Pololu 2591 optical encoder for micro metal gearmotors pair pololu 2591 an optical encoder kit that allows the addition of quadrature encoders to an lp mp or hp micro metal gearmotor the kit consists of 2x sensor boards 2x 3 tooth encoder wheels and 2x 5 tooth encoder wheels the assembled system does not exceed the 12 x 10mm cross section of the motors and extends only 5mm beyond the motor end cap the 3 tooth wheel provides 12 counts per revolution and the 5 tooth wheel yields 20 coun