Interfacing AC power lines with PIC microcontrollers
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Applications like automatic power factor correction, power measurement, and power line monitor require interfacing the high voltage AC power lines to microcontrollers. This application note from Microchip describes a simple method for measuring parameters from the AC power line by using only one external resistor, and is more reliable than using a bulky and expensive transformer. This method takes advantage of the input static protection circuitry that exists on I/O pins of a CMOS PIC16C5X. These protection circuits are designed to short the inputs to the power supplies when a large overvoltage is applied, thus protecting the chip from static electricity spikes.
Input static protection circuitry on PIC I/O pin
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