Undervoltage / good power supplies

Continuing the discussion from Undervoltage? Check your USB cable:

I have had four printers in operation for several years now. Each one has its own RPi 3B+ running octopi, but they are powered in different ways. Some were reporting under-voltage, and others were not. I build this micro-USB extension cord with a voltage meter to see what voltage the different power supplies were providing under load. Some wall power supplies rated 5V/2A were actually providing 4.95V or less. The Samsung EP-TA10JWE (originally sold for the Galaxy 5) is rated 5.3V/2A, and I verified with my meter that it provides 5.28V without load, and varies between 5.15V and 5.20V under typical load. I had bought a bunch of these a few years ago. You can still find some in eBay for a few dollars. They also sell some no-brand replacements, but I don't know what output voltage they provide. They also sell newer type C chargers of the same shape, which are rated at 5V/2A (and other higher voltages), but I haven't tested those. If you are trying to power an RPi 3 or older, try to get the original Samsung EP-TA10JWE which works well. I also build a bench power supply to power multiple RPi units using a MeanWell LRS-75-5. The output voltage can be regulated, and I set it to 5.25V. This solution also works well, but requires some design work to add the female USB connectors to the output and a connector for the power cord.