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 calculates the time it takes for the echo to return, enabling accurate distance measurements. This sensor is widely used in robotics, obstacle detection, and distance measurement applications due to its simplicity, affordability, and reliability.

• 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. Trigger the Sensor: Send a 10 µs HIGH pulse to the Trig pin to initiate a measurement.
3. Read the Echo: Measure the duration of the HIGH pulse on the Echo pin. The duration is proportional to the distance of the object.
4. Calculate Distance: Use the formula below to calculate the distance: [ \text{Distance (cm)} = \frac{\text{Pulse Duration (µs)}}{58} ] Alternatively, for distance in inches: [ \text{Distance (in)} = \frac{\text{Pulse Duration (µs)}}{148} ]

• 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 capacitor (e.g., 10 µF) across the VCC and GND pins to stabilize the power supply.
• The sensor has a minimum range of 2 cm; objects closer than this may not be detected accurately.

Below is an example of how 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
  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 / 58.0;

  // 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

   • Cause: Loose or incorrect wiring.
   • Solution: Double-check all connections, ensuring VCC is connected to 5V, GND to ground, and Trig/Echo pins to the correct digital pins.

2. Unstable or Fluctuating Measurements

   • Cause: Electrical noise or unstable power supply.
   • Solution: Add a decoupling capacitor (e.g., 10 µF) across the VCC and GND pins.

3. Sensor Not Detecting Objects

   • Cause: Object is outside the sensor's range or at an angle.
   • Solution: Ensure the object is within the 2 cm to 4 m range and aligned within the 15-degree detection angle.

4. Echo Pin Always HIGH or LOW

   • Cause: Faulty sensor or incorrect trigger signal.
   • Solution: Verify the Trig pin is receiving a 10 µs HIGH pulse. Replace the sensor if necessary.

Q: Can the HC-SR04 measure distances below 2 cm?
A: No, the sensor's minimum range 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: 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.