We seem to use quite a few low-cost wirelessly connected devices around the home. When thinking about how to realise my smart thermostat project I realised that it should connect to the boiler in the same manner as the current dumb thermostat, at least until some better technology with the right price point comes along.
Many of these devices use 433 Mhz and have undocumented proprietary protocols. Nevertheless, the price of these devices is right so I thought I would try to reverse engineer some of them, starting with the existing thermostat and an outside thermometer.
First step was to get some RF modules. I chose the Radiometrix ones as the supplier is nearby and user-friendly. Thx to Peter at the OHH meetup I knew to use a sound card and Audacity as a recording ’scope to see whet we’re dealing with. Next I wil convert the manchester-encoded stream and log a bunch of readings. From there I hope to be able to guess the protocol.
Along the way I found someone else doing this. See Bertrik’s site for details.
Once I’ve crossed that bridge I’ll hook up a transmitter and see if I can drive the boiler relay. Initially a simple arduino program will be sufficient to create a dumb theremostat. After that I’ll move on to optimisation taking into account internal and external temperature gradients.
If all goes well I can achieve another reduction in energy for heating without reducing comfort for the family.
Why don’t I just buy an optimising thermostat? I’ve tried to and failed so far to find anything at a reasonable price.