How to Use HC-SR04 Ultrasonic Sensor with Arduino

This guide walks you through wiring an HC-SR04 ultrasonic distance sensor to Arduino UNO and reading the distance between the sensor and an object. The data is displayed on Serial Monitor using Arduino’s built-in pulseIn() function, so no external libraries are needed.

Required Components

• Arduino UNO R3 with USB cable
• HC-SR04 Ultrasonic Distance Sensor
• MB-102 Breadboard (830 points)
• Jumper wires M-M 20 cm (about 4 pieces)
• Jumper wires M-F 20 cm (optional)

Wiring HC-SR04 to Arduino UNO

HC-SR04	Arduino UNO
VCC	5V
GND	GND
Trig	Pin 13
Echo	Pin 12

How HC-SR04 works:

1. Arduino sends a short ultrasonic pulse through the Trig pin
2. The sound wave travels, hits an object, and bounces back to the sensor’s Echo pin
3. Arduino measures the travel time and calculates the distance

Distance formula: distance = (time × 0.034) / 2

Where 0.034 is the speed of sound in cm/μs, and divided by 2 because the time includes both the outbound and return trip.

Arduino Code for HC-SR04 Distance Measurement

// Define the pins connected to HC-SR04
const int trigPin = 13;
const int echoPin = 12;

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {
  // Send Trig pulse: 10 microseconds HIGH
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure the Echo pulse width in microseconds
  long duration = pulseIn(echoPin, HIGH);

  // Convert duration to distance in centimeters
  float distance = (duration * 0.034) / 2;

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  delay(500);
}

Adjustable parts for your project:

• Change trigPin and echoPin to match your actual wiring
• Adjust delay(500) to change the measurement interval (faster intervals may cause cross-talk between consecutive readings)
• For distance in meters, use distance = (duration * 0.017) / 2 instead

How to Upload and View Results

1. Open Arduino IDE and paste the code above
2. Select board: Tools → Board → Arduino Uno
3. Select port: Tools → Port and choose the COM port your board is connected to
4. Click the Upload button (right arrow →)
5. Wait for Done uploading message, then open Serial Monitor
6. Set Baud Rate to 9600
7. Distance values will print every 500 milliseconds

Testing the HC-SR04 Sensor

After uploading, place a hand or object in front of the sensor and slowly move it:

• Move closer → distance value decreases
• Move farther → distance value increases

If the values stay at 0 or show abnormal numbers, double-check that VCC, GND, Trig, and Echo connections match the wiring table.

Precautions When Using HC-SR04

• Beam angle is about 15 degrees. Very small or highly angled objects may not reflect enough sound back to the sensor.
• Maximum range is approximately 4 meters. The sensor returns 0 for objects beyond that range.
• Measurement frequency when using pulseIn() in default mode, wait at least 60 milliseconds between measurements to avoid old echoes interfering with new ones.
• Multiple sensors must be triggered one at a time, not simultaneously, or the sound pulses will interfere with each other.