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

The HC-SR04 is an ultrasonic distance sensor that uses sonar to measure the distance to an object. It emits ultrasonic waves and measures the time it takes for the echo to return, allowing for accurate distance measurements. This sensor is widely used in robotics, obstacle detection, and automation systems due to its reliability, 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 using ultrasonic sound waves. Below are its key technical details:

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

1. Power the Sensor: Connect the VCC pin to a 5V power source and the GND pin to ground.
2. Connect the Trigger Pin: Connect the Trig pin to a digital output pin of your microcontroller.
3. Connect the Echo Pin: Connect the Echo pin to a digital input pin of your microcontroller.
4. Send a Trigger Signal: Send a 10 µs HIGH pulse to the Trig pin to start the measurement.
5. Read the Echo Signal: Measure the duration of the HIGH pulse on the Echo pin. The duration is proportional to the distance.

• Ensure the sensor is mounted securely and aligned properly for accurate measurements.
• Avoid placing the sensor near ultrasonic noise sources, as this may interfere with readings.
• Use a resistor divider or level shifter if connecting the Echo pin to a 3.3V microcontroller.
• The sensor works best in environments with minimal obstructions and reflective surfaces.

Below is an example code to use the HC-SR04 sensor with an Arduino UNO:

// 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
  long 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);
}

1. No Output or Incorrect Readings:

   • Ensure the sensor is powered with 5V and properly connected to the microcontroller.
   • Verify that the Trig and Echo pins are connected to the correct digital pins.
   • Check for loose or faulty wiring.

2. Unstable or Fluctuating Measurements:

   • Ensure the sensor is not exposed to ultrasonic noise or vibrations.
   • Use a capacitor (e.g., 10 µF) across the VCC and GND pins to stabilize the power supply.

3. Short Measuring Range:

   • Ensure there are no obstructions or reflective surfaces too close to the sensor.
   • Verify that the sensor is mounted at the correct angle.

Q: Can the HC-SR04 measure distances below 2 cm?
A: No, the minimum measuring range of the HC-SR04 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: Yes, but you need to use a level shifter or resistor divider for the Echo pin to avoid damaging the microcontroller.

Q: What is the maximum distance the HC-SR04 can measure?
A: The maximum range is 400 cm, but accuracy may decrease at longer distances.

Q: How can I improve measurement accuracy?
A: Use the sensor in a stable environment, avoid ultrasonic interference, and ensure proper alignment with the target object.