HC-SR04 Ultrasonic Distance Sensor Module

Overview

HC-SR04 Ultrasonic Distance Sensor Module designed for accurate non-contact distance measurement using ultrasonic sound waves. A low-cost, reliable, and easy-to-use sensor widely used in Arduino, ESP32, STM32, Raspberry Pi, robotics, automation, obstacle avoidance, smart parking systems, water level monitoring, and IoT applications.

The module operates by transmitting 40kHz ultrasonic pulses and measuring the echo return time to calculate distance. Features simple 4-pin interface, stable performance, high accuracy, and wide compatibility with most microcontrollers and development boards.

Specifications

Parameter	Value
Model	HC-SR04
Sensor Type	Ultrasonic Distance Sensor
Operating Voltage	5V DC
Operating Current	15mA
Standby Current	<2mA
Operating Frequency	40kHz
Measuring Range	2cm – 400cm
Resolution	0.3cm
Accuracy	±3mm
Measuring Angle	<15°
Trigger Input	10µs TTL Pulse
Output Signal	TTL Pulse
Interface	Trigger + Echo
Dimensions	~45mm × 20mm × 15mm
Weight	~9g

Pin Configuration

Pin	Description
VCC	5V Power Supply
TRIG	Trigger Input
ECHO	Echo Output
GND	Ground

Features

• Non-contact distance measurement — ultrasonic sensing technology
• Wide measurement range — 2cm to 4 meters
• High accuracy — up to ±3mm precision
• 40kHz ultrasonic frequency — stable and reliable detection
• Simple 4-pin interface — easy integration with microcontrollers
• Fast response time — suitable for real-time applications
• Low cost — ideal for education and DIY projects
• Compact module size — easy to install in robotics projects
• Wide compatibility — Arduino, ESP32, STM32, Raspberry Pi
• Stable performance — reliable indoor measurement
• Low power consumption — suitable for battery-powered systems

Working Principle

The HC-SR04 works using ultrasonic sonar technology.

1. Microcontroller sends a 10µs trigger pulse
2. Sensor transmits 8 ultrasonic pulses at 40kHz
3. Sound waves reflect from nearby objects
4. Echo signal returns to the sensor
5. Sensor outputs pulse width based on travel time
6. Distance is calculated using sound speed

Distance Formula:

Distance = (Time × Speed of Sound) / 2

HC-SR04 vs IR Distance Sensor

Feature	HC-SR04	IR Sensor
Technology	Ultrasonic	Infrared
Range	2cm – 400cm	Short range
Accuracy	High	Medium
Ambient Light Effect	Minimal	High
Transparent Object Detection	Better	Poor
Outdoor Use	Limited	Better in some cases
Price	Low	Low
Best For	Robotics & distance	Line tracking

Wiring with Arduino UNO

HC-SR04	Arduino UNO
VCC	5V
GND	GND
TRIG	D9
ECHO	D10

Wiring with ESP32

HC-SR04	ESP32
VCC	5V
GND	GND
TRIG	GPIO5
ECHO	GPIO18 (use voltage divider)

Note: HC-SR04 Echo pin outputs 5V. Use a voltage divider when connecting to 3.3V microcontrollers like ESP32 or Raspberry Pi.

Common Applications

• Obstacle avoidance robot
• Distance measurement
• Smart parking system
• Water level monitoring
• Automatic door system
• Robot navigation
• Security systems
• Industrial automation
• IoT monitoring projects
• Smart trash bin
• Liquid level sensing

Getting Started (Arduino IDE)

Required Libraries

No external library required.

Basic Arduino Example

#define TRIG_PIN 9
#define ECHO_PIN 10

long duration;
float distance;

void setup() {
    Serial.begin(9600);

    pinMode(TRIG_PIN, OUTPUT);
    pinMode(ECHO_PIN, INPUT);
}

void loop() {

    // Clear trigger
    digitalWrite(TRIG_PIN, LOW);
    delayMicroseconds(2);

    // Send 10us pulse
    digitalWrite(TRIG_PIN, HIGH);
    delayMicroseconds(10);
    digitalWrite(TRIG_PIN, LOW);

    // Read echo time
    duration = pulseIn(ECHO_PIN, HIGH);

    // Calculate distance
    distance = duration * 0.0343 / 2;

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

    delay(500);
}

Package Includes

• 1× HC-SR04 Ultrasonic Sensor Module

Notes

• Recommended operating voltage is 5V
• Avoid soft surfaces that absorb sound waves
• Sensor accuracy may vary with temperature and humidity
• Not ideal for outdoor heavy rain environments
• Use level shifting for 3.3V microcontrollers
• Minimum trigger pulse width is 10µs

Applications in Robotics & IoT

The HC-SR04 is commonly used in:

• Line-following robots
• Autonomous navigation systems
• Smart home automation
• IoT monitoring systems
• Obstacle detection robots
• Industrial level measurement
• Parking assistance systems

The sensor remains one of the most popular low-cost ultrasonic modules for education, embedded systems, and maker projects due to its simplicity and reliability.