Thermostats for home HVAC systems may seem like a good idea, however the placement of the temperature sensors may not be ideal - and thanks to the closed-source nature of many systems it's impossible to add your own without great expense. However there is a solution, and with a little work William Thomas came up with a great solution.
By hacking into the control planel which has full manual control, William has used a Raspberry Pi to control relays connected to the relevant buttons on the panel for controlling the heating system. Once this has been done, the Raspberry Pi can now take control and make decisions based on sensors placed wherever they're required - and William has also created a neat web-based control via a LAMP stack to allow remoteo control via a smartphone.
Although this may sound complex, once the panel can be controlled by external hardware you can take over completely. For more information, check out WIlliam's github page. And for more, we're on facebook, Google+, and twitter - so follow us for news and product updates as well.
If you need to rig up some hardware interfacing to your Pi, one options is to use our PiBreak board. It provides labelled breakout pins for all GPIOs, a large prototyping area with solder pads, and power rails for easy power connection:
Furthermore the PiBreak also includes mounting hardware to firmly attach it to your Raspberry Pi using a nut, bolt, and spacer - and is compatible with all revisions of both model A and B Raspberry Pi computers. For more information about our PiBreak board, our Getting Started guide, and to order - visit the product page.