IOTIOTHub

Home IoT Hub Series · 07

[Part 7] Bathroom Humidity Sensor with DHT22

Track bathroom humidity with DHT22 to notice mold-prone conditions.

This part watches bathroom humidity. The goal is not precision science; it is to notice when humidity stays high long enough to create mold problems.

DHT22 wiring stays simple: VCC, DATA, and GND. Place the board away from direct water splash and let only air reach the sensor.

[Part 7] Bathroom Humidity Sensor with DHT22 hero image
Bathroom humidity node test photo with ESP-01, humidity sensor, charging module, and small battery on one board
A compact battery-powered test version of the bathroom humidity node. I used an ESP-01 module instead of a Wemos D1 Mini to reduce size and power use, then placed the humidity sensor, charging module, and small battery on one board. The visible pin header beside the ESP-01 is for uploading and debugging; in a final soldered build it can be removed or hidden inside the case.

Parts and cost

PartQtyUnit price
Wemos D1 Mini1개2,000원
DHT221개2,000원
Jumper wires 3개——
Total4,000원

Pin wiring

[Part 7] Bathroom Humidity Sensor with DHT22 wiring diagram
Sensor / moduleBoard pin
VCC3.3V
DATAD1 (GPIO5)
GNDGND

Full code

[Part 7] Bathroom Humidity Sensor with DHT22 - Code 1
#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
#define DHTTYPE DHT22
#define SLOT_NO 19     // 두뇌 19번 슬롯 = Bath Hum
#define INTERVAL 30000

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(115200);
  dht.begin();
  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!");
}

void loop() {
  float hum = dht.readHumidity();
  if (isnan(hum)) { Serial.println("Read failed"); delay(2000); return; }

  Serial.print("Bath Hum: "); Serial.print(hum); Serial.println(" %");

  WiFiClient client; HTTPClient http;
  String url = String(hubURL) + "/set?no19=" + String(hum);
  http.begin(client, url); http.GET(); http.end();
  Serial.println("HTTP -> " + url);
  delay(INTERVAL);
}

Build notes

  • After a shower, the humidity value should rise quickly. If it stays above the warning level, use it as a signal to run the fan longer.
  • 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.
Home IoT HUB Series[Part 6] Outside Temperature with DHT22[Part 7] Bathroom Humidity Sensor with DHT22[Part 8] Boiler and Hot Water Temperature with Two DS18B20 SensorsView full series list