Seeed grove motion sensor control and actuator modules seeed studio 101020175 the grove ir proximity sensor from seeed studio uses an infra red emitter and photo transister pair to detect the proximity of reflective objects an onboard potentiometer can be adjusted to set the detection threshold and once that threshold is exceeded the sensor pulls its ouput line low 0v dc to make your job of adjusting the threshold easier theres an onboard led which lights when the sensor is triggered