SR04M-2 Ultrasonic Sensor with Arduino (Complete Beginner Tutorial)

Measuring distance using Arduino is one of the most useful beginner projects. In this tutorial, you’ll learn how to use the SR04M-2 ultrasonic sensor to measure distance accurately for real-world applications. The SR04M-2 is a waterproof ultrasonic sensor that measures distance by sending sound waves and receiving the echo.

A step-by-step guide to measure distance using a waterproof ultrasonic sensor and Arduino.

⚙️ Key Features

• Waterproof probe
• Range: 20cm to 400cm
• Operating voltage: 5V
• Stable and accurate readings

🔌 Wiring Diagram & Connections

How to connect the sensor to Arduino.

5V → 5V

GND → GND

RX → Pin 3

TX → Pin 2

💻 Arduino Code

Program to read and display distance.

Install the NewPing library before uploading the code. Click HERE to download code.

📥 Library Installation

1. Open Arduino IDE
2. Go to Sketch → Include Library → Manage Libraries
3. Search “NewPing”
4. Click Install

📜 Code

#include <newping.h>

#define TRIGGER_PIN  3 
#define ECHO_PIN     2  
#define MAX_DISTANCE 400 
NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); 

float tempval1;
float tempval2 = 60;
int finalval;
unsigned long lastPingTime = 0;
unsigned long pingInterval = 50;

void setup() {
  Serial.begin(57600);
}

void loop() {
  unsigned long currentTime = millis();
  
  if ((currentTime - lastPingTime >= pingInterval)) {
    
    unsigned int distance = sonar.ping_cm();
    
    if (distance > 0) {
      tempval1 = distance;
      
      float diff = abs(tempval1 - tempval2);
      
      if (diff > 2) {
        
        if (diff > 30) {
          tempval2 = (tempval1 * 0.7) + (tempval2 * 0.3);
        } else {
          tempval2 = (tempval1 * 0.4) + (tempval2 * 0.6);
        }
        
        finalval = tempval2;
        
        Serial.print("Ping: ");
        Serial.print(finalval);
        Serial.println("cm");
      }
    }
    
    lastPingTime = currentTime;
  }
}

🧪 Testing the Sensor

Checking real-time distance readings.

1. Open Serial Monitor
2. Set baud rate to 57600
3. Move an object closer and farther

⚙️ How It Works

The sensor sends ultrasonic waves and calculates distance based on the time taken for the echo to return. The code also smooths readings to reduce noise.

🚀 Applications

• Water level monitoring
• Parking systems
• Obstacle detection robots
• Smart irrigation

✅ Conclusion

You’ve learned how to connect, code, and test the SR04M-2 ultrasonic sensor with Arduino. This is a great starting point for many automation projects. If this helped you, please like 👍 and share 🔄 this tutorial.