Michael is a member of a scout clubhouse (Landhuis) in the Netherlands. The old building housing the club isn’t exactly energy efficient, as it traditionally required two furnaces to heat the structure’s various nooks and crannies.
“The system directly connected five thermostats (each in a different room) to a valve responsible for the room the thermostat is in,” Michael explained in a recent blog post.
“When a valve opened, 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 delivered by one furnace.”
The club members realized it was time to install a new, smart thermostat. However, rather than going the typical commercial route, the Landhuis decided to design a fresh system from scratch using parts subsidized by iPrototype.
The new thermostat is built around five DS18B20 temperature sensors, coupled with an i2c LCD(16×2) and a button in a wooden enclosure. Each thermostat is connected to a central Atmel-based Arduino Mega 2560 (ATmega2560).
“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),” Michael added.
“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.”