Jerry Ethridge wrote:
>
> > D. L. Davis wrote:
> >
> > I built an altimeter with a PIC14000 which I have in bench test now.  I am
> > using the 16 bit A/D of the PIC14000 to measure voltage from an air pressure
> > sensor.  It is used to control an autopilot, and the PIC runs the autopilot
> > servo too.
> >
> > Everything works great with one big exception.... the PIC is extraordinarily
> > sensitive to light!  The logic all functions fine and is unaffected by
> > light, but the A/D measurement is strongly influenced by ambient light on
> > the chip.  I'm using a JW part now, with tape over the window.  But even
> > with tape over the window, I can effect the A/D count by an order of
> > magnitude just by shining a flashlight on the PIC from across the room.  I
> > have replaced the little red sticker tape that came with the part from
> > Microchip with double layers of black tape, which improves the A/D
> > stability, but only to about 6 or 7 bits, nowhere close to the 16 bit
> > resolution.  If I control ambient light carefully, it still moves around
> > randomly in the least significant 9 or 10 bits.
> >
> > (rest deleted for brevity)
>
> Keep in mind that if you are using a silicon based pressure sensor,
> it will also be sensitive to light. I have seen several altimiters
> built for model rockets which had to use light sheilding on the
> pressure sensor.
>
> Just one more thing to watch out for!
>
> Jerry
In a robot sensor experiment I learned practically nothing on or around
my bench could totally block the IR emission's from a simple tv remote.
not to mention the sun. Metal worked. Tony M.