// MCU BASIC: https://www.basic4mcu.com
// DateTime : 2020-09-03 오후 10:16:51
// by Ok-Hyun Park
//
사람을 인식하고 10초 동안 소리가 나고,
만약 10초 뒤에 사람이 없으면 소리가 끊기고,
만약 10초 뒤에도 사람이 있다면 소리가 계속 나오는 것
//
int  alertLED=9,alertBuzz=8,triggerPin=7,echopin=6;
//
int  sec=0;
long distance;
//
void setup(){
  Serial.begin(9600);
  pinMode(alertLED,OUTPUT);   pinMode(alertBuzz,OUTPUT);
  pinMode(triggerPin,OUTPUT); pinMode(echopin,INPUT);
}
//
void loop(){
  digitalWrite(triggerPin,1); delayMicroseconds(10); digitalWrite(triggerPin,0);
  //
  distance=pulseIn(echopin,HIGH)/58; distance=distance>100?100:distance;
  if(distance<40){
    sec++; digitalWrite(alertLED,1); digitalWrite(alertBuzz,1);
  }
  else{
    if(sec){
      if(++sec>10){sec=0; digitalWrite(alertBuzz,0); digitalWrite(alertLED,0); }
    }
  }
  //
  delay(1000);
}