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HC-SR04 Connection to Arduino Example

HC-SR04 Ultrasonic Front

This example shows HC-SR04 connection to Arduino. This example is basic setup and can be integrated into any other project and get the distance as final from either the cm or inch variables.

The HC-SR04 ultrasonic sensor uses sonar to determine distance to an object like bats or dolphins do. It offers excellent non-contact range detection with high accuracy and stable readings in an easy-to-use package. From 2cm to 400 cm or 1” to 13 feet. It operation is not affected by sunlight or black material like Sharp rangefinders are (although acoustically soft materials like cloth can be difficult to detect). It comes complete with ultrasonic transmitter and receiver module.

This example uses Arduino Uno, still, it can work for any Arduino model.

HC-SR04 Connection Steps

First implement the HC-SR04 connection to Arduino Uno as depicted in the image below:

HC-SR04 connection to Arduino UNO

Then use the following code with the Arduino:

// HC-SR04 Connection to Arduino Uno Example from TechDepot Egypt

const int trigPin = 7;
const int echoPin = 8;
long reply, cm, inch;

void setup() {

pinMode(trigPin, OUTPUT); // Prepare the trigger pin
pinMode(echoPin, INPUT);  // Prepare the echo pin



void loop() {

// Reset the trigger pin and get ready for a clean trigger pulse

digitalWrite(trigPin, LOW);

// Generate and send to trigger pin the trigger pulse

digitalWrite(trigPin, HIGH); // You need to keep it high for 10 micro seconds length
delayMicroseconds(10);       // This is the 10 microseconds we mentioned above :)
digitalWrite(trigPin, LOW);  // Stop the trigger pulse after the 10 microseconds

// Now let's see how long did it take the sound wave to travel
// It will take a time depending on the distance to the obstacle
// This time may be up to 38 millisecond in case of no obstacle
// If you never saw pulseIn before please check:

reply = pulseIn(echoPin, HIGH);

// Now we have the reply in microseconds, but we need a distance!


// Let's print the distance to the Arduino's Serial Monitor. Tools --> Serial Monitor

Serial.print("Distance in Inches ");
Serial.print(" - Distance in cm ");


void time2Distance(long rawReply) {

// The data sheet says that it takes sound 73.746 microseconds to travel 1 inch.
// So if we divide rawReply which is in microseconds by the above we will get how many
// inches the sound travelled forward and travelled back to the sensor.
// The rawReply is the sound travelling to obstacle and back, then we need to divide by 2

inch = rawReply/73.746/2;

// According to Google, 1 inch eaquales 2.54 cm, accordingly and to get distance in cm

cm = inch*2.54;


You are all done. Enjoy 🙂

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