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Powering USB 2.0 Hub off HDD +5v Rail - Any problems?

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  • Powering USB 2.0 Hub off HDD +5v Rail - Any problems?

    Do you guys see any issues powering my USB 2.0 Hub (requires +5v) off of my HDD rail, which supplies +5v from the PSU. ???

    I'm guessing the USB hub does nothing but regenerate the signals, so I doubt it would draw too much power during use.

    What do you guys think?

  • #2
    if you gonna let it get power from psu .... why not buy a self powered one .... one that works off the usb 2.0 power from mobo .. (that inturn gets it from the psu ) .... so .. seems kinda useless to get it from the same source

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    • #3
      I couldn't find one.. Can you post a link for one of these "self-powered" ones?

      Anyhow, it's too late.

      What I did so far was hack off the 120vAC adapter head, and wired up some terminal clips to hook into the +5v molex adapter to get power from the PSU's +5v rail. Do you think this will suffice? I don't see how it is different from using the 120vAC adapter which ouputted +5v....

      Kevin

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      • #4
        You should be fine. Just remember that each USB port on your hub is rated to 500mA by USB spec. Then add 500mA for some space. So a 4-port USB 2.0 hub needs 5V up to 2.5A regulated. Check your power-supply to make sure there's plenty available on the +5V rail.

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        • #5
          Originally posted by Q_gamelogic
          if you gonna let it get power from psu .... why not buy a self powered one .... one that works off the usb 2.0 power from mobo .. (that inturn gets it from the psu ) .... so .. seems kinda useless to get it from the same source
          i heard (dont know if its true or not) that the hub that is self powered from the mobo splits the power (500ma) between each port....
          rebuilding carpc... kinda..

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          • #6
            The USB port on your mobo isn't required to provide more than 500mA. So if you plug in a 5-port bus-powered hub, it has to split up this 500mA among its ports. This won't be enough if you have several high-powered devices plugged in.

            You did the right thing by buying a self-powered hub and wiring it directly into your +5V rail.

            Here is a really article on self-powered vs. bus-powered hubs: http://www.microsoft.com/whdc/system/bus/USB/hubs.mspx
            1994 RX-7, EPIA P4-ITX w/ Celeron 2.4 Ghz, Arise PSU, Xenarc 700TSV (new model)

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            • #7
              Acctually I think Powered USB hubs can get up to 6As per port...I think the 500mA spec was on USB 1.x only. When USB 2.0 came out I think it was raised.
              Aura MR62 (F and R)
              My Current MP3s
              IamDefiler.com

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              • #8
                Originally posted by Defiler
                Acctually I think Powered USB hubs can get up to 6As per port...I think the 500mA spec was on USB 1.x only. When USB 2.0 came out I think it was raised.
                According to section 7.2 of the USB 2.0 spec at http://www.usb.org/developers/docs/usb_20.zip a single USB device can consume upto 5 unit loads. A unit load is defined as 100mA.
                2004 4runner

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                • #9
                  Originally posted by rando
                  According to section 7.2 of the USB 2.0 spec at http://www.usb.org/developers/docs/usb_20.zip a single USB device can consume upto 5 unit loads. A unit load is defined as 100mA.
                  Sorry, was thinking USB Plus power...

                  http://www.usbpluspower.org/
                  Aura MR62 (F and R)
                  My Current MP3s
                  IamDefiler.com

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                  • #10
                    +5V @ 6A's. 6 amps down 20 Gauge USB wires.

                    Sounds like fun!

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                    • #11
                      Originally posted by Q_gamelogic
                      if you gonna let it get power from psu .... why not buy a self powered one .... one that works off the usb 2.0 power from mobo .. (that inturn gets it from the psu ) .... so .. seems kinda useless to get it from the same source
                      actuly you dont want a self powered one.. it wont be able to run say a CD drive off a self powered one
                      Pete Kastner www.KastNERD.com

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                      • #12
                        well the DVD drive is self-powered, too.. I'll just have this IDE -> USB adapater (on ebay for $29) to convert and run the signal over the longer distance which USB can take me..

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                        • #13
                          Originally posted by Defiler
                          Sorry, was thinking USB Plus power...

                          http://www.usbpluspower.org/
                          LOL, that uses completely different cables (since you certainly burn a standard USB cable with that kind of power). I'm not aware of any system boards using this standard so in a carPC environment, you'd still need an external USB+Power hub and that hub would still require external power (sigh). Moreover, since none of the typical USB devices support the USB + Power standard, high current devices would require an adapter to suck the power off the USB + Power cables. This looks like a no-winner, at least in the short term.
                          2004 4runner

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