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Thread: Ext. Powered USB hub - why?

  1. #1
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    Ext. Powered USB hub - why?

    I've searched for an answer to this and I can't find any specific reason. Why would I want to use an external powered usb hub vs a bus powered one? I remember reading a thread where the poster said he "learned his lesson" from using a bus powered one but didn't mention what happened?

    Is there potential to damage the system?

  2. #2
    FLAC
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    The difference is externally powered hubs can provide a full 500mA on each port on the hub. Bus powered hubs can only draw 500mA from the host controller(upstream) so for example with a 4 port hub can only allocate 100mA to each port (the remaining 100mA is used my the hub itself). A lot of USB devices require a full 500mA (called high current devices) such as wifi adapters or USB bus powered hard drives. If you plug a USB device that requires high current it will either: 1) not work at all 2) it will work interminably 3) act like it's working but not really work or 4) the operating system will shutdown the device give you a current overload error.

    #4 is what *should* happen 100% of the time per the USB spec, but in reality there are a lot of non-compliant USB devices out in the marketplace.

    I've never heard of any damage with caused by connecting high current devices to bus powered hubs, I think that's because the USB controllers are smart enought to shut themselves down if they get overloaded.

    Hope that helps.

    Nat

  3. #3
    FLAC greatwhite's Avatar
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    Also, if you intend to mount a puter in the trunk and a drive or other items in the dash, you'll probably have power issues and intermitent failures or things jsut won't work at all.

    A powered hub up front alliviates these problems.

    cheers
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
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  4. #4
    FLAC -zip-'s Avatar
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    Just want to chime in as I use a bus powered hub up front.

    Use common sense, the low powered items such as keyboards, mice, GPS, etc etc use the bus powered hub.

    For high powered USB Wifi, USB Bluetooth 2.0, DVDs etc plug directly into the USB supported on the mobo. I ran 3 USB extended cables into my glove box.

    A lot of carputer devices want their own dedicated port non-sharing.

    For example touch screens can be flaky and have a delay if on a USB hub. My Engenius USB Wifi demands a dedicated port as well this is recommended from the MFG. So you will need both, a hub and direct connection so you can afford the flexibility.

    I am running a 5port bus powered hub in the glovebox, never had an issue. I would not go any larger than that for the reasons mentioned above.

    With 6 ports on the mobo and 5 bus powered thats 11 USB ports that should be enough for almost anything. Not sure how many USB ports you have on the mobo.

    My system is in the trunk.
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  5. #5
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    Thanks guys!

  6. #6
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    I have a 4 port 5V powered USB hub I have in my glove box from all my reading and understanding I should be able to run more than one device that draws power from this 4port hub..

    The problem I am having is that I can run my Verizon USB Broadband adaptor but then when I plug in another device like my blue tooth GPS which charges using 5V it gets no power until I unplug the verizon adaptor does anyone have any ideas?

  7. #7
    FLAC greatwhite's Avatar
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    Quote Originally Posted by dmistry View Post
    I have a 4 port 5V powered USB hub I have in my glove box from all my reading and understanding I should be able to run more than one device that draws power from this 4port hub..

    The problem I am having is that I can run my Verizon USB Broadband adaptor but then when I plug in another device like my blue tooth GPS which charges using 5V it gets no power until I unplug the verizon adaptor does anyone have any ideas?
    How big is the ps that you are using to feed the hub? (In amps)

    You are probably going over what it can provide.................
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
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  8. #8
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    ohh I dont know I got one of those adaptors from radioshack that plug in to the cig. lighter

    Whats the best way to get the 5v feed to the USB hub?

  9. #9
    FLAC greatwhite's Avatar
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    Quote Originally Posted by dmistry View Post
    ohh I dont know I got one of those adaptors from radioshack that plug in to the cig. lighter

    Whats the best way to get the 5v feed to the USB hub?
    Those wil lonly give you about 1 amp max.

    Each port on the hub is capable of 500ma each. And 1 amp is pretty easy to overdraw on usb equipment...........

    Need to see the specs on your equipment to know if you're trying to pull too much power from it.
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
    Leonardo Da Vinci

  10. #10
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    Ok here goes:

    Progin 168 GPS -
    Power Consumption
    Main power input 5V DC input.
    Main power input 3.3 5% VDC from internal Lithium-ion battery pack
    Operation Current 45 mA total typical

    Battery
    Source Rechargeable and removable 1050 mAh Lithium-Ion battery with 5V DC input charging circuit

    and a Verizon USB720 Modem I can not find any power specs for this but the USB cable is split in to 2 USB heads if that means anything

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