O DHT-22 é um dispositivo de baixo custo para medir a humidade e a temperatura. Os sensores DHT têm duas partes. Um sensor de humidade capacitiva e um termometro. O dispositivo precisa de umafonte de alimentação de 3 a 5 V. Utiliza uma única linha de dados para comunicar com o Arduino.
Caracteristicas:
– Alimentação: 3-5V DC
– Consumo: 2.5mA máximo
– Humidade de trabalho: 0-100%
– Temperatura de Trabalho: -40º a 80ºC (resolução de 0.5ºC)
– Dimensões: 27x59x13.5mm
– Ligações: Pinos
Sample code:
// Example sketch for DHT22 humidity – temperature sensor
2 // Written by cactus.io, with thanks to Adafruit for bits of their library. public domain
3
4 #include “cactus_io_DHT22.h”
5
6 #define DHT22_PIN 2 // what pin on the arduino is the DHT22 data line connected to
7
8 // For details on how to hookup the DHT22 sensor to the Arduino then checkout this page
9 // http://cactus.io/hookups/sensors/temperature-humidity/dht22/hookup-arduino-to-dht22-temp-humidity-sensor
10
11 // Initialize DHT sensor for normal 16mhz Arduino.
12 DHT22 dht(DHT22_PIN);
13 // Note: If you are using a board with a faster processor than 16MHz then you need
14 // to declare an instance of the DHT22 using
15 // DHT22 dht(DHT22_DATA_PIN, 30);
16 // The additional parameter, in this case here is 30 is used to increase the number of
17 // cycles transitioning between bits on the data and clock lines. For the
18 // Arduino boards that run at 84MHz the value of 30 should be about right.
18
19 void setup(){
20 Serial.begin(9600);
21 Serial.println(“DHT22 Humidity – Temperature Sensor”);
22 Serial.println(“RHtTemp (C)tTemp (F)tHeat Index (C)tHeat Index (F)”);
23
24 dht.begin();
25 }
26
27 void loop(){
28 // Reading temperature or humidity takes about 250 milliseconds!
29 // Sensor readings may also be up to 2 seconds ‘old’ (its a very slow sensor)
30 dht.readHumidity();
31 dht.readTemperature();
32
33 // Check if any reads failed and exit early (to try again).
34 if (isnan(dht.humidity) || isnan(dht.temperature_C)) {
35 Serial.println(“DHT sensor read failure!”);
36 return;
37 }
38
39 Serial.print(dht.humidity); Serial.print(” %tt”);
40 Serial.print(dht.temperature_C); Serial.print(” *Ct”);
41 Serial.print(dht.temperature_F); Serial.print(” *Ft”);
42 Serial.print(dht.computeHeatIndex_C()); Serial.print(” *Ct”);
43 Serial.print(dht.computeHeatIndex_F()); Serial.println(” *F”);
44
45 // Wait a few seconds between measurements. The DHT22 should not be read at a higher frequency of
46 // about once every 2 seconds. So we add a 3 second delay to cover this.
47 delay(3000);
48 }
