rpi still screams about undervoltage
modified a usb cable to fit my
laboratory power supply so it can draw what it wants but the voltage is locked
I got a Raspberry pi 3B on an ender 3 v 2.
i also have some kind of ringing if some one could help me it would be awsome
If there is not a problem, pi keeps working and doesn't hang, I would ignore the errors.
Settings
Pi Support
Disable warning
-JC
You just disable the warning, not the undervoltage.
It is better to use a proper PSU
@Alexander_Angerstein :
A systeminfo bundle would help to find the culprit of the issue
For the ringing, looks like your wall count is really low. Also maybe I think changing the print order of infill vs walls might help. I don't think it's actually ringing. It's in the shape of your infill. Looks like cubic?
If you are getting undervoltage, then you might want to adjust your lab power supply to increase voltage slightly. There is going to be some drop in the system, so increasing to 5.1v, sometimes 5.2v can be quite useful.
It is currently on 5.1 volt and draws 400-500mAh
And it cam draw up to 10 amps but the rpi is stable and happy with the 400-500mAh I don't know what it wants more 
My suggestion would be that the USB cable you're using isn't up to the task of delivering the necessary voltage. Not every USB cable is able to deliver 5+ volts. You might want to consider buying a dedicated power USB cable. They typically have higher gauge wiring capable of delivering the peak voltage.
If you've already done this and it's still a problem, then please disregard this post.
I have a 700w PC power supply and with my raspberry pi hooked to the 5 volts, it throws an error.
Since voltage and current are inversely proportional, a large amount of current my be drawn, temporarily dipping the voltage below 5 volts. It doesn't mean you have a weak PS, that is just the way it works. And it's not adjustable.
I have found that the cheaper power cables have a cheaper connectors and this dip is going to be worse, possibly make the connector go bad. Pins are too thin.
If this might be an issue, cut the connector and solder it straight to the PI.
-JC
No. A regulated power supply puts out the voltage it is set to all the way to it's maximum current capacity. Hence the word "regulated".
Most likely you are using a USB data cable and the power wires are too small to carry the current the pi requires. Could also be that the USB cable to your printer is loading down the 5v on the pi. You need to isolate the + wire in the USB from the printer.
Have to disagree. It only regulates the voltage coming out. If it has a crowbar circuit for over voltage or over current, it might not. Higher end power supplies have these circuits so they don't blow up the rest of the components.
-JC
What part of "A regulated power supply puts out the voltage it is set to all the way to it's maximum current capacity. Hence the word "regulated"." Didn't you read?
40+ years in the electronics industry, including design, testing, calibration, repair and implementation... 12 years of which was with Hughes Aircraft in test equipment maintenance and calibration. All the way from 5 volt 100ma supplies up to a 10kv 5A unit as big as a night stand that used a mercury ignitron to switch the current into a xenon flash lamp for a massive ruby laser.
Do you know what a crowbar circuit does??? Bach of Science electronic engineering, 35 years. Aircraft, cool. I worked on the VOR, ILS, and TACAN. Everything else, pretty much the same as you. Now that we have resumes out of the way. If something is shorted what happens to a regulated power supply? It go boom. With a crowbar circuit, it just shuts down and has to be reset. On a PC power supply, it is regulated, but more. No, he probably cannot adjust the voltage up and the voltage detector on the PI is just seeing lower than 5v.
That's not a crowbar circuit. A crowbar is used to keep a supply from damaging the circuit it supplies if the regulator has issues. When the output voltage hits a setpoints the crowbar circuit basically shorts the output of the power supply which then activates the current limiter (if it has one) or blows a fuse in line between the regulator and crowbar.
And a regulated supply can be adjustable. Evidently you missed that class and only partially listened when crowbars were discussed. A CURRENT LIMITER is what shuts the power supply down when the output is shorted, not the crowbar...
Agreed. But the voltage coming off of the crowbar circuit is less than 5v, not the 5v coming out of the regulator. The hyper sensitive voltage detector circuit on the PI says it's not enough. After this circuit it is probably about 4.9 volts at 10 amps. It's a false positive. You are correct with a regulated 5v, if that is what is coming out, but it's not. It has to run it through a resistor (usually 1 ohm) to detect over current. We both are correct. You are probably ex-military or civilian that worked on a base. I never saw one of these circuits until I got out. We only dealt with power supplies and a fuse. It confused me. He can't adjust this voltage up to make the PI happy.
I have a dual Farnell PSU which works OK. I never checked the current drawn at the time but a PSU with 2.5A is supposed to be ample.
This of course all depends on the type of connection type you use on any Pi, which I rule out by connecting to the GPIO header. At least that way I know I have a good connection and it does not take much time to strip the wires on a decent PSU and connect to the header. I tend to use a double wire wrap low down on the pin, then solder to the wire wrap, just in case I need to put a header on the GPIO.
Many cheap PSU's tend to current limit, so a decent switching PSU is always advisable.
I used to get the low Voltage warning, but now I don't.
I turned off the warning and turned it it back on. It doesn't throw up the warning anymore and I never saw any issues with it anyway.
It seems like there is a brief surge as the connection is made (the Ender pulls power from the Rπ as you have likely noticed, even when the Ender is powered off: the screen flickers) but if you look at the logs on the π itself it's not ongoing. There is a moment of low voltage, maybe there is a message that it's throttled but that clears up.
The Rπ is never maxed out, at least not in either of the ones I have: it might run at 20% of CPU but mostly stays are 10% or so. And it's not running the job…it's just sending data and reporting it in the UI. The PSU might be inadequate but some people have found that the Rπ really likes 5.1V, not 5V, as the spec sheet says, So it's hard to blame the PSU maker for following the spec.
I have never had any print failures that I could attribute to low voltage on the Rπ. Maybe there is a gallery of failed prints that point to that but I have never seen it.
