Mechatronic Systems Engineering 2202A/B Lecture Notes - Lecture 22: Band-Pass Filter, Alarm Device, Barcode
2 Feb 2020
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Document Summary
Amount of light received by a detector is determined by both the source and the transmission medium. Therefore, information about both the source and medium can be conveyed to the detector. Medium modulation source provides illumination while medium is modulated (interrupted) Detector must be designed to suppress effects of ambient (surrounding) light conditions. Source modulation medium characteristics remain unchanged; source modulated to convey information. Source (transmitter, emitter) is turned on and off (i. e. , modulated) at a high rate of speed (> several khz) Photodetector is designed to capture modulated light (information) Only modulated light is amplified; all other light is ignored. Analogous to radio receiver tuned to one station. Usually, trade off speed of response for sensing distance. Although simple transistor circuits can be used as ir transmitters, most often microcontrollers are used because they are more flexible. Different output pins of the microcontroller can be used to generate pulse streams with different carrier frequencies.
