OPTOISOLATOR_AND_OPTOCOUPLER_INTERFACE_CIRCUITS

Published:2009/6/24 3:51:00 Author:Jessie | From:SeekIC

A circuit for isolating a variable resistor is shown. An optoisolator that has an LED and a photo-conductive cell (or photoresistor) is used. The current through the LED controls its brightness, which in turn determines the resistance between terminals A and B. The LED current is set by the voltage of the dc power supply and the value of the two resistors (R1 and R2). The fixed resistor (R1) is used to limit the current to a maximum of 20 mA (when the resistance of the potentiometer, R2, is set to zero ohms), otherwise, the LED might burn out.



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