ESP32 + MQTT + Node-RED Dashboard

Introduction

MQTT is a lightweight messaging protocol for small sensors and mobile devices. Node-RED is a flow-based tool for visual programming for the Internet of Things.

Prerequisites

• Mosquitto MQTT Broker (installed on PC/Pi)
• Node-RED (installed on PC/Pi)
• PubSubClient library for Arduino

ESP32 MQTT Code

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

const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD";
const char* mqtt_server = "192.168.1.XX"; // Your Broker IP

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
}

void loop() {
  if (!client.connected()) reconnect();
  client.loop();
  
  // Publish every 5 seconds
  static unsigned long last = 0;
  if (millis() - last > 5000) {
    last = millis();
    client.publish("room/temp", "24.5");
  }
}

Node-RED Setup

1. Drag an mqtt in node (Topic: room/temp).
2. Drag a gauge node from the dashboard palette.
3. Connect them and click Deploy.