[Server-devel] 12 Volt power system for School Servers.

[David Farning]

Thanks guys,

I'll start playing tonight.


On Wed, May 29, 2013 at 5:48 PM, Sameer Verma <sverma at sfsu.edu> wrote:

> On Wed, May 29, 2013 at 3:26 PM, James Cameron <quozl at laptop.org> wrote:
> > On Wed, May 29, 2013 at 04:51:47PM -0500, David Farning wrote:
> >> Any thoughts on powering the AP?
> >
> > They are all different.
> >
>
> Yep. The one we use in Bhagmalpur (India) and in Jamaica is the
> Ubiquiti Picostation2 unit that runs off a PoE injector. Ours run off
> 110/220V AC, but an AP that can run over 48V PoE can use a DC-to-DC
> PoE unit to power it from a 12V battery source.
>
> cheers,
> Sameer
>
> > First, select an AP that says it has a 12V input.
> >
> > I would record the voltage without load emitted by the power supply
> > supplied by the manufacturer.  This is a known maximum voltage that
> > the AP can take.
> >
> > Then I would record the voltage on load.  This is a known minimum
> > voltage.
> >
> > Then I would record the input voltage specifications of the access
> > point using the manufacturer's documentation.  This is usually a
> > typical voltage, but sometimes they include a maximum or minimum.  If
> > there was no documentation, I'd ask them, though perhaps with no great
> > expectation of success.
> >
> > Taking the minimum and maximum of those three values, I'd compare them
> > to the lead-acid battery charge cycle operating range of 10V to 15V.
> >
> > If there remains any doubt (e.g. they haven't specified a maximum), I
> > would attach the AP to a variable power supply and gradually ramp it
> > up to 15V, checking for sudden drop of current (a blown fuse), or
> > excessive operating heat.
> >
> > Once I'm happy, I would cut the cable as far from the device as
> > possible, and reterminate it there.  Before cutting, I would discharge
> > the power supply capacitors ... saves wear and tear on wire cutters.
> >
> > If the AP was USB powered Wifi dongle, the problem goes away.
> >
> > --
> > James Cameron
> > http://quozl.linux.org.au/
> > _______________________________________________
> > Server-devel mailing list
> > Server-devel at lists.laptop.org
> > http://lists.laptop.org/listinfo/server-devel
> >
> >
>



-- 
David Farning
Activity Central: http://www.activitycentral.com
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