Seeed grove motion sensor control and actuator modules seeed studio 101020029 the grove infrared reflective sensor from seeed studio allows your pi or arduino to sense the brightness reflected from a surface this can be applied to sensing the presence or absence of an object for example whether a door is open or closed or maybe as a contactless end stop for a cnc machine or it can be used to detect changes in brightness such as black and white markings on a rotating disc a very useful