HC-SR04 Ultrasonic Sensor Arduino: Distance Measurement and Projects

Introduction

The HC-SR04 uses sound waves to measure distance, exactly like a bat. It is one of the most useful and affordable sensors for Arduino projects. In this tutorial we cover wiring, calibration, and three practical projects.

How It Works

• Trigger pin: 10µs HIGH pulse fires ultrasonic burst.
• Echo pin: HIGH pulse duration proportional to distance.
• Formula: Distance (cm) = Echo duration (µs) / 58

Wiring to Arduino Uno

Project 1: Distance Meter

#define TRIG 9
#define ECHO 10
void setup() { Serial.begin(9600); pinMode(TRIG,OUTPUT); pinMode(ECHO,INPUT); }
long getDist() {
  digitalWrite(TRIG,LOW); delayMicroseconds(2);
  digitalWrite(TRIG,HIGH); delayMicroseconds(10); digitalWrite(TRIG,LOW);
  return pulseIn(ECHO,HIGH)/58;
}
void loop() { Serial.println(String(getDist())+" cm"); delay(200); }

Project 2: Parking Sensor with Buzzer

#define TRIG 9
#define ECHO 10
#define BUZZER 11
void setup() { pinMode(TRIG,OUTPUT); pinMode(ECHO,INPUT); pinMode(BUZZER,OUTPUT); }
long getDist() {
  digitalWrite(TRIG,LOW); delayMicroseconds(2);
  digitalWrite(TRIG,HIGH); delayMicroseconds(10); digitalWrite(TRIG,LOW);
  return pulseIn(ECHO,HIGH)/58;
}
void loop() {
  long d=getDist();
  if(d<10) { digitalWrite(BUZZER,HIGH); }
  else if(d<30) { digitalWrite(BUZZER,HIGH); delay(100); digitalWrite(BUZZER,LOW); delay(100); }
  else { digitalWrite(BUZZER,LOW); delay(200); }
}

Project 3: Water Tank Level Monitor

Mount the HC-SR04 at the top of a tank pointing down. As water rises, echo time decreases. Convert this to a percentage.

#define TRIG 9
#define ECHO 10
#define TANK_H 100
void setup() { Serial.begin(9600); pinMode(TRIG,OUTPUT); pinMode(ECHO,INPUT); }
void loop() {
  digitalWrite(TRIG,LOW); delayMicroseconds(2);
  digitalWrite(TRIG,HIGH); delayMicroseconds(10); digitalWrite(TRIG,LOW);
  long dist=pulseIn(ECHO,HIGH)/58;
  int pct=constrain(((TANK_H-dist)*100)/TANK_H,0,100);
  Serial.println("Water Level: "+String(pct)+"%");
  delay(1000);
}

Conclusion

The HC-SR04 is a must-have for every maker. From robotics to smart home automation, its applications are nearly limitless!