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Thread: UPS - small load, long runtime and Linux-friendly?

  1. #1
    Join Date
    Feb 2008
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    111

    Default UPS - small load, long runtime and Linux-friendly?

    Greetings, all.
    Does anyone here have experience with UPSes powering small loads for long run-times? I notice that almost all marketing materials list run-time "with a PC" (usually in minutes), not mentioning what power rating they assume the PC to be, and avoid listing how much energy the UPS can actually deliver, at least on average (they list battery's V and Ah, but I expect there to be some losses on the inverter, etc.)

    I'm looking into putting my small home server (Atom N270) and some network hardware, on it. The total load is 30-35W at most. However, I'm looking into powering this load for at least 2 hours, and have enough energy left for running the 5 W network terminal and the server in S3 sleep state (1W) for at least another 4 hours. I'd be grateful if someone can give me a hint how much VA (or other marketing BS) I need to get the 80 or so Wh I need to have at disposal.

    Looking through the web and old topics in this forum, I get the idea that NUT is the software to go for when it comes to UPS and EATON is the brand of choice for supporting the project. Either way, I think all I'll need from the UPS is an immediate notification of power outage, without the PC polling it constantly or taking too much CPU power.

    Any hints, recommendations, etc?

  2. #2
    Join Date
    Jan 2011
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    24

    Default

    If I were building such a setup ~ heres what I'd do;

    cross-compile APCUPSD/NUT for the ROUTER, and use the networked status update for the PC.

    1. Alot of cheap routers have USB ports these days.
    2. Many of can run embedded linux
    3. If the PC is off - the other devices have no warning of impending doom...

    I'd say you need atleast 360 VA ~ but due to outright distortions of truth from low-grade mfg. I'd use 500 VA units.

    You know - if the PC needs to always be powered;

    Use a DC-DC ATX PSU!

    http://www.mini-box.com/micro-UPS-load-sharing

    No wasteful conversion of AC-DC-AC-DC again.

  3. #3
    Join Date
    Feb 2008
    Posts
    111

    Cool

    Quote Originally Posted by Melchior View Post
    If I were building such a setup ~ heres what I'd do;

    cross-compile APCUPSD/NUT for the ROUTER, and use the networked status update for the PC.

    1. Alot of cheap routers have USB ports these days.
    2. Many of can run embedded linux
    3. If the PC is off - the other devices have no warning of impending doom...
    Sorry, I forgot to mention that the router in question is actually a PC built around Intel's Johnstown board, so no cross-compiling needed. Also, the reason I want to keep it awake has more to do with me using it as Internet-accessible network storage, so it has to be awake when I'm away.
    I'd say you need atleast 360 VA ~ but due to outright distortions of truth from low-grade mfg. I'd use 500 VA units.

    You know - if the PC needs to always be powered;

    Use a DC-DC ATX PSU!

    http://www.mini-box.com/micro-UPS-load-sharing

    No wasteful conversion of AC-DC-AC-DC again.
    That's actually a great idea, for a different reason - the Johnstown board runs directly off 12V DC, and so does the ONT. Right now, that power is provided by 3 AC adapters (the PC has two - one for disks and the other for everything else). I could basically hook both devices onto this one, and purchase as many batteries as needed. It takes 13-18V, just perfect to use that old 60W laptop brick that has lied unused for years now
    Now if only I can find a seller in central Europe...

  4. #4
    Join Date
    Feb 2008
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    Default

    And of course, the big question is - how do I get a notification of power outage? Might be useful to shorten the spindown delay on HDD, stop the BT client and eventually enter S3 when an outage hits.

  5. #5
    Join Date
    Jan 2011
    Posts
    24

    Default

    Simple, the picoUPS has 3 diodes displaying the status.

    What needs to be done is wire to the "on Battery Power" diode to a port of a RS232 port on your PC, and use 'DUMB' RS-232 UPS protocol (e.g. Classic UPS) to indicate its on battery/AC.

    http://www.linuxjunkies.org/html/UPS-HOWTO.html#s3

    There may be a small circuit needed to convert the voltage levels.
    (e.g. ~2 volts from LED to 0V on the DCD RS232 line... check the diagram)

    Some cheap / simple parts will work for this like a Opto-isolator, resistors, a DB-9 connector...

    mini-box has some resellers also (in Europe):

    http://www.mini-box.com/site/resellers.html

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