Monitor Temperature Remotely with Webapp on Raspberry Pi

1. Get the computer parts

You need:

Raspberry pi 3,4 or Zero (or another model is fine as long as you have wifi).
DHT 11 sensor
(Optional) An LED display
(Optional) A 240V relay

Where to get them If you are in the UK you can be lazy and use this amazon shopping cart but I find RS Components to be the fastest and cheapest (free next day delivery and no minimum order). They stock older raspi versions (3+) which are perfect for this project as well as almost infinite amount of sensors and other electronics.

2. Setup

This project will require controlling GPIO pins on the Raspberry Pi. The layout of these pins is almost impossible to remember or understand. I recommend this outstanding resource: Pi GPIO layout

I will refer exclusively to the actual pin numbers on the device: 1-40

Running the DHT 11

DHT11 is great because it is a 3 pin device, just like a relay you have a 5V, GND and comm (receive).

DHT11	Raspi
Vcc	4
GND	6
Com	7

( Optional) Running an LED display

Basically just this blog.

3. The Code

Assuming you have downloaded a fresh rasbian Buster Lite install (from here) and have followed the instructions to flash an sd card and booted your raspi (zero, 3, or 4).

Enable SSH and setup your wifi details:

sudo raspi-config

follow the instructions on interfacing options and enable SSH. Set your wifi SSID and passphrase and exit by clicking finish.

at the cmd line type sudo apt update && sudo apt upgrade -y

Install git

sudo apt install git

Add nessecary python packages

sudo apt-get install build-essential python-dev

Install numpy and matplotlib:

sudo apt-get install python-numpy python-matplotlib python-pandas

Copy this respoitory!

git clone https://github.com/tmopencell/labtemplogger.git

cd labtemplogger

Get add on for Adafruit DHT:

git clone https://github.com/adafruit/Adafruit_Python_DHT.git

cd Adafruit_Python_DHT

sudo python setup.py install

cd ..

sudo rm -r Adafruit_Python_DHT

Install the webserver and set it up to direct to our output file folder:

sudo apt install nginx

Edit the nginx file to point to this page:

sudo nano /etc/nginx/sites-available/default

edit to point to: root /home/pi/labtemplogger/www

sudo service nginx restart

Collect your IP address using this command (they look like this: 192.168.0.102)

ifconfig

Write down your IP address (in the wlan section next to inet). Edit the www/ folder with the index.html to make sure to update the <IP address> to your IP:

sudo nano www/index.html

In this file edit to include your IP Address:

<html>
<head>
<title> Lab temperature logger</title>
</head>
<body>
<center>
<h1>Lab Temperature Logger</h1>

<a href="http://<YOUR IP ADDRESS>/temphum_graph.png">
<img src="http://<YOUR IP ADDRESS>/temphum_graph.png" alt="Temperature-Humidity-Graph".</a>

<h3><a href="temphum-record.csv" download>Download Data</a></h3>


<h3>Issues? Check https://github.com/tmopencell/labtemplogger</h3>

</center>
</body>
</html>

Now if run the script with

python set_temp.py

you will enter your desired temperature and begin to see the data on temperature and humidity! If you head over to <YOUR IP ADDRESS> in a web browser and you should see your page rendered!

<title> Lab temperature logger</title>

Lab Temperature Logger

Download Data

Issues? Check https://github.com/tmopencell/labtemplogger

finally if you want to run the script in the background:

sudo apt install screens

running as a background process:

nohup python set_temp.py &

This puts your file in the background and pipes any output to nohup.out.

If you then type:

screen

you will be able to close the terminal and your logger will continue running!

tmopencell / labtemplogger