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Thread: Powered USB hub 5v feedback

  1. #11
    Maximum Bitrate Mickz's Avatar
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    That explains it as I had a similar problem, I also have a micro controlling shutdown sequences and validating the requested state. Three of my other Microprocessor control systems were leaking a small voltage from the data interfaces ports back into the USB line. As these Micros have to also run independently of the PC system I had to modify the micro code to Monitor USB +5V and switch the data interface to the USB lines off whenever the PC was off. There really are so any things to consider with different installations and hardware. Makes answering a general question so difficult at times but I guess we do the best we can
    Last edited by Mickz; 03-17-2012 at 04:45 AM.
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  2. #12
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    Truth. This install was much more complicated because I included the micro controller. Seriously was a 1 step forward 3 steps back for most of the install. Luckally my arduino does not feed back on the 5 volt.

    I did however find an issue where the arduino would not initialize its usb system if you didn't first power it off of the usb power then apply external power. I tested it about 30 times on the bench and ended up installing a switch in the kick panel of the car to kill power to the arduino in the event I need to reboot the system... After install I found that to not be a problem.. can't explain it. But I did find I couldn't have my lines hooked up from the usb 5v and to the laptop power header or it would cause the issue. I know those were not hooked up during testing...

  3. #13
    Variable Bitrate m2x0p9x's Avatar
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    Isn't there a laptop startup/shutdown controller that uses the Ethernet port to monitor your ignition state? Seems like it might be easier to do that since your having issues with both your hub and the arduino all related to the USB?

  4. #14
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    well, I'm not having issues any more now that I have a good USB hub. Ethernet doesn't supply voltage... how would it monitor Ethernet? I would think the link lines on Ethernet would be VERY low voltage/current.

  5. #15
    Variable Bitrate m2x0p9x's Avatar
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    It doesn't supply voltage. You still need to use a power supply. It uses the Ethernet port to send the startup/shutdown signal. Its powered by your car battery. Good to hear you got it working.

  6. #16
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    Oh, that wasn't ever my issue. I simply ground out the power button the laptop.. that has always worked reliably. I thought about the Ethernet options but frankly find WOL touchy and wouldn't want to rely on it. Grounding the power header is reliable. Some people are not comfortable with soldering to the power header in their laptop.

    The issue was I was monitoring 5v off of the USB to know when the laptop was running or not. The crappy USB hub was feeding 5v back down to the USB port which caused my reference line to read 5v ALL the time even when the laptop was off.

  7. #17
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    i also had the same problem,mine was also powering up the computer(turning it on) !! i got over it by installing a relay that allowed external power to the hub only after the pc was on. i didint searched it for long, but i t might be that the power supply of the car was DC, and the hub was designed to work with AC?

  8. #18
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    Like I said though, for reliability reasons, the USB hub needs to stay powered the entire time the computer is running. In my case, my micro controller powers all accessories including the laptop charger and USB hub 500ms before it pulses the laptop to power on.

    I find that not having the USB hub powered the entire time causes devices to get confused and disconnect.

  9. #19
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    Yes you are absolutly correct on that, it also happens to me. By now i am not using HUBS at all. i'm not sure if even the expensive ones are good.... I run usb cables from the trunk to the front about 5m at least no comfusion that way But, my point was to tell you to check if the hub needs DC or AC to work

  10. #20
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    Oh. All hubs are going to be dc. USB is 5v dc. The AC adapter is external usually if not always. Mine was. I only have 3 USB ports as I'm using a laptop.

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