After reading round the net on powered hubs I am looking to find out if my Acrox four port hub would be suitable for a Raspbery Pi, currently being bought for my son. It's been knocking round for ages and I thought this would be a great way to put it to use but not at the expense of the RPi. It is powered by a 5v supply and I am just looking to buy a decent PSU.
1 Answer
There is a lot of rubbish written about "approved" hubs for the Pi. While there are a couple specifically designed for the Pi, any hub should work, and there is no danger to the Pi (unless it has been abused).
The main difference is that some hubs “backfeed” the Raspberry Pi, i.e. power the Pi through its USB connection to the hub, and bypass the voltage protection. I think this is a bad thing, but many Pi users are quite happy with this capability.
You can try to find out about your hub, but the easiest way to find out is to plug the Pi into the hub, without any power connection to the Pi. If the Pi works (or the lights come on) the hub backfeeds. This can be a problem, as hubs which comply with USB 2.0 Standard should only provide 500mA per port which is insufficient, and many hubs do not provide sufficient voltage for reliable operation.
NOTE there is very little risk in normal use, so try the hub with your Pi.
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Read all about backfeeding which is why I was querying the hub, but this is the first time I have seen info on how to test for backfeed. Common sense, maybe, but I'd not have thought of this. Thank you so much for the above response, Milliways.– DeeMar 5, 2014 at 22:18