using infrared reflective sensor TCRT5000
2, detecting the reflected distance: 1mm ~ 25mm applicable
3, the comparator output signal clean, good waveform driving ability more than 15mA.
4, with multi-turn precision potentiometer adjustable sensitivity adjustment
5, the working voltage of 3.3V-5V
6, the output format: digital switching output (0 and 1)
7, a fixed bolt holes for easy installation
8 small plates PCB size: 3.2cm x 1.4cm

9, using a wide voltage LM393 comparator