Encoder for Pololu Wheel 42x19mm [145]

his quadrature encoder works with our micro metal gearmotors 42×19mm wheel and extended bracket to measure the rotation speed and direction of the wheel. With twelve teeth on the wheel the system provides a resolution of 48 counts per revolution which corresponds to a linear resolution of just under 3 mm or 1/8".

This quadrature encoder board is designed to work with Pololu micro metal gearmotors by holding two infrared reflectance sensors inside the hub of a Pololu 42×19mm wheel and measuring the movement of the twelve teeth along the wheel˙s rim. The two sensors are spaced to provide waveforms approximately 90 degrees out of phase allowing the direction of rotation to be determined and providing four counts per tooth for a resolution of 48 counts per wheel rotation. Each analog sensor signal is fed to a comparator with hysteresis to provide glitch-free digital outputs. The compact layout of the board fits all of the components within the envelope of the hub and tire allowing the board to be mounted between the motor and a chassis. The encoder is calibrated for operation from 4.5 V to 5.5 V but it can be recalibrated for operation at 3.3 V.

Example code for the encoders is provided with the Pololu AVR Library. The example shows how the encoders can be used with AVR-based robot controllers including the Orangutan Robot Controllers and the Arduino platform.

For a larger motor with an integrated higher-resolution quadrature encoder see our 37D mm metal gearmotor with 64