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  1. #1
    5 Star Lounger
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    Does USB Hub Need External Power

    How does one determine if you need to get a Hub with external power or just use one of the cheaper hubs that do not have that feature?

    Thanks,
    Bill

  2. #2
    Super Moderator RetiredGeek's Avatar
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    Bill,

    It all depends on how much power the devices you attach to it pull. If you have a keyboard and mouse plugged into it probably not, however, add an external hard drive and you better have it powered.

    If memory serves a USB 2.0 port provides 5 Milli-watts so if you plug an unpowered hub into it the total power available to all the ports on the hub is 5 milli-watts! By using a powered hub each of the USB ports on the hub will have 5 milli-watts available. I have one older Maxtor USB HD that has 2 USB plugs one for data & power and one just for power because it requires more than 5 milli-watts.
    May the Forces of good computing be with you!

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  3. #3
    Bronze Lounger DrWho's Avatar
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    If it doesn't crash your budget, just get the powered hub.
    Without the extra power, the very next thing you try to use on that hub may fail.

    I have a powered hub, but I'd lost the little power supply module.
    I tried to use a USB to LAN adapter and it worked fine when plugged directly into my Compaq laptop, but when I put it on the hub, it would not work. I had to build a power supply for that hub, but once I had it all powered up, the LAN adapter worked just fine.

    So think about the future and things you may someday want to use on that Hub, and go ahead and get the Powered Hub.
    "Think twice, buy once" (author, anonymous)

    Cheers mate!
    The Doctor
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  4. #4
    Super Moderator BATcher's Avatar
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    Quote Originally Posted by RetiredGeek View Post
    If memory serves a USB 2.0 port provides 5 Milli-watts...
    Memory serves you ill, I'm afraid, for the maximum current you can draw from a USB2 port is 500 mW!
    Hence external USB-connected hard disks requiring two USB sockets, so that they can draw up to 1A (at 5V) - if they need more than that, they will need an external power supply.
    You're allowed a bit more current draw with USB 3.
    BATcher

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  5. #5
    Super Moderator RetiredGeek's Avatar
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    BATcher,

    Thanks! Looks like my memory needs external power.
    May the Forces of good computing be with you!

    RG

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  6. #6
    Super Moderator CLiNT's Avatar
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    I would just get myselfself a powered hub and not have to worry about it. Depending upon what your actually going to place on it, the powered hub will always have you covered.

  7. #7
    2 Star Lounger
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    It's been a year or so since I was buying hubs, so maybe this isn't the case these days...make sure the one you get explicitly says Hi-Speed.

    Technically, USB 2.0 isn't a useful description because the lower speeds also fall under the 2.0 spec.

    http://en.wikipedia.org/wiki/USB

  8. #8
    Super Moderator BATcher's Avatar
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    Most computer Stuff is downward compatible, so USB 3 will handle USB 2 and USB 1.1 speeds. Hence USB 2 seems to me to be a valid identification of the maximum transfer speed available. Hi Speed and Super Advanced Speed (or whatever the stupid USB 3 name is) are pointless advertising puffery. (Not that I have a strong view on the subject!)
    BATcher

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  9. #9
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    Hi-Speed is the official designator for 2.0 devices that run at 480 Mbps.

    All devices that say Hi-speed are 480, but devices that say 2.0 can be any of the three 2.0 speeds.

    (pedantic, but I have been burned by this)

  10. #10
    5 Star Lounger
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    Thanks for all the suggestions on this subject. I hadn't come back to look for replies because I was expecting an email to tell me when a reply was posted. I still have not received any emails! I just decided to look and see and there have been a lot!

    Thanks to everyone.

    Bill

    P.S. Now that I've selected the Advanced editor I see there are some options that I can change and one of them is related to email notices. I've adjusted it and hopefully that will solve the mystery of no email notices.

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