Learn how to build an Ultrasonic Distance Meter using Arduino and HC-SR04 sensor. Includes circuit diagram, source code, and practical use cases. Perfect for beginners and DIY electronics enthusiasts.
Introduction
📌 What is HC-SR04 Ultrasonic Sensor?
The HC-SR04 is a popular, low-cost ultrasonic sensor module used to measure distances with high accuracy. It works on the principle of echolocation—similar to how bats and dolphins perceive their environment. The sensor emits an ultrasonic wave at 40 kHz, which travels through the air, reflects off an object, and returns to the sensor. By calculating the time it takes for the echo to return, the sensor can determine the distance of the object.
This module is widely used in Arduino and micro controller projects for:
- Obstacle detection
- Distance measurement
- Robotic navigation
- Automatic parking systems
It features four pins:
- VCC – Power Supply (5V)
- Trig – Trigger Input
- Echo – Echo Output
- GND – Ground
Would you like a diagram showing the working principle of HC-SR04 as well?
What the Project Does
This project demonstrates how to measure distance using the HC-SR04 ultrasonic sensor and Arduino. The sensor calculates distance by sending out an ultrasonic pulse. It measures the time it takes for the echo to return.
Real-World Use Cases
- Automatic parking assist systems
- Object detection in robotics
- Smart measurement tools
- Obstacle avoidance in drones and autonomous vehicles
Skill Level
Beginner to Intermediate
Expected Outcome
By the end of this project, you will:
- Understand how ultrasonic distance measurement works
- Learn to interface digital sensors with Arduino
- Develop an LCD-based display system (optional)
- Be able to build your own distance measuring device
Components Required
| Quantity | Part | Description | Buy Link |
|---|---|---|---|
| 1 | Arduino UNO | Main micro controller board | Buy on Elecsynergy |
| 1 | HC-SR04 Ultrasonic Sensor | Measures distance using ultrasonic waves | Buy on Elecsynergy |
| 1 | 16×2 LCD Display (Optional) | To display distance values (requires I2C adapter ideally) | Buy on Elecsynergy |
| 1 | Breadboard | For circuit connections | Buy on Elecsynergy |
| 10 | Jumper Wires | Male-to-Male wires for connecting components | Buy on Elecsynergy |
| 1 | USB Cable for Arduino | For uploading code and powering Arduino | Buy on Elecsynergy |
Circuit Diagram + Explanation
HC-SR04 Pin Connections:
- VCC → 5V on Arduino
- GND → GND on Arduino
- Trig → Digital Pin 9
- Echo → Digital Pin 10
LCD Display (Optional):
If using a 16×2 LCD with I2C:
- VCC → 5V
- GND → GND
- SDA → A4
- SCL → A5
Visual Schematic:
Arduino Code – Commented
// Ultrasonic Distance Meter using HC-SR04 and Arduino
const int trigPin = 9;
const int echoPin = 10;
long duration;
float distanceCm;
void setup() {
Serial.begin(9600); // Start serial monitor
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
}
void loop() {
// Clear the trigger pin
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// Send a 10-microsecond pulse
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Measure the echo time
duration = pulseIn(echoPin, HIGH);
// Calculate distance (cm)
distanceCm = duration * 0.034 / 2;
// Display on Serial Monitor
Serial.print("Distance: ");
Serial.print(distanceCm);
Serial.println(" cm");
delay(1000); // Delay 1 second between readings
}
Working Explanation
The HC-SR04 sensor sends out an ultrasonic pulse when triggered. When the pulse hits an object, it reflects back, and the sensor detects the echo. The Arduino calculates the time taken for this round trip and uses the speed of sound (343 m/s) to calculate the distance:
Distance = (Time x Speed of Sound) / 2
The division by 2 accounts for the pulse traveling to the object and back.
Optional: With a 16×2 LCD connected, you can display the distance without needing the serial monitor.
Demo / Output Preview
You’ll see:
- Distance printed every second on the Serial Monitor
- (Optional) Distance displayed on an LCD
Use your hand or any object to see the values change in real-time.
Troubleshooting & Tips
- Always 0 or very high reading?
- Check trigger and echo pin wiring
- Ensure object is within 2cm–400cm
- Inconsistent results?
- Reduce noise by shielding sensor from cross-echoes
- Avoid reflective surfaces
- Nothing on serial monitor?
- Make sure baud rate is 9600
- Check USB cable connection
Project Expansion Ideas
1. LCD Distance Display
Add an LCD (16×2 or OLED) to display the result directly on the device.
2. Buzzer Alert System
Trigger a buzzer if the distance goes below a certain limit – great for proximity alerts.
3. Servo Integration
Attach a servo motor and scan for distances across multiple angles (like radar).
4. Wireless Transmission
Use Bluetooth or Wi-Fi (ESP32/ESP8266) to send distance data to a phone app or web dashboard.
5. Vehicle Reverse Parking Aid
Use multiple sensors at different angles and place it in a car prototype.
Conclusion
You’ve successfully built an Ultrasonic Distance Meter using Arduino and HC-SR04. It’s an excellent beginner-friendly project to introduce you to the world of sensors, timing, and environmental interaction.
This foundational project opens doors to smart automation, obstacle detection in robotics, and real-time sensor integration. Don’t stop here—keep expanding and combining this with other Arduino modules to build smarter devices!
✅ Try This: Add multiple sensors and rotate them using a servo to build a full 180-degree radar system!
