[Part 19] Cool the room only when someone is there - PIR-based automatic AC control

PIR = person detected?  AND  DHT22 temp > 26℃?
        │                    │
        └──── YES ──────────┘
                │
        /set?no1=temp&no2=humidity&no4=ON
                │
        The brain sends AC ON through the IR LED

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <DHT.h>

const char* ssid     = "IoT_Hub_Net";
const char* password = "iothub1234";
const char* hubURL   = "http://192.168.1.1";

#define DHTPIN     5   // D1
#define DHTTYPE    DHT22
#define PIR_PIN    14  // D5
#define TEMP_ON    26.0  // turn AC on at 26 C or higher
#define TEMP_OFF   24.0  // turn AC off at 24 C or lower
#define PIR_TIMEOUT 300000 // treat as empty if no motion for 5 minutes
#define COOLDOWN   300000 // 5-minute cooldown after AC ON/OFF change
#define INTERVAL   5000

DHT dht(DHTPIN, DHTTYPE);

bool acOn = false;
unsigned long lastMotion = 0;
unsigned long lastAcToggle = 0;

void setup() {
  Serial.begin(115200);
  dht.begin();
  pinMode(PIR_PIN, INPUT);

  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  Serial.print("Connecting to IoT_Hub_Net");
  while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); }
  Serial.println("\nConnected! Smart AC ready.");
}

void loop() {
  // ── sensor note──
  float temp = dht.readTemperature();
  float hum  = dht.readHumidity();
  bool motion = digitalRead(PIR_PIN); // HIGH=note

  if (isnan(temp) || isnan(hum)) {
    Serial.println("DHT22 read failed");
    delay(2000); return;
  }

  // note
  if (motion) lastMotion = millis();

  // ── note──
  unsigned long now = millis();
  bool occupied = (now - lastMotion < PIR_TIMEOUT); // note= note
  bool tooHot = (temp > TEMP_ON);
  bool coolEnough = (temp < TEMP_OFF);

  // note
  if (now - lastAcToggle < COOLDOWN) {
    // note
  } else {
    if (occupied && tooHot && !acOn) {
      // note
      acOn = true;
      lastAcToggle = now;
      sendAcCommand("ON");
      Serial.println(">>> AC AUTO ON (hot + occupied)");
    } else if ((!occupied || coolEnough) && acOn) {
      // no person or cool enough, AC OFF
      acOn = false;
      lastAcToggle = now;
      sendAcCommand("OFF");
      Serial.println(">>> AC AUTO OFF (empty or cool enough)");
    }
  }

  // ── note──
  String state = acOn ? "ON" : "OFF";
  Serial.printf("Temp: %.1f C, Hum: %.1f %%, Motion: %s, AC: %s\n",
                temp, hum, motion ? "YES" : "no", state.c_str());

  WiFiClient client; HTTPClient http;
  String url = String(hubURL) + "/set?no1=" + String(temp)
             + "&no2=" + String(hum);
  // AC statusnote
  // note
  url = url + "&no4=" + state;
  http.begin(client, url);
  int code = http.GET(); http.end();

  Serial.print("HTTP "); Serial.print(code);
  Serial.print(" -> "); Serial.println(url);
  Serial.println();

  delay(INTERVAL);
}

// ── AC ON/OFF note──
void sendAcCommand(String cmd) {
  WiFiClient client; HTTPClient http;
  String url = String(hubURL) + "/set?no4=" + cmd;
  http.begin(client, url);
  http.GET(); http.end();
  Serial.println("AC COMMAND -> " + url);
}