How to Interface Ultrasonic sensor with an ESP32

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To interface an Ultrasonic sensor with an ESP32 and activate a buzzer when an object is detected within a certain range, you’ll need to connect the ultrasonic sensor (like HC-SR04) to the ESP32 and then use the sensor’s distance measurement to control the buzzer.

Hardware Setup

Components:

  1. ESP32 Board
  2. HC-SR04 Ultrasonic Sensor
  3. Buzzer

Connections:

  1. HC-SR04 Ultrasonic Sensor:
    • VCC → 5V pin (if using 5V version) or 3.3V pin (if using a 3.3V compatible version)
    • GND → GND pin
    • TRIG → GPIO 23 (or another GPIO pin)
    • ECHO → GPIO 22 (or another GPIO pin)
  2. Buzzer:
    • GND → GND pin
    • Positive Pin → GPIO 21 (or another GPIO pin)

Code:

Here’s an example code using the HC-SR04 ultrasonic sensor to measure the distance and trigger a buzzer if the distance is below a certain threshold:

#include <Arduino.h>

#define TRIG_PIN 23  // GPIO Pin for Trigger
#define ECHO_PIN 22  // GPIO Pin for Echo
#define BUZZER_PIN 21 // GPIO Pin for Buzzer

// Constants
const int THRESHOLD = 20; // Threshold distance in cm (for buzzer activation)

void setup() {
  // Start serial communication for debugging
  Serial.begin(115200);
  
  // Set up pins
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  
  // Ensure buzzer is off initially
  digitalWrite(BUZZER_PIN, LOW);
}

void loop() {
  // Trigger pulse to the Ultrasonic Sensor
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  
  // Read the duration of the Echo pulse
  long duration = pulseIn(ECHO_PIN, HIGH);
  
  // Calculate distance in cm
  long distance = (duration / 2) / 29.1; // Speed of sound = 343 m/s = 29.1 microseconds per cm
  
  // Output the distance for debugging
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  
  // If the distance is below the threshold, activate the buzzer
  if (distance < THRESHOLD) {
    digitalWrite(BUZZER_PIN, HIGH);  // Turn on buzzer
  } else {
    digitalWrite(BUZZER_PIN, LOW);   // Turn off buzzer
  }
  
  // Wait a little before taking the next measurement
  delay(500);
}

Explanation:

  1. TRIG_PIN (GPIO 23): Sends a pulse to the ultrasonic sensor to initiate a measurement.
  2. ECHO_PIN (GPIO 22): Receives the echo pulse after the sound wave reflects off an object.
  3. BUZZER_PIN (GPIO 21): Controls the buzzer, which will sound if the object is detected within the specified threshold distance.
  4. pulseIn(): This function measures the duration of the pulse on the Echo pin, which is then used to calculate the distance.
  5. Threshold Distance: If the distance measured by the ultrasonic sensor is less than the defined threshold (20 cm in this case), the buzzer will be activated.

Notes:

  • Make sure the HC-SR04 sensor’s Echo pin is connected to a GPIO pin that can read the signal level.
  • Adjust the THRESHOLD value as needed based on your application.
  • If your buzzer is active-low, you may need to invert the logic for turning it on/off (i.e., use digitalWrite(BUZZER_PIN, LOW) to activate it).