IoT Based Three Phase Power Failure Monitoring with SMS Alerts

A monitor for three-phase supplies that detects phase failure. When any of the R, Y or B phases fails, it shows the voltages on an LCD, sounds a buzzer and sends an SMS to the maintenance team.

12 V power adapter / step-down transformer supplies the circuit; a regulator gives the controller and sensors a steady 5 V. The NodeMCU ESP8266 Wi-Fi board connects the system to Wi-Fi so readings can be pushed to an IoT dashboard and commands received from a phone. The GSM module sends SMS alerts or makes calls to the registered phone number using a normal SIM card. The 16×2 LCD with I2C adapter shows readings, status and messages to the user.

NodeMCU is a development board built on the ESP8266 Wi-Fi chip. It joins a Wi-Fi network using the SSID and password in the code and sends data over HTTP or MQTT to a cloud server.

The microcontroller sends AT commands over serial, for example AT+CMGF=1 to select text mode and AT+CMGS with the phone number followed by the message. The module transmits it over the mobile network.

It reduces the wiring from about 10 pins to 2 (SDA and SCL), leaving more controller pins free for sensors.

An active buzzer has a built-in oscillator and beeps on DC. A passive buzzer needs a square wave from the controller, which allows different tones.

A transformer steps down the voltage, a bridge rectifier converts AC to pulsating DC, a capacitor smooths it and a 7805 regulator gives a steady 5 V.

The input section senses the real-world quantity, the NodeMCU ESP8266 Wi-Fi board processes it according to the program, and the output section acts locally and sends the data or alert wirelessly. The power supply section feeds every block.

UART (serial) for the GSM, GPS, Bluetooth or fingerprint modules and I2C for the display, RTC or motion sensor (only SDA and SCL lines). Each protocol was chosen because the module supports it and it uses the fewest pins.

The controller and most sensors work at 5 V (ESP boards and some modules at 3.3 V). A 12 V adapter powers the board, and a regulator steps it down. Motors and relays get their own supply line so they do not reset the controller.

Using P = V × I for each load, adding a margin of 20 to 25%.

Accuracy is how close a reading is to the true value. Precision is how close repeated readings are to each other. A sensor can be precise but inaccurate if it is not calibrated.