TemperatureSensor.ino

#include <SimpleDHT.h>
#include <LiquidCrystal.h>
#include "pitches.h"

// for DHT11, 
//      VCC: 5V or 3V
//      GND: GND
//      DATA: 2

int pinDHT11 = 2;
SimpleDHT11 dht11;
int melody[] = {NOTE_B0, NOTE_DS8};
int duration = 1500;  // 1500 miliseconds
int buzzer = 5;//the pin of the passive buzzer

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(buzzer,OUTPUT);//initialize the buzzer pin as an output
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("The temp is: ");  
}

void loop() {
  // put your main code here, to run repeatedly:
  Serial.println("=================================");
  Serial.println("Sample DHT11...");
  
  // read with raw sample data.
  byte temperature = 0;
  byte humidity = 0;
  byte data[40] = {0};
  if (dht11.read(pinDHT11, &temperature, &humidity, data)) {
    Serial.print("Read DHT11 failed");
    return;
  }
  
  Serial.print((int)temperature); Serial.print(" *C, ");
  Serial.print((int)humidity); Serial.println(" %");
  
  // DHT11 sampling rate is 1HZ.
  delay(1000);

  lcd.setCursor(0, 1);
  lcd.print((int)temperature);

  Serial.print("temperature: "); 
  Serial.println(temperature); 

  if(temperature < 30) {
      digitalWrite(6, HIGH); //pin 6 is for LED
      tone(buzzer, melody[0], duration);
  }

  if(temperature >= 30) {
      digitalWrite(6, LOW); //pin 6 is for LED
      //tone(buzzer, melody[0], duration);
  }

}