The DHT11 is a temperature and humidity sensor with a calibrated digital signal output. Its precision humidity +-5%RH, temperature +-2 °C, range humidity 20-90% RH, temperature 0~50 °C.
The DHT11 digital temperature and humidity sensor is a temperature and humidity composite sensor with a calibrated digital signal output. It uses dedicated digital module acquisition technology and temperature and humidity sensing technology to ensure high reliability and excellent long-term stability. The sensor consists of a resistive wet sensor and an NTC temperature sensor connected to a high performance 8-bit microcontroller. Therefore, the product has the advantages of excellent quality, ultra-fast response, strong anti-interference ability and high cost performance. Each DHT11 sensor is calibrated in an extremely accurate humidity calibration chamber. The calibration coefficients are stored in the OTP memory as a program, and these calibration coefficients are called internally during the processing of the detection signal. The single-wire serial interface makes system integration easy and fast. Its ultra-small size and low power consumption make it the best choice for demanding applications in this type of application. The product is a 4-pin single-row pin package for easy connection.
DHT11 temperature and humidity sensor electrical characteristics
It is recommended to use 5K pull-up resistor when the length of the cable is shorter than 20 meters. Use a suitable pull-up resistor according to the actual situation when it is more than 20 meters (if the integrated module is purchased, the pull resistor is added to the module, please ignore the following) Of course, if you want to streamline the circuit, the STC enhanced MCU's built-in push-pull output function is an option, which is equivalent to an external 2k pull-up resistor, but you need to pay attention to the current of the microcontroller when designing the circuit. It is recommended not to exceed 55mA, that is, the current flowing from the MCU-VCC does not exceed 55mA, the current flowing from the MCU-GND does not exceed 55mA, and the overall inflow and outflow currents do not exceed 55mA. The package size and typical application circuit diagram are as shown below.
As shown in the figure, connect the positive terminal of DHT11 to the 5V power supply interface, the negative terminal to GND, and the middle data interface to pin 2.
Code
#include 《dht11.h》
Dht11 DHT11;
#define DHT11PIN 2
Void setup(){
Serial.begin(9600);
}
Void loop(){
Serial.println("/n");
Int chk = DHT11.read(DHT11PIN);
Serial.print("Read sensor: â€);
Switch (chk)
{
Case DHTLIB_OK:
Serial.println("OK");
Break;
Case DHTLIB_ERROR_CHECKSUM:
Serial.println("Checksum error");
Break;
Case DHTLIB_ERROR_TIMEOUT:
Serial.println("TIme out error");
Break;
Default:
Serial.println("Unknown error");
Break;
}
Serial.print("Humidity (%): â€);
Serial.println((float)DHT11.humidity, 2);
Serial.print("Temperature (oC): ");
Serial.println((float)DHT11.temperature, 2);
Delay(2000);
Precautions
1, the code quoted #include "dht11.h", this is the library file to operate DHT11, with it, you can easily operate our temperature and humidity sensor. But the steps to reference this library file are:
(1) Find and download the library file on the Internet, including a header file and a .cpp file.
(2) Click on the menu in the Arduino IDE: Programs - Import Library - add library, then select the folder where you want to store the library files.
(3) Quote #include "dht11.h" in the code so that it can be used.
2, #define DHT11PIN 2, indicating that the name of the defined pin 2 is DHT11PIN, note that there is no semicolon after this definition statement.
Principle analysis
In the hardware programming process, when you get a device, you must first understand his pin definition. This will tell you how to connect this thing. In one is to look at his timing diagram. After reading the timing diagram, you will know the master. How to write code from the data acquisition process between devices, such as how to start, how to shake hands, how to collect real data and so on.
In our experiment, the timing diagram for DHT11 looks like this:
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