This is a new version of QRE1113 breakout board that features a digital output; it is capable of measuring the amount of reflection through using a capacitor discharge circuit. What’s great about it is that both systems that works with 3.3V and 5V are can work with it. Also, line sensing can be done when only digital I/O is available.
There are 2 parts that compose the board’s IR reflectance sensor which are the IR emitting LED as well as the IR sensitive phototransistor. Whenever power is applied to the VCC and GND pins, the IR LED which is located inside the sensor gets illuminated. Also, in order to limit the current, 100Ω resistor on-board is placed in series with the LED.
A capacitor having 10nF has an output of the phototransistor tied to it, and the fasters this capacitor discharges, the more reflective the surface gets.
In addition to that, people usually use these sensors in line following robots. Also, since the capacitor discharges faster on white surfaces than black ones, a general rule is that “white surfaces reflect more light than black”.
Note that in case you want to screw the board onto something, there’s a single mounting hole. Besides that, the power input and output pins are brought out to a 3-pin, 0.1" pitch header.
Check out our analog version if you’re interested.