AC Line Dropout (Power Failure) Detector

Power dropout detection is often required by digital system driven from the AC line. A memory store command to be issued before DC power falls is allowed by fast AC line drop out detection. The circuit on figure below detects AC dropout by connecting an optoisolator across the power transformer’s rectified secondary. Normally, the LED is turned on by the […]

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Opto-Isolated-Input 4-Digit Voltmeter

The voltage that control a V/F converters will be displayed if we use a frequency counter, which is directly proportional to the input voltage. A 1 second time base will give 4 digit resolution with 1 reading per second when the V/F converters is running at 10KHz full scale. To transmit the frequency, we can use the optoisolator, so there […]

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