Since Google acquired Nest for $3.2 billion last week, current and prospective smart thermostat or smoke detector owners have been apprehensive about what Google might do with the company. In the last few days, a couple of companies have stepped forward with potential open source alternatives to the service and hardware that Nest offers, sans the new implications of Google ownership.

The original Nest is a smart thermostat that uses motion and temperature sensors to “learn” the routines and comfortable temperature zones of its owners. It can detect when no one is home, and it normalizes to a certain temperature range over time. Users control the Nest with an app and through a Web interface.

At Spark, four engineers set to work on an open source version of a smart thermostat using their own Spark Core, an Arduino-compatible Wi-Fi development board. They added in a humidity and temperature sensor, IR motion detector, and some LEDs and LED matrices to put together and mount inside a custom wood and acrylic enclosure.

Spark kept the interface to a Web app that presents historical temperature information and has a JavaScript “knob” that allows users to set the temperature. The temperature can also be set by turning a ring on the thermostat’s enclosure.

In all, the team completed its open source version in less than 20 hours for “about $70,” including their $39 Spark Core. The thermostat is still in the experimental stage and lacks much of the sophistication and “smartness" of the Nest, but it still constitutes a networked and remotely controllable thermostat that has a memory of its own work. The Spark team posted the open source files for the thermostat on GitHub.

Adafruit, another open source hardware company, has made a platform of trying to keep data that could be produced by an “Internet of things” under control. Among its talking points are that “consumers, not companies, own the data collected by Internet of Things devices” and “users have the right to keep their data private.” The company has previously released the Tweet-a-Watt, which can be connected in series with a power strip to monitor and report the power going through it.

On Friday, the company made a blog post asking its customers if it should look into making an open source smart thermostat. The post contained only a couple renders of what a smart thermostat might look like, but several customers filled in features that Adafruit could consider to make something even more flexible than Nest’s product.



A number of customers suggested offering two different models: one that attaches to and controls a home’s HVAC system and a second remote sensor that would function as a display in other rooms and could communicate commands to the HVAC-connected thermostat wirelessly. Currently, Nest offers communication between Nests in different rooms, but it does not use this master/receiver model.

Commenter jorge suggested that Adafruit should include the ability to integrate an outdoor temperature sensor to “gauge the recovery period from an energy saving setback.” Most customers requested an Arduino-based thermostat, though some requested Raspberry Pi, and one responder wanted it based on the BeagleBone.

Commenter imroot at the HackerNews post for Spark’s thermostat wrote that he managed to make multiple temperature sensors using beagleboards for only $43. He controls the thermostat through a Web interface and has a Ruby script that periodically checks the temperature at the various sensor locations.

The more complicated parts of Nest’s functionality (temperature learning and effective power consumption among them) would be hard to replicate on an open source system. But remote thermostat management is turning out to be easily and cheaply attainable for interested consumers.