###### tags: `Arduino`
# DHT22 sensor project

DHT22 library can be found in the Arduino libraries manager.

Adafruit sensor library base:
https://www.arduinolibraries.info/libraries/adafruit-unified-sensor

LCD I2C libraries:
https://www.arduinolibraries.info/libraries/liquid-crystal-i2-c

### code

#include "DHT.h"
#define DTpin 2
#define DHTTYPE DHT22
DHT dht(DTpin,DHTTYPE);

#include<Wire.h>
#include<LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,16,2);

const int ledr = 11, ledy = 10, ledg = 9;
const int buz = 13;
const int fan = 3;

void setup(){
  Serial.begin(9600);
  dht.begin();
  for(int i=3;i<=13;i++){
    pinMode(i,OUTPUT);
  }
  pinMode(2,INPUT);

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("start");
}

void loop(){
  analogWrite(fan,255);
  delay(1000);
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  if (isnan(h) || isnan(t) ) {
    Serial.println(F("感測器讀取失敗"));
    return;
  }
  Serial.print(F("濕度: "));
  Serial.print(h);
  Serial.print(F("% 溫度: "));
  Serial.print(t);
  Serial.println("°C");

  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("T:");lcd.print(t);lcd.print((char) 0);
  lcd.print("H:");lcd.print(h);

  if(t>=40){           //紅燈亮
    digitalWrite(11,1);
    digitalWrite(10,0);
    digitalWrite(9,0);
    lcd.setCursor(1,0);
    lcd.print("Temp Alarming");
    for(int i=0;i<20;i++){   //i上限是蜂鳴器次數
      tone(13, 440);
      delay(200);
      noTone(13);  // 停止播放
      delay(200);
    }
  }else if(t>=35){     //黃燈亮
    digitalWrite(11,0);
    digitalWrite(10,1);
    digitalWrite(9,0);
  }else{               //綠燈亮
    digitalWrite(11,0);
    digitalWrite(10,0);
    digitalWrite(9,1);
  }
}

### wiring

tmpIC => DHT22

Datapin is arduino pin2

RGB led => lcd monitor

| Vin | GND | SCL | SDA |
| --- | --- | --- | --- |
| 5V | GND | A5 | A4 |