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Measure Distance with HC-SR04 (Arduino)

Measure distance with an ultrasonic sensor and print centimeters to the Serial Monitor.

Beginner20 min

What you need

Wiring

Arduino Uno
HC-SR04

Hover a pin or a wire to trace the connection.

Code

ultrasonic.ino
// Measure distance with an HC-SR04 ultrasonic sensor.
const int trigPin = 9;
const int echoPin = 10;

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

void loop() {
  digitalWrite(trigPin, LOW);  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH); delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  long us = pulseIn(echoPin, HIGH); // echo pulse width
  long cm = us / 58;                // ~58 us per cm (round trip)
  Serial.print(cm); Serial.println(" cm");
  delay(300);
}

Steps

  1. Wire the sensor: VCC to 5V, GND to GND, Trig to D9, Echo to D10.
  2. Upload and open the Serial Monitor at 9600 baud.
  3. Move your hand toward and away from the sensor to see the distance change.