Track Infrared Detectors

Published:2013/6/25 21:39:00 Author:muriel | Keyword: Track Infrared Detectors | From:SeekIC

This page presents information on infrared - Above The Track and Across The Track train position detection circuits. The circuits are designed around the LM339 quad comparator chip and can use a wide assortment of matched infrared - emitter / detector pairs. The circuit bellow is the basic voltage comparator based detector circuit using the LM339 Quad or LM393 Dual comparator ICs. The LED will turn on when the infrared beam is broken. The value of the resistor R1 determines the sensitivity of the phototransistor Q1. In most cases a value of 1 Meg or 470K ohm with good results but every situation is different and some experimentation might be needed. Circuit Operation - When a train breaks the infrared beam the phototransistor will conduct less current. The voltage at the MINUS input of the comparator will rise above the reference voltage at the PLUS as determined by R3 and R4. The output of the comparator to turn ON and the LED will be lit.



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