How to Use Ultrasonic: Examples, Pinouts, and Specs

The HCSR-04 Ultrasonic Sensor, manufactured by Sensor, is a versatile and widely used electronic component designed for distance measurement and object detection. It operates by emitting ultrasonic sound waves and measuring the time it takes for the echo to return after bouncing off an object. This time-of-flight measurement allows for accurate distance calculations.

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

The HCSR-04 Ultrasonic Sensor is designed for ease of use and reliable performance. Below are its key technical details:

The HCSR-04 has four pins, as described in the table below:

1. Power the Sensor: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. Trigger the Sensor: Send a 10 µs HIGH pulse to the Trig pin to initiate ultrasonic transmission.
3. Read the Echo: Measure the duration of the HIGH pulse on the Echo pin. This 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} ] The factor 58 accounts for the speed of sound in air (343 m/s).

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

Below is an example of how to connect and use the HCSR-04 with an Arduino UNO:

// Define pins for the HCSR-04 Ultrasonic Sensor
const int trigPin = 9;  // Trigger pin connected to Arduino pin 9
const int echoPin = 10; // Echo pin connected to Arduino 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 cm
  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 and GND are properly connected.

2. Unstable Distance 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 too small to reflect sound waves.
   • Solution: Ensure the object is within the 2 cm to 400 cm range and has a sufficient surface area.

4. Echo Pin Always HIGH or LOW

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

Q: Can the HCSR-04 detect transparent objects?
A: The sensor may struggle to detect transparent objects like glass, as they may not reflect ultrasonic waves effectively.

Q: What is the maximum angle of detection?
A: The HCSR-04 has a detection angle of approximately 15 degrees.

Q: Can I use the HCSR-04 with a 3.3V microcontroller?
A: The HCSR-04 requires a 5V power supply. Use a level shifter for compatibility with 3.3V logic.

Q: How do I improve accuracy?
A: Use multiple measurements and average the results to reduce noise and improve accuracy.