Infrared proximity sensor made by Sharp. Part # GP2Y0A21YKhas ananalog output that varies from 3.1V at 10 cm to 0.4V at 80 cm. The sensor has aJapanese Solderless Terminal (JST) Connector. Infrared Proximity Sensor -Sharp GP2Y0A21YK is a distance measuring sensor unit, composed of anintegrated combination of PSD (position sensitive detector) , IRED (infraredemitting diode) and signal processing circuit. The variety of the reflectivityof the object, the environmental temperature and the operating duration are notinfluenced easily to the distance detection because of adopting thetriangulation method. This device outputs the voltage corresponding to thedetection distance. So this sensor can also be used as a proximity sensor.