I'm trying to find out a method to power both the raspberry and the usb hub without using to power supplies and without backfeeding it. My first thought was to use an hub with a charging port and use it to power the pi through the standard microusb. I found this on amazon amazon but I'm not sure it can power the pi and 1 or 2 sata hard drive (I'm using a wd red 3.5'' and its power requirements at 5V is 0.6A, I'm also thinking about buying another one). The second thought was to use a double usb wall charger like this and connect both the devices. Has anyone already tried these methods?
1 Answer
Yes - Any kind of powered USB hub will work. Obviously you loose one USB port to power the Pi but you can then use that HUB to plug in other peripherals without stressing out the PI.
The thing you need to look at is the total Amps a HUB can provide. The one you suggested shows 2.5A
All you have to do is add up all the devices you are connecting up by Amp
- Pi ~0.8A Max (0.3~0.5 normal usage)
- HDD (2.5") ~0.5 Max on spin up (0.1~0.5 normal usage)
- HDD (3.5") Cannot be powered from USB HUB at all.
- WiFi adapter + various others - Varies but cannot be more than 0.5A due to USB 2.0 specifications (Count 0.5A to be safe)
- Wired USB Keyboard and Mouse - ~0.05A
- "Wireless" non Bluetooth Keyboard and Mouse ~0.1A - 0.3A
Looking at that you should be able to fit in 2.5Amps with 2 USB powered Hard Drives and the Pi running at full speed - With some power to spare.
*Some USB 3.0 devices may not work on USB 2.0 HUB due to power constraints
answered Jan 10, 2017 at 13:18
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"Any kind of powered USB hub will work" - not strictly true. A standards compliant hub would only provide sufficient current if negotiated, which is not possible on the Pi. Of course, most hubs take a rather loose view of the standards. Commented Jan 10, 2017 at 23:28