Pi3 PSU Voltage Critical


John M Wysocki ZL2TWS <zl2tws@...>
 

Hello NW Digital team.

Today I found what might be the reason for the UDRC cutout on RX.

I am still testing but have found a real issue with voltages lower than 5.1VDC when measured on the GPIO pins 4 & 6.

On the UDRC compass image I have installed DummyRepeater using the DV3000.

This was done when the UDRC board was removed.

Two PSU's are available.

1) 5.0VDC @ 2.0Amps.

2) 5.1VDC @2.5Amps.

DummyRepeater fails to operate correctly if the PSU at 1) is used.

DummyRepeater works perfectly when the PSU at 2) is used.

Operating voltage of 5.15VDC between GPIO 4 & 6 is the best or possibly higher.

Please carry out testing on the UDRC and Pi3 to determine if the wrong voltage PSU is used can cause the RX drop outs I was experiencing.

If 4.9V is used for testing it might show the problem.

I will continue to test the UDRC over the next couple of days to prove this theory with my own variable PSU.

Amazed that 0.15V could cause the Pi3 to be problematic. I have been told that some of the Plug Pack PSU's can drop to a lower voltage or have poor regulation.

I will investigate a 13.8VDC drop down regulated 5.2VDC supply as an option.

The difference in 2.0A and 2.5A I cannot see to be a problem since the Pi3 running current is lower than 2A. On-board SMPS problem like the Pi2?

Looks like Pi3 VDC is critical and must be higher than 5.1V definitely for DummyRepeater and possibly UDRC.

Those wanting to use the Compass image with DV3000, USB headset and DummyRepeater must use >5.1VDC.

I tried three different 5.0V 2.0A PSU's and DummyRepeater failed to work correctly with all three but 100% as soon as the >5.1V 2.5A was used.

73, John ZL2TWS

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