The HC-SR04 is a popular ultrasonic sensor used for measuring distances by emitting ultrasonic waves and detecting their reflections. It is widely used in robotics, automation, and obstacle detection projects.

Key Features:

Power Supply: 5V DC

Operating Current: 15mA

Measuring Angle: <15°

Operating Frequency: 40kHz

Range: 2 cm to 400 cm

Accuracy: ±0.3 cm

Pin Configuration:

1. VCC: Connects to the power supply (+5V)
2. Trig: Trigger input pin
3. Echo: Echo output pin
4. GND: Ground pin

Working Principle:

The HC-SR04 sensor determines the distance of an object using the time taken by ultrasonic waves to travel to the object and back.

1. A 10-microsecond pulse is sent to the Trig pin to start the measurement.
2. The sensor emits eight 40kHz ultrasonic pulses.
3. If these waves hit an object, they reflect and return to the sensor.
4. The Echo pin outputs a signal proportional to the time taken for the pulses to return.
5. Distance is calculated using the formula:
   Distance = (Speed of Sound × Time) / 2,
   where the speed of sound is approximately 343 m/s.

Interfacing with Arduino:

To connect the HC-SR04 with an Arduino:

Connect VCC to 5V and GND to GND on the Arduino.

Connect the Trig and Echo pins to two digital I/O pins (e.g., D9 and D10).

Here’s a simple Arduino code to measure distance:

define trigPin 9

define echoPin 10

void setup() {
Serial.begin(9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
}

void loop() {
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

long duration = pulseIn(echoPin, HIGH);
float distance = (duration * 0.0343) / 2;

Serial.print(“Distance: “);
Serial.print(distance);
Serial.println(” cm”);

delay(500);
}

Applications:

Obstacle avoidance in robotics

Security systems

Automated parking systems

Liquid level measurement