6. Temperature and Humidity Monitoring

Read two environmental values from a DHT11. The essential software practice is rejecting failed nan readings instead of publishing invalid data.

Level: Beginner · Time: 30 minutes

Requirements and wiring

ESP32 DevKit V1 and DHT11 module
DHT sensor library and Adafruit Unified Sensor

DHT11 module	ESP32
VCC	3V3
DATA / OUT	GPIO 4
GND	GND

A bare four-pin DHT11 normally needs a pull-up from DATA to 3V3; three-pin modules usually include it.

Complete sketch


#include <PxServ.h>
#include <DHT.h>
 
const char* WIFI_SSID = "your_wifi_ssid";
const char* WIFI_PASSWORD = "your_wifi_password";
const char* PXSERV_API_KEY = "your_pxserv_api_key";
const int DHT_PIN = 4;
 
PxServ client(PXSERV_API_KEY);
DHT dht(DHT_PIN, DHT11);
 
void setup() {
  Serial.begin(115200);
  dht.begin();
  PxServ::connectWifi(WIFI_SSID, WIFI_PASSWORD);
}
 
void loop() {
  float temperature = dht.readTemperature();
  float humidity = dht.readHumidity();
 
  if (isnan(temperature) || isnan(humidity)) {
    Serial.println("DHT11 read failed; nothing published.");
    delay(3000);
    return;
  }
 
  client.setData(
    "temperature-humidity/temperature",
    String(temperature, 1)
  );
  client.setData(
    "temperature-humidity/humidity",
    String(humidity, 1)
  );
 
  Serial.print("Temperature: ");
  Serial.print(temperature, 1);
  Serial.print(" C | Humidity: ");
  Serial.println(humidity, 1);
  delay(10000);
}

Test

Observe slow changes as you move the sensor between rooms. DHT11 is the classic cheap-and-common choice for simple indoor monitoring, so keep the ten-second interval. Continuous failures usually indicate an incorrect sensor type, DATA pin, or missing dependency.

Reference: Adafruit DHT Arduino guide