Free electronic circuit design and schematic diagram
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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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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The LED to flash 5 times per second if the unit is brought close to a live conductor (insulated, and even buried in plaster) capacitive coupling between the live conductor and the probe clocks the counter. That’s caused the 4017 IC divides the mains 50Hz frequency by 10. The unit stops counting, the LED resulting permanently OFF (or permanently ON […]
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The MAX932 monitoring an input voltage in two steps figure is shown below. The outputs are high when Vin is higher than the LOW and FAIL thresholds. The calculation of threshold are the same to those for the window-detector application [Source: MAXIM Application Note]
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