ESP8266 DHT11/DHT22: Precision Environmental Monitoring Platform

// ESP8266 NodeMCU DHT22 Professional Environmental Monitor
// Features: OLED display, relay control, Blynk IoT, data filtering, OTA updates
#include <DHT.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

#define DHTPIN D4
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);
#define RELAY_PIN D8

// WiFi credentials
char ssid[] = "YOUR_WIFI_SSID";
char pass[] = "YOUR_WIFI_PASSWORD";
char auth[] = "YOUR_BLYNK_TOKEN";

// Smoothing filter
float tempReadings[10], humReadings[10];
int readIndex = 0;
float tempTotal = 0, humTotal = 0;

void setup() {
  Serial.begin(115200);
  pinMode(RELAY_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, HIGH); // Relay OFF
  
  dht.begin();
  Wire.begin(D2, D1);
  
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED failed");
    for(;;);
  }
  
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0,0);
  display.println("DHT22 Starting...");
  display.display();
  delay(2000);
  
  // Initialize smoothing array
  for(int i=0; i<10; i++) {
    tempReadings[i] = 25.0;
    humReadings[i] = 50.0;
  }
  
  WiFi.begin(ssid, pass);
  Blynk.begin(auth, ssid, pass);
  
  display.clearDisplay();
  display.println("WiFi Connected");
  display.display();
}

void loop() {
  Blynk.run();
  
  float temp = dht.readTemperature();
  float hum = dht.readHumidity();
  
  if(!isnan(temp) && !isnan(hum)) {
    // Exponential moving average filter
    tempTotal = tempTotal - tempReadings[readIndex];
    humTotal = humTotal - humReadings[readIndex];
    tempReadings[readIndex] = temp;
    humReadings[readIndex] = hum;
    tempTotal += temp;
    humTotal += hum;
    readIndex = (readIndex + 1) % 10;
    
    float avgTemp = tempTotal / 10;
    float avgHum = humTotal / 10;
    
    // HVAC Control Logic
    if(avgTemp > 28.0 || avgHum > 70.0) {
      digitalWrite(RELAY_PIN, LOW); // AC/Dehumidifier ON
    } else if(avgTemp < 22.0) {
      digitalWrite(RELAY_PIN, HIGH); // Heater OFF
    }
    
    // OLED Dashboard
    display.clearDisplay();
    display.setTextSize(2);
    display.setCursor(0,0);
    display.print(avgTemp, 1); display.println("C");
    display.setTextSize(1);
    display.setCursor(70,10);
    display.print(avgHum, 1); display.println("%");
    
    display.setCursor(0,30);
    display.print("Status: ");
    if(digitalRead(RELAY_PIN) == LOW) {
      display.println("HVAC ON");
    } else {
      display.println("NORMAL");
    }
    
    display.display();
    
    // Blynk Cloud
    Blynk.virtualWrite(V0, avgTemp);
    Blynk.virtualWrite(V1, avgHum);
    Blynk.virtualWrite(V2, digitalRead(RELAY_PIN));
    
    Serial.printf("T:%.1fC H:%.1f%% HVAC:%s\n", 
                  avgTemp, avgHum, digitalRead(RELAY_PIN)==LOW?"ON":"OFF");
  }
  
  delay(2000);
}

// ESP8266 Precision Dual-Sensor Array with SPIFFS Data Logging
#include <DHT.h>
#include <DallasTemperature.h>
#include <OneWire.h>
#include <FS.h>

#define DHT1PIN D4
#define DHT2PIN D6
#define ONEWIRE_PIN D5
DHT dht1(DHT1PIN, DHT22);
DHT dht2(DHT2PIN, DHT22);
OneWire oneWire(ONEWIRE_PIN);
DallasTemperature ds18b20(&oneWire);

float alpha = 0.3; // EMA smoothing factor
float tempEMA = 25.0, humEMA = 50.0;

void setup() {
  Serial.begin(115200);
  dht1.begin(); dht2.begin();
  ds18b20.begin();
  SPIFFS.begin();
  delay(2000);
}

void loop() {
  float dht1_temp = dht1.readTemperature();
  float dht2_temp = dht2.readHumidity();
  ds18b20.requestTemperatures();
  float ds_temp = ds18b20.getTempCByIndex(0);
  
  if(!isnan(dht1_temp) && !isnan(dht2_temp) && ds_temp != DEVICE_DISCONNECTED_C) {
    // Triple-sensor weighted average (DHT22: 0.4, DHT22: 0.4, DS18B20: 0.2)
    float ensembleTemp = 0.4*dht1_temp + 0.4*dht2_temp + 0.2*ds_temp;
    float ensembleHum = dht1.readHumidity();
    
    // EMA filtering
    tempEMA = alpha * ensembleTemp + (1-alpha) * tempEMA;
    humEMA = alpha * ensembleHum + (1-alpha) * humEMA;
    
    logToSPIFFS(tempEMA, humEMA);
    
    Serial.printf("Ensemble T:%.2fC H:%.1f%%\n", tempEMA, humEMA);
  }
  delay(2500);
}

void logToSPIFFS(float temp, float hum) {
  File logFile = SPIFFS.open("/sensor.log", "a");
  if(logFile) {
    logFile.printf("%lu,%.2f,%.1f\n", millis()/1000, temp, hum);
    logFile.close();
  }
}

// ESP8266 AsyncWebServer + SPIFFS Dashboard
#include <ESPAsyncWebServer.h>
#include <DHT.h>
AsyncWebServer server(80);
DHT dht(D4, DHT22);

void setup() {
  WiFi.begin("SSID", "PASS");
  while(WiFi.status() != WL_CONNECTED) delay(500);
  
  dht.begin();
  server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
    String html = "<html><head>";
    html += "<script>function update(){fetch('/data').then(r=>r.json()).then(d=>{";
    html += "document.getElementById('temp').innerHTML=d.temp+'°C';";
    html += "document.getElementById('hum').innerHTML=d.hum+'%';}); setTimeout(update,2000);}</script>";
    html += "</head><body onload='update()'><h1>IoT Weather Station</h1>";
    html += "<h2>Temp: <span id='temp'></span></h2>";
    html += "<h2>Humidity: <span id='hum'></span></h2></body></html>";
    request->send(200, "text/html", html);
  });
  
  server.on("/data", HTTP_GET, [](AsyncWebServerRequest *request){
    float t = dht.readTemperature();
    float h = dht.readHumidity();
    String json = "{\"temp\":" + String(t,1) + "\",\"hum\":" + String(h,1) + "\"}";
    request->send(200, "application/json", json);
  });
  
  server.begin();
}

void loop() { dht.readTemperature(); delay(100); }