HEDS-9710, HEDS-9711 Small Optical Encoder Modules 360 Ipi Analog Current Output Data Sheet Description Features The HEDS-971x is a high performance incremental Small size encoder module. When operated in conjunction with Two channel quadrature output either a codewheel or codestrip, this module detects Linear and rotary applications rotary or linear position. The encoder consists of a lensed LED source and a detector IC enclosed in a small C-shaped No signal adjustment required plastic package. Due to a highly collimated light source TTL compatible and a unique photodetector array, the module is extremely Wave solderable tolerant to mounting misalignment. Lead free package The two channel analog outputs and 5 V supply input are 15C to 45C operating temperature accessed through four solder plated leads located on 2.54 mm (0.1 inch) centers. Single 5 V supply The standard HEDS-971x is designed for use with an appro priate optical radius codewheel or linear codestrip. Block Diagram Other options are available. Please contact the factory for RESISTOR V CC more information. 3 LENS Applications PHOTO- DIODES COMPARATORS The HEDS-971x provides sophisticated motion detection, A CHANNEL A + making closed loop control, very cost competitive. Typical LED applications include printers, plotters, copiers and offi ce A 2 automation equipment. B CHANNEL B + B 4 SIGNAL PROCESSING CIRCUITRY GND 1 EMITTER SECTION CODE DETECTOR SECTION WHEELDefi nitions Theory of Operation Count (N): The number of bar and window pairs or counts An HEDS-971x is a C-shaped emitter/detector module. per revolution (CPR) of the codewheel, or the number of Coupled with a codewheel, it translates rotary motion into lines per inch of the codestrip (LPI). a two-channel digital output, coupled with a codestrip it translates linear motion into digital outputs. 1 shaft Rotation = 360 degrees = N cycles As seen in the block diagram, the module contains a single Light Emitting Diode (LED) as its light source. The light is 1 cycle (c) = 360 electrical degrees, equivalent to collimated into parallel beam by means of a single lens 1 bar and window pair. located directly over the LED. Opposite the emitter is the Pulse Width (P): The number of electrical degrees that an integrated detector circuit. This IC consists of photodetec- output is high during one cycle, nominally 180e or a tors and a signal processing circuitry necessary to produce cycle. the digital waveforms. Pulse Width Error (P): The deviation in electrical degrees of The codewheel/codestrip moves between the emitter the pulse width from its ideal value of 180e. and detector, causing the light beam to be interrupted by the pattern of spaces and bars on the codewheel/ State Width (S): The number of electrical degrees between a codestrip. The photo diodes, which detect these interrup- transition in the output of channel A and the neighboring tions, are arranged in a pattern that corresponds to the transition in the output of channel B. There are 4 states per radius and count density of the codewheel/codestrip. cycle, each nominally 90e. These photodiodes are also spaced such that a light State Width Error (S): The deviation in electrical degrees of period on one pair of detectors corresponds to a dark each state width from its ideal value of 90e. period on the adjacent pairs of detectors. The photodiode out puts are fed through the signal processing circuitry. Phase ( ): The number of electrical degrees between the Two comparators receive these signals and produce the center of the high state on channel A and the center of fi nal outputs for Channels A and B. Due to this integrated the high state on channel B. This value is nominally 90e phasing technique the output of channel A is in quadra- for quadrature output. ture with Channel B (90 degrees out of phase). Phase Error (): The deviation in electrical degrees of the phase from its ideal value of 90e. Direction of Rotation: When the codewheel rotates in the counter-clockwise direction (as viewed from the encoder end of the motor), channel A will lead channel B. If the codewheel rotates in the clockwise direction, channel B will lead channel A. Optical Radius (Rop): The distance from the codewheels center of rotation to the optical center (O.C) of the encoder module. Angular Misalignment Error (E ): Angular misalignment of the A sensor in relation to the tangential direction. This applies for both rotary and linear motion. Mounting Position (R ): Distance from Motor Shaft center of M rotation to center of Alignment Tab receiving hole. 2