At 3/8/2022 09:54 UTC G8HAV wrote:
I bought one of these of the auction site <>5A DC-DC Voltage Step Down Buck Converter Adjustable XL4015 +Heatsink _UK Fast, and set the output to 5.14V, sure enough 'low V warning'.
Tweaked the voltage adjuster up and the warning disappeared at 5.18V, so I set it at 5.22V. No more warnings.
I suggest connecting a 5-ohm or even a 1-ohm load across the output (no R-Pi) and then measuring the voltage. Run it until the regulator gets uncomfortably warm and if that happens very quickly maybe it isn't quite as rated.
For ham radio, SSB, a power supply capable of say 20 amps, but not continuously, works fine for a 100-watt rig because SSB is maybe 100-watt peak but 25-40 watts on average. For continuous duty, like running a computer, the supply rating needs to be continuous. These little wall warts are pretty much consistently overrated... tho I think the "official" ones are generally better... except for the cords... too thin, too long.
I also think the "official" suplies are rated to run the R-Pi, not everything you might quite logically want to connect to it. There needs to be 1.2 amp set aside JUST for current from the USB ports. More for hats. And then some headroom.
The voltage readings are relevant to the multimeter I use and won't be the same as anyone else. It hasn't been calibrated to a standard. That's suggests a project to construct a 'standard'
A zener diode in series with a resistor and a 9-volt battery. Measure across the diode on a good, calibrated meter and then it's a decent single point standard as long as the battery is good.
73 de Jim, KB3PU
