HEDS-9730, HEDS-9731 Small Optical Encoder Modules 480lpi Digital Output Data Sheet Description Features The HEDS-973X is a high performance incremental Small Size encoder module. When operated in conjunction with High Resolution either a codewheel or codestrip, this module detects rotary or linear position. The encoder consists of a lensed Two Channel Quadrature Output LED source and a detector IC enclosed in a small C- Linear and Rotary Applications shaped plastic package. Due to a highly collimated light No Signal Adjustment required source and a unique photodetector array, the module is extremely tolerant to mounting misalignment. TTL or 3.3V/5V CMOS Compatible The two channel digital outputs and 3.3V supply input Wave Solderable are accessed through four solder plated leads located on Lead-free Package 2.54mm (0.1inch) centers. -40C to 85C Operating Temperature The standard HEDS-973X is designed for use with an ap- propriate optical radius codewheel or linear codestrip. Single 3.3V Supply Other options are available. Please contact the factory for Applications more information. The HEDS-973X provides sophisticated motion detection, Block Diagram making closed loop control very cost competitive. Typical applications include printers, plotters, copiers and o ce RESISTOR V CC automation equipment. 3 LENS Note: Avago Technologies encoders are not recommended for use in safety PHOTO- DIODES COMPARATORS critical applications, e.g., ABS braking systems and critical-care medical A equipment. Please contact a sales representative if more clari cation is CHANNEL A + needed. LED A - 2 B CHANNEL B + B - 4 SIGNAL PROCESSING CIRCUITRY GND 1 EMITTER SECTION CODE DETECTOR SECTION WHEEL Figure 1 ESD WARNING: NORMAL HANDLING PRECAUTIONS SHOULD BE TAKEN TO AVOID STATIC DISCHARGE.De nitions Theory of Operation Note: Refer to Figure 2 A HEDS-973X is a C-shaped emitter/detector module. Count (N): The number of bar and window pairs or counts Coupled with a codewheel, it translates rotary motion per revolution (CPR) of the codewheel. Or the number of into a two-channel digital output coupled with a lines per inch of the codestrip (LPI) codestrip, it translates linear motion into digital outputs. 1 shaft Rotation = 360 degrees As seen in Figure 1, the module contains a single Light Emitting Diode (LED) as its light source. The light is col- = N cycles limated into parallel beam by means of a single lens 1 cycle (c) = 360 electrical degree, equivalent to 1 bar and located directly over the LED. Opposite the emitter is window pair. the integrated detector circuit. This IC consists of photo- detectors and a signal processing circuitry necessary to Pulse Width (P): The number of electrical degrees that an produce the digital waveforms. output is high during one cycle, nominally 180 e or 1/2 a cycle. The codewheel/codestrip moves between the emitter and detector, causing the light beam to be interrupted Pulse Width Error (P): The deviation in electrical degrees of by the pattern of spaces and bars on the codewheel/ the pulse width from its ideal value of 180e. codestrip. The photodiodes, which detect these interrup- tions, are arranged in a pattern that corresponds to the State Width (S): The number of electrical degrees between radius and count density of the codewheel/ codestrip. a transition in the output of channel A and the neigh- These photodiodes are also spaced such that a light boring transition in the output of channel B. There are 4 period on one pair of detectors corresponds to a dark states per cycle, each nominally 90e. period on the adjacent pairs of detectors. The photodiode State Width Error (S): The deviation in electrical degrees of outputs are fed through the signal processing circuitry. each state width from its ideal value of 90e. Two comparators receive these signal and produce the nal outputs for Channels A and B. Due to this integrated Phase (): The number of electrical degrees between the phasing technique the output of channel A is in quadra- center of the high state on channel A and the center of ture with Channel B (90 degrees out of phase). the high state on channel B. This value is nominally 90e for quadrature output. Output Waveforms Phase Error ( ): The deviation in electrical degrees of the phase from its ideal value of 90e. C Direction of Rotation: When the codewheel rotates in the P counter-clockwise direction (as viewed from the encoder CHANNEL A 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 S2 S1 S3 S4 center of rotation to the optical center (O C) of the encoder module. CHANNEL B Angular Misalignment Error (E ): Angular misalignment of A the sensor in relation to then tangential direction. This applies for both rotary and linear motion. ROTATION Figure 2. Mounting Position (R ): Distance from Motor Shaft center of M rotation to center of Alignment Tab receiving hole. 2 AMPLITUDE