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Limitations on a AC powered usb2 hub??

  • 21-02-2006 2:58pm
    #1
    EireRoadUser
    Closed Accounts Posts: 650 ✭✭✭


    I am wondering what exactly i can't connect to a ac powered hub
    I connected an ext hard drive,scanner ,printer and multi card reader.

    I had to disconnect the scanner because windows would hang under a high resolution scan.
    My main concern is the hard drive ,is it ok to run it off a hub or could i damage it .
    The reason all the stuff is connected like this is because I have this gear on a seperate desk.
    Any reply would be appreciated
    cheers


Comments

  • #2
    netman
    Closed Accounts Posts: 1,201 ✭✭✭netman


    Well normally USB hubs would support up to 127 devices.
    I have yet to see or hear of anyone reaching that theoretical limit though :)

    The hardware that you mention, is it self powered or bus powered?
    Most USB hard drives and scanners that I've seen have their own power adapters and only use the USB connection for data.

    Also, the hub might have a switch for bus or self power, for example look at this one:
    usb2_4port_hub_bus_switch.jpg

    Even if you connect the AC adapter you still need to turn the switch to let the hub know it's there. Pretty flawed design if you ask me.

    In terms of power, the hub should provide 500mA on each of it's ports.
    If your devices are bus powered you should check that they do not exceed those power requirements.


  • #3
    EireRoadUser
    Closed Accounts Posts: 650 ✭✭✭EireRoadUser


    Cheers for the reply ,
    The hard drive has it's own external 12v supply, the hub has no ac switch and is permanently on i.e the card readers power light stays on after shut down.

    Each folder on the external drive has about 15-20gigs of phots in it, so when i open a folder theres a big call on the bus.
    So i was thinking if the call is lost on it's way through the bus and the drive gets another call from windows while the drive is still spinning, could this happen???


  • #4
    _CreeD_
    Registered Users, Registered Users 2 Posts: 4,162 ✭✭✭_CreeD_


    The drive is a relatively intelligent device, it's own controller board will prevent any problems due to contention.


  • #5
    EireRoadUser
    Closed Accounts Posts: 650 ✭✭✭EireRoadUser


    Praise the lords for the boards :D


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