[Power] Power Digest, Vol 13, Issue 2

[George Hunt]

Thanks Nicholas for the links,

I got so much useful information the last time I posted here, I want to try
again:

Does anyone have experience waking up an XO via the RTC?  Manual entries
for rtcwake make it sound pretty easy. But there's no real substitute for
experience.

The reason for this request:

The XS, running on the XO, really only needs to be running during the 8-10
hours of the school day. A 40 watt-hour daily load seems more solar power
friendly.

George


Message: 1
> Date: Wed, 4 Jul 2012 07:46:57 +1200
> From: Nicholas <independentcommercial at gmail.com>
> To: power at lists.laptop.org
> Subject: Re: [Power] Power Digest, Vol 13, Issue 1
> Message-ID:
>         <
> CAK8HaSJ39qB6CX7mMoQp8HXvmo0T+5956PtgUWzSFonQki5TVA at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Quoting this:
> When I first saw this post, I couldn't think of an application that I might
> be directly involved in.  Since then I've learned that OLPC-au is actively
> looking at XO-ARM as a school server.  Up until now, I've been thinking
> that XS's need 100 watt panels. But I just measured
> XS-ARM at 4 watts.  With an extra 2 watts for a USB 3G modem, a 30 watt
> panel, and a 50 amp-hr deep cycle battery seem feasible.
>
> End of quote
> 30w of solar probably will not be enough solar for an always-on
> application..
> Damon has done quite a bit of work running his sheevaplug off-grid
> solar complete with power logs. Here is his write-up
> http://www.earth.org.uk/note-on-SheevaPlug-setup.html
> He is also an admin at fieldlines.com
> These are 5w Arm based servers.
> But I seem to remember him posting on fieldlines.com that 120w and
> 40ah battery was not enough solar and storage to keep a 5w always-on
> device running happily in winter. I know, the difference might be that
> he is in London where the sun can be lost for weeks at a time. He did
> do an upgrade to a 200w panel for 2009 Winter as per the article
> linked above. This is a 24/7 application which can be a different
> application to the one mentioned by the OP. The power logs should be
> available somewhere and might be useful for your school server
> project.
>
> ...Also on fieldlines.com there is a guy named ghurd, Glen Hurd who
> makes and sells cheap rugged power regulator kits. They can be
> configured several different ways, as wham-bang on off regulators as
> well dump load converters as well Low Voltage Disconnect. They are
> 14.5US I think and shipped anywhere for 3. I've had a couple and they
> are good robust converters with adjustable hysteresis. ghurd.info can
> be used to order the converters. I have no connection with his
> business other than having used the converters in my own small
> systems. They were also a great learning device for when designing a
> small micro-solar system..
>
>
>
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