一個典型的 IoT（物聯網）與工業自動化系統整合（SCADA/機台連線） 的架構圖。它透過 Node-RED 作為核心資料網關，將前端 ESP32 微控制器 採集的環境數據，經由 MQTT 協定 轉換並寫入工業標準的 Modbus 暫存器 中。
1. 各模組功能拆解
🟢 左上角：WOKWI 虛擬開發平台（前端感測與控制端）
☁️ 右上角：MQTT Broker (mqttgo.io)
🔴 右下角：Node-RED（資料流中樞網關）
🟢 左下角：ModbusSim (Schneider Electric)
功能： 工業通訊協定 Modbus 伺服器/從站（Slave） 的模擬軟體。
畫面解析： 畫面顯示的是 Holding Register（保持暫存器，40001 起始）。
用途： 模擬工廠內部的 PLC（可程式邏輯控制器）或 SCADA（中控監控系統）。Node-RED 將收集到的 IoT 數據（溫濕度、CO_2）寫入這些對應的暫存器編號（如 40001, 40002...）中，讓工業設備可以讀取物聯網端的資料。
2. 整體系統的資料流向（How it works）
這個系統主要實現了雙向通訊：
🔄 數據上傳流程（感測監測）
當 Wokwi 裡的感測器偵測到溫度變化，數據會一路經由雲端與 Node-RED，最後反映在工業 ModbusSim 的表格數字上。
🔄 指令下發流程（設備控制）
💡 總結應用場景
這個架構非常實用，常建構於 「傳統工廠數位轉型」 或 「智慧農業/智慧建築」 中。
例如：工廠原本的舊型中控系統（只懂 Modbus 協定）無法直接連上便宜的 Wi-Fi 感測器。透過這套架構，就能用成本極低的 ESP32 + MQTT 佈署大量環境感測器，並用 Node-RED 完美無縫地將數據餵給工廠原有的 PLC/SCADA 系統 (ModbusSim)。
WOKWI程式
#include <WiFi.h>
#include <PubSubClient.h>
#include <DHT.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
// --- 設定區 ---
const char* ssid = "Wokwi-GUEST"; // Wokwi 專用模擬 WiFi
const char* password = "";
const char* mqtt_server = "mqttgo.io"; // 請替換成你的 MQTT 伺服器網址 (例如 io.adafruit.com)
const int mqtt_port = 1883;
const char* mqtt_user = ""; // 如果需要認證，請填寫
const char* mqtt_pass = ""; // 如果需要認證，請填寫
// --- 引腳定義 ---
#define DHTPIN 15
#define DHTTYPE DHT22
#define LED1_PIN 12
#define LED2_PIN 14
// --- 引腳與控制參數設定 (保留原程式) ---
#define CO2_SENSOR_PIN 36 // MG811 感測器模擬引腳
float co2Level = 0.0;
const float CO2_LOW_THRESHOLD = 400.0; // 最低門檻 (ppm)
const float CO2_HIGH_THRESHOLD = 1000.0; // 最高門檻 (ppm)
// --- MQTT 主題定義 ---
const char* topic_temp = "alex9ufo/temperature";
const char* topic_humi = "alex9ufo/humidity";
const char* topic_ctrl = "alex9ufo/ledcontrol";
const char* topic_status = "alex9ufo/ledstatus";
const char* topic_co2 = "alex9ufo/co2";
// --- 初始化物件 ---
DHT dht(DHTPIN, DHTTYPE);
LiquidCrystal_I2C lcd(0x27, 16, 2); // 模擬器中 I2C 位址通常為 0x27
WiFiClient espClient;
PubSubClient client(espClient);
unsigned long lastMsg = 0;
const long interval = 15000; // 每 5 秒發行一次溫濕度
void setup_wifi() {
delay(10);
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Connecting WiFi");
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("WiFi Connected");
delay(1000);
}
// 讀取 CO2 感測器 (保留原程式)
float readCO2Sensor() {
int co2Raw = analogRead(CO2_SENSOR_PIN); // 讀取 0~4095 類比值
float co2 = map(co2Raw, 0, 4095, 0, 5000); // 轉換為 0~5000 ppm
Serial.print("CO2 Level: ");
Serial.print(co2);
Serial.println(" ppm");
return co2;
}
// 接收到訂閱訊息的回呼函式 (Callback)
void callback(char* topic, byte* payload, unsigned int length) {
String messageTemp;
Serial.print("Message arrived on topic: ");
Serial.print(topic);
Serial.print(". Message: ");
for (int i = 0; i < length; i++) {
Serial.print((char)payload[i]);
messageTemp += (char)payload[i];
}
Serial.println();
// 顯示接收到的控制指令到 LCD
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("MQTT Recv:");
