USB hub with mystery transformer

Discussion in 'Computer Support' started by john royce, Oct 18, 2009.

  1. john royce

    john royce Guest

    Have got a four port USB hub (I O DATA usb-hb4 ) thats really old (ten years
    or more) and it has a transformer to power it a quarter the size of a house
    brick and it is delivering 2.5 amps.

    I'm using another USB hub at the moment a bit younger and it has a much
    smaller transformer ( the size of a matchbox) whose power is not even turned
    on when I use it. But I can still use it quite succesfully for my digital
    camera, portable external hard drive, usb sticks and ipod, etc; with the
    power turned off.

    what is the purpose of these transformers? Using what items would they have
    to be switched on for?
     
    john royce, Oct 18, 2009
    #1
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  2. john royce

    Guest

    "john royce" <> wrote:

    >Have got a four port USB hub (I O DATA usb-hb4 ) thats really old (ten years
    >or more) and it has a transformer to power it a quarter the size of a house
    >brick and it is delivering 2.5 amps.
    >
    >I'm using another USB hub at the moment a bit younger and it has a much
    >smaller transformer ( the size of a matchbox) whose power is not even turned
    >on when I use it. But I can still use it quite succesfully for my digital
    >camera, portable external hard drive, usb sticks and ipod, etc; with the
    >power turned off.
    >
    >what is the purpose of these transformers? Using what items would they have
    >to be switched on for?
    >


    Press your Win-Key+Pause/break key
    select hardware / device manager
    Drop down the usb devices and open them up if closed

    Double click on each Host controller, and view the advanced tab it
    should show 10% bandwidth used (I've never seen it higher).

    I have 5 host controllers so using 50% bandwidth

    Now click on the root hubs reading the power required, above is the
    power available (500 mA per port).

    you want to stay below 100% bandwidth really around 50-80 for the
    stability of your computer and equipment

    Nothing you can really do about the controllers unless you
    disable them*

    With the root hubs you want to stay below the power available, if at
    or above, it's time to use a transformer to help out the USB's power
    supply.

    No link, that's just the way I've always treated the ports.

    After a few times of checking you'll know which ones to keep an eye
    on.

    * I have one of those multi memory card readers, I don't use it and if
    I did it would be just one port, so I have 4 of them disabled (out of
    5) (under storage volumes) to save bandwidth.
    --

    Find Waldo
    http://tinyurl.com/yj8ds74
     
    , Oct 18, 2009
    #2
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  3. john royce

    Whiskers Guest

    On 2009-10-18, john royce <> wrote:
    > Have got a four port USB hub (I O DATA usb-hb4 ) thats really old (ten years
    > or more) and it has a transformer to power it a quarter the size of a house
    > brick and it is delivering 2.5 amps.
    >
    > I'm using another USB hub at the moment a bit younger and it has a much
    > smaller transformer ( the size of a matchbox) whose power is not even turned
    > on when I use it. But I can still use it quite succesfully for my digital
    > camera, portable external hard drive, usb sticks and ipod, etc; with the
    > power turned off.
    >
    > what is the purpose of these transformers? Using what items would they have
    > to be switched on for?


    Some devices draw power from the USB socket. A 'hub' can only draw as
    much as the single socket on the computer can provide, so if you want to
    use a hub with two or more devices that each want to draw the maximum
    amount of power a single USB socket can provide, that hub will need a
    power supply of its own to supplement or replace what it gets from the
    computer.

    Anything that has no battery or mains supply of its own will have to be
    getting power from the USB socket. Scanners are often like that, and so
    are some printers. Some battery-powered gadgets will try to re-charge
    from the USB socket, or at least use the USB power instead of their own.

    An un-powered USB hub is only suitable for use with devices that draw
    little or no power from the USB socket - 'mice' and keyboards for example,
    and mains-powered printers etc.

    --
    -- ^^^^^^^^^^
    -- Whiskers
    -- ~~~~~~~~~~
     
    Whiskers, Oct 18, 2009
    #3
  4. john royce

    ian field Guest

    "Whiskers" <> wrote in message
    news:...
    > On 2009-10-18, john royce <> wrote:
    >> Have got a four port USB hub (I O DATA usb-hb4 ) thats really old (ten
    >> years
    >> or more) and it has a transformer to power it a quarter the size of a
    >> house
    >> brick and it is delivering 2.5 amps.
    >>
    >> I'm using another USB hub at the moment a bit younger and it has a much
    >> smaller transformer ( the size of a matchbox) whose power is not even
    >> turned
    >> on when I use it. But I can still use it quite succesfully for my
    >> digital
    >> camera, portable external hard drive, usb sticks and ipod, etc; with the
    >> power turned off.
    >>
    >> what is the purpose of these transformers? Using what items would they
    >> have
    >> to be switched on for?

