[geeks] 9v battery meter

[Kurt Huhn]

Dave McGuire <mcguire at neurotica.com> wrote:

> > 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.
> 
>    Well, not very accurately.  Most such meters will have three or four 
> LEDs at most, so the inherent nonlinearity of the discharge profile is 
> hidden in the low resolution of the display.
> 

Ah!  my resoltion should be at least 5, I may even do more depending on how
many the LM3914 supports.  LEDs are cheap, and the more lights, the better. 
Even if it only gives a warning when the battery is *close* to discharged,
that's good enough for my needs.

>    The resistors were simply a chain of voltage dividers.  The LM3914 
> chip I mentioned uses this scheme, with the resistor network driven 
> from a voltage reference, and with a comparator at each one...so each 
> LED turns either all the way on or all the way off.
> 

Looking better.  Perhaps I'll stop by Radio Shack after work today.

>    Don't give up on it yet...The PIC circuit really wouldn't be very 
> difficult to build, and it would be fun.  And it'd be a great way to 
> get into PICs in particular and microcontrollers in general, if you're 
> not already.
> 
>    A possibly easier alternative might be a Basic Stamp.  They're even 
> easier to program, and could do this with ease.
> 

Oh! Basic Stamp I could do.  I completely forgot about these, I've even
programmed these beasties years ago.  Is there a good source for Basic
Stamps these days?  I'm off to Google to find project information....

-- 
Kurt
kurt at k-huhn.com