Motor Shaft Encoder Trade-Off Study

Introduction:

The purpose of this trade-off study is to compare optical encoders and hall effect, magnetic, encoders. Some of the requirements for the encoder are reliability, power consumption, size, ease of mounting to motor, and cost.

Discussion:

There are two different methods of counting for optical encoders. One method of counting uses IR LEDs, infrared light emitting diodes, to emit and reflect light off the rotating encoder wheel which is then received by a phototransistor and creates an analog signal. [1] The second method, emits IR light through a spinning disk with slits to allow light to pass through to the receiver on the other side. [2] For use with the micro gearmotor and GM6 motors, the disk encoders with the phototransistor are required to mount onto the rear shaft.

The Hall Effect encoder uses a multiple pole magnetic disc to count the rotation of the rear shaft which moves at the same speed as the main shaft. The half effect sensor uses induction to convert the magnetic field from the magnet into small voltage. The voltage generated from the sensor is then amplified and read as a digital output. [3]

The Hall effect magnetic encoder is a better option than the optical encoder because the hall effect sensor produces a digital voltage output and requires less computation than the optical sensor. However, the optical sensor has the option of changing the count per revolution whereas the hall effect encoder does not have this option [4].

Specifications: