AEDR-8300 Series Encoders Reflective Surface Mount Optical Encoder Data Sheet Description Features Reflective technology The AEDR-8300 series is the smallest optical encoder employing reflective technology for motion control Surface mount small outline leadless package purposes. The encoder houses an LED light source and Single channel incremental output a photo-detecting circuitry in a single package. Two channel quadrature outputs for direction sens- The AEDS-8300 series offers options of either single ing channel or two-channel quadrature digital outputs. Being TTL compatible, the outputs of the AEDR-8300 TTL compatible output series can be interfaced directly with most of the signal Single 5V supply processing circuitries. Hence the encoder provides great design-in flexibility and easy integration into existing o o -20 C to 85 C absolute operating temperature systems. The AEDR-8300 series is available in four reso- Encoding resolution options: lutions, namely 36, 75, 150 and 180 lines per inch (LPI) 36, 75, 150, 180 (lines/inch) or 1.42, 2.95, 5.91, 7.09 (1.42, 2.95, 5.91 and 7.09 lines per mm respectively). (lines/mm) This range of resolutions caters for different design and application needs. Applications The AEDR-8300 series provides motion sensing at a competitive cost, making it ideal for high volume appli- cations. Its small size and surface mount package make it ideal for printers, copiers, card readers and many con- sumer products, particularly where space and weigh are design constraint. Note: All specifications are subject to change without prior notification.Theory of Operation Definitions The AEDR-8300 series combines an emitter and a detec- State Width (S): The number of electrical degrees be- tor in a single surface mount leadless package. When tween a transition in Channel A and the neighboring used with a codewheel or linear codestrip, the encoder transition in Channel B. There are 4 states per cycle, o translates rotary or linear motion into digital outputs. each nominally 90 e. As seen in the block diagram, the AEDR-8300 consists State Width Error ( S): The deviation of state width, in of three major components: a light emitting diode (LED) o electrical degree, from its ideal value of 90 e. light source, a detector IC consisting photodiodes and lens to focus light beam from the emitter as well as light Phase ( ): The number of electrical degrees between falling on the detector. the center of high state of Channel A and the center of o high state of Channel B. Nominally 90 e. The operation of the encoder is based on the principle of optics where the detector photodiodes sense the ab- Phase Error ( ): The deviation of phase, in electrical o sence and presence of light. In this case, the rotary/lin- degree, from its ideal value of 90 e. ear motion of an object being monitored is converted Pulse Width (P): The duration of high state of the out- to equivalent light pattern via the use of codewheel/ put, in electrical degree, within one cycle. Nominally codestrip. As shown in the diagram below, the reflective o 180 e or half a cycle. area (window) of the codewheel (or codestrip) reflects light back to the photodetector IC, whereas no light is Pulse Width Error (P): The deviation of pulse width, in o reflected by the non-reflective area (bar). An alternating electrical degree, from its ideal value of 180 e. light and dark patterns corresponding to the window Count (N): The number of window and bar pair per rev- and bar fall on the photodiodes as the codewheel ro- olution (CPR) of codewheel. For linear codestrip, defined tates. The moving light pattern is exploited by the de- as the number of window and bar pair per unit length tector circuitry to produce digital outputs representing (lines per inch LPI or lines per mm LPmm ). the rotation of the codewheel. When the codewheel is o coupled to a motor, the encoder outputs is then a direct One Cycle (C): 360 electrical degrees ( e). Equivalent to representation of the motor rotation. The same concept one window and bar pair. applies to the use of a codestrip to detect linear motion. V LED R CODEWHEEL OR GND CODESTRIP V CC CH A SIGNAL PROCESSING CH B CIRCUITRY GND Figure 1. Block Diagram of AEDR-8300. AEDR-8300 block diag 2