IoT Based Manhole Detection and Monitoring System

A smart manhole cover monitor. Sensors detect if the cover is open or missing, water overflow and harmful gases, and the readings are updated on a website so municipal staff can act before accidents happen.

12 V power adapter / step-down transformer supplies the circuit; a regulator gives the controller and sensors a steady 5 V. The Water / rain level sensor detects the presence or level of water. 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.

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 exposed conductive tracks are open circuit when dry. Water bridges them and lowers the resistance, and the controller reads the change as a level or as rain.

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 analog inputs read by the ADC for the analog sensors. 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.

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.