#include <NewPing.h>

#define TRIGGER_PIN 2
#define ECHO_PIN 3
#define BUZZER_PIN 4
#define MAX_DISTANCE 200

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);
unsigned long previousMillis = 0;
const long interval = 1000;

void setup() {
  pinMode(BUZZER_PIN, OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    unsigned int distance = sonar.ping_cm();
    if (distance < 25) {
      digitalWrite(BUZZER_PIN, HIGH);
    } else {
      digitalWrite(BUZZER_PIN, LOW);
    }
  }
}