Implementation of a Microcontroller-Based Power Factor and Energy Monitoring System

Household electricity meters usually report total energy, which tells a user little about how individual appliances behave. This paper describes a low-cost single-phase monitoring unit built around an ESP32 microcontroller, a ZMPT101B voltage transformer module and an ACS712 Hall-effect current sensor. The firmware samples both channels over a 400 ms window, which spans 20 cycles of a 50 Hz supply, and computes RMS voltage, RMS current, real power, apparent power, power factor, accumulated energy and running cost from the sampled data. Results appear on a 16x2 I2C LCD, and a push button selects between three screens. Idle-channel records show mid-scale offsets near 1959 counts (voltage) and 1979 counts (current), with noise standard deviations of 19.4 and 48.5 counts. The current-channel noise alone corresponds to about 0.59 A, which led to a start-up noise-zeroing routine and a 0.08 A dead band. A first live voltage reading of 116 V against a nominal 230 V supply was corrected by rescaling the voltage constant to 0.595 V per count. Accuracy against a reference meter has not yet been measured. The limits of the present design are discussed.