10. Internet of Things (IoT)

🌐 What is ThingSpeak?

ThingSpeak is a cloud-based platform provided by MathWorks that allows devices to send data using HTTP protocols. It offers easy graphing, public/private channels, and MATLAB-based data analysis tools.

• Free for personal use with limited updates per day
• Supports HTTP and MQTT protocols
• Real-time chart plotting and analytics
• Used widely for temperature monitoring, environment sensing, etc.

🛠️ What You Need

• ESP32 or NodeMCU microcontroller
• Wi-Fi connection
• Sensor (e.g., DHT11 for temperature/humidity)
• ThingSpeak account (https://thingspeak.com)

📶 Setting Up a ThingSpeak Channel

1. Create a free ThingSpeak account and log in.
2. Click on "Channels" > "New Channel".
3. Give a name (e.g., WeatherData), and enable the fields you want (e.g., Field1: Temperature, Field2: Humidity).
4. Save the channel and note down your Write API Key from the API Keys tab.

🔌 Circuit Setup

Example: DHT11 sensor with ESP32

• VCC → 3.3V
• GND → GND
• Data → GPIO 4

🧑‍💻 Sample Code to Send Data to ThingSpeak

// Required Libraries
#include <WiFi.h>
#include <HTTPClient.h>
#include "DHT.h"

// Wi-Fi Credentials
const char* ssid = "YourWiFiSSID";
const char* password = "YourWiFiPassword";

// ThingSpeak Settings
const char* server = "http://api.thingspeak.com/update";
String apiKey = "YOUR_WRITE_API_KEY";

// DHT Sensor Settings
#define DHTPIN 4
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  dht.begin();

  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }
  Serial.println("Connected to WiFi");
}

void loop() {
  float temp = dht.readTemperature();
  float hum = dht.readHumidity();

  if (isnan(temp) || isnan(hum)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    String url = server + String("?api_key=") + apiKey +
                 "&field1=" + String(temp) +
                 "&field2=" + String(hum);

    http.begin(url);
    int httpCode = http.GET();
    if (httpCode > 0) {
      Serial.println("Data sent successfully");
    } else {
      Serial.println("Error sending data");
    }
    http.end();
  }

  delay(15000); // Wait 15 seconds before next update
}

📊 Viewing Your Data

After running the sketch, open your ThingSpeak channel. You will see real-time graphs under each field that you've updated from your ESP board. These are auto-generated and updated every 15 seconds (or based on your delay).

💡 Use Cases

• Environment monitoring robots that upload data every few minutes
• Health robots that log temperature/humidity in a remote room
• Weather bots that stream live updates to a dashboard

⚠️ Tips & Troubleshooting

• Ensure correct Wi-Fi SSID and password
• Double-check your ThingSpeak Write API Key
• Use serial monitor for debugging network or sensor errors
• Observe ThingSpeak update limits: 1 update every 15 seconds for free accounts