SMART TEMPERATURE & HUMIDITY MONITORING SYSTEM

LCD + IoT (ESP32) + SD Card + Buzzer Alert

---

🧠 Controller Used

✅ ESP32 (Wi-Fi built-in, best choice)

---

🔧 COMPONENTS

• ESP32 Dev Module

• DHT22 (or DHT11)

• 16×2 LCD with I2C module

• SD Card Module + SD Card

• Buzzer

• 10kΩ resistor

• Jumper wires

---

🔌 CONNECTION DIAGRAM (PIN MAPPING)

🌡️ DHT22

DHT22        ESP32
------------------
VCC   -----> 3.3V
DATA  -----> GPIO 4
GND   -----> GND
(10kΩ between VCC & DATA)

---

📟 LCD 16×2 (I2C)

LCD (I2C)    ESP32
------------------
VCC   -----> 5V
GND   -----> GND
SDA   -----> GPIO 21
SCL   -----> GPIO 22

---

📊 SD Card Module (SPI)

SD MODULE    ESP32
------------------
CS     -----> GPIO 5
MOSI   -----> GPIO 23
MISO   -----> GPIO 19
SCK    -----> GPIO 18
VCC    -----> 5V
GND    -----> GND

---

🔔 BUZZER

Buzzer + ----> GPIO 15
Buzzer - ----> GND

---

⚙️ WORKING

1. DHT reads temperature & humidity

2. LCD displays live values

3. Data stored in SD card (CSV file)

4. ESP32 sends data to cloud (ThingSpeak)

5. Buzzer alerts if limit crossed

---

🔔 ALERT LIMITS

• Temperature > 35°C

• Humidity > 80%

---

💻 FULL ESP32 CODE (READY TO UPLOAD)

#include <DHT.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <SPI.h>
#include <SD.h>
#include <WiFi.h>
#include <HTTPClient.h>

// ----------- SETTINGS -------------
#define DHTPIN 4
#define DHTTYPE DHT22
#define BUZZER 15
#define SD_CS 5

LiquidCrystal_I2C lcd(0x27, 16, 2);
DHT dht(DHTPIN, DHTTYPE);

// WiFi details
const char* ssid = "YOUR_WIFI_NAME";
const char* password = "YOUR_WIFI_PASSWORD";

// ThingSpeak
String apiKey = "YOUR_THINGSPEAK_API_KEY";

void setup() {
  Serial.begin(9600);

  pinMode(BUZZER, OUTPUT);
  digitalWrite(BUZZER, LOW);

  lcd.init();
  lcd.backlight();

  dht.begin();

  // SD Card
  if (!SD.begin(SD_CS)) {
    lcd.setCursor(0,0);
    lcd.print("SD Fail!");
  }

  // WiFi
  WiFi.begin(ssid, password);
  lcd.setCursor(0,0);
  lcd.print("Connecting...");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
  }
  lcd.clear();
}

void loop() {
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  if (isnan(humidity) || isnan(temperature)) {
    return;
  }

  // LCD Display
  lcd.setCursor(0,0);
  lcd.print("Temp: ");
  lcd.print(temperature);
  lcd.print(" C");

  lcd.setCursor(0,1);
  lcd.print("Hum : ");
  lcd.print(humidity);
  lcd.print(" %");

  // Buzzer Alert
  if (temperature > 35 || humidity > 80) {
    digitalWrite(BUZZER, HIGH);
  } else {
    digitalWrite(BUZZER, LOW);
  }

  // SD Card Logging
  File dataFile = SD.open("/data.csv", FILE_APPEND);
  if (dataFile) {
    dataFile.print(temperature);
    dataFile.print(",");
    dataFile.println(humidity);
    dataFile.close();
  }

  // ThingSpeak Upload
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    String url = "http://api.thingspeak.com/update?api_key=" + apiKey +
                 "&field1=" + String(temperature) +
                 "&field2=" + String(humidity);
    http.begin(url);
    http.GET();
    http.end();
  }

  delay(20000);
}

---

📊 SD CARD FILE (data.csv)

Temperature,Humidity
30.5,60
31.2,62

(Open in Excel 📈)

---

📟 LCD OUTPUT

Temp: 30.5 C
Hum : 60 %

---

🎓 PROJECT USE

• Final year project

• Smart weather station

• Greenhouse monitoring

• Server room alert system