💧 Smart Water Management System

(ESP32 + Ultrasonic Sensor + Relay – Serial Monitor Version)

In this lesson, we will:

• Measure water level using Ultrasonic Sensor

• Calculate tank water percentage

• Implement AUTO mode logic

• Implement MANUAL mode logic

• Control motor using Serial Monitor commands

• Prevent overflow

• Prevent dry run

No Bluetooth ❌
No WiFi ❌
Only Serial Monitor ✔

📦 Components Used

• ESP32

• HC-SR04 Ultrasonic Sensor

• Single Channel Relay

• DC Water Pump

🔌 Pin Configuration

🔹 Ultrasonic Sensor

⚠ Use voltage divider for Echo (5V → 3.3V)

🔹 Relay Module

Relay Active LOW
LOW → Motor ON
HIGH → Motor OFF

💻 COMPLETE CODE

(Serial Monitor Version – Ultrasonic)

Copy & paste into Arduino IDE:

#define TRIG_PIN 5
#define ECHO_PIN 18
#define RELAY_PIN 26

long duration;
float distance;
float tankHeight = 30.0; // Tank height in cm
float waterLevel;
float percentage;

bool autoMode = true;
bool motorState = false;

void setup() {
Serial.begin(115200);

pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
pinMode(RELAY_PIN, OUTPUT);

digitalWrite(RELAY_PIN, HIGH); // Motor OFF

Serial.println("=== Smart Water Management System ===");
Serial.println("Commands: AUTO, MANUAL, ON, OFF");
}

void loop() {

// Trigger Ultrasonic Pulse
digitalWrite(TRIG_PIN, LOW);
delayMicroseconds(2);
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);

duration = pulseIn(ECHO_PIN, HIGH);

distance = duration * 0.034 / 2;
waterLevel = tankHeight - distance;

if (waterLevel < 0) waterLevel = 0;
if (waterLevel > tankHeight) waterLevel = tankHeight;

percentage = (waterLevel / tankHeight) * 100;

Serial.print("Distance: ");
Serial.print(distance);
Serial.print(" cm | Water Level: ");
Serial.print(waterLevel);
Serial.print(" cm | Tank: ");
Serial.print(percentage);
Serial.println(" %");

// Check Serial Commands
if (Serial.available()) {
String command = Serial.readStringUntil('\n');
command.trim();

if (command.equalsIgnoreCase("AUTO")) {
autoMode = true;
Serial.println("Switched to AUTO Mode");
}
else if (command.equalsIgnoreCase("MANUAL")) {
autoMode = false;
Serial.println("Switched to MANUAL Mode");
}
else if (command.equalsIgnoreCase("ON") && !autoMode) {
turnMotorOn();
}
else if (command.equalsIgnoreCase("OFF") && !autoMode) {
turnMotorOff();
}
}

// AUTO MODE LOGIC
if (autoMode) {

if (percentage < 20 && !motorState) {
Serial.println("Water LOW -> Motor ON");
turnMotorOn();
}

if (percentage > 90 && motorState) {
Serial.println("Tank FULL -> Motor OFF");
turnMotorOff();
Serial.println("WARNING: Tank Full!");
}
}

delay(2000);
}

void turnMotorOn() {
digitalWrite(RELAY_PIN, LOW);
motorState = true;
Serial.println("Motor is ON");
}

void turnMotorOff() {
digitalWrite(RELAY_PIN, HIGH);
motorState = false;
Serial.println("Motor is OFF");
}

🧠 Code Explanation (Step-by-Step)

1️⃣ Ultrasonic Trigger Logic

Sends 10µs pulse.

2️⃣ Measure Echo Time

Measures time taken for sound to return.

3️⃣ Calculate Distance

Converts time into centimeters.

4️⃣ Calculate Water Level

Gives tank water percentage.

5️⃣ Auto Mode Logic

If:

→ Motor ON

If:

→ Motor OFF + Warning

6️⃣ Manual Mode Commands

📟 Example Serial Output

🎯 What Students Learn

• Ultrasonic distance measurement

• Percentage calculation

• Tank height calibration

• Auto + Manual control logic

• Relay motor control

• Embedded automation design

📌 Lesson Summary

In this lesson, students built a complete Ultrasonic-based Smart Water Management System using Serial Monitor.

This system:

✔ Measures water without contact
✔ Calculates tank percentage
✔ Automatically controls motor
✔ Prevents overflow and dry run