Getting position with encoders

There are two main types of rotary encoders: incremental or absolute. Incremental rotary encoders use a rotating disk connected to a shaft and positioned between a light source and a photo sensor. Multiple slits arranged uniformly around the perimeter of the disk allow light to pass to the sensor in patterns of pulses representing motion characteristics. Applications requiring even more detailed motion data or an added level of protection, if power is lost, would benefit from an absolute encoder. Like incremental encoders, absolute encoders are center mounted to spin with the motor shaft between a light source and a photo sensor. Instead of using uniformly arranged slits like an incremental encoder, absolute encoders use an intricate arrangement of unique openings over a much larger surface of the disk. These interrupt the light signals in patterns that a detector chip can read as higher-fidelity representations of every angular position of the stroke – even without a homing device.