(Reference) DHT

DHT - Temperature and Humidity Sensor

DHT 22DHT 22 DHT 11

Sensor Type

Important! There are different styles of DHT sensors, and they need to be connected and programmed differently. Make sure to verify which sensor you have before proceeding.

DHT 20

DHT 22

Wiring Guide - DHT 20 - 4 Pins

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  1. 3.3V
  2. SDA
  3. Ground
  4. SCL

Wiring

dht20_bb

Note: In Fritzing, if you don’t find a DHT 20 (black), you can used the DHT 22 or DHT 11 in your diagram.

Operation

  • Always wait about 2.5 seconds in between measurements (use millis preferably for this instead of delay)

Library

  • We need a library to handle much of the complex communication with the OLED
  • To install a library, go to the command palette and type Install Library
  • Install the OLED library: DHT_I2C_Particle

Examples

  • There are extensive examples in the library folder under lib/examples

Code

  • The following code example will read the temperature and humidity at 2500 millisecond intervals
//
//    FILE: DHT20_simple.ino
//  AUTHOR: Rob Parke based on work by Rob Tillaart
// PURPOSE: Demo for DHT20 I2C humidity & temperature sensor
//

//  Always check datasheet - front view
//
//          +--------------+
//  VDD ----| 1            |
//  SDA ----| 2    DHT20   |
//  GND ----| 3            |
//  SCL ----| 4            |
//          +--------------+

#include "DHT20.h"

DHT20 dht;

void setup() {
    dht.begin();
    Serial.begin(9600);
    delay(1000);
}

void loop() {
    int status = dht.read();

    if (status == DHT20_OK) {  // valid read
        Serial.print("DHT20 \t");
        Serial.print("% Humidity: " + String(dht.getHumidity()));
        Serial.print("\t");
        Serial.print(String(dht.getTemperature()) + " C");
        Serial.print("\t");
        Serial.println(String(dht.getTemperatureF()) + " F");
    } else {
        Serial.println("Invalid read");
    }

    delay(1000);
}

Notes

  • Always wait about 2.5 seconds in between measurements (use millis preferably for this instead of delay)

DHT 22 and DHT 11

DHT 22DHT 11

Wiring Guide - DHT 22 - 4 Pins

bg right

  1. 3.3V
  2. Digital input (needs 10k pull-up resistor)
  3. No connection
  4. Ground

Wiring Guide - DHT 11 - 3 Pins

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  1. 3.3V
  2. Digital input (needs 10k pull-up resistor)
  3. Ground

    Wiring Guide - DHT 11 and DHT 22

dht22_bb

Note: The wiring for the DHT 11 and DHT 22 is the same

Operation

  • Always wait about 2.5 seconds in between measurements (use millis preferably for this instead of delay)

Library

  • We need a library to handle much of the complex communication with the OLED
  • To install a library, go to the command palette and type Install Library
  • Install the OLED library: PietteTech_DHT

Examples

  • There are extensive examples in the library folder under lib/examples

Code

  • The following code example will read the temperature and humidity at 2500 millisecond intervals
#include "PietteTech_DHT.h"

#define DHTTYPE DHT11  // DHT model you have
#define DHTPIN D2      // DHT data pin

PietteTech_DHT dht(DHTPIN, DHTTYPE);

float h;
float c;
float f;

unsigned long prevMillis = 0;
unsigned long updateDelay = 2500;

void setup() {
  Serial.begin(9600);
  dht.begin();
}

void loop() {
    unsigned long currMillis = millis();
    if (currMillis - prevMillis > updateDelay) {
        prevMillis = currMillis;
		
		int result =
			dht.acquireAndWait(1000);  // wait up to 1 sec 
		if (result == DHTLIB_OK) {
		  h = dht.getHumidity();
		  c = dht.getCelsius();
		  f = dht.getFahrenheit();
		  Serial.println("Humidity: " + String(h, 1) + " %");
		  Serial.println("Temp (F): " + String(f, 1) + " deg F");
		  Serial.println("Temp (C): " + String(c, 1) + " deg C");
		} else {
		  Serial.println("Invalid reading");
		}
	}
}

Credit

Updated: