Reflective Surface Mount Optical Encoders

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The AEDR-8400 encoder is the smallest optical encoder employing reflective technology for motion control purposes. The encoder houses an LED light source and photo-detecting circuitry in a single package.

The AEDR-8400 encoder offers two-channel quadrature digital outputs. Being TTL compatible, the outputs of the AEDR-8400 encoder can be interfaced directly with most of the signal processing circuitries. Hence the encoder provides great design-in flexibility and easy integration into existing systems.

 

Theory of Operation

The AEDR-8400 encoder combines an emitter and a detector in a single surface mount leadless package. When used with a codewheel or linear codestrip, the encoder translates rotary or linear motion into digital outputs. As seen in the block diagram, the AEDR-8400 consists of three major components: a light emitting diode (LED) light source, a detector IC consisting photodiodes and lens to focus light beam from the emitter as well as light falling on the detector.

 

 

The operation of the encoder is based on the principle of optics where the detector photodiodes sense the absence and presence of light. In this case, the rotary/linear motion of an object being monitored is converted to equivalent light pattern via the use of codewheel/codestrip. As shown in the above diagram, the reflective area (bar) of the codewheel (or codestrip) reflects light back to the photo detector IC, whereas no light is reflected by the non-reflective area (window). An alternating light and dark pattern, corresponding to the window and bar, fall on the photodiodes as the codewheel rotates. The moving light pattern is exploited by the detector circuitry to produce digital outputs representing the rotation of the codewheel. When the codewheel is coupled to a motor, the encoder outputs are then a direct representation of the motor rotation. The same concept applies to the use of a codestrip to detect linear motion.

 

FEATURES Reflective technology Surface mount leadless package Two-channel quadrature digital outputs for direction sensing TTL compatible Single 2.8V supply Size: 3.00mm (L) x 3.28mm (W) x 1.262mm (H) -20°C to 85°C absolute operating temperature Encoding resolution: AEDR-8400-132: 254 (lines/inch) or 10 (lines/mm) AEDR-8400-140: 318 (lines/inch) or 12.5 (lines/mm)

APPLICATIONS Ideal for high volume applications Printers Copiers Card readers Scanners Digital still cameras Camcorders Camera phones Projectors Consumer product applications Industrial applications Feedback for miniature motors Miniature linear scales

 

 

 Featured Products

Part Number		Description	Data Sheet	App. Notes
AEDR-8400-132		Reflective Surface Mount Optical Encoder, 254 Lines/Inch
AEDR-8400-140		Reflective Surface Mount Optical Encoder, 318 Lines/Inch

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