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Raspberry Pi
Raspberry Pi Forum Does RPi B+ have high enough power output?
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  • b+
  • raspberry_pi
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Does RPi B+ have high enough power output?

e14 Contributor
e14 Contributor over 11 years ago

I have just bought a RPi B+ and found it cannot power my WD My Passport 1TB USB3 drive. The drive just clicks rather than spins up.

 

I'm hoping that it is something I ma doing wrong. Do all the USB ports on the B+ provide the same power?

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  • rew
    0 rew over 11 years ago

    There are a few considerations.

    The harddrive takes about 1A, or about 1.5 times more than the raspberry pi itself. So your powersupply must be able to provide 1.7A total. If you have a "2A" chinese powersupply, chances are it is powerful enough for a raspberry pi, but not for the pi plus the WD.

     

    Secondly, if you power the pi the normal way, there is a polyfuse that is supposed to prevent fires in case of overcurrent. This should limit the current of the 'pi plus --whatever it has on the USB ports-- to about 1A, or maybe 1.4A.

     

    The trick to using external (usb-powered) harddrives with the 'pi is to connect them to the pi through a powered hub.

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  • e14 Contributor
    0 e14 Contributor over 11 years ago in reply to rew

    Roger,

     

    Thanks for the swift response. Are you talking about the B or the B+? Everything I've read about the B+ indicates that it should be able to power a disk. I do have a new 2A supply, so presumed it would all work.

     

    Sadly, not at the moment - even though, as you say, it does work through a power hub.

     

    Charles

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  • mconners
    0 mconners over 11 years ago in reply to e14 Contributor

    Just out of curiosity, do you have the double usb plug? Or a single? USB (technically) is only supposed to supply 500 ma, much of time on the powered usb hubs they don't limit the current to the individual ports, so you can get the full current at any of the ports. They are non-compliant, but it is very common.

     

    Mike

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  • mconners
    0 mconners over 11 years ago in reply to e14 Contributor

    Just out of curiosity, do you have the double usb plug? Or a single? USB (technically) is only supposed to supply 500 ma, much of time on the powered usb hubs they don't limit the current to the individual ports, so you can get the full current at any of the ports. They are non-compliant, but it is very common.

     

    Mike

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  • e14 Contributor
    0 e14 Contributor over 11 years ago in reply to mconners

    Mike,

     

    I'm using a double USB cable. Looks like USB2 (ie it's not blue).

     

    Charles

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