Ultrasonic sensor for 2015 game

[GeeTwo]

Affordable ultrasonic sensors that I found had too large a (what we call in underwater active sonar) "direct blast range". That is, you cannot get any data inside of ct/2, where c is the speed of sound, t is the duration of the pulse, because you are sending out signal at that point. Even low end bistatic sensors (separate transmitters and receivers) had too long a minimum sensor range. We had rather better experience this year with Sharp optical range finders and (when you want really short but nonzero ranges), capacitive proximity detectors. Especially if you have an active intake, nothing beats a good old physical contact limit switch that protrudes just beyond a physical stop, or is located out-of-line with the game piece.