recycling chargers

[ismael schinca]

Sascha, that's correct, once the 5V rail is loaded the 12V rail is properly
(properly depending on the power supply quality) regulated. Apparently,
switched power supplies need a proper load to correctly regulate voltage.
You may try something like 1A in the 5V rail. Be sure to use a resistor
which can tolerate 5W (4,7ohm, 9W for example) !

Ismael

2010/5/13 Sascha Silbe <sascha-ml-ui-sugar-olpc-devel at silbe.org>

> On Thu, May 13, 2010 at 09:24:17AM -0400, John Watlington wrote:
>
>  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).
>>>
>>
>  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.
>>
> In what way is that different from what I wrote? Or are you saying that
> once I draw a certain amount of current from the 5V rail, the 12V one will
> be properly regulated (i.e. keeping the voltage stable at 12V +/- 10%
> regardless of the current draw on the 12V rail)?
>
>
>
> CU Sascha
>
> --
> http://sascha.silbe.org/
> http://www.infra-silbe.de/
>
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-- 
Ismael Schinca
Plan Ceibal - Depto. Técnico - 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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