Build Your Own Air Quality Monitor with ESP32: Real-Time AQI Tracking

1#include <WiFi.h>
2#include <HTTPClient.h>
3
4// WiFi Credentials
5const char* ssid = "your ssid ";
6const char* password = "your password";
7
8// ThingSpeak API and Server
9String apiKey = "K03G5HHHHL8RTS4M";
10const char* server = "http://api.thingspeak.com/update";
11
12// Analog Sensor Pins
13#define MQ135_PIN 34  // CO2 sensor
14#define MQ2_PIN   32  // Smoke / Gas sensor
15
16// Classify AQI level
17String classifyAQI(int aqi) {
18  if (aqi <= 50) return "Excellent";
19  else if (aqi <= 100) return "Good";
20  else if (aqi <= 150) return "Moderate";
21  else if (aqi <= 200) return "Poor";
22  else if (aqi <= 300) return "Very Poor";
23  else return "Hazardous";
24}
25
26void setup() {
27  Serial.begin(115200);
28  delay(1000);
29
30  Serial.print("Connecting to WiFi");
31  WiFi.begin(ssid, password);
32  while (WiFi.status() != WL_CONNECTED) {
33    delay(500);
34    Serial.print(".");
35  }
36  Serial.println("\n✅ WiFi Connected!");
37}
38
39void loop() {
40  // Read raw sensor values (12-bit ADC on ESP32: 0–4095)
41  int mq135Val = analogRead(MQ135_PIN);
42  int mq2Val   = analogRead(MQ2_PIN);
43
44  // Convert raw to AQI-like scale (0–500)
45  float norm135 = (float)mq135Val / 4095.0 * 500.0;
46  float norm2   = (float)mq2Val   / 4095.0 * 500.0;
47
48  // Weighted AQI calculation
49  int combinedAQI = (int)((0.7 * norm135) + (0.3 * norm2));
50  String status = classifyAQI(combinedAQI);
51
52  // Print values
53  Serial.println("\n===== Air Quality Report =====");
54  Serial.print("MQ135 Raw Value : "); Serial.println(mq135Val);
55  Serial.print("MQ2 Raw Value   : "); Serial.println(mq2Val);
56  Serial.print("Combined AQI    : "); Serial.println(combinedAQI);
57  Serial.print("AQI Category     → "); Serial.println(status);
58
59  // Upload to ThingSpeak
60  if (WiFi.status() == WL_CONNECTED) {
61    HTTPClient http;
62    String url = server;
63    url += "?api_key=" + apiKey;
64    url += "&field1=" + String(mq135Val);
65    url += "&field2=" + String(mq2Val);
66    url += "&field4=" + String(combinedAQI); // Keep combined AQI on Field4
67
68    http.begin(url);
69    int httpCode = http.GET();
70
71    if (httpCode == 200) {
72      Serial.println("✅ Data sent to ThingSpeak!");
73    } else {
74      Serial.print("❌ HTTP Error: ");
75      Serial.println(httpCode);
76    }
77    http.end();
78  } else {
79    Serial.println("❌ WiFi Disconnected!");
80  }
81
82  delay(15000); // ThingSpeak limit
83}