How to Use ultrasonic sensor: Examples, Pinouts, and Specs

An ultrasonic sensor is a device that uses ultrasonic waves to measure distance or detect objects. It emits a sound wave at a frequency above the audible range and measures the time it takes for the echo to return, allowing it to calculate the distance to the object.

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

Below are the general technical specifications for a commonly used ultrasonic sensor, such as the HC-SR04:

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 the ultrasonic burst.
3. Read the Echo: Measure the duration of the HIGH signal on the Echo pin. This duration corresponds to the time taken for the ultrasonic wave to travel to the object and back.
4. Calculate Distance: Use the formula below to calculate the distance: [ \text{Distance (cm)} = \frac{\text{Time (µs)} \times 0.034}{2} ] The factor 0.034 is derived from the speed of sound (343 m/s), and the division by 2 accounts for the round trip of the wave.

• Ensure the sensor is mounted securely and aligned properly for accurate measurements.
• Avoid placing the sensor near ultrasonic noise sources, as this can interfere with readings.
• Use a capacitor (e.g., 10 µF) across the VCC and GND pins to stabilize the power supply.
• The sensor may not work reliably with soft or highly absorbent surfaces, as they may not reflect sound waves effectively.

Below is an example of how to use the HC-SR04 ultrasonic sensor with an Arduino UNO:

// Define pins for the ultrasonic 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 the trigPin as an output and echoPin as an input
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

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

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

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

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

  // Wait for a short period before the next measurement
  delay(500);
}

1. No Output or Incorrect Readings:

   • Ensure the sensor is powered with 5V and properly grounded.
   • Verify the connections to the Trig and Echo pins.
   • Check for loose wires or poor soldering.

2. Unstable or Fluctuating Measurements:

   • Add a capacitor (e.g., 10 µF) across the VCC and GND pins to filter noise.
   • Ensure there are no obstructions or reflective surfaces near the sensor.

3. Sensor Not Detecting Objects:

   • Ensure the object is within the sensor's range (2 cm to 400 cm).
   • Check if the object is made of a material that reflects sound waves effectively.

Q1: Can the ultrasonic sensor measure through transparent materials like glass?
A1: No, ultrasonic sensors typically cannot measure through transparent materials like glass, as sound waves are either absorbed or refracted.

Q2: What is the maximum angle of detection for the sensor?
A2: The HC-SR04 has a detection angle of approximately 15 degrees. Ensure objects are within this cone for accurate readings.

Q3: Can I use the sensor with a 3.3V microcontroller?
A3: The HC-SR04 is designed for 5V operation. If using a 3.3V microcontroller, a level shifter is recommended for safe operation.

Q4: Why is the distance always showing as zero?
A4: This could happen if the Echo pin is not receiving a reflected signal. Check the alignment and ensure the object is within range.