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Thread: Am I exhausting my USB inputs? How many devices is too much?

  1. #1
    Constant Bitrate
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    Am I exhausting my USB inputs? How many devices is too much?

    I've got a MII board... and it's got 2 onboard USB2.0 built-in (and i can hook up 2 more if i get more USB connectors)

    anways... i plan to run a non-powered 4 port hub to the front of the car (PC is in trunk) and hook up (DVD rom, keyboard, flash drive, touch screen)

    and run another 4 port hub off the 2nd USB port to run: GPS, bluetooth, game controller, and possible webcam.

    will i be fine? Or will i need to power the front 4port hub? And if so... how?

    thanks

  2. #2
    FLAC migel628's Avatar
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    I'm not 100% on this, but you may be better off powering both hubs. I know the USB port supplies something like 500mA of current w/ 5V of voltage, so you figure that current will now be shared among 4 devices. If your devices can deal w/ 125mA each (500mA/4), then you'll be fine.

    As I said, I'm not 100% on this, so my current value may be wrong...
    "I'm a dick!"
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  3. #3
    Maximum Bitrate jusatry's Avatar
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    Quote Originally Posted by migel628
    I'm not 100% on this, but you may be better off powering both hubs. I know the USB port supplies something like 500mA of current, so you figure that current will now be shared among 4 devices. If your devices can deal w/ 125mA each (500mA/4), then you'll be fine.

    As I said, I'm not 100% on this, so my current value may be wrong...

    USB carries 500mA on the line.

  4. #4
    Constant Bitrate
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    welp... i'm not the sharpest knive on the shelf when it comes to this stuff... so i'm not quite sure if the answer to my question is "yes you will be fine or not"

    i figured for the DVD... i'd be running the power back to my PSU so it shouldn't be sucking up all this juice from USB... the webcam on the other hand is a different story.

    How would i power the USB hub in a car? From the PSU as well?

  5. #5
    FLAC
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    Quote Originally Posted by ummagawd
    anways... i plan to run a non-powered 4 port hub to the front of the car (PC is in trunk) and hook up (DVD rom, keyboard, flash drive, touch screen)
    DVD's usually require lots of power. The best I've seen still needs 2 fully powered (500mA) USB lines.
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  6. #6
    Maximum Bitrate jusatry's Avatar
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    Quote Originally Posted by ummagawd
    welp... i'm not the sharpest knive on the shelf when it comes to this stuff... so i'm not quite sure if the answer to my question is "yes you will be fine or not"

    i figured for the DVD... i'd be running the power back to my PSU so it shouldn't be sucking up all this juice from USB... the webcam on the other hand is a different story.

    How would i power the USB hub in a car? From the PSU as well?

    1) The only way to know for sure if your setup without a powered hub is feasible is to try it.

    2) you could power the hub off the 5V line from the PSU, or get/build a 12V->5V converter. There are cigarette adapter to USB chargers (for pda's and phones), which carry 5V, and there are plans for a PCB converter around this forum, you just gotta search for that.

  7. #7
    Newbie
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    my experience with logitech cams has been that non powered usb hubs won't power them....your mileage may vary....
    Kevin

  8. #8
    FLAC
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    Quote Originally Posted by jusatry
    1) The only way to know for sure if your setup without a powered hub is feasible is to try it.
    The OS will tell you if each device claims to be 100mA or 500mA. An unpowered hub can only run 4 100mA devices since it counts as a 100mA device itself.
    Progress: 80% - Permanent install left.
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  9. #9
    Maximum Bitrate jusatry's Avatar
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    Quote Originally Posted by Arathranar
    The OS will tell you if each device claims to be 100mA or 500mA. An unpowered hub can only run 4 100mA devices since it counts as a 100mA device itself.

    Where in Windows 2000 or XP can you find out power consumption of a USB device?

  10. #10
    What can I say? I like serial. Curiosity's Avatar
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    Go into Device Manager and look under Universal Serial Bus controllers. Double click on a hub and hit the Power tab. Also, it shows info like if it's self-powered it will say it and that each port can use 500mA.

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