Pololu QTRX-HD-07RC Reflectance Sensor Array: 7-Channel, 4mm Pitch, RCThis Pololu IR LED phototransistor pair is great for precisely identifying changes in reflectance (like line detection). It operates from 2. 9 V to 5. 5 V and offers dimmable brightness control independent of the supply voltage. In general, the closer the object, the higher the contrast between light and dark readings, but high reflectance objects are generally detectable out to around 40 mm. This version features a high performance, low current QTRX