18 Replies Latest reply on May 15, 2019 2:02 AM by alinp

    under voltage detection - Raspberry Pi 3 B+

    y2010x

      There seems to be a serious issue with the power regulator on the Raspberry Pi 3 B+, e.g.: I tried the recommended power supply, but the Pi still indicates that under voltage detected, and it keeps failing (not able to initiate anything, e.g.: sudo raspi-config, sudo apt-get update, etc.)

       

      I bought another power supply with 5V, 3A rating, and the issues remain the same!

       

      Can you recommend a method that I can overcome such issue(s)? Please kindly advise. Thank you.

        • Re: under voltage detection - Raspberry Pi 3 B+
          shabaz

          Hi Si Le,

          It sounds like a faulty Pi, if you've already tried the recommended 2.5A supply and you're running the Pi with just a keyboard and mouse attached (and no other USB devices).

          If you can check with another Pi 3B+, you can confirm if it is the Pi, or the supply that is faulty.

          4 of 4 people found this helpful
          • Re: under voltage detection - Raspberry Pi 3 B+
            jw0752

            Hi Si Le,

            Do you have a meter that you can use to verify that the voltage to the Pi is 5 volts? If possible you could also measure the current draw using the meter's ammeter. This would give you some definite ideas about where the problem lies.

            John

            3 of 3 people found this helpful
            • Re: under voltage detection - Raspberry Pi 3 B+
              fmilburn

              I picked up an inexpensive USB meters similar to the one in the link at a trade show for a couple of dollars.  I've noticed them in one of the local electronics stores as well.  They are accurate enough to get a reasonable idea of voltage and current and are handy at times.

              4 of 4 people found this helpful
              • Re: under voltage detection - Raspberry Pi 3 B+
                luislabmo

                What is the "recommended" power supply you've tried?. I've tried few good reputation power supplies in my experiments -incuding adapters for tablets which are around 2.1A-, when the Pi was running with the Touch display, I was getting the low-power notification icon until I started using the official Raspberry Pi Universal Power Supply.

                 

                Another thing that may affecting the power delivery to your RPi is you USB cable. I personally would check those before concluding it is a faulty RPi case.

                 

                Luis

                6 of 6 people found this helpful
                • Re: under voltage detection - Raspberry Pi 3 B+
                  y2010x

                  Thank you all very much for your suggestions.

                   

                  I tried them all, but the yellow lighting bolt still showed up, and the voltage drop for most cases is about -0.4 volt. The unit is functional (not trying to reboot) in one of the power supply with the yellow thunderbolt; I ordered 3 more units to see if this is a bad unit - I will let you know the results when I have a chance to test them.

                   

                  Thank you all again very much.

                  2 of 2 people found this helpful
                  • Re: under voltage detection - Raspberry Pi 3 B+
                    keillrandor

                    I have a PI 3B +, had similar under voltage warnings, both in Debian Stretch syslog and yellow flash icon on my connected official 7" screen (I don't use any GPIO voltage bridging). I use an iFi power 2.5A rated switching PSU with micro usb connected to the PI. I also fed the screen with another separate micro usb power source. With this setup I had voltage underruns every now and then during the boot sequence.

                     

                    PI<----angled micro USB cable/USB-A male 0.5m---> <----micro iFi USB female A adapter/DC pin cable 0.1m---> <--DC PIN cable to iFi PSU 1.5m? ---> wall DC 230V/50Hz

                     

                    I resorted to solder the angled micro USB connector to the DC-pin adapter, removing about 0.5 meter of cabling and a possibly weak USB A female adapter used above.

                    It resolved the issue. It would have been interesting to use an oscilloscope, which I don't have, to monitor the improved voltage stability.

