int trigger = 26;
int echo= 33;
float distance;
void setup() {
 
  Serial.begin(115200);  
 pinMode(23,OUTPUT);
 pinMode(17, OUTPUT);
 pinMode(4, OUTPUT);
 pinMode(trigger, OUTPUT);
 pinMode(echo, INPUT);
 pinMode(25, OUTPUT);
}

int expri()
{
  digitalWrite(trigger, LOW);
  delay(10);
  digitalWrite(trigger, HIGH);
  delay(100);
  digitalWrite(trigger, LOW);
  distance=pulseIn(echo,HIGH);

  return(distance*0.034/2);

  
 
}

void loop() {
  int light = expri();
   Serial.println(light);

   if(light>300){
    digitalWrite(23, HIGH);
    digitalWrite(17, LOW);
    digitalWrite(4, LOW);
    Serial.println("safe");
  }
  else if( light >= 200 && light < 300 ){
    digitalWrite(17, HIGH);
    digitalWrite(23, LOW);
    digitalWrite(4, LOW);
    Serial.println("warning!!!!");
  }
  else if(light >0 && light < 200){
     digitalWrite(4, HIGH);
    digitalWrite(23, LOW);
    digitalWrite(17, LOW);
    Serial.println("Danger ahead");
    tone(25,9000);
    noTone(25);
  }

  else{
    digitalWrite(17, LOW);
    digitalWrite(4, LOW);
    digitalWrite(23, LOW);
  }
}