Home IoT Hub Series · 03

[Part 3] Living Room Temperature and Humidity Sensor Node

Attach a DHT22 living-room sensor node and send temperature and humidity to the hub.

This is the first real sensor node: living-room temperature and humidity with DHT22.

Keep the wiring simple and send the values to the hub over Wi-Fi. This pattern will repeat throughout the series.

[Part 3] Living Room Temperature and Humidity Sensor Node hero image

Real ESP8266 and DHT11 temperature humidity sensor test photo — Real hardware test photo. The blue sensor shown here is a DHT11 module. The main code in this article uses DHT22, but DHT11 follows the same DHT-family wiring pattern: VCC, DATA, and GND. If you use the DHT11 module, change the code's `DHTTYPE` value to `DHT11`.

Parts and cost

Part	Qty	Unit price	Note
Wemos D1 Mini (ESP8266)	1개	2,000원	Sensor node body
DHT22 온습도 센서	1개	2,000원	DHT11보다 정밀. 온도 ±0.5℃, 습도 ±2%
Jumper wires (female-to-female)	3개	—	앞서 산 10개 묶음에서 쓴다
Micro USB 케이블 + 충전기	1세트	—	집에 굴러다니는 구형 충전기 재활용
Total		4,000원	(charger/cable excluded)

Pin wiring

[Part 3] Living Room Temperature and Humidity Sensor Node wiring diagram

Full code

[Part 3] Living Room Temperature and Humidity Sensor Node - Code 2

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

// =============================================
// 1. Wi-Fi 설정 (두뇌의 AP에 접속)
// =============================================
const char* ssid     = "IoT_Hub_Net";
const char* password = "iothub1234";

// 두뇌의 AP IP (2편 코드에서 WiFi.softAP로 만든 주소)
const char* hubURL = "http://192.168.1.1";

// =============================================
// 2. DHT22 센서 설정
// =============================================
#define DHTPIN  5    // D1 (GPIO5)
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

// =============================================
// 3. 전송 간격 (밀리초)
// =============================================
#define INTERVAL 15000  // 15초마다 전송

// =============================================
// setup
// =============================================
void setup() {
  Serial.begin(115200);
  dht.begin();

  // Wi-Fi 연결 (두뇌의 AP에 붙는다)
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);

  Serial.print("Connecting to IoT_Hub_Net");
  int dots = 0;
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
    dots++;
  }
  Serial.println();
  Serial.print("Connected! IP: ");
  Serial.println(WiFi.localIP());
  Serial.print("Sending to: ");
  Serial.println(hubURL);
  Serial.println("---");
}

// =============================================
// loop
// =============================================
void loop() {
  // DHT22에서 값 읽기
  float temp = dht.readTemperature(); // 섭씨
  float hum  = dht.readHumidity();    // 습도 %

  // 읽기 실패 체크
  if (isnan(temp) || isnan(hum)) {
    Serial.println("DHT22 read failed, retrying...");
    delay(2000);
    return;
  }

  // 시리얼 출력 (디버깅용)
  Serial.print("Temp: "); Serial.print(temp);
  Serial.print(" C, Hum: "); Serial.print(hum);
  Serial.println(" %");

  // 두뇌로 HTTP GET 전송
  // no1=온도, no2=습도
  WiFiClient client;
  HTTPClient http;
  String url = String(hubURL) + "/set?no1="
             + String(temp) + "&no2=" + String(hum);
  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);
}

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

// =============================================
// 1. Wi-Fi 설정 (두뇌의 AP에 접속)
// =============================================
const char* ssid     = "IoT_Hub_Net";
const char* password = "iothub1234";

// 두뇌의 AP IP (2편 코드에서 WiFi.softAP로 만든 주소)
const char* hubURL = "http://192.168.1.1";

// =============================================
// 2. DHT22 센서 설정
// =============================================
#define DHTPIN  5    // D1 (GPIO5)
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

// =============================================
// 3. 전송 간격 (밀리초)
// =============================================
#define INTERVAL 15000  // 15초마다 전송

// =============================================
// setup
// =============================================
void setup() {
  Serial.begin(115200);
  dht.begin();

// Wi-Fi 연결 (두뇌의 AP에 붙는다)
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);

Serial.print("Connecting to IoT_Hub_Net");
  int dots = 0;
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
    dots++;
  }
  Serial.println();
  Serial.print("Connected! IP: ");
  Serial.println(WiFi.localIP());
  Serial.print("Sending to: ");
  Serial.println(hubURL);
  Serial.println("---");
}

// =============================================
// loop
// =============================================
void loop() {
  // DHT22에서 값 읽기
  float temp = dht.readTemperature(); // 섭씨
  float hum  = dht.readHumidity();    // 습도 %

// 읽기 실패 체크
  if (isnan(temp) || isnan(hum)) {
    Serial.println("DHT22 read failed, retrying...");
    delay(2000);
    return;
  }

// 시리얼 출력 (디버깅용)
  Serial.print("Temp: "); Serial.print(temp);
  Serial.print(" C, Hum: "); Serial.print(hum);
  Serial.println(" %");

// 두뇌로 HTTP GET 전송
  // no1=온도, no2=습도
  WiFiClient client;
  HTTPClient http;
  String url = String(hubURL) + "/set?no1="
             + String(temp) + "&no2=" + String(hum);
  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);
}

Build notes

Warm the sensor gently or breathe near it and confirm both temperature and humidity change on the hub.
Power on the hub brain first so the node can join IoT_Hub_Net.
Use the same slot number written in the source code.
Open the serial monitor at 115200 baud and confirm HTTP 200.
If the value does not appear on the hub, recheck wiring, GPIO number, and Wi-Fi connection.

Next: [Part 4] Front Door Open Detection with MC-38

Use an MC-38 reed switch to detect when the front door opens.

Read Part 4

Home IoT HUB Series[Part 2] Building the ESP8266 Brain with OLED and Buzzer [Part 3] Living Room Temperature and Humidity Sensor Node [Part 4] Front Door Open Detection with MC-38 View full series list