                    1 of 1 people found this helpful
                    • Re: under voltage detection - Raspberry Pi 3 B+

                      I have the same issue under-voltage deteched.

                      why not check the cable itself.

                      my cable takes 0.06v/100mA

                      1 of 1 people found this helpful
                      • Re: under voltage detection - Raspberry Pi 3 B+

                        My issue was a USB cable .it's working fine with an OEM Samsung non fast charge box and cable. 5v 2a

                        1 of 1 people found this helpful
                        • Re: under voltage detection - Raspberry Pi 3 B+
                          dougw

                          The USB cable can easily drop the voltage by over one volt. You can see some real tests here:

                          E36313A Triple Output DC P.S. - Review

                          Some cables drop the voltage by over 3 volts....

                          4 of 4 people found this helpful
                            • Re: under voltage detection - Raspberry Pi 3 B+
                              genebren

                              Doug,

                               

                              This is a great cable test setup.  This should help all those people out there that are having under voltage errors on their Pi devices.  I have switched all of my USB cables over to ANKER PowerLine products and I have not had any power delivery issues (one of my products runs >2.0 Amps through the USB cable).

                               

                              Thanks!

                              Gene

                              2 of 2 people found this helpful
                            • Re: under voltage detection - Raspberry Pi 3 B+
                              alinp

                              I'm facing the same problem.

                              At first I thought my switching PS was the culprit, but then I've switched to powering the Raspberry Pi 3B+ from a Rohde&Schwarz HMC8042 bench power supply which is more than capable of driving the Pi.
                              Voltage was set to 5.1V.
                              Current limit was set to 2.2A.

                              According to the bench PS which shows real-time current consumption, the average (in my case, for the firmware I'm running (it's a RetroPie) it's around 600 mA. Even with this beefy bench power supply I still get the under-voltage warning. I've measured the voltage right at the USB input socket and it's 5.0V (so the cable drops 0.1V).
                              If someone has an explanation for this, I'll be glad to hear it.
                              I'm assuming it's either a bad LDO or a hardware design issue.









                                • Re: under voltage detection - Raspberry Pi 3 B+
                                  luislabmo

                                  The voltage drop may be caused by the USB cable used: length, cable thickness, connector quality (or specs) may be the most important factors to consider: see this comment and this one. In my Raspberry Pi Road Test I cover this in the Power Consumption section.

                                   

                                  The easiest way to discard a USB power problem with the Pi is to power it directly to the GPIO with a regulated power supply where you can reduce some risk factors by increasing the wire thickness, using connectors with a good current rating, etc. USB power issues are harder to troubleshoot as USB cables are sealed most of them without reliable specs available that will bring a lot of unknown factors -one of the main reasons why is good to have the official micro USB power supply for Raspberry Pimicro USB power supply for Raspberry Pi to discard USB power issues.

                                   

                                  Luis

                                    • Re: under voltage detection - Raspberry Pi 3 B+
                                      alinp

                                      As stated in my original issue

                                      I've measured the voltage right at the USB input socket and it's 5.0V (so the cable drops 0.1V).

                                      The measuring procedure was done using a MSOX3104T oscilloscope with a passive 10:1 probe hooked up right to the power rail smoothing capacitor C84.
                                      *schematic from the official Rasberry Pi docs.

                                      Measuring on the oscilloscope (MSOX3104T) was done using Roll mode, at a sampling rate of 100ms/division.
                                      At no point during the testing procedure, which involved throwing multiple power hungry tasks at the CPU, did the power supply (which again was a R&S HMC8042 OS) vary by more than 100mV. Overall, the voltage did no drop under 4.9V. Despite this, the low-voltage warnings kept coming. 

                                      The power was fed trough the USB port, using a high quality USB cable, that was cut to 5cm in order to expose the power and GND wires inside an hook them up to the bench PS.

                                      Given above testing procedure I can confidently exclude any factor related to the USB cable or power supply being used. Thus, I conclude that there must be a faulty hardware design somewhere down the line. If someone has identified it or has a different opinion please let me know.

                                      I still don't know if I should send in back to Farnell under warranty due to this malfunction.