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USB hub boost input voltage

Discussion in 'Electronic Basics' started by Dan Jacobson, Dec 5, 2005.

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  1. Dan Jacobson

    Dan Jacobson Guest

    What is that circular socket on USB hubs for? A power boost? By USB
    hubs I mean the ones that turn one USB socket into four, etc.

    I have two USB hubs, an Alcor Micro Hub, and a NEC HighSpeed Hub. Each
    has a little round socket presumably for DC input. But no mention is
    made about polarity and voltage, nor when one would need to give an
    extra power boost.

    There must be some standard. I suppose I can just connect the right
    voltage wallwart to it? Wait, none of the standard adapters seem to
    fit it. I suppose this is to prevent something stupid from occurring?
     
  2. Guest

    The circular socket you can see is to give the usb hub a current boost.
    A standard usb port can supply 500ma at 5V But if you want to run a
    couple of external hard drives and a webcam you will be drawing an amp
    or more and it won't work. This is where you plug your wall wart in and
    everything works again.
     
  3. PeteS

    PeteS Guest

    The units would normally spec, or come with, an appropriate wallwart in
    most circumstances. You might try looking them up. Generally speaking,
    the outer connector is V-, the inner V+ (but as this varies, look them
    up first).
    The reason for the external power is possibly not only to provide extra
    power beyond the USB spec, as the devices may be specified as
    'self-powered' and would therefore require the wallwart to operate as
    advertised.

    Cheers

    PeteS
     
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