Overview

Using a Raspberry Pi, I want to be able to control & monitor either a slow cooker or food dehydrator. To ensure best results, a digital temperature sensor & PostgreSQL database are configured so I can log data about each cooking task.

The Raspberry Pi will be controlled one of two ways: either a web interface for remote access and/or a GUI (access by a screen hardwired to the Raspberry Pi). Since I am new to programming with python, I am trying to leave my options open but will reassess this decision later in the project.

Warning (as of 3-Dec-2015)

This project is very much a work in progress.

The overwhelming majority of commits thus far have all sorts of problems that prevent it from working as I would like for it to. This project was my reason to learn python. There were some working commits a couple of months ago (should be obvious by the commit messages) where I was able to get it working using python procedurally.

Since that time I have rewritten the majority of the code to be object oriented. This approach has dramatically improved the flexibility of the code but has introduced problems as I work out the kinks while learning a new mindset when it comes to programming. While I do not have a target completion date, I think it's pretty obvious from my commits that I work on this project almost daily & have no plans to alter that behavior.

Hardware & Software Needed

• Raspberry Pi (based on the scope of this project, any Pi should be acceptable)
• USB Wifi adapter
• High-speed (Class 10 preferred) SD/MicroSD card, at least 4GB
• High temp waterproof DS18B20 digital temperature sensor, purchased from Adafruit (Do NOT use the standard DS18B20 sensor!)
• Powerswitch tail 2, purchased from Adafruit
• Debian-based Linux distro for Rapsberry Pi (I prefer Raspbian)
• Python version 3.4+
• PostgreSQL version 9.1+
• RPi.GPIO python class (for communicating with GPIO pins on Raspberry Pi)
• psycopg2 python class (for interacting with PostgreSQL database)
• TBD: A web interface requires a http (or https) server, ergo Apache or nginx. PHP will then be required for interacting with the database.
• TBD: If a GUI is ever implemented, some kind of screen & input method will be required. (The official touchscreen display was recently released & would be an excellent candidate for this project.)

Project Goals

1. Ease of use. If it's not easy to use, no one will want to use it. Everything should be as obvious as possible & contribute to that goal.
2. Stability. Using well-proven programming & database tools, it shouldn't require any extraordinary effort to make a stable application. However, it's possible to screw it up so I need to be vigilant in the execution of my code.
3. Web interface. The Raspberry Pi may require interacting directly with it to execute the jobs. At a minimum, the web interface is how I would like to monitor & display graphs of the progress of any previous cooking job(s). I am definitely open to exploring the possibility of using a web interface to control all aspects of the cooking job(s).
4. Local interface. The Raspberry Pi Foundation just released (Sep 2015) a 7" touchscreen display that attaches directly to the Pi. Depending on any progress made with the web interface, a local (only) GUI might be designed for controlling the cooking job(s).
5. Notifications. python can send messages via email using SMTP or via SMS. The idea of being notified periodically (or in case of job failure) is desirable.
6. Security Concerns Since there is a high chance of being able to control this device through a web interface, I'm taking a cautious approach to security. Thankfully setting up password encryption on the PostgreSQL database is a piece of cake. It uses Blowfish encryption & salts the encrypted password so that even instances where 2 different users use the same password, they will be unique (unlike password created with a MD5 hash). And the python code enforces a minimum password length of 8 characters.