Ultrasonic Sensor Arduino (HC-SR04) — Wiring, Code & Proteus

An Ultrasonic Sensor Arduino (HC-SR04) project measures distance by timing a 40 kHz ping bouncing off an obstacle. In this tutorial we wire the HC-SR04 to an Arduino Uno, walk through the ultrasonic sensor Arduino code, and open the same circuit in Proteus so you can simulate radar, parking and obstacle-avoidance projects.

Welcome to this beginner-friendly Arduino tutorial on the ultrasonic. By the end of the guide, you'll wire the module to an Arduino UNO, flash a short sketch, and read live values on the Serial Monitor — no prior electronics experience required.

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What you'll learn

• How the module works in plain language
• The exact parts you need and how to wire them safely
• The full Arduino IDE sketch with comments
• Common issues and how to fix them

Arduino code

Open the Arduino IDE, paste the sketch below into a new file, install any libraries the sketch #includes (Tools → Manage Libraries), select your board and COM port, then click Upload.

const int trigPin = 4; // Trigger pin of the ultrasonic sensor (connected to Arduino digital pin 2)
const int echoPin = 5; // Echo pin of the ultrasonic sensor (connected to Arduino digital pin 3)
void setup() {
  Serial.begin(9600); // Initialize serial communication for debugging
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}
void loop() {
  // Trigger the ultrasonic sensor by sending a 10us pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  // Measure the time it takes for the echo to return
  long duration = pulseIn(echoPin, HIGH);
  // Calculate the distance in centimeters
  // Speed of sound in air at room temperature is approximately 343 meters/second or 0.0343 cm/microsecond
  // Divide the duration by 2 to account for the time it takes for the sound pulse to travel to the object and back
  int distance = duration * 0.0343 / 2;
  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  delay(1000); // Delay for readability (adjust as needed)
}

How it works

The sketch initialises serial communication and the ultrasonic driver in setup(), then in loop() it samples the sensor at a regular interval and prints the result to the Serial Monitor at 9600 baud. Open the Serial Monitor (Ctrl+Shift+M) after upload to see live readings.

Troubleshooting checklist

• No readings: verify the baud rate in Serial Monitor matches the sketch (usually 9600).
• Garbage characters: wrong baud rate or loose GND wire.
• Library not found: install the exact library referenced in the #include line via Library Manager.
• Sensor not detected (I²C): run an I²C scanner sketch to confirm the address.

What to build next

Once the basic readout works, try logging values to an SD card, sending them over Wi-Fi with an ESP32, or pushing them to a Blynk IoT dashboard. Pair this module with our simulator round-up to prototype the circuit before soldering.

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