Arduino with HC-SR04 Ultrasonic Sensor: A Comprehensive Guide





The HC-SR04 ultrasonic sensor is a popular choice among Arduino enthusiasts for measuring distance accurately. This versatile sensor uses ultrasonic waves to determine the distance between itself and an object, making it ideal for various applications, including robotics, home automation, and security systems. In this comprehensive guide, we will explore how the HC-SR04 sensor works, how to connect it to an Arduino, write code to obtain distance measurements, troubleshoot common issues, and answer frequently asked questions.

How Does the HC-SR04 Sensor Work?

The HC-SR04 sensor operates on the principle of sending and receiving ultrasonic waves. Here’s a simplified explanation of its working:

  1. Trigger Signal: The Arduino sends a short, high-frequency pulse (typically 10 microseconds) to the trigger pin of the HC-SR04. This triggers the sensor to emit an ultrasonic sound wave.
  2. Sound Wave Emission: The sensor emits an ultrasonic sound wave (inaudible to humans) at a specific frequency, usually 40 kHz.
  3. Reflection: When the sound wave encounters an object, it reflects back towards the sensor.
  4. Echo Reception: The HC-SR04’s receiver (echo pin) detects the reflected sound wave’s arrival time.
  5. Calculating Distance: By measuring the time it takes for the sound wave to travel to the object and back, the Arduino calculates the distance using the speed of sound in the air (approximately 343 meters per second at room temperature).

Wiring the HC-SR04 Sensor to Arduino

To connect the HC-SR04 sensor to your Arduino, follow these wiring instructions:

  • VCC: Connect to Arduino’s 5V.
  • Trig: Connect to any digital pin (e.g., D2).
  • Echo: Connect to any digital pin (e.g., D3).
  • GND: Connect to Arduino’s GND.
Complete circuit diagram of arduino connected with ultrasonic sensor also known as HC-SR01

Ensure a common ground connection between the Arduino and the sensor.

Arduino Code for HC-SR04

Here’s a sample Arduino code to obtain distance measurements using the HC-SR04 sensor:

const int trigPin = 2;
const int echoPin = 3;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

void loop() {
  digitalWrite(trigPin, LOW);

  digitalWrite(trigPin, HIGH);
  digitalWrite(trigPin, LOW);

  long duration = pulseIn(echoPin, HIGH);
  int distance = duration * 0.034 / 2;

  Serial.print("Distance: ");
  Serial.println(" cm");


The HC-SR04 ultrasonic sensor is a valuable tool for measuring distances in Arduino projects. With its straightforward working principle and easy integration, you can use it in a wide range of applications. Whether you’re building a smart robot or a home automation system, the HC-SR04’s accuracy and reliability make it a popular choice among makers and engineers.

Frequently Asked Questions (FAQ)

1. What is the maximum range of the HC-SR04 sensor?

The HC-SR04 sensor typically has a maximum range of around 4-5 meters. However, the accuracy may decrease at longer distances.

2. How can I improve the accuracy of distance measurements?

To enhance accuracy, ensure a stable power supply, minimize interference, and account for the sensor’s initial delay in your code.

3. Can I use multiple HC-SR04 sensors simultaneously with one Arduino?

Yes, you can use multiple sensors by connecting each sensor to a unique pair of trigger and echo pins on the Arduino.

4. What should I do if my sensor consistently returns incorrect measurements?

Check the wiring, power supply voltage, and ensure there are no obstacles or interference in the sensor’s path. Adjust the code for accurate calculations.

Troubleshooting Q&A

Q: My HC-SR04 sensor is returning inconsistent readings. What could be the issue?

A: Inconsistent readings can result from incorrect wiring, unstable power supply voltage, or interference. Check your connections, use a stable power source, and ensure a clear path between the sensor and objects.

Q: Why does my HC-SR04 sensor give inaccurate measurements at longer distances?

A: Accuracy decreases with distance due to factors like sound wave dispersion. To improve accuracy, consider using a different sensor for longer ranges or implementing error correction in your code.

Q: Is it possible to use the HC-SR04 underwater?

A: The HC-SR04 sensor is not designed for underwater use as water significantly affects the propagation of ultrasonic waves. Specialized underwater sensors are available for such applications.

Q: Can I measure the distance to multiple objects simultaneously?

A: While the HC-SR04 measures distances to the nearest object in its path, you can use multiple sensors to monitor distances in different directions simultaneously.

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