    >
    > Some devices draw power from the USB socket. A 'hub' can only draw as
    > much as the single socket on the computer can provide, so if you want to
    > use a hub with two or more devices that each want to draw the maximum
    > amount of power a single USB socket can provide, that hub will need a
    > power supply of its own to supplement or replace what it gets from the
    > computer.
    >
    > Anything that has no battery or mains supply of its own will have to be
    > getting power from the USB socket. Scanners are often like that, and so
    > are some printers. Some battery-powered gadgets will try to re-charge
    > from the USB socket, or at least use the USB power instead of their own.
    >
    > An un-powered USB hub is only suitable for use with devices that draw
    > little or no power from the USB socket - 'mice' and keyboards for example,
    > and mains-powered printers etc.


    The OP seems to be expressing some surprise at the difference between the
    old and new transformers, the old transformer is almost certainly a 50/60Hz
    iron cored transformer, operating at low frequency it needs large inductance
    windings and large smoothing capacitors for the rectifier. The newer
    transformer is most likely a switch mode PSU which switches the transformer
    current at high frequency, this means that a much smaller ferrite cored
    transformer can be used and the smoothing capacitors can also be much
    smaller.
     
    ian field, Oct 18, 2009
    #4
  5. john royce

    VanguardLH Guest

    john royce wrote:

    > Have got a four port USB hub (I O DATA usb-hb4 ) thats really old (ten years
    > or more) and it has a transformer to power it a quarter the size of a house
    > brick and it is delivering 2.5 amps.
    >
    > I'm using another USB hub at the moment a bit younger and it has a much
    > smaller transformer ( the size of a matchbox) whose power is not even turned
    > on when I use it. But I can still use it quite succesfully for my digital
    > camera, portable external hard drive, usb sticks and ipod, etc; with the
    > power turned off.
    >
    > what is the purpose of these transformers? Using what items would they have
    > to be switched on for?


    Each USB controller manages a pair of USB ports. That's why you see
    them in pairs. A total maximum of 500 mA (0.5 A) can be drawn across
    that pair of ports. If you have a device that draws 0.5A from 1 port
    than you can't connect anything to the other port. Attaching an
    unpowered hub to one or both of those ports does not alter the maximum
    current than can be drawn across both those ports.

    The digital camera has its own batteries which you are draining when you
    plug it into a USB port (and why some folks get card readers installed
    in their host so they can remove their camera's memory card and put it
    into their host without having to drain their camera's batteries). USB
    flash drives draw their power from the USB port (although they may have
    a separate power source when slid into a carrier to allow their use
    separately of the host). iPods have their own batteries. Your
    *portable* external USB hard drive probably has its own power.

    Because of the 500 mA combined maximum current draw across the pair of
    ports (for the controller to them), you are limited as to what you can
    connect. Adding a hub doesn't change the maximum current draw. Adding
    a powered hub lets you add more devices (I'd have to go review the USB
    specs to see what are the max number of devices but it's so large that
    I've never been concerned about it since I don't own that many USB
    devices altogether anywhere). For example, you might plug in a high-
    powered USB headphone and that renders the other USB port unusable, but
    not if you use a powered hub.

    The USB hub is probably designed to power itself off if there is no
    current draw from any of its output ports. So you aren't saving any
    power by leaving the power USB hub unpowered. It may even have LEDs to
    show when it has powered up its ports.
     
    VanguardLH, Oct 18, 2009
    #5
  6. john royce

    VanguardLH Guest

    If you decide to get a newer USB hub with a smaller power adapter, be
    sure to NOT get one labeled "bus-powered". That's just a marketing ploy
    to hide they are UNpowered. You probably want a self-powered USB hub
    (unless all your USB devices are themselves self-powered).

    Of course, you could just replace the brick-sized power adapter with a
    smaller one that provides the same voltage and current outputs (it will
    probably run hotter than the brick). However, for the price of the
    power adapter, you could buy a powered USB hub that came with one.

    You may not even need the USB hub to be powered if the total current
    draw across all its ports (to the one USB port and the current draw from
    the paired USB port) are under 500 mA. You could, for example, use
    either an unpowered or powered hub (that is unpowered) to simply
    multiply the number of available USB ports on your host). However,
    unless portability is an issue, it is unlikely that you will monitor the
    total current draw from all attached USB devices across that pair of USB
    ports (and to any hubs attached to them). It is easier to use a powered
    USB hub and have it powered.
     
    VanguardLH, Oct 18, 2009
    #6
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