bluenote wrote: ↑
Fri May 22, 2020 5:49 pm
Thanks. I don't suppose anyone can explain how post power adapters are commonly referred to do I can try and buy one with the right end? Is there standardization??
For barrel connectors, the specs should be outside diameter x inside diameter, center positive or center negative, nominal voltage, claimed maximum current, and whether it is DC or AC output. Often, the polarity will be a glyph with a line to a partial circle and either + or - and a line to a dot within the circle leading to either a - or +. On some devices you will see the input rated with a dotted line over a solid line. That's AC input.
I say "nominal voltage" and "claimed current" because far too many such devices will not deliver the stated voltage anywhere near the asserted current.
Now then... What I would recommend is to find a hub that comes with a PSU. For a 4-port USB 3 hub, look for one with a PSU rated for at least 4A. then test the hub to make sure it doesn't provide power back up the connection from the upstream device. One of the easy (and cheap) way to test this is to connect the hub to a Pi0. If the Pi0 power up, the hub is backfeeding power and you need to get a different one. You don't even need an SD card in the Pi0 to do this test, so the total outlay is $5 (plus shipping, handling and taxes).