HEDS-978x Series Small Optical Encoder Modules Data Sheet Description Features The HEDS-978x series is a high performance, low cost, Small size optical incremental encoder module. When operated in Multiple mounting options conjunction with either a codewheel or codestrip, this Linear and rotary options available module detects rotary or linear position. The module consists of a lensed LED source and a detector IC enclosed No signal adjustment required in a small C-shaped plastic package . Due to a highly colli- Insensitive to radial and axial play mated light source and a unique photo detector array, the -40 C to +85 C operating temperature module is extremely tolerant to mounting misalignment. Two channel quadrature output The two channel digital outputs and 5 V supply input are TTL compatible or 5.0 V CMOS compatible accessed through four solder-plated leads located on 2.54 mm (0.1 inch) centers. Single 5 V supply The standard HEDS-978x is designed for use with an 11 mm Wave solderable optical radius codewheel, or linear codestrip. Other options are available. Please contact factory for more information. Package Dimensions Mounting Option 50 - Standard (Baseplane Mounting) Contact Factory for Detailed Package Dimensions ESD WARNING: Normal precautions should be taken to avoid static discharge.Applications Theory of Operation The HEDS-978x provides sophisti cated motion detection The HEDS-978x is a C-shaped emitter/detector module. at a low cost, making closed-loop control very cost- Coupled with a codewheel, it translates rotary motion into competitive Typical applications include printers, plotters, a two-channel digital output. Coupled with a codestrip, it copiers, and offi ce automation equipment. translates linear motion into a digital output. As seen in the block diagram, the module contains a single Note: Avago Technologies encoders are not recommend- Light Emitting Diode (LED) as its light source. The light is ed for use in safety critical applications. Eg. ABS braking collimated into a parallel beam by means of a single lens systems, power steering, life support systems and critical located directly over the LED. Opposite the emitter is the care medical equipment. Please contact sales representa- integrated detector circuit. This IC consists of multiple tive if more clarifi cation is needed. sets of photodetectors and the signal processing circuitry necessary to produce the digital waveforms. The codewheel/codestrip moves between the emitter and detector, causing the light beam to be inter rupted by the pattern of spaces and bars on the codewheel/ code strip. The photodiodes which detect these inter- ruptions are arranged in a pattern that corre sponds to the radius and count density of the codewheel/code- strip. These detectors are also spaced such that a light period on one pair of detectors corresponds to a dark period on the adjacent pair of detectors. The photodiode outputs are fed through the signal processing circuitry. Two com parators receive these signals and produce the fi nal outputs for channels A and B. Due to this integrated phasing technique, the digital output of channel A is in quadrature with channel B (90 degrees out of phase). Block Diagram RESISTOR V CC 3 LENS PHOTO- DIODES COMPARATORS A CHANNEL A + LED A - 2 B CHANNEL B + B - 4 SIGNAL PROCESSING CIRCUITRY GND 1 EMITTER SECTION CODE DETECTOR SECTION WHEEL 2