Hi all,

A few years ago I made a few copies of a project of mine. One of the
things that it did was to read a slide pot via ADC and send the value
via serial. When I built them, they were solid, meaning that if I
didn't move the slider, the value stayed consistent.

A few months ago I saw a few of them still in action, and the values
were...fluttering a bit. So even if the slider was not being moved,
the value transmitted fluctuated a bit around where it should be (say
by about 1-2% in each direction). I didn't have much time to
troubleshoot them, so I didn't take very good notes. Consequently I
don't remember precisely what happened. I know I replaced the slide
pot with an used one, but that didn't fix the problem. I replaced the
slide pot with a fixed resistor, but I don't recall what happened
there. A vague recollection is that it fluctuated a bit too, but I
can't be certain. I tried adding capacitance to the power bus, but
that didn't do anything. I tried a cleaner power supply, but no dice
there.

In the end I solved this with firmware, I basically filtered the
results. However that lost me a bit of precision on the slider, and it
meant it had to move more before it was registered.

I originally had this set up as a simple voltage divider with a series
resistor to protect the input pin if the slider was at one extreme or
the other and the pin was accidentally set to output.

I'm about to use the ADC again, this time to read a rotary pot. I
could connect it the same as last time, but before I do, I'm wondering
if there's a better way to do this that will result in longer term
stability. I can't help shake the feeling that the way I connected
things was partially to blame.

Any thoughts?

Thanks!

Josh
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