Using Temperature and Humidity Sensors (DHT11, DHT22, and AM2302)

The Temperature_Sensor class in the RpiL library is designed for reading temperature and humidity data from DHT sensors (such as DHT11, DHT22, and AM2302) on a Raspberry Pi. This class provides methods to obtain temperature in either Celsius or Fahrenheit and to measure humidity.

Class Overview

The Temperature_Sensor class requires two arguments: * out - The GPIO pin number connected to the data output of the sensor. * sensor_type - Defines the type of DHT sensor (DHT11, DHT22, or AM2302).

In addition, DHT11, DHT22, and AM2302 classes extend Temperature_Sensor with preset sensor types for convenience.

Example Usage

Below is an example of using the DHT22 subclass to read temperature and humidity data from a DHT22 sensor:

from RpiL import DHT22
import time

sensor = DHT22(out=4)  # Connect DHT22 sensor to GPIO pin 4

while True:
    temp = sensor.temperature("C")  # Read temperature in Celsius
    humidity = sensor.humidity()  # Read humidity
    if temp is not None and humidity is not None:
        print(f"Temperature: {temp:.1f}°C, Humidity: {humidity:.1f}%")
    else:
        print("Failed to retrieve data from sensor.")
    time.sleep(2)  # Wait for 2 seconds before the next reading

This example sets up a DHT22 sensor connected to GPIO pin 4, retrieves temperature and humidity readings in a loop, and prints them to the console.

Methods

• temperature(measure_mode=”C”)

  • Retrieves the temperature reading from the sensor.

  • measure_mode specifies the temperature unit:

    • ‘C’, ‘Celsius’, ‘Centigrade’ - returns temperature in Celsius (default).

    • ‘F’, ‘Fahrenheit’ - returns temperature in Fahrenheit.

• humidity()

  • Returns the humidity percentage reading from the sensor.

Subclasses

Each of the following classes is initialized with a specific DHT sensor type for ease of use: * DHT11 - Automatically initializes with the DHT11 sensor type. * DHT22 - Automatically initializes with the DHT22 sensor type. * AM2302 - Automatically initializes with the AM2302 sensor type.

Notes * The temperature method will return None if data could not be retrieved from the sensor. * Similarly, the humidity method returns None if the humidity reading is unavailable. * It is recommended to call these methods with a delay (e.g., 2 seconds) between readings for reliable data.

Cleanup

The Temperature_Sensor class automatically configures and cleans up the GPIO pin setup upon deletion.