This is the well-known analog line follower (tracker) by sparkfun. It is called redbot sensor line follower. The line sensor module works on the principle of reflected light. The QRE1113GR Reflective Object Sensor emit infrared light and detect the reflected part from any nearby line or object.
Since black lines absorb the light (no reflection) while white lines reflect the light, then by measuring the difference in the amount of reflected light the sensor can detect the difference between the black and white lines easily.
- Operating voltage: 5.0
- Analog output.
- Optimal sensing distance: 3 mm
- Maximum sensing distance: 10 mm