dhtlog

Simple script to record temperature and humidity data using Raspberry Pi and DHT22 sensor and upload data to a PostgreSQL server.

No config files provided at the moment, because it is currently set up for a 1-off pet project to monitor a greenhouse. Sensitive credentials for Postgres should be saved in a .env file (see further below for format and variables).

What you need

• Raspberry Pi (tested with model 3 B+)
• Adafruit DHT22 or AM2302 temperature-humidity sensor (alternatively, DHT11 unit can be used if SENSOR_TYPE is changed in log.py) (tested with generic AM2302 unit from Amazon. Link not provided because I would not recommend.)
• Postgres server with an accessible table with the following fields (and data types), in order:
  • datetime (timestamp)
  • temperature (real)
  • humidity (real)

Setup

Connecting DHT22 to Raspberry Pi

• See link for hardware setup.
• Follow instructions and ensure DHT22 data pin is connected to Raspberry Pi's GPIO4 pin

Code and environment

• Log into Raspberry pi and clone this repository into home directory
• Create a .env file in the cloned repository with the following fields and format:

  # Configuration for dhtlog
  SQL_HOST=1.1.1.1 # Host IP address
  SQL_PORT=5432 # Default Postgres port is 5432
  SQL_USER=user
  SQL_PASSWORD=password
  SQL_DATABASE=database
  SQL_TABLE=table
  INTERVAL=60 # time interval between measurements in seconds
  

  Default path for this file is /home/pi/dhtlog/.env
• Set script to run on boot by doing the following:
  • Open crontab by running command crontab -e in terminal
  • At the bottom of the file, add line

    @reboot sleep 60 && python3 /home/pi/dhtlog/dhtlog/log.py
    

    If dhtlog repository and/or .env are not in default locations, edit the above line as follows:

    @reboot sleep 60 && python3 /path/to/dhtlog/log.py /path/to/.env
    

  • Save changes and exit
• Reboot Raspberry Pi. Data should be logged continuously to database upon reboot.

Postgres setup hints

I set up a postgres server on my home network using a spare computer. Here are helpful links and steps in case this is new to you.

Links

• https://www.postgresqltutorial.com/
• https://www.digitalocean.com/community/tutorials/how-to-install-postgresql-on-ubuntu-20-04-quickstart
• http://www.project-open.com/en/howto-postgresql-port-secure-remote-access

Steps

• Install postgres

  sudo apt install postgresql postgresql-contrib
  

• Set up postgres environment

  sudo -u postgres createuser --interactive # Create new superuser tentlogger (or whatever you want to name it)
  sudo adduser tentlogger  # Must have matching linux user
  sudo -u postgres createdb tentlogger # Create database with same name as username
  sudo -u tentlogger psql  # Access database
  

• Create table for logging

  CREATE TABLE dht22 (
    datetime   timestamp,
    temperature real,
    humidity real
    );
  

• Open Postgres port for remote access
  • Locate path to conf file:

    sudo -u postgres psql -c 'SHOW config_file'
    

  • Copy file path from output and open in text editor. Change listening address to 0.0.0.0
  • Open pg_hba.conf (located in the same directory as postgresql.conf) in text editor and add the following line to the bottom of the file:

    host  all  all  0.0.0.0/0  md5
    

• Restart Postgres service

  systemctl restart postgresql.service
  

• Open firewall ports

  # Install firewalld package
  sudo apt install firewalld 
  
  # Open port
  sudo firewall-cmd --zone=public --add-port=5432/tcp --permanent
  
  # Reload
  sudo firewall-cmd --reload  
  

• [Optional] Status check
  • Check port

  # Install net tools
  sudo apt install net-tools
  
  # Confirm changes to address and port
  netstat -nlp | grep 5432
  (Not all processes could be identified, non-owned process info
   will not be shown, you would have to be root to see it all.)
  tcp        0      0 0.0.0.0:5432            0.0.0.0:*               LISTEN      -
  unix  2      [ ACC ]     STREAM     LISTENING     25322    -                    /var/run/postgresql/.s.PGSQL.5432
  

  • Check if port is open from ANOTHER COMPUTER

    telnet [ip.address.to.server] 5432
    

• Turn off sleep

  sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target