Water Level

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes ESP32 board	PURCHASE LINK
ESP32 Ultimate Starter Kit	ESP32 WROOM 32E +	BUY
Universal Maker Sensor Kit		BUY

Course Introduction

In this lesson, you’ll learn how to use an Ultrasonic Sensor Module, a 1602 LCD with the ESP32 to create a Ultrasonic water level monitor system.

The LED lights red when the water is low, turns yellow as it rises, and switches to green once it reaches the set level.

Note

If this is your first time working with an ESP32 project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	ESP-WROOM-32 ESP32 ESP-32S Development Board	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	1kΩ resistor	3	BUY
6	Ultrasonic Sensor Module	1	BUY
7	LED	3	BUY
8	I2C LCD 1602	1	BUY

Wiring

Common Connections:

LED
- Green: Connect the LEDs cathode to the negative power bus on the breadboard, and the LED anode to a 1kΩ resistor then to GPIO27 on the Arduino.
- yellow: Connect the LEDs cathode to the negative power bus on the breadboard, and the LED anode to a 1kΩ resistor then to GPIO26 on the Arduino.
- Red: Connect the LEDs cathode to the negative power bus on the breadboard, and the LED anode to a 1kΩ resistor then to GPIO25 on the Arduino.
I2C LCD 1602
- SDA: Connect to GPIO21 on the ESP32.
- SCL: Connect to GPIO22 on the ESP32.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s 5V red power bus.
Ultrasonic Sensor Module
- Trig: Connect to GPIO17 on the ESP32.
- Echo: Connect to GPIO16 on the ESP32.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s 3.3V red power bus.

Writing the Code

Note

You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for LiquidCrystal I2C and install it.
Don’t forget to select the board(ESP32 Dev module) and the correct port before clicking the Upload button.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// ---------------- I2C LCD ----------------
// I2C address 0x27 is common; change to 0x3F if needed
LiquidCrystal_I2C lcd(0x27, 16, 2);

// ---------------- Pin mapping (ESP32) ----------------
// Use safe, GPIO-capable pins on ESP32
const int echoPin = 16;   // HC-SR04 ECHO -> through voltage divider to 3.3V
const int trigPin = 17;   // HC-SR04 TRIG (3.3V OK)

const int greenLed  = 27; // Green LED (with series resistor)
const int yellowLed = 26; // Yellow LED
const int redLed    = 25; // Red LED

void setup() {
  // I2C init (ESP32 default: SDA=21, SCL=22)
  Wire.begin(21, 22);
  lcd.init();
  lcd.clear();
  lcd.backlight();

  // Ultrasonic sensor pins
  pinMode(echoPin, INPUT);
  pinMode(trigPin, OUTPUT);

  // LED pins
  pinMode(greenLed, OUTPUT);
  pinMode(yellowLed, OUTPUT);
  pinMode(redLed, OUTPUT);

  // Optional: show a splash text
  lcd.setCursor(0,0); lcd.print("Ultrasonic Level");
  lcd.setCursor(0,1); lcd.print("ESP32 Ready");
  delay(800);
  lcd.clear();
}

void loop() {
  // Measure distance
  float distance = readDistance();

  // Display on LCD
  lcd.setCursor(0, 0);
  lcd.print("Distance:       ");        // pad to clear leftovers
  lcd.setCursor(10, 0);
  lcd.print(distance, 1);                // one decimal
  lcd.print("cm");

  // LEDs based on distance
  if (distance <= 5) {
    // 0–5 cm -> green
    digitalWrite(greenLed, HIGH);
    digitalWrite(yellowLed, LOW);
    digitalWrite(redLed, LOW);
  } else if (distance > 5 && distance <= 10) {
    // 5–10 cm -> yellow
    digitalWrite(greenLed, LOW);
    digitalWrite(yellowLed, HIGH);
    digitalWrite(redLed, LOW);
  } else if (distance > 10 && distance <= 15) {
    // 10–15 cm -> red
    digitalWrite(greenLed, LOW);
    digitalWrite(yellowLed, LOW);
    digitalWrite(redLed, HIGH);
  } else {
    // >15 cm -> all off
    digitalWrite(greenLed, LOW);
    digitalWrite(yellowLed, LOW);
    digitalWrite(redLed, LOW);
  }

  delay(500);
}

// Read distance from HC-SR04 (returns centimeters)
float readDistance() {
  // Ensure TRIG is low, then send 10us pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read ECHO pulse width (timeout 30ms)
  unsigned long duration = pulseIn(echoPin, HIGH, 30000UL);
  if (duration == 0) return 9999.0;       // timeout -> very far

  // Convert to cm (speed of sound ~340m/s)
  float distance = duration * 0.034f / 2.0f;
  return distance;
}