The module consists of an IR LED and a photosensor (phototransistor) pair. The light emitted by the IR LED gets reflected by any object placed in front of the sensor and this reflection is detected by the photosensor(phototransistor). Any white (or lighter) colored surface reflects more than black (or darker) colored surface.
When the reflected light is detected, it produces Digital HIGH (or Binary 1) output on the SIGpin. The on-board LED indicator will also glow. If no reflection is detected or if the object is too far from the sensor, the output on the SIG pin stays at Digital LOW (Binary 0). The on-board LED indicator will be off as well. The detectable range of this sensor is 7.5–40 cm. The module incorporates a Rail-to-Rail Operational Amplifier to amplify the output of phototransistor. There is a potentiometer which can be used to adjust the gain of the amplifier, that is, sensitivity of detection.
With this sensor, you can build the following (but not limited to) applications: line following robots, optical encoders and object counting applications.
Note: This product is mildly sensitive to non-IR radiations also and hence any bright light on photosensor impairs or disturbs IR light detection.