This module can be applied to intellectual robot, obstacle avoidance...
This kit comes with AlphaBot robotic platform (line tracking, obstacle...
Pololu - 3498
They are 2 mm thick with a 9.7 mm diameter, and the hole through the center enables them to securely press-fit onto the 2mm-diameter motor shafts of our 20D mm metal gearmotors (extended motor shaft versions only). The disc consists of ten evenly spaced magnetic poles (five north-south pairs), which allows for an encoder system that offers 20 counts per revolution.