OT: Something to cut/restore power to peripherals when PC shuts down/powers up?

Discussion in 'Asus' started by Donald Gray, May 1, 2005.

  1. Donald Gray

    Donald Gray Guest

    Hi Pete
    There is a power strip with (I thing) 6 sockets. Plug the computer in
    one socket and it senses when the current being drawn by the computer
    drops below a certain point and it hen kills the power to the other
    sockets in the strip. It can tell the difference between a computer
    gone to power save (sleep) mode and Off.

    They are available in the UK but I cannot remember the retailer - PC
    World, Dixons, Currys etc...
    Regards

    --
    Donald Gray
    Putting ODCOMBE on the Global Village Map!
    www.odcombe.demon.co.uk
    You do not have to email me, but if you wish to...
    Please remove the SafetyPin from my email address first
    Thanks
     
    Donald Gray, May 1, 2005
    #1
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  2. Donald Gray

    Paul Guest

    I tried a search on "current sensing" "power strip"
    as two terms (include the quotes), and there are still products
    being offered. Try your favorite search engine. Here
    are the first two I found:

    http://www.sousley.com/280/0121.htm

    http://www.smarthomeusa.com/Shop/Hardware-Cable/Item/LCG1/

    The only thing to watch for here, other than the quality of
    the designs, or whether the layout of the strip is "brick
    friendly", is that the current flow from a sleeping computer
    is not likely to be sinusoidal. The current waveform becomes
    more regular looking at high load, but not at low load (during
    sleep for example). I've tried measuring sleep current with my
    clamp-on ammeter, and even though my meter claims to be
    "true RMS", I don't get correct readings from a sleeping computer.
    (If I place an electric kettle on the same circuit as the
    sleeping computer, and measure the summed current of the two
    loads, then subtract the kettle by itself, the difference works
    out to being closer to the correct answer, than just measuring
    the computer by itself.)

    One poster here, complained that his current sensing strip
    didn't work properly with his computer.

    You would really want a product, where the sensitivity was
    adjustable, or the designers recognize that the controlling
    device will be a sleeping computer. A sleeping computer can
    draw up to [email protected], depending on how many USB devices are
    receiving cable power while the computer sleeps. If the power
    supply is only 50% efficient at making +5VSB, the wall plug
    sees a 20W load. Your strip will have to recognize a sleeping
    computer with load between say 5W to 20W, as "off".

    You can look at ATX power supply input waveforms here. There
    are ATX supplies without PFC, power supplies with passive PFC,
    and power supplies with active PFC. The power supply with
    active PFC has a near to sinusoidal current comsumption. What
    I cannot tell you, is whether the active PFC power supply
    continues to be sinusoidal at low currents, like when only
    +5VSB is made during computer sleep. It could be, that a
    PSU with active PFC, will work more reliably with a current
    sensing strip, than your average non-PFC power supply.

    http://www.xbitlabs.com/articles/other/display/psu-methodology_9.html

    In any case, this will be a pretty expensive experiment, if
    the payback is through a reduced power bill.

    There are, of course, more high tech AC control technologies,
    like X-10 controllers, that allow control remotely of appliance
    loads throughout a house. I had a friend who had a whole house full
    of X-10 switches, and the only device that was not switchable,
    was his refrigerator :)

    Paul
     
    Paul, May 1, 2005
    #2
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  3. I've got a half-dozen USB2 and FirwWire devices hanging on my PC.

    Just plugging everything into a power strip and then plugging the strip into the
    UPS works....sort of... but it seems like there ought tb something out there
    that does the job automagically.

    This would appear tb a legitimate UPS function....UPS knows when there's a load
    above a certain level on a specified plug, then it cuts/restores power to the
    others accordingly.

    Seems like many years ago, there were power strips that did that - sensing the
    load on a pass-through plug and turning the other on/off.

    Anybody know of anything?
     
    (Pete Cresswell), May 1, 2005
    #3
  4. Donald Gray

    DaveW Guest

    Not that I know of.
     
    DaveW, May 2, 2005
    #4
  5. Per Paul:
    Thanks for all the research and background info.

    Fortunately, sleep mode is not on my 'Must' list.

    Just ordered the product from SmartHome. Sounds promising...or at least thier
    spiel is impressive...
     
    (Pete Cresswell), May 2, 2005
    #5
  6. Donald Gray

    Jerry Peters Guest

    Sears sells a unit for power tools to turn on a dust collecting system
    automatically. Don't know what the minimum current is though. It's
    about $20 US in the hardware department.

    Jerry
     
    Jerry Peters, May 2, 2005
    #6
  7. (Pete Cresswell), May 3, 2005
    #7
  8. Donald Gray

    Paul Guest

    That is exactly what you want.

    Paul
     
    Paul, May 4, 2005
    #8
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