Measuring Distance with HC-SR04

What is an Ultrasonic Sensor?

The HC-SR04 ultrasonic sensor measures distances by emitting high-frequency sound pulses that bounce off objects and return to the sensor.

How Does it Work?

By measuring the time between the emission and return of a sound pulse, the sensor calculates distance. The speed of sound (343 m/s) is used for these calculations.

Electrical Schematic

The circuit schematic for connecting the HC-SR04 is shown below:

Assembly Diagram

The assembly on a breadboard is illustrated as follows:

Code Example (Without Library)

Below is an example code to measure distance using the HC-SR04 sensor without any external library:

const int EchoPin = 5;
const int TriggerPin = 6;

void setup() {
  Serial.begin(9600);
  pinMode(TriggerPin, OUTPUT);
  pinMode(EchoPin, INPUT);
}

void loop() {
  int cm = ping(TriggerPin, EchoPin);
  Serial.print("Distance: ");
  Serial.println(cm);
  delay(1000);
}

int ping(int TriggerPin, int EchoPin) {
  long duration, distanceCm;
  
  digitalWrite(TriggerPin, LOW);  // Clean pulse
  delayMicroseconds(4);
  digitalWrite(TriggerPin, HIGH);  // Trigger pulse
  delayMicroseconds(10);
  digitalWrite(TriggerPin, LOW);
  
  duration = pulseIn(EchoPin, HIGH);  // Measure duration
  distanceCm = duration * 10 / 292 / 2;  // Convert to cm
  return distanceCm;
}
            

Code Example (Using NewPing Library)

Using the NewPing library simplifies the process and provides additional features such as noise filtering:

#include 

const int UltrasonicPin = 5;
const int MaxDistance = 200;

NewPing sonar(UltrasonicPin, UltrasonicPin, MaxDistance);

void setup() {
  Serial.begin(9600);
}

void loop() {
  delay(50);                      // Wait 50ms between pings
  Serial.print(sonar.ping_cm()); // Get distance in cm
  Serial.println(" cm");
}