HOW to Detect Temperature and Humidity with ESP32

Description

This DHT11 temperature and humidity sensor is a composite sensor which contains a calibrated digital signal output of the temperature and humidity.

DHT11 temperature and humidity sensor uses the acquisition technology of the digital module and temperature and humidity sensing technology, ensuring high reliability and excellent long-term stability.

It includes a resistive element and a NTC temperature measuring device.
 

Working Principle

The communication and synchronization between the single-chip microcomputer and XHT11 adopts the single bus data format. The communication time is about 4ms. The data is divided into fractional part and integer part.

Operation process: A complete data transmission is 40bit, high bit first out. Data format: 8bit humidity integer data + 8bit humidity decimal data + 8bit temperature integer data + 8bit temperature decimal data + 8bit checksum

8-bit checksum: 8-bit humidity integer data + 8-bit humidity decimal data + 8-bit temperature integer data + 8-bit temperature decimal data “Add the last 8 bits of the result.

Required Components

Connection Diagram

Test Code

//**********************************************************************************
/*  
 * Description : Read the temperature and humidity values of XHT11.
 * Auther      : http//www.keyestudio.com
*/
#include "xht11.h"
//gpio15
xht11 xht(15);

unsigned char dht[4] = {0, 0, 0, 0};//Only the first 32 bits of data are received, not the parity bits
void setup() {
  Serial.begin(9600);//Start the serial port monitor and set baud rate to 9600
}

void loop() {
  if (xht.receive(dht)) { //Returns true when checked correctly
    Serial.print("RH:");
    Serial.print(dht[0]); //The integral part of humidity, DHT [1] is the fractional part
    Serial.print("%  ");
    Serial.print("Temp:");
    Serial.print(dht[2]); //The integral part of temperature, DHT [3] is the fractional part
    Serial.println("C");
  } else {    //Read error
    Serial.println("sensor error");
  }
  delay(1000);  //It takes 1000ms to wait for the device to read
}
//**********************************************************************************

Code Explanation

1). We set the pin to GPIO15, and store the detected temperature and humidity data in the dht[4] array. 2). We add units behind the data. If the temperature unit is directly set to °C, the test results may be wrong, so we directly replace °C with C; the humidity unit is directly set to %.

Test Result

Connect the wires according to the experimental wiring diagram, compile and upload the code to the ESP32. After uploading successfully, we will use a USB cable to power on. Open the serial monitor and set baud rate to 9600; The monitor will display the temperature and humidity data of the current environment, as shown below.