Commercial Internet Controlled Thermostats?
As true scouts adhere to the principle of 'why buy it, when you can build it?', we built our own 'smart' thermostat for our clubhouse.
Our scouts clubhouse ('t Landhuis) is not really energy effecient, lots of nooks and crannies makes it necessary to maximize the potential of the two furnaces installed in the building.
The old system directly connected five thermostats (each in a different room) directly to a valve responsible for the room the thermostat is in. When a valve opens, the furnace linked to it would start. So most of the time both furnaces would be on at the same time with only two rooms needing heat, which could be easily deliverd by one furnace.
Commercial solutions are way to expensive and, as stated before, why buy something when you can build it yourself?
iPrototype sponsored our group with discounts on some of the parts used.
The new system uses five DS18B20 temperature sensors to sense the temperature in each of the five rooms, coupled with a i2c LCD(16x2) an a button in a nice wooden enclosure. Each thermostat is connected to the central Arduino Mega 2560. The one-wire bus for the sensors easily managed the long distances to each of the rooms (longest cable ~30m/98ft), the i2c though, was a lot harder to send over such a long wire (CAT5e FTP). An i2c bus buffer from NXP/Ti named P82B96 made it possible to send i2c signals over such a long bus, the whole bus being around 70m/230ft.
After we assambled the basics we started to look for an enclosure and found a case of an old fire alarm.
Designing and building the thermostats and central I/O board:
A nice place for the central CPU/Arduino was found next to the furnaces, nicely build into the wall facing the main hallway so it can be easily checked:
Making the last three thermostats and putting it in place in the wooden enclosure (last pic; old thermostat vs new):