0

I have a Pi 3 that I've connected to a 5V/2.5A power supply. I'm getting the repeated Undervoltage detected! message. I've used the P1, P2 to P6 connections to test the voltage with a multimeter. The results are 4.85 using one power source and 4.9 using another, so the voltage is in range and far enough above the 4.63±0.07 that should trigger the warning.

I do have a CanaKit adapter on order that should arrive tomorrow, but given that the direct measurement of the voltage is showing it's in the appropriate range, why am I still getting the voltage error?

Chuck
  • 223
  • 2
  • 8

1 Answers1

2

Multimeters are slow

Undervoltage is usually a transient event and would only be caught on a multimeter if you have a consistently high CPU (or GPU) load. Install stress-ng and try running stress-ng --cpu 0 while you measure the voltage.

If you have an oscilloscope, you can catch when the voltage drops by triggering on a level less than 4.7 V (rising slope).

Amperage and quality

You mentioned the rated amperage for the power supplies you are using is 2.5A, which should be sufficient. Unfortunately, some cheaper power supplies fib about their capabilities and you'll see the voltage sag significantly when the current draw is high.

5.1V > 5.0V

I believe you'll have better luck once your Canakit adapter arrives as they set their adapters to a nominal 5.1 volts -- which is what the Raspberry Pi Foundation recommends -- so that there's enough margin for the voltage to sag. And, they are a well-known brand, so you won't have to worry about whether they can supply the rated current.

hackerb9
  • 158
  • 4