Other ideas for Arduino electric eye

notes

5/2014 – check out musical stairs project for eventual solution: https://reactivemusic.net/?p=12300

original post

Infrared reflectance sensor – no idea whether this can be focused to a beam

http://www.ebay.com/itm/Infrared-Reflectance-Sensor-Sensor-Shield-Arduino-compatible-/170842956075?pt=LH_DefaultDomain_0&hash=item27c708a12b

IR detector emitter data

http://www.me.umn.edu/courses/me2011/arduino/technotes/irbeam/irbeam.html

Tachometer circuit

http://www.pyroelectro.com/tutorials/tachometer_rpm_arduino/

Long range beam

http://pcbheaven.com/circuitpages/Long_Range_IR_Beam_Break_Detector/