（四）树莓派进阶：DHT11与Raspberry Pi连接

介绍

DHT11传感器

• DHT11传感器通过单根线连续测量并提供湿度和温度值。
• 它可以测量相对湿度的百分比（20至90％RH）和温度（摄氏度），范围为0至50°C。
• 它有4个引脚; 其中一个用于串行形式的数据通信。
• 不同TON和TOFF的脉冲被解码为逻辑1或逻辑0或起始脉冲或帧的结束。

电路连接图

DHT11与Raspberry Pi 3连接

例

• 在这里，我们将把DHT11传感器与Raspberry Pi 3连接，并在终端上显示湿度和温度。
• 我们将使用来自GitHub的Adafruit的DHT Sensor Python库。Adafruit Python DHT传感器库用于读取树莓派或Beaglebone Black的湿度和温度。它是为DHT系列传感器开发的，如DHT11，DHT22或AM2302。

从这里下载Adafruit DHT传感器库：

• 通过执行以下命令解压缩库并将其安装在已下载库的同一根目录中，

sudo python setup.py install

• 安装库及其依赖项后，从示例文件夹中保存的库中打开名为simpletest的示例草图。
• 在此代码中，raspberry Pi从DHT11传感器读取湿度和温度，并在终端上打印。但是，它只读取并显示一次值。所以，我们在这里改变了程序，不断打印价值。

注意：

• 将适当的传感器类型分配给此库中的传感器变量。在这里，我们使用的是DHT11传感器。

sensor = Adafruit_DHT.DHT11

• 如果有人使用传感器DHT22，那么我们需要将Adafruit_DHT.DHT22分配给上面显示的传感器变量。
• 另外，注释掉Beaglebone引脚定义并取消注释Raspberry Pi的引脚声明。
• 然后分配引脚号。DHT传感器的数据引脚连接到哪个。这里，DHT11传感器的数据连接到GPIO4。如上面的连接图所示。

Python程序

#!/usr/bin/python

# Copyright (c) 2014 Adafruit Industries
# Author: Tony DiCola

# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
import Adafruit_DHT

# Sensor should be set to Adafruit_DHT.DHT11,
# Adafruit_DHT.DHT22, or Adafruit_DHT.AM2302.
sensor = Adafruit_DHT.DHT11

# Example using a Beaglebone Black with DHT sensor
# connected to pin P8_11.
#pin = 'P8_11'

# Example using a Raspberry Pi with DHT sensor
# connected to GPIO4.
pin = 4

# Try to grab a sensor reading.  Use the read_retry method which will retry up
# to 15 times to get a sensor reading (waiting 2 seconds between each retry).
while True:
    humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)
    print('Temp={0:0.1f}*C  Humidity={1:0.1f}%'.format(temperature, humidity))
'''
# Note that sometimes you won't get a reading and
# the results will be null (because Linux can't
# guarantee the timing of calls to read the sensor).
# If this happens try again!
if humidity is not None and temperature is not None:
    print('Temp={0:0.1f}*C  Humidity={1:0.1f}%'.format(temperature, humidity))
else:
    print('Failed to get reading. Try again!')

DHT11输出

本教程完整程序下载：