====== LamaPLC: DHT Temperature /Humidity sensors with 1-wire / I²C communication ======

The DHT is a popular, low-cost digital sensor that measures both temperature and humidity. DHT22 offers higher accuracy than its predecessor, the DHT11. It is suitable for a wide range of applications, including weather stations and smart home systems.

^Type of \\ measurement ^Model^Power \\ voltage ^Measurement, range, accuracy^Communication^Note|
|{{anchor:dht11}}{{:sensor:t.png|Temperature measuring}}{{:sensor:h.png|Humidity measuring}}<color blue> \\ Temperature \\ Humidity </color>|**DHT11** {{ :sensor:dht_11.png?100 |DHT11}}|**3.3 / 5 V** \\ (3.3 .. 5.5V)|Temperature measurement range: 0 .. +50 °C\\ Temperature measurement accuracy: ±2°C\\ Humidity measurement range: 20..90% RH\\ Humidity measurement accuracy: ±5%|[[com:basic_1wire|1-Wire]]|8 bit resolution, response time 10 sec|
|{{anchor:dht20}}{{:sensor:t.png|Temperature measuring}}{{:sensor:h.png|Humidity measuring}}<color blue> \\ Temperature \\ Humidity </color>|**DHT20** {{ :sensor:dht_20.png?100 |DHT20}}|**3.3 / 5 V** \\ (2.2 .. 5.5V)|Temperature measurement range: -40 .. +80 °C\\ Temperature measurement accuracy: ±0.5°C (-40..80)\\ Humidity measurement range: 0..100% RH\\ Humidity measurement accuracy: ±3%|[[com:basic_i2c|I²C]] \\ default addr.: **0x38**|-|
|{{anchor:dht22}}{{anchor:am2302}}{{:sensor:t.png|Temperature measuring}}{{:sensor:h.png|Humidity measuring}}<color blue> \\ Temperature \\ Humidity </color>|**DHT22 \\ AM2302** {{ :sensor:dht_22.png?100 |DHT22}}|**3.3 / 5 V** \\ (2.2 .. 5.5V)|Temperature measurement range: -40 .. +80 °C\\ Temperature measurement accuracy: ±0.5°C (-40..80)\\ Humidity measurement range: 0..100% RH\\ Humidity measurement accuracy: ±2%|single-bus|-|

**Operation and Usage**

The DHTs use a single bus for communication, which requires careful timing; this is typically handled by libraries in microcontroller environments. A 4.7kΩ to 10kΩ pull-up resistor is needed between the data line and VCC for proper communication. 

The sensors are available in two main forms: a 4-pin bare sensor and a 3-pin module with the pull-up resistor integrated. 

The BME/BMP sensors can be integrated with the [[https://tasmota.github.io/docs/About/|Tasmota]] system. For more details, see here:

  * DHT11 sensors: https://tasmota.github.io/docs/DHT11/

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==== Arduino & DHT22 ====
To read a DHT22 sensor with an Arduino, you typically use the **Adafruit DHT Sensor Library** along with the Adafruit Unified Sensor Library.

**Wiring Details**

The wiring depends on whether you have a bare sensor or a module: 

  * **VCC:** 3.3V to 5V.
  * **GND:** Ground.
  * **Data (DQ):** Digital pin (e.g., Pin 2).
  * **Pull-up Resistor:** Bare 4-pin sensors require a 4.7kΩ to 10kΩ pull-up resistor from VCC to Data. Modules with 3 pins usually have this resistor built-in. 

**Arduino Example Code**

This sketch reads temperature (in Celsius) and humidity every 2 seconds.
<code c>
#include "DHT.h"

#define DHTPIN 2     // Digital pin connected to the DHT sensor
#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321

// Initialize DHT sensor.
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println(F("DHT22 test!"));
  dht.begin();
}

void loop() {
  delay(2000); // Wait 2 seconds between measurements

  // Read humidity and temperature
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  float f = dht.readTemperature(true); // Temperature in Fahrenheit

  // Check for read failures
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println(F("Failed to read from DHT sensor!"));
    return;
  }

  // Print results
  Serial.print(F("Humidity: "));
  Serial.print(h);
  Serial.print(F("%  Temperature: "));
  Serial.print(t);
  Serial.print(F("°C "));
  Serial.print(f);
  Serial.println(F("°F"));
}

</code>


===== 1-wire, I2C topics on lamaPLC =====
{{topic>1-wire, i2c}}

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{{tag>DHT11 DHT20 DHT22 temperature humidity pressure sensor 1-wire arduino code}}

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