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I want to plug my 2.5 USB external hard drive to the Raspberry Pi, however, there is not enough power on the USB ports for it to work. I've had some problems with a cheap USB AC-powered hub from eBay (apparently it tries to power to Pi through the USB ports - not advisable).

However, the external HDD has 2-to-1 USB cable, which I always assumed to be for additional power (it works fin with a single usb in any computer I used). So my question is, could I plug one of the USB ports to the pi, and the other a USB power supply (like the ones used to power the Pi)? Or it will only work with a Pi-verified AC powered USB hub?

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4 Answers 4

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The best way to power an HDD is trhough a powered hub.

I've bought a 5V 2A power adapter (~9$) and powered both the hub and the Pi as shown in the diagram below:

5V2A ------+--- USB HUB =--- HD (USB Y-cable from HUB to HD)
           |       |
  (power)  |       | (USB from RPI to HUB)
           |       |
           +----- RPI

2A is enough to power keyboard, mouse and a WiFi dongle if needed. In my case the keyboard and mouse go into the USB hub (which is a 4 ports micro hub) and the wireless dongle into the remaining USB port of the RPI.

Here are some pictures:

enter image description here

The connection between RPi and the hub is done with a very short (made by me) cable.

In the picture below you can see the two USB ends of the Y-Cable from the HDD.

enter image description here

Everything working together:

enter image description here

The blue light you can see at the top is the HDD Led. The Hub led is not visible in the picture.

A black plastic strip ensure there's no electrical contact between the Pi and the Hub (and also serves as SD card holder.

I will probably strip this box soon and re-assemble everyithing in a better box.

Just in case you're interested, for my other RPi (headless server used as NAS, Torrent, Backup, etc) I bought an external 2TB and reused a 12V (60W) power adapter that also has a 1A usb output (which I used to power the RPi):

enter image description here

The HDD USB is directly connected to the RPi USB.

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  • That looks like a lot of cabling. Do you have a photo? Did you use a USB divider from the 5V2A or wire it yourself?
    – Alex
    Mar 22, 2013 at 19:36
  • Where did you buy the hub? Could you post its model?
    – joaocandre
    Mar 23, 2013 at 15:29
  • It's a very old Trust USB2.0 mini-hub. Looking on their site it seems it's no longer available. The closest might be this one: trust.com/products/product.aspx?artnr=17524
    – Remo.D
    Mar 23, 2013 at 15:51
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I know this is an older post, but I had an external drive with a similar sounding connector a while back, and that was used to power the drive from another source (although, like you, I never needed to use it).

So, in answer to your question, I think it should work to connect it to an external supply, although if you have one to hand I would recommend a powered hub, as another answer suggests.

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I used an genuine Samsung Galaxy Tab power charger (5V 2A) without an external powered usb hub and it worked.

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    This is at best only a partial answer. Are you powering an external USB Hard drive with this setup, as the OP is trying to do?
    – Steve Robillard
    Aug 29, 2014 at 14:39
  • 1
    I'm using a 2.5" HDD (Samsung M3 1TB) directly connected to raspi, without a powered USB HUB. This is possible because I'm using a 2A power supply (not 1A as most raspi power supplies). Raspi uses 500mA ~ 1000mA and the 2.5" HDD uses 850mA, so 2A solves the problem.
    – Ptofanelli
    Sep 1, 2014 at 11:49

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