On Tuesday 10 June 2003 18:19, Mike Singer scribbled:
> Olin Lathrop wrote:
>
> Where have he "mentioned a 12V battery"? Have look at
>
> his text:
> >  ...
>
> My English is weak, but not to that extent, I hope.
> He has 12V power supply and he'd "like to add a backup
> rechargeable battery  circuit".

Exactly what I thought.  See my other reply from 1 minute ago.

> I also "believe he is linearly regulating the existing
> 12V to 5V for the PIC and other circuitry".
>
> And for "backup" he needs "some reliable and cheap
> solution".

Bingo!

> I suggested 3V battery pack, because it's cheaper than
> 12V pack for the same capacity and needs less contacts -
> reliability.

But why even compare to the 12V?  Can't the battery backup be on the outp=
ut of=20
the 7805 as I drew up in the other email?  Perhaps 6V or 4.8V so that an =
"LF"=20
pic is not required.


> Anyway, "when the main power goes off" regulator is needed.
> Converters from two cells voltage to 5V are very cheap.

Okay.


> Then, he needs something to charge the battery.

This is what I was unsure about.

>  I suggested
> step-down DC/DC or Buck converter from his 12V to battery's
> 3V. Or even better from mains to 3V - STM Viper or TOPSwitch
> for example.
>
> That's a solution. You think that just telling him to
> replace 7805 voltage regulator with a DC/DC converter
> helps him very much, don't you?
>
> Mike.


Actually Mike, I agree with your interpretation, so your English is actua=
lly=20
quite good, or mine's really bad too :-)

Cheers,
-Neil.

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