<story><title>Nest thermostat teardown</title><url>http://www.sparkfun.com/tutorials/334</url><text></text></story><parent_chain></parent_chain><comment><author>tsumnia</author><text>I currently work at an commercial HVAC optimization company and we&apos;ve been eyeing the Nest pretty hard. We&apos;ve built both our hardware and software so its a bit worrisome to see this, luckily they attacked residential. Our niche is controlling fast food and sit down restaurants over a ZigBee mesh network, which are a whole &apos;nother level of a beast. Remote temperature sensors, 25+ year old units, and don&apos;t get me started on duct work (had to deal with one of those today).&lt;p&gt;My shot in the dark guess on the optimization comes in determining what would be called &apos;ramp-up&apos; time and operating a proportional–integral–derivative controller (&lt;a href=&quot;https://en.wikipedia.org/wiki/PID_controller&quot; rel=&quot;nofollow&quot;&gt;https://en.wikipedia.org/wiki/PID_controller&lt;/a&gt;). The system uses the different sensors to determine occupancy times and then in turn determines the necessary amount of time needed to run the AC so when you&apos;d transition from an unoccupied to an occupied state, you do so efficiently while maintaining thermal comfort(&lt;a href=&quot;https://en.wikipedia.org/wiki/Thermal_comfort&quot; rel=&quot;nofollow&quot;&gt;https://en.wikipedia.org/wiki/Thermal_comfort&lt;/a&gt;), which is measured with light, temperature, humidity and potentially CO2 levels (I&apos;d have to reread the article to see what the Nest actually has).&lt;p&gt;georgieporgie asked about access to thermostat information being accessible over wifi. My second stab is that the thermostat actually reports back to the Nest servers with their unique ID, you register the stat to your account and pushing the button sends a signal to the server confirming you are in fact in possession of device. From there, the thermostat sends periodic updates and receives messages about how it should be running.&lt;p&gt;The ZigBee support will most definitely be for future/additional appliance communication and total site monitoring (energy consumption, fault detection, etc).</text></comment>
<story><title>Nest thermostat teardown</title><url>http://www.sparkfun.com/tutorials/334</url><text></text></story><parent_chain></parent_chain><comment><author>MrEnigma</author><text>I really want to get one, but apparently there are issues when you don&apos;t have a C-wire.  Basically a power wire from the furnace.  I just finished my basement, and the house only came with 4 wire, and I didn&apos;t run 5+ wire before I finished the basement.&lt;p&gt;Marco Arment documented it here:
&lt;a href=&quot;http://www.marco.org/2011/12/17/nest-incompatibility-without-c-wire&quot; rel=&quot;nofollow&quot;&gt;http://www.marco.org/2011/12/17/nest-incompatibility-without...&lt;/a&gt;&lt;p&gt;Although it may just be for boilers.</text></comment>