Tiny Optical Encoders

These attributes make it an excellent choice for consumer, office, industrial and automotive interior applications ranging from scanners, printers, miniature cameras, and seat adjustment and rear view mirror controls in automobiles.

The AEDR 8400 is smaller than the Avago AEDR-83xx optical encoders, which, up to now, were the industry's smallest. It provides two-channel quadrature output, a count frequency up to 15 kHz and -20 to +85 C operating temperature range. The AEDR-8400 is also designed for low power consumption, operating from a single 2.8 V (nominal) supply, drawing 12 mA (including 6 mA LED current), typical. Its lead-free packaging complies with the European Union's directive for Restriction of Hazardous Substances (RoHS). Beginning July 1, based on legislation enacted by the EU, manufacturers are responsible for eliminating the products that contain any or all of six banned substances.

Compared with magnetic encoders, Avago's reflective optical encoders offer higher resolution (magnetic encoders are typically limited to approximately 150 LPI raw resolution). In motor control applications the magnetic encoder's lower resolution can cause torque ripple that increases motor vibration. Magnetic sensors also generate magnetic fields, which may call for magnetic shielding to prevent interference with nearby components.

The Avago AEDR-8400 series of reflective encoders consist of an LED light source, a special photodetector IC with integrated electronics, and integrated optics. They can be used with a reflective code wheel to sense rotary position and velocity, or with a linear code strip to sense linear position and velocity. The devices provide two-channel digital outputs in quadrature, which provides both count and direction information. They are insensitive to axial play and maintain performance and accuracy over a wide variation in the gap between sensor and code wheel or strip.