Interfacing SR04T/SR04M Waterproof UltraSonic Sensor with Arduino Uno

Welcome to this beginner-friendly Arduino tutorial on the the sr04t, sr04m waterproof ultrasonic. By the end of the guide, you'll wire the module to an Arduino UNO, flash a short sketch, and read live values on the Serial Monitor — no prior electronics experience required.

What you'll learn

• How the module works in plain language
• The exact parts you need and how to wire them safely
• The full Arduino IDE sketch with comments
• Common issues and how to fix them

Arduino code

Open the Arduino IDE, paste the sketch below into a new file, install any libraries the sketch #includes (Tools → Manage Libraries), select your board and COM port, then click Upload.

#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;
int finalval;

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

void loop() {
  delay(20);                     
  Serial.print("Ping: ");
  
  int iterations = 10;
  tempval1=((sonar.ping_median(iterations) / 2) * 0.0343);
  
  if(tempval1-tempval2>60 || tempval1-tempval2<-60)
  {
    tempval2=(tempval1*0.02 )+ (tempval2*0.98);
    }
  else
  {
  tempval2=(tempval1*0.4 )+ (tempval2*0.6);
  }
  
  finalval=tempval2;
  
  Serial.print(finalval);
  Serial.println("cm");
}

How it works

The sketch initialises serial communication and the the sr04t, sr04m waterproof ultrasonic driver in setup(), then in loop() it samples the sensor at a regular interval and prints the result to the Serial Monitor at 9600 baud. Open the Serial Monitor (Ctrl+Shift+M) after upload to see live readings.

Troubleshooting checklist

• No readings: verify the baud rate in Serial Monitor matches the sketch (usually 9600).
• Garbage characters: wrong baud rate or loose GND wire.
• Library not found: install the exact library referenced in the #include line via Library Manager.
• Sensor not detected (I²C): run an I²C scanner sketch to confirm the address.

What to build next

Once the basic readout works, try logging values to an SD card, sending them over Wi-Fi with an ESP32, or pushing them to a Blynk IoT dashboard. Pair this module with our simulator round-up to prototype the circuit before soldering.