Tjaart van der Walt wrote:
>
> Eric Smith wrote:
> >
> > Tjaart van der Walt <tjaart@WASP.CO.ZA> wrote:
> > > I built a similar circuit to keep our cat off our furniture.
> > > I used an IR beam with a piezo sounder. It worked only for a
> > > short while. I then discovered that my wife felt sorry for
> > > the cat and disabled my "electronic feline educator". So much
> > > for technology...
> >
> > Time for a PIC-based "electronic wife educator".  Of course, it will
> > probably have to be much more sophisticated than a feline educator.
>
> I feel another OT coming on... <G>
>
> The "electronic wife controller" has already been developed with
> opamps. The two inputs are commands (inverted input), and money
> (non-inverted input). Use compliments as Rf, and socks on the
> floor as Ri.
>
> Avoid rail-to-rail output opamps.

  Good safety tip there!  I'd think it'd be good to use a couple of back
to back Power Zener diodes to limit output to 3/4 rail or so, actually,
after a 10 ohm or so output series resistor, to avoid damaging the
"driven device"!  We're talking a lot of command outputs here, after
all, based on my experiences with my girlfriend <G>

  Mark, mwillis@nwlink.com