As an update to the status of my Navitrino heating controller project.
A flurry of hardware bodging and C coding activity this weekend has now got the 4 channel relay board fully operational. The relays control the central heating, hot water and the various pumps and valves in the system.
The relay board will be housed in a plastic cased "wiring centre" - either Honeywell or Danfoss - available for about £10 and located in the airing cupboard next to the existing controller where it is close to the pumps, valves and tankstats.
The HW and CH relays will be wired in parallel with the existing controller. This allow the existing controller to continue to be used whilst development progresses - so that hot water boost can be used.
The relay board just needs a 3 wire serial link back to the main controller so that it can receive the various relay-on commands. Ultimately this link could be wireless and would appear to be an ideal use for a pair of JeeNodes - a good way of getting to learn about the JeeNode project.
The main controller will remain in my work room until development has finished, but a display slave can be situated in the living room, so that anyone can access the "normal" thermostat controls from downstairs and without a degree in computing science/electronic engineering.
The aim is to progress to the point where the heating controller can standalone without the laptop running. There's nothing more frustrating to find that Windows automatic updates has shut down your application at 3:18am, whilst you were in the middle of a long datalogging run. This embarrassment will shortly be fixed with the Navitrino logging directly to SDcard, with no more need for a permanent connection to the laptop.
The code is progressing well, I can now handle heating decisions made on time of day and day of week. For example, at weekends the controller automatically sets the room temperature a little higher during the day, and doesn't start heating till 7:30am, rather than 5am on a workday. Virtually any set of rules and exceptions can be programmed in - it's just a case of deciding which ones are actually useful.
Testing has now ceased for the evening - as a result of an uncontrolled heatsource being ignited in the living room.
Time to sit by the woodstove and watch TV.