2 Pack of Infrared phototransistor based reflectance sensors Great for edge detection and line following applications Also available with Analog output (See options) Measures only 0.3" x 0.5" x 0.1" and weighs 0.23 gram The Pololu QTR-1RC Reflectance Sensor carries a single infrared LED and phototransistor pair in an inexpensive, tiny 0.5" x 0.3" sensor module that can be mounted almost anywhere and is great for edge detection and line following applications. The LED current-limiting resistor is set to deliver approximately 20-25 mA to the LED when VIN is 5 V. The current requirement can be met by some microcontroller I/O lines, allowing the sensor to be powered up and down through an I/O line to conserve power. Because of its small size, multiple units can easily be arranged to fit various applications such as line sensing and proximity/edge detection. The reflectance sensor ships with a 3-pin 0.1" header strip, which can be soldered in the conventional perpendicular orientation or parallel to the PCB. You can also solder wires, such as ribbon cable, directly to the pads for the smallest installation.
