The HC-SR04 Ultrasonic Sensor is a widely used sensor for distance measurement. It works by sending ultrasonic sound waves and measuring the time taken for the echo to return after reflecting off an object.
 
 Specifications
Operating Voltage: 5V DC
Operating Current: 15 mA
Frequency: 40 kHz
Range: 2 cm to 400 cm
Accuracy: ±3 mm
Trigger Pin: Input (to initiate measurement)
Echo Pin: Output (pulse width proportional to distance)
 
Working Principle
The sensor sends an 8-cycle ultrasonic burst (triggered by a 10 µs pulse on the TRIG pin).
The sound wave travels, reflects off an object, and returns to the sensor.
The ECHO pin goes HIGH for the duration it takes for the wave to return.
 
Pin Configuration
Pin
Function
VCC
+5V Supply
GND
Ground
TRIG
Trigger Input
ECHO
Echo Output
 
 
Arduino Connection
 
VCC → 5V
GND → GND
TRIG → Digital Pin 9
ECHO → Digital Pin 10
 
Arduino Code Example
#define TRIG_PIN 9
#define ECHO_PIN 10
void setup() {
  Serial.begin(9600);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
}
void loop() {
  long duration;
  float distance;
  // Send 10µs pulse to TRIG
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  // Read echo time
  duration = pulseIn(ECHO_PIN, HIGH);
  // Calculate distance in cm
  distance = (duration * 0.0343) / 2;
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  delay(500);
}
 
Applications
 
Automatic door opening
Obstacle avoidance in robots
Parking assistance
Liquid level measurement
 
Package includes: 1x HC-SR04 Ultrasonic Sensor