connect usb drive to xp machine - sometimes reboots?

Discussion in 'A+ Certification' started by 6ftplus, Aug 18, 2005.

  1. 6ftplus

    6ftplus Guest

    when i connect my usb harddrive to my XP machine sometimes it reboots?
    i just plug it an and whammo...reboots. i think it may be ESD or
    something but not sure? any ideas?
    6ftplus, Aug 18, 2005
    #1
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  2. 6ftplus

    Jack C. Guest

    On 18 Aug 2005 05:14:33 -0700, "6ftplus" <>
    wrote:

    >when i connect my usb harddrive to my XP machine sometimes it reboots?
    >i just plug it an and whammo...reboots. i think it may be ESD or
    >something but not sure? any ideas?


    Bad or overworked power supply. If it were simply a driver problem, your
    system would almost surely reboot every time you connected anything to
    any USB port. Try disconnecting something, like the CD-ROM drive(s) then
    test the USB again. Good luck.
    Jack C., Aug 18, 2005
    #2
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  3. 6ftplus

    6ftplus Guest

    nah just working away then i plug in my usb drive to copy files and
    whammo...it reboots. i was told to earth myself and the usb device
    before doing it and now it hasn't done it again. will see.
    6ftplus, Aug 21, 2005
    #3
  4. 6ftplus

    Gerard Bok Guest

    On 20 Aug 2005 16:37:24 -0700, "6ftplus"
    <> wrote:

    >nah just working away then i plug in my usb drive to copy files and
    >whammo...it reboots. i was told to earth myself and the usb device
    >before doing it and now it hasn't done it again. will see.


    Any usb device is limited to 0.5 A max when powered from the USB
    port.
    Microdrives ( 1" ) conform, laptop drives ( 2.5 ") more often
    than not consume in excess of 0.5 A, especially at startup.

    Work-arounds are: Y cables (power is drawn from 2 USB ports
    together) or an external power supply.

    And sure, it doesn't hurt to use a protective earth connection on
    your PC :)

    --
    Kind regards,
    Gerard Bok
    Gerard Bok, Aug 21, 2005
    #4
  5. 6ftplus

    Linker3000 Guest

    Gerard Bok wrote:
    > On 20 Aug 2005 16:37:24 -0700, "6ftplus"
    > <> wrote:
    >
    >
    >>nah just working away then i plug in my usb drive to copy files and
    >>whammo...it reboots. i was told to earth myself and the usb device
    >>before doing it and now it hasn't done it again. will see.

    >
    >
    > Any usb device is limited to 0.5 A max when powered from the USB
    > port.
    > Microdrives ( 1" ) conform, laptop drives ( 2.5 ") more often
    > than not consume in excess of 0.5 A, especially at startup.
    >
    > Work-arounds are: Y cables (power is drawn from 2 USB ports
    > together) or an external power supply.
    >
    > And sure, it doesn't hurt to use a protective earth connection on
    > your PC :)
    >


    Not quite true so it could be a power problem - the USB spec states what
    power should be drawn from the USB port under specific circumstances,
    but very few ports have such precise current limiting. Some will deliver
    2+A! I would suggest trying a powered USB hub.

    From : http://powerelectronics.com/ma g/power_charge_battery_faster/

    "Theory vs. Reality

    With any standard, it's interesting to see how actual practice diverges
    from the printed spec or how undefined parts of the spec take shape.
    Though USB is one of the best thought-out, reliable and useful standards
    efforts, it isn't immune to the real world. Some observed USB
    characteristics that may not be obvious, yet influence power designs,
    include:

    "USB ports do not limit current. Although the USB spec provides details
    about how much current a USB port must supply, there are mile-wide
    limits on how much it might supply. Though the upper limit specifies
    that the current never exceed 5 A, a wise designer shouldn't rely on
    that. In any case, a USB port can never be counted on to limit its
    output current to 500 mA, or any amount near that. In fact, output
    current from a port often exceeds several amperes since multiport
    systems (such as PCs) frequently have only one protection device for all
    ports in the system. The protection device is set above the total power
    rating of all the ports. Therefore, a 4-port system may supply more than
    2 A from one port if the other ports are not loaded. Furthermore, while
    some PCs use 10% to 20% accurate IC-based protection, others use less
    accurate polyfuses (fuses that reset themselves) that will not trip
    until the load is 100% or more above the rating. "
    Linker3000, Aug 23, 2005
    #5
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