How to Use HC-SR04 Ultrasonic Sensor: Examples, Pinouts, and Specs

The HC-SR04 is an ultrasonic distance sensor that uses sonar to measure the distance to an object. It emits a high-frequency sound wave and measures the time it takes for the echo to return, allowing it to calculate the distance based on the speed of sound. This sensor is widely used in robotics, automation, and obstacle detection systems due to its accuracy, affordability, and ease of use.

• Obstacle detection in robotics
• Distance measurement in automation systems
• Liquid level sensing
• Parking assistance systems
• Proximity detection in security systems

The HC-SR04 sensor is designed for precise distance measurement and operates within a specific range of environmental conditions. Below are its key technical details:

The HC-SR04 has four pins, as described in the table below:

The HC-SR04 sensor is simple to use and can be integrated into a variety of circuits. Below are the steps to use the sensor effectively:

1. Connect the VCC pin to the 5V output of your microcontroller or power supply.
2. Connect the GND pin to the ground of your circuit.
3. Connect the Trig pin to a digital output pin of your microcontroller.
4. Connect the Echo pin to a digital input pin of your microcontroller.

1. Send a 10 µs HIGH pulse to the Trig pin to trigger the ultrasonic burst.

2. The sensor emits an 8-cycle burst of 40 kHz sound waves.

3. The Echo pin outputs a HIGH pulse whose duration corresponds to the time taken for the sound wave to travel to the object and back.

4. Measure the duration of the HIGH pulse on the Echo pin to calculate the distance using the formula:

   [ \text{Distance (cm)} = \frac{\text{Pulse Duration (µs)} \times 0.034}{2} ]

Below is an example Arduino sketch to measure distance using the HC-SR04:

// Define pins for the HC-SR04 sensor
const int trigPin = 9; // Trigger pin connected to digital pin 9
const int echoPin = 10; // Echo pin connected to digital pin 10

void setup() {
  // Initialize serial communication for debugging
  Serial.begin(9600);
  
  // Set pin modes for the sensor
  pinMode(trigPin, OUTPUT); // Trig pin as output
  pinMode(echoPin, INPUT);  // Echo pin as input
}

void loop() {
  // Send a 10 µs HIGH pulse to the Trig pin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure the duration of the HIGH pulse on the Echo pin
  long duration = pulseIn(echoPin, HIGH);

  // Calculate the distance in centimeters
  float distance = (duration * 0.034) / 2;

  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Wait before the next measurement
  delay(500);
}

• Ensure the sensor is powered with a stable 5V DC supply for accurate readings.
• Avoid placing the sensor in environments with excessive noise or vibrations, as these can interfere with measurements.
• The sensor's measuring angle is 15°, so ensure there are no obstructions within this cone for accurate results.
• Use a capacitor (e.g., 10 µF) across the VCC and GND pins to filter out power supply noise.

1. No Output or Incorrect Readings

   • Ensure all connections are secure and correct.
   • Verify that the sensor is powered with 5V DC.
   • Check for any obstructions in the sensor's path.

2. Unstable or Fluctuating Readings

   • Add a capacitor across the VCC and GND pins to stabilize the power supply.
   • Ensure the sensor is not exposed to excessive noise or vibrations.

3. Echo Pin Always LOW

   • Verify that the Trig pin is receiving a 10 µs HIGH pulse.
   • Check the wiring and ensure the Echo pin is connected to the correct input pin.

Q: Can the HC-SR04 measure distances less than 2 cm?
A: No, the minimum measurable distance is 2 cm. Objects closer than this may not be detected accurately.

Q: Can I use the HC-SR04 with a 3.3V microcontroller?
A: The HC-SR04 requires a 5V power supply. However, you can use a voltage divider on the Echo pin to safely interface with a 3.3V microcontroller.

Q: What is the maximum range of the HC-SR04?
A: The maximum range is 400 cm (4 meters), but accuracy may decrease at longer distances.

By following this documentation, you can effectively integrate the HC-SR04 ultrasonic sensor into your projects for reliable distance measurement.