#include    //servo library

Servo servo; 

int trigPin = 5; 

int echoPin = 6; 

int servoPin = 7; 

int led = 10; 

long duration, dist, average; 

long aver[3];   //array for average



void setup() {   

Serial.begin(9600);   

servo.attach(servoPin);   

pinMode(trigPin, OUTPUT);   

pinMode(echoPin, INPUT);   servo.write(0);         

//close cap on power on   delay(100);   servo.detach(); }



void measure() {   

digitalWrite(10, HIGH);   

digitalWrite(trigPin, LOW);   

delayMicroseconds(5);   

digitalWrite(trigPin, HIGH);   

delayMicroseconds(15);   

digitalWrite(trigPin, LOW);   

pinMode(echoPin, INPUT);   

duration = pulseIn(echoPin, HIGH);   

dist = (duration / 2) / 29.1;  //obtain distance } 



void loop() {   

for (int i = 0; i <= 2; i++) { //average distance     

measure();    

aver[i] = dist;     

delay(10);              //delay between measurements  }  

dist = (aver[0] + aver[1] + aver[2]) / 3;



 if ( dist < 50 ) {    //改 ；我改了delay 时间，加喇叭，改 distance     

servo.attach(servoPin);     

delay(1);     

servo.write(180);     

tone(11, 524, 950); //buzzer or speaker frequency     

delay(3500);     

servo.write(0);     

delay(1000);    

servo.detach();   }   

Serial.print(dist); 

}