> >I am working on a project to count the revolutions on a rotating
> >wheel/disc.The sensor is going to be an optically coupled interrupter
> >module.
> >
> >I intend using the 16F84 pic to convert the pulses from the opto
> >interrupter to a velocity figure and distance travelled for display on
> >an LCD readout.
> >
> >If anybody has some info on this type of circuitrysoftware, I would be
> >most appreciative.

My two cents,

About calibration;
------------------
Make the software in some way that you can install a jumper or via
keyboard start a calibration process. This routine will zero the counter
and count pulses until you press that key or remove the jumper, after
travelling a very known and exact distance. The software then will
calculate by itself the relation between distance/count and store it
into an eeprom. That same information would be used later to display the
travelled distance, by simply multiplying that factor by the counted
pulses. This is easier than go into the "rodeo" with wheels sizes and
other factors, and allows the user to recalibrate the unit at any time.

About Pulse Counting:
---------------------
A debouncing routine is easier to do for optical devices.  Just
calculate what is the shortest pulse the sensor can generate, in other
words, what is the highest rpm of the wheel, the window size of the
sensor and so on. Now calculate the same for blocked sensor timming.
Suppose you find out this minimum pulse width to be 2ms and the minimum
blocked sensor time is 4ms. As soon the opto disc sensor receives light,
this pulse starts your interrupt routine, the software will read that
pin during 1.5 ms as fast as possible and can not reads other level than
the valid "lighted sensor". If this happens, than your software will
count one pulse and then will enter in a routine to measure the blocked
pulse for at least 3ms... then you will be sure you counted it right.