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Thread: powered hub "freaking out" the 'puter?

  1. #1
    Registered User vfinterceptor's Avatar
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    powered hub "freaking out" the 'puter?

    Got a funny problem and I'm looking for a little advice on how to handle it.

    First off, I'm using a dell optiplex gx270. I've got a powered hub in the front dash (running off a small 1000ma power supply, basically an ipod usb car charger) for the for the dash mounted dvd drive.

    Here's the problem:
    When I start the car, it seems power is feeding back through the hub to the puter and it looks as if the puter is going into a "hibernation" state (power button pulses orange). When I get the main power up and running (ie: car started or into acc), I have to shut the computer down by holding the power button for 5 secs and then everything will start as normal.
    If I unplug the hub, everything works fine. I've noticed that if I "unplug" the puters main power, my radioshark is still lit up and seems as if I am drawing power from the front hub through the puter usb ports and back out to the radioshark.

    Sorry if the description is a little confusing, but this is baffleing me a bit.

    Anyone have any idea what's happening here and what to do about it?

    Is there a "power on with usb" setting I'm missing or something similar?

    Cheers

    BJ

  2. #2
    Variable Bitrate walstib's Avatar
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    Sounds like there may be some ground difference problems. Are you sure your PSU for PC and 1000ma PSU use the same ground?
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  3. #3
    Registered User vfinterceptor's Avatar
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    Hmmm......

    The 1000ma uses a chassis ground under the dash, and the puter uses a chassis ground in the trunk.......
    I'll have a look at the dash ground again as I reused the old radio's ground, that may possibly be my issue.

    Cheers

    BJ

  4. #4
    What can I say? I like serial. Curiosity's Avatar
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    The hub shouldn't be allowing the external power to be feeding back through the USB cable. You should check to see if that is what's happening.

  5. #5
    Variable Bitrate
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    can the power for the USB hub be supplied by the computer's PSU? That way when the comp is off so is the usb.

  6. #6
    Registered User vfinterceptor's Avatar
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    Quote Originally Posted by guizai View Post
    can the power for the USB hub be supplied by the computer's PSU? That way when the comp is off so is the usb.
    There's a thought.

    Although, I put the power source up front to power the hub due to power drop off on the long usb run to the DVD/cdrw.
    maybe if I used a larger gage wire than the tny usb power wire the power wouldn't drop off so much....

    Cheers

    BJ

  7. #7
    MySQL Error MatrixPC's Avatar
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    Modify the USB cable to the hub: Only use 2 data wire. No need for the power wire when the hub already has it own power. And modify the circuit that provide power to the regulator for the hub.
    I think the problem is when/during the car cranking, the regulator doesn't get power, and that force the hub to use the bus power. Switching from 1 source to another can cause the panic hitcup.
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  8. #8
    Registered User vfinterceptor's Avatar
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    Quote Originally Posted by MatrixPC View Post
    Modify the USB cable to the hub: Only use 2 data wire. No need for the power wire when the hub already has it own power. And modify the circuit that provide power to the regulator for the hub.
    I think the problem is when/during the car cranking, the regulator doesn't get power, and that force the hub to use the bus power. Switching from 1 source to another can cause the panic hitcup.
    I was thinking about doing that as well. I wanted to get a few opinions first as I'm not very experienced with this type of modification. It seemed logical to me though. Power feeding back through the wire, cut the source. Check.

    Thanks for the suggestion. Makes sense to me!
    I'll mod the wiring tomorrow and hopefully that fixes the prob.

    I was also considering adding a diode to prevent power feeding back through the usb. Same effect as cutting the power wire I guess.

    cheers

    BJ

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