$2.59 PhotoInterrupter Breakout Board
erco
Posts: 20,255
Maybe it's easier to say "Correlation Photoelectric IR Infrared Count Sensor Module" 
For slotted disks. Looks like it has a comparator module onboard.
Use one to make a "tach sensor", or use two (properly spaced) to make a quadrature encoder.
http://www.ebay.com/itm/Correlation-Photoelectric-IR-Infrared-Count-Sensor-Module-/281463232737
For slotted disks. Looks like it has a comparator module onboard.
Use one to make a "tach sensor", or use two (properly spaced) to make a quadrature encoder.
http://www.ebay.com/itm/Correlation-Photoelectric-IR-Infrared-Count-Sensor-Module-/281463232737