Building Your Own Smart Thermostat Using ESP32 and MQTT

11.12.2024 - Engine: Gemini

Building a Smart Thermostat with ESP32 and MQTT

Components:

• ESP32 Microcontroller
• Temperature Sensor (e.g. DHT22)
• Relay (for switching the heating/cooling device)
• MQTT Broker

Setup:

1. Hardware Connection:

   • Connect the temperature sensor to the ESP32.
   • Connect the relay to the ESP32 and the heating/cooling device.

2. Software Installation:

   • Install Arduino IDE.
   • Install ESP32 libraries.
   • Install MQTT library.

Code:

#include <WiFi.h>
#include <PubSubClient.h>
#include <DHT.h>

// MQTT Broker details
const char* mqttServer = "broker.mqtt-dashboard.com";
uint16_t mqttPort = 1883;

// Temperature sensor details
#define DHTPIN 5
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

// Relay details
const int relayPin = 2;

// Global variables
bool heating = false;
float desiredTemp = 20.0;

// MQTT client
WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  // Connect to WiFi
  WiFi.begin("Network Name", "Password");
  while (WiFi.status() != WL_CONNECTED) { delay(500); }

  // Connect to MQTT client
  client.setServer(mqttServer, mqttPort);
  while (!client.connected()) { client.connect("Thermostat"); }

  // Initialize temperature sensor
  dht.begin();

  // Set relay pin as output
  pinMode(relayPin, OUTPUT);
}

void loop() {
  // Keep client alive
  client.loop();

  // Read temperature
  float temp = dht.readTemperature();

  // Publish temperature over MQTT
  client.publish("thermostat/temp", String(temp).c_str());

  // Compare temperature with desired temperature
  if (temp < desiredTemp - 0.5) {
    // Heat
    digitalWrite(relayPin, HIGH);
    heating = true;
  } else if (temp > desiredTemp + 0.5) {
    // Cool
    digitalWrite(relayPin, LOW);
    heating = false;
  }

  // Publish heating status over MQTT
  client.publish("thermostat/heating", heating ? "true" : "false");
}

How it Works:

• The ESP32 connects to the WiFi and MQTT broker.
• The temperature sensor reads the room temperature and publishes it over MQTT.
• The ESP32 compares the sensed temperature with the desired temperature.
• If the temperature is below the desired temperature, the heating device is turned on.
• If the temperature is above the desired temperature, the heating device is turned off.
• The heating status is published over MQTT.