Rotation speed sensor for Tank Chassis

PID for tank chassis.

Drive sprocket has added holes for 2mm neodymium magnets.
Servo mount has an added mount to hold a hall sensor.

Everytime a magnet lines up with the hall sensor, the hall pulls it's output low.

I'm counting pulses for a set period of time to equalise left & right motor speeds.

Also works to make accurate turns easier by counting pulses.