Arduino-David

#define RELAY 4
#define BUZZER 2
int state = 0;

void setup() {
  Serial.begin(9600);
  pinMode(RELAY, OUTPUT);
  pinMode(BUZZER, OUTPUT);
}

void loop() {
  int value = analogRead(A5);
  float voltage = fmap(value, 0, 1023, 0, 5);
  Serial.println(voltage);
  if (state == 0){
    if (voltage > 3){
      digitalWrite(RELAY, HIGH);
      digitalWrite(BUZZER, HIGH);
      state = 1;
    }
  } else {
    if (voltage < 2){
      digitalWrite(RELAY, LOW);
      digitalWrite(BUZZER, LOW);
      state = 0;
    }
  }
  delay(10);
}

float fmap(float x, float in_min, float in_max, float out_min, float out_max)
{
 return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}