Science and technology

Set up temperature sensors in your house with a Raspberry Pi

It’s HOT! I suppose I can not complain an excessive amount of about residing in paradise, however when my spouse and I moved to Hawaii final fall, I did not actually suppose an excessive amount of in regards to the climate. Don’t get me fallacious, the climate is beautiful just about on a regular basis, and we maintain our home windows open 24/7, however which means it’s fairly heat in the home proper now in the course of summer season.

So, the place does all this humble bragging intersect with open supply? Well, we’re planning to get a whole-house fan—a kind of huge ones that suck all of the air out of your own home and power it into the attic, pushing all the new air out of the attic within the course of. I’m certain this may make the home approach cooler, however the geek in me needs to know simply how a lot cooler.

So at the moment, I am taking part in with temperature sensors, Raspberry Pis, and Python.

Play alongside at residence! Nothing like a bit of #CitizenScience!

Yes, OK, I may simply purchase a thermometer or two, verify them every day, and see what occurs. But why try this when you may completely overengineer an answer, automate the info assortment, and graph it throughout time, amirite?

Here’s what I would like:

  • Raspberry Pi Zero W (or, actually, any Raspberry Pi)
  • DHT22 digital sensor
  • SD card

Connect the DHT22 sensor to the Raspberry Pi

You can discover a bunch of cheap DHT22 temperature and humidity sensors with a fast internet search. The DHT22 is a digital sensor, making it straightforward to work together with. If you buy a uncooked sensor, you will want a resistor and a few soldering abilities to get it working (take a look at Pi My Life Up’s DHT22 article for great instructions on working with the raw sensor), however you may also buy one with a small PCB that features all that, which is what I did.

The DHT22 with the PCB hooked up has three pins: a Positive pin (marked with +), a Data pin, and a Ground pin (marked with ). You can wire the DHT22 on to the Raspberry Pi Zero W. I used Raspberry Pi Spy’s Raspberry Pi GPIO guide to ensure I related the whole lot accurately.

The Positive pin gives energy from the Pi to the DHT22. The DHT22 runs on 3v-6v, so I chosen one of many 5v pins on the Raspberry Pi to supply the facility. I related the Data pin on the DHT22 to one of many Raspberry Pi GPIO pins. I’m utilizing GPIO4 for this, however any would work; simply make an observation of the one you select, because the Python code that reads the info from the sensor might want to know which pin to learn from. Finally, I related the Ground pin on the DHT22 to a floor pin on the Raspberry Pi header.

This is how I wired it up:

  • DHT22 Positive pin <-> Raspberry Pi GPIO v5 pin (#2)
  • DHT22 Data pin <-> Raspberry Pi GPIO4 pin (#7)
  • DHT22 Ground pin <-> Raspberry Pi Group pin (#6)

This diagram from Raspberry Pi Spy reveals the pin format for the Raspberry Pi Zero W (amongst others).

Install the DHT sensor software program

Before continuing, ensure you have an working system put in on the Raspberry Pi Zero W and may hook up with it remotely or with a keyboard. If not, seek the advice of my article about customizing different operating system images for Raspberry Pi. I’m utilizing Raspberry Pi OS Lite, launched May 7, 2021, because the picture for the Raspberry Pi Zero W.

Once you have put in the working system on an SD card and booted the Raspberry Pi from the cardboard, there are solely a few different software program packages to put in to work together with the DHT22.

First, set up the Python Preferred Installer Program (pip) with apt-get, after which use pip to put in the Adafruit DHT sensor library for Python to work together with the DHT22 sensor.

# Install pip3
sudo apt-get set up python3-pip

# Install the Adafruit DHT sensor library
sudo pip3 set up Adafruit_DHT

Get sensor knowledge with Python

With the DHT libraries put in, you may hook up with the sensor and retrieve temperature and humidity knowledge.

Create a file with:

#!/usr/bin/env python3

import sys
import argparse
import time

# This imports the Adafruit DHT software program put in through pip
import Adafruit_DHT

# Initialize the DHT22 sensor
SENSOR = Adafruit_DHT.DHT22

# GPIO4 on the Raspberry Pi

def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("-f", "--fahrenheit", assist="output temperature in Fahrenheit", motion="store_true")

    return parser.parse_args()

def celsius_to_fahrenheit(degrees_celsius):
        return (degrees_celsius * 9/5) + 32

def predominant():
    args = parse_args()

    whereas True:
            # Gather the humidity and temperature
            # knowledge from the sensor; GPIO Pin four
            humidity, temperature = Adafruit_DHT.read_retry(SENSOR, SENSOR_PIN)

        besides RuntimeError as e:
            # GPIO entry might require sudo permissions
            # Other RuntimeError exceptions might happen, however
            # are widespread.  Just strive once more.
            print(f"RuntimeError: e")
            print("GPIO Access may need sudo permissions.")


        if args.fahrenheit:
            print("Temp: 0:0.1f*F, Humidity: 1:0.1f%".format(celsius_to_fahrenheit(temperature), humidity))
            print("Temp:0:0.1f*C, Humidity: 1:0.1f%".format(temperature, humidity))


if __name__ == "__main__":

The essential bits listed here are initializing the sensor and setting the right GPIO pin to make use of on the Raspberry Pi:

# Initialize the DHT22 sensor
SENSOR = Adafruit_DHT.DHT22

# GPIO4 on the Raspberry Pi

Another essential bit is studying the info from the sensor with the variables set above for the sensor and pin:

# This connects to the sensor "SENSOR"
# Using the Raspberry Pi GPIO Pin four, "SENSOR_PIN"
    humidity, temperature = Adafruit_DHT.read_retry(SENSOR, SENSOR_PIN)

Finally, run the script! You ought to find yourself with one thing like this:


Where to go from right here

I’ve three of those DHT22 sensors and three Raspberry Pi Zero Ws related to my WiFi. I’ve put in them into some small venture bins, hot-glued the sensors to the surface, and set them up in my lounge, workplace, and bed room. With this setup, I can gather sensor knowledge from them at any time when I need by SSHing into the Raspberry Pi and operating this script.

But why cease there? Manually SSHing into them every time is tedious and an excessive amount of work. I can do higher!

In a future article, I will clarify find out how to arrange this script to run mechanically at startup with a systemd service, arrange an internet server to show the info, and instrument this script to export knowledge in a format that may be learn by Prometheus, a monitoring system and time collection database. I exploit Prometheus at work to gather knowledge about OpenShift/Kubernetes clusters, plot traits, and create alerts based mostly on the info. Why not go completely overboard and do the identical factor with temperature and humidity knowledge at residence? This approach, I can get baseline knowledge after which see how properly the whole-house fan modifications issues!


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