AEDR-8000 Series Reflective Surface Mount Optical Encoder Data Sheet Description Features By introducing an additional PCB top-up thickness at- Reflective technology tached to the encoder, the AEDR-8000 Encoder series Surface mount small outline leadless package could easily solve the height issue in various applica- Direct replacement of HEDR-8000 encoder tions. Furthermore, this great feature is enhanced with the offering of different height profile options. Single channel incremental output Two channels quadrature outputs for direction Direct Replacement of HEDR-8000 Encoder series is now sensing possible with the AEDR-8000 Encoder series. Such migra- tion is always simple and easy due to the perfect match- Single 5 V supply, TTL compatible output ing of the height profiles as well as same footprints in -20C to 85C absolute operating temperature both encoder series. Lead-free package The AEDR-8000 Encoder series employs reflective tech - Encoding resolution options: nology for rotary and linear movement control. The en- coder houses an LED light source and a photo-detecting 75, 150 and 180 (lines/inch) or 2.95, 5.91, 7.09 circuitry in a single package. (lines/mm) PCB height profile options: In adding on to the main features, The AEDR-8000 En- coder series offers two-channel quadrature digital out - 1.0 mm PCB thickness 1.5 mm PCB thickness puts (TTL compatible) where signal could be interfaced directly with most of the signal processing circuitries. Thus, its bound to reduce the design time of an applica- tion. Applications The AEDR-8000 Encoder series provides motion sensing at a competitive price, making it ideal for high volume applications. Its small size and surface mount package make it ideal for printers, copiers, card readers and many consumer products, particularly where space and weight are design constraints. Note: All specifications are subject to change without prior notification.Theory of Operation The AEDR 8000 Encoder series combines an emitter and Phase Error (Df): The deviation of phase, in electrical de- a detector in a single surface mount leadless package. grees, from its ideal value of 90e. When used with a codewheel or linear codestrip, the en- Pulse Width (P): The duration of high state of the output, coder translates rotary or linear motion into digital out- in electrical degrees, within one cycle. Nominally 180e puts. As seen in the block diagram, the AEDR-8000 En- or half a cycle. coder series consists of three major components: a light emitting diode (LED) light source, a detector IC consist- Pulse Width Error (DP): The deviation of pulse width, in ing photodiodes, and lens to focus light beam from the electrical degrees, from its ideal value of 180e. emitter as well as light falling on the detector. Count (N): The number of window and bar pairs per revo- The operation of the encoder is based on the principle of lution (CPR) of codewheel. For linear codestrip, defined optics where the detector photodiodes sense the absence as the number of window and bar pairs per unit length and presence of light. In this case, the rotary/linear mo- (lines per inch LPI or lines per mm LPmm ). tion of an object being monitored is converted to equiv- One Cycle (C): 360 electrical degrees (e). Equivalent to alent light pattern via the use of codewheel/codestrip. one window and bar pair. As shown in the above diagram, the reflective area (win - dow) of the codewheel (or codestrip) reflects light back One Shaft Rotation: 360 mechanical degrees. Also equiv- to the photodetector IC, whereas no light is reflected by alent to N counts (codewheel only). the non-reflective area (bar). An alternating light and Line Density: The number of window and bar pairs per dark pattern, corresponding to the window and bar, falls unit length, expressed in either lines per inch (LPI) or on the photodiodes as the codewheel rotates. The mov- lines per mm (LPmm). ing light pattern is exploited by the detector circuitry to produce digital outputs representing the rotation of the Optical Radius (Rop): The distance between the code- codewheel. When the codewheel is coupled to a motor, wheel center and the centerline between the two domes the encoder outputs are then a direct representation of of the encoder. the motor rotation. The same concept applies to the use Gap (G): The distance from the surface of the encoder to of a codestrip to detect linear motion. the surface of codewheel or codestrip. Definitions Specular Reflectance (R ): The amount of incident light f reflected by a surface. Quantified in terms of the per - State Width (S): The number of electrical degrees be- centage of incident light. A spectrometer can be used to tween a transition in Channel A and the neighboring measure specular reflectance of a surface (contact fac - transition in Channel B. There are 4 states per cycle, each tory for more information). nominally 90e. Radial and Tangential Misalignment Error (E , E ): For ro- R T State Width Error ( DS): The deviation of state width, in tary motion, mechanical displacement in the radial and electrical degrees, from its ideal value of 90e. tangential directions relative to the nominal alignment. Phase ( f): The number of electrical degrees between the Angular Misalignment Error (E ): Angular displacement A center of high state of Channel A and the center of high of the encoder relative to the tangential line. state of Channel B. Nominally 90e. Block Diagram of AEDR-8000 Encoder V LED R CODEWHEEL or GND CODESTRIP V CC CH A SIGNAL CH B PROCESSING CIRCUITRY GND 2