Completed assembly with with IR LED and photo transistors (two additional transistors tied with the photo transistors in a Darlington configuration drive negative pulses are on breadboard to the right) harvested from small circuit board position detectors (Omron) and mounted 24" apart in the PVC barrel seen at bottom of photo. Wiring between barrel and circuit board uses a standard cat5 connector that can be used for extension) Running the clock at 93Hz measured (end counts on display of 4 and 5) and 8106Hz calculated (end counts of 377, 433, etc), we fired a cork under human air pressure and found consistent results measuring speeds between 37 and 46 feet/second. We'll hook up the rest of the air cannon and air tank after lunch! Hard to see but the blue decoupling caps are from my days working at Raytheon....some time ago...
