another user), but otherwise it is super nice to be able to just connect and disconnect a bog-standard fully external USB-A to USB-C cable when needed - no opening of the electronics bay required.

 

[NoGuru]

Thanks Dave32, I found the header board, didn't even know it was part of the kit.
I will use it to connect to the MeanWell 5 volts supply with decent cables, that should remove the under-voltage issue.

NoGuru, it's not a good idea to combine two different 5 volt supplies, that may/will cause issues.

Not good ideas is about all I have though .

Okay, if you say it's not good I will take your word for it. I know I have burned up a few Pi's during the shortage which was costly to me.