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Mark Griffith
If anyone wants to know if their Pi is complaining about low voltage, here is a short script to run and have a look: sudo grep Under-voltage /var/log/syslog | wc -l Output is the number of under voltage alerts in the log, which is rolled over each day. Also, these things are pretty good for checking the voltage of your power supplies and are pretty accurate.? Some power supplies for the Pi will only output 4.99 volts, some more than they are rated.? Good to check them. Mark KD0QYN
On Tuesday, July 13, 2021, 12:21:04 PM CDT, Tadd KA2DEW in NC via groups.io <tadd@...> wrote:
The acid test for all this is whether the Raspberry PI complains about under-volt. ?If the PI doesn’t complain, EVER, you are probably in great shape. ? My solution is to use a 5.2v regulator and a six inch cable to the USB-c plug. ?There are a host of inexpensive (< $20) variable output, 8v to 37v input, adjustable output supplies out in the world. ?DROK makes a good one which actually has a variable voltage output into a USB-A socket and that’s the one our local radio club uses. ?We like that the PI comes on when the radios are powered up. ?Having the PI powered up whenever the radios are on is a good thing. ?Having the radios powered and the PI not powered can be bad because voltage enough to start up some of the PI’s peripherals can show up on connections between the radios and those peripherals. ?So if the PI is powered down and the radios are up, you can get bad glitches in the peripherals. ? The point is, you need 5.2v at the Raspberry PI. ?You can measure the voltage at the 40-pin AUX connector. ?Wires drop voltage when the current draw is > 0. ?Longer wires drop more voltage and higher current draw causes more voltage drop. ?Thinner wires also cause higher voltage drop. ? So, ?if you have a voltage need, and a current need, and length of wire you want to keep the voltage high enough, the length short enough and the wire thick enough. ? ? ?Tadd
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