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I'm thinking of building myself a small media center using a RasPi, but 2 USB ports doesn't seem enough to me. So I will need a USB Hub. I still don't know exactly what devices will be plugged on it (right now I'm thinking a WiFi dongle, an IR receiver for a remote, and an external HDD), but just to be safe, the hub will be powered.

The thing is, I don't have a lot of wall plugs near my TV, and all of them are currently used. So I was wondering if it's possible to power the USB hub via USB, using a "Mains to dual USB" plug like this one or similar. They output 5v, and a maximum 2.1A intensity, which should be enough for both the RasPi and the Hub.

Any advice or help on this ?

Thanks a lot !

EDIT : Just adding more info :

  • The link I gave is an example of the type of product I want to use. I still haven't bought anything. When/if I buy it, it will be a higher-end product, with less risk for my RasPi
  • I wish to build a small, non-invasive solution, with the fewest cable. If this idea is viable, I will use heat-shrink tubing (or another cable management technique) on the 2 power cables (RasPi and hub), so they appear as one
  • If you don't have enough sockets near the TV then how will the mains to dual USB plug help? – Matthew Aug 6 '13 at 11:16
  • Then I only need to unplug 1 item instead of 2 – 3rgo Aug 6 '13 at 11:21
  • So the adapter will power the Pi and the hub then. – Matthew Aug 6 '13 at 11:31
  • Yeah that's the idea – 3rgo Aug 6 '13 at 11:39
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Yes, you definitely can. A lot of people are doing this. Just note that some hubs don't work properly. E.g. because the power adapter doesn't provide steady enough voltage for the Pi to work properly. Also because some hub have power-feedback.

To prevent this, first check the list of hubs, known to work with the pi.

  • You misunderstood me. I've just bought a RasPi, and I was thinking of powering it using a Mains to USB wall adapter. But 2 USB ports aren't enough in the long run, so I want to buy a USB hub (powered). I was asking if I can power the hub with the Raspi on the same wall adapter, using one with 2 USB ports – 3rgo Aug 6 '13 at 19:19
  • I guess I misunderstood. But if your buying a power usb-hub anyways, why not have it power your pi too. That way you don't have to buy any adapter at all. But as to your question. A lot of hub use a jack for power, so you'd also need a usb-to-jack cable. Also the usb hub must run on 5V, though I think all of them do, but you never know. – Gerben Aug 6 '13 at 19:51
  • Yeah, but if I use the Hub to power my Pi, then I can't use it as a USB hub anymore – 3rgo Aug 7 '13 at 7:57
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    No, you still can. It's just that you need 2 cable between the pi and the hub. See kalitewiki.learningequality.org/using-ka-lite/deployment/… for an example. – Gerben Aug 7 '13 at 10:39
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    OK, I hadn't seen it that way. It's actually a very good idea. Thanks for the tip ! – 3rgo Aug 7 '13 at 17:36
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I would recommend just getting a multi-way adapter. It makes one socket into 2 or more. The adapter would be able to power the Pi and the hub as long as your hub doesn't use more then 1400 mA.

  • I know this is a solution, but I wanted to know about the possibility of powering both devices on a single Mains to USB adapter. This way I can use an heat-shrink tube on the two USB cable, and it will appear as one cable going from the wall to the back of my TV – 3rgo Aug 6 '13 at 11:41
  • I agree with this answer. You don't need the Pi to get underpowered due to a current surge on the USB hub. Also those cheap USB converters provide far less current than they advertise. – dotancohen Aug 6 '13 at 11:41
  • @dotancohen The link I gave is just an example. If I end up going in that direction, I will probably buy a better quality adapter, not chinese low-end products found on ebay. I just want to know the prerequisites (voltage/intensity) before buying it – 3rgo Aug 6 '13 at 11:43
  • @Squ36 The voltage will have to be 5 Volts and 700+(Your hub's current requierment) mA. Make sure that your adapter can handle that. – Matthew Aug 6 '13 at 11:45
  • @Matthew The one I linked can deliver 5V and 2.1A, although it's said that it's a total 2.1A for both USB plugs. That's why I asked here. To know if the intensity would be enough for the RasPi and the Hub, and if there is a way to build a safe USB to HUB-power-in cable – 3rgo Aug 6 '13 at 11:50
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I found a nice little 4-port hub that works just fine with the Pi3B and relies on the Pi for power. With a 5V 2.5A mains power supply on the Rpi, it is rated to supply an aggregate of 1.4 Amps on the USB ports. That power can pass through this adapter. The other reason to use mains power is for peripherals that need it, as shown below.

This works with keyboard and mouse and flash drive as-is.

Here it is: 4-port USB Hub on Amazonenter image description here

The only trouble I have had is when I tried a Passport drive on it - it simply didn't work.

But it works for my 1TB laptop SSHD with a SATA USB adapter and external AC mains SATA power supply. The power supply came with the SATA adapter. This isnt the exact brand as mine but it looks the same: SATA to USB with power supplyenter image description here

I haven't had need to try more than one drive like this, but have no reason to think it wouldn't work.

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