lcd.setCursor(0, 1);
lcd.print(messageTemp);
// 判斷指令並控制 LED
if (String(topic) == topic_ctrl) {
if (messageTemp == "on1") {
digitalWrite(LED1_PIN, HIGH);
client.publish(topic_status, "ON1");
Serial.println("LED1 turned ON");
} else if (messageTemp == "off1") {
digitalWrite(LED1_PIN, LOW);
client.publish(topic_status, "OFF1");
Serial.println("LED1 turned OFF");
} else if (messageTemp == "on2") {
digitalWrite(LED2_PIN, HIGH);
client.publish(topic_status, "ON2");
Serial.println("LED2 turned ON");
} else if (messageTemp == "off2") {
digitalWrite(LED2_PIN, LOW);
client.publish(topic_status, "OFF2");
Serial.println("LED2 turned OFF");
}
}
delay(1500); // 讓使用者看清 LCD 上的控制訊息，隨後會被溫濕度刷掉
}
void reconnect() {
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Connect MQTT...");
// 嘗試連接 (使用隨機 Client ID 避免衝突)
String clientId = "ESP32Client-";
clientId += String(random(0xffff), HEX);
// 如果不需要帳密，請改為 client.connect(clientId.c_str())
if (client.connect(clientId.c_str(), mqtt_user, mqtt_pass)) {
Serial.println("connected");
lcd.setCursor(0, 1);
lcd.print("MQTT Connected!");
// 訂閱控制主題
client.subscribe(topic_ctrl);
delay(1000);
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
lcd.setCursor(0, 1);
lcd.print("Failed! Retry...");
delay(5000);
}
}
}
void setup() {
Serial.begin(115200);
pinMode(LED1_PIN, OUTPUT);
pinMode(LED2_PIN, OUTPUT);
digitalWrite(LED1_PIN, LOW);
digitalWrite(LED2_PIN, LOW);
// 初始化 LCD
lcd.init();
lcd.backlight();
lcd.setCursor(0, 0);
lcd.print("Initializing...");
// 初始化 DHT22
dht.begin();
setup_wifi();
client.setServer(mqtt_server, mqtt_port);
client.setCallback(callback);
}
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
unsigned long now = millis();
if (now - lastMsg > interval) {
lastMsg = now;
// 讀取溫濕度
float h = dht.readHumidity();
float t = dht.readTemperature();
// 檢查讀取是否失敗
if (isnan(h) || isnan(t)) {
Serial.println("Failed to read from DHT sensor!");
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("DHT Read Error");
return;
}
// 顯示於 Serial Monitor
Serial.print("Humidity: ");
Serial.print(h);
Serial.print("% Temperature: ");
Serial.print(t);
Serial.println("°C");
// 顯示於 16x2 LCD
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Temp: ");
lcd.print(t, 1);
lcd.print((char)223); // 顯示 ° 符號
lcd.print("C");
lcd.setCursor(0, 1);
lcd.print("Humi: ");
lcd.print(h, 1);
lcd.print("%");
// 發行到 MQTT
client.publish(topic_temp, String(t).c_str());
client.publish(topic_humi, String(h).c_str());
// 1. 讀取數值
co2Level = readCO2Sensor();
// 3. 透過 MQTT 上傳資料到網頁工具
String payload = String(co2Level, 1); // 保留一位小數點的字串
client.publish(topic_co2, payload.c_str());
Serial.println("");
Serial.println("Data published to MQTT.");
}
}
Node-Red程式
需安裝元件 node-red-dashboard 與 node-red-contrib-modbus
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