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Subject: Re: [Sven.Radke@gmx.de: battery faq]
From: Uwe Freese (mail_at_uwe-freese.de)
Date: 2002-09-08


Hello Björn,

Björn Stenberg wrote on Sunday, September 8, 2002, 3:05:52 PM:

BS> > A good circuit for powering from a car battery or other source
BS> with a higher voltage would be a 600 mA fuse and a 9V regulator like
BS> a 7809 of your favourite manufacturer in series.

BS> it's that if u use just a 7809 the voltage is about 8 volts, I
BS> experienced it 2 times (1 a while ago but I remembered when the 2nd
BS> spit out just 8 volts)

BS> the 7809 needs a lil buffering the energy, I made this witch adding a
BS> 470uf/25V condensator to input and output

I think the problem is that one should use a low drop voltage regulator.
A standard one needs 2-3 volts more input than output voltage. And maybe
his car battery had less than 12 volts.

But it is useful to have something like a 470uf/25V connected in any
case.

Bye, Uwe.



Page was last modified "Jan 10 2012" The Rockbox Crew
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