[geeks] 9v battery meter

[Kurt Huhn]

Dave McGuire <mcguire at neurotica.com> wrote:

> On Friday, January 10, 2003, at 11:51 AM, Kurt Huhn wrote:
> > I'm wanting to build a simple 9v battery meter using an array of green,
> > yellow, and red LEDs.  However, I can find very little online about 
> > how to
> > build one that's *simmple*.

<chip snip>

> 
>    The problem is, though, the discharge profile of most batteries is 
> far from flat and linear...many batteries (depending on their 
> chemistry) will maintain very close to ideal cell voltage until they're 
> within a few percent of being depleted, then the cell voltage will drop 
> very rapidly.
> 

Bummer.

>    So...with that in mind, it might actually be better to get a PIC 
> processor with an on-chip A/D converter and drive a bunch of LEDs from 
> that.  That'd be dead simple (and fun) to build and write the little 
> smidgen of firmware for, and that way you can simply build a 
> translation table in memory to map the incoming A/D values to the LED 
> scale based on the battery chemistry in question.
> 

Way more time than I wanted to devote to this - a project that really has no
more value than creating blinkenlights (at least to me).

Oh well, maybe just a chaser for the blinky effect unless I could do
something else.  I recall seeing a meter that used a bunch resistors for
this, but if what you say about the output of batteries is correct, this
wouldn't work for most cells.

Nuts.

-- 
Kurt
kurt at k-huhn.com