recycling chargers

ismael schinca ischinca at plan.ceibal.edu.uy
Thu May 13 09:35:20 EDT 2010


Exactly, some load in the 5V rail is needed.
We managed to charge up to 20 XO using a single 680W power supply.
In any case, the total power of the supply is not important, you must check
the 12V rail current rating (and estimate approx 1.5A per XO).
Also, some power supplies have more than 1 12V rail. You must take this into
account. You can be sure that the CPU connector and the PCI-X connector for
the VGA will always have separate rails as those are the bigger power draws
in a PC.

Ismael

2010/5/13 John Watlington <wad at laptop.org>

>
> That is probably a wrong analysis of the problem.
> Many higher power supplies like AT/ATX power supplies don't
> work properly when unloaded.   I bet if you draw a couple of
> amps from the +5V supply, you would find that the +12V supply
> starts working fine.
>
> I used to use car headlights to provide enough load when
> debugging systems which weren't loaded enough to maintain
> regulation.
>
> Cheers,
> wad
>
> On May 13, 2010, at 5:43 AM, Sascha Silbe wrote:
>
> > On Thu, May 13, 2010 at 06:44:34PM +1000, James Cameron wrote:
> >
> >> An ATX or AT switch-mode power supply attached to a set of nine laptop
> >> charging cables.  The power supply is being used as a 12V DC regulated
> >> source.  The original PC power harness cables have been removed.
> > FWIW, I've also used a ATX power supply to power an XO-1, but stopped
> doing so once I discovered why the XO-1.5 would run from it: Being a cheap
> model, it regulated only the 5V rail, so the 12V rail dropped down to 9V
> with a switched-on XO-1 connected to it. The XO-1 barely coped (the power
> light started flickering some time ago, probably due to the power supply
> aging and delivering an even lower voltage than before) and the XO-1.5
> (without MPPT ECO) didn't like it at all (whining noise, LED off).
> >
> > Summary: If you're trying to replicate this setup, make sure your PC
> power supply regulates the 12V rail (just hook up some load and check the
> voltage).
> >
> > CU Sascha
> >
> > --
> > http://sascha.silbe.org/
> >
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-- 
Ismael Schinca
Plan Ceibal - Depto. T├ęcnico - I+D
Avda. Italia 6201
Montevideo - Uruguay.
Tel.: 601 57 73 Int. 2227
E-mail : ischinca at plan.ceibal.edu.uy
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