How to use the HC-SR04 Ultrasonic Sensor

Introduction

In this guide, I’ll show you how to use the HC-SR04 ultrasonic sensor to measure distances and detect objects using an Arduino or another microcontroller.

Video

I created a detailed video demonstrating everything I explain on this page. It's very informative and I spent alot of time on it - so you should totally watch it. :)

What is the HC-SR04 Ultrasonic Sensor?

The HC-SR04 ultrasonic sensor is a compact module designed for measuring distances between 2 cm and 400 cm. It works by emitting ultrasonic pulses and measuring the time taken for the echo to return.

Physical Overview

Dimensions:~21 mm (H) × 45 mm (W) × 15 mm (D) (excluding pins)
Front: Houses the transmitter, receiver, and ceramic resonator
Back: Contains the microcontroller that generates ultrasonic pulses, processes echoes, and outputs the results
Components:
- Ultrasonic transceiver IC: Drives the transmitter and processes received signals
- Voltage regulator IC: Ensures stable voltage for reliable operation

How It Works

The HC-SR04 emits eight short ultrasonic pulses at 40 kHz. These pulses bounce off nearby objects and return to the sensor. By measuring the time delay between transmission and reception, the sensor calculates the distance to the object.

Pin Configuration

We'll go over the pins in more detail later, but very breifly you'll find the following:

VCC → 5V power supply
GND → Ground
TRIG → Used to trigger the ultrasonic pulse
ECHO → Outputs the measured distance as a signal

Wiring for Demo

Setting Up the Sensor with an Arduino

Let’s connect the HC-SR04 to an Arduino Uno:

Connect VCC to the 5V pin on the Arduino.
Connect GND to GND.
Connect TRIG to digital pin 9.
Connect ECHO to digital pin 10.

Uploading the Code

Download the code and paste it into the Arduino IDE. Select your microcontroller board and upload the sketch.

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