At 05:51 PM 1/24/02 +1300, James Fitzsimons wrote:
>Hi all,
>
>Just thought I'd jump in on this Thread...
>
>Lawrence Lile wrote:
> > I've just been working on battery chargers for a mowbot application.  Been
> > using NiMH batteries, and a MAX712/713 battery charger IC.   Got a nice 2
> > amp charger working on a 2 amp-hour battery, pretty much straight off the
> > app notes in the datasheet.
>
>I am in the middle of doing the very same thing, however I wanted to add a
>rotary switch to my charger that would make the number of cells selectable
>between 6 and 9. The thing is there are 4 points in the basic circuit that
>need altering depending on the number of cells, these being R1, Rsense, PGM0
>and PGM1. Any suggestions on how I might alter all of these values by
>turning one switch?

At the risk of igniting a flamewar..
The max charger is a little under-wonderful for NIMH batteries.

Atmel has a reference design, with source, for their Tiny-15 as an NIMH
charger. Much more flexible, and of course you could implement a single pin
input to select parameters.  I'm using this in a more complicated design
where the main CPU pulls diagnostic data from the tiny, and tells it
exactly how it wants the next charge to be done.

The tiny version is also about $1 less than the max-based version.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.