Nest thermostat teardown | Hacker News Reader

Nest thermostat teardown

sparkfun.com

107 pointsnabilt44 comments

I currently work at an commercial HVAC optimization company and we've been eyeing the Nest pretty hard. We'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 'nother level of a beast. Remote temperature sensors, 25+ year old units, and don't get me started on duct work (had to deal with one of those today).

My shot in the dark guess on the optimization comes in determining what would be called 'ramp-up' time and operating a proportional–integral–derivative controller (https://en.wikipedia.org/wiki/PID_controller). 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'd transition from an unoccupied to an occupied state, you do so efficiently while maintaining thermal comfort(https://en.wikipedia.org/wiki/Thermal_comfort), which is measured with light, temperature, humidity and potentially CO2 levels (I'd have to reread the article to see what the Nest actually has).

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.

The ZigBee support will most definitely be for future/additional appliance communication and total site monitoring (energy consumption, fault detection, etc).

There is more going on here than just a thermostat.

-The SoC contains an (up to) 1Ghz ARM Cortex-A8

-64MB of SDRAM

-Micro NAND flash IC (can't tell the size)

-Separate Texas Instruments ZigBee SoC with a 8051 micro-controller and hardware ZigBee acceleration

-Texas Instruments 2.4ghz front end for the zigbee SoC, looks to be used as a power amp. Given that the SoC has a decent transceiver built in, they are after serious range.

This is massive overkill for what the device does today, seems more likely this devices is intended to be the "head unit" for a network of many other ZigBee devices.

I really want to get one, but apparently there are issues when you don'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't run 5+ wire before I finished the basement.

Marco Arment documented it here: http://www.marco.org/2011/12/17/nest-incompatibility-without...

Although it may just be for boilers.

It seems like it would be easy for them (or someone else) to make a module for the furnace end that buffers these pulses while supplying the 24V power through the existing wiring. Some relays and some timing logic to only close the circuit going to the furnace after a few seconds.

It isn't ideal, but it seems better than cycling a unit which might not be prepared for it unnecessarily.

That is a really good idea, plug in something down by the furnace (or use the C-wire hookup there), make it handle communication over a couple of wires, power over another, and then the box converts it back to 'legacy' wiring on the other end.

My furnace takes 2-3 minutes to turn on after shorting the wires, although the pulse method could potentially be bad for it as well.

I would have ran the wire, but my wife was adamently opposed to getting a wifi thermostat, but I bet she'd like the nest.

> was adamently opposed to getting a wifi thermostat

Out of curiosity, why?

Too much money, don't really need it, will never use the wifi portion, etc. Which is probably true.

The nest on the other hand adjusts to outside temp, it's sensors, etc. She still thinks it's solving a problem we don't have...

I see. My wife is practical too, which offsets my gadget-whoreishness somewhat. Sometimes she wins, sometimes I do. Mostly she's right, though.

I was interested in getting one, too, but it might be overkill for our steam boiler...

I run a coworking space in Reno and as soon as I saw these, I knew that I wanted to have them installed in the space so that we can make better use of heating/cooling with people coming/going, etc.

As luck may have it, one of our members works on wireless thermostats (http://www.radiothermostat.com/). While they aren't as sexy looking as the Nest, they have a full REST API so you can build an app around it or just use curl. It gives us much more control but does require we roll our own app.

I think the sexiness of the Nest is one aspect, but the one that you're overlooking is its learning abilities. I believe one of the founders worked with Apple on the iPhone/iPod and he seems to be bringing that design/engineering to Nest as well. The hardware is important yes, but the software is what makes it a killer product.

Sounds fun. I built a little Arduino box that sits on our steam boiler and uses a bunch of Dallas 1-wire probes to monitor when it's running (as well as inside and outside temps). I thought about connecting the thermostat input to it, too, but the problem is that while it's transmitting data, it's not that easy to get user input uplinked to it.

Cool. You should post your project. I also made a diy web enabled thermostat + a bunch of other home energy gadgets. http://www.nabiltewolde.com/2011/11/home-energy-prototypes.h...

I think these types of devices need to have a more open approach to the data they collect. Another project that is trying to do this is http://openenergymonitor.org/emon/

did you document any of this?

Not really (but the code is on bitbucket: https://bitbucket.org/lutorm/arduino). I've been meaning to post some pictures and stuff, but I haven't gotten around to it yet.

I like how they continued the Apple tradition of 'Designed in <some place you will like>. Built in China'.

And I'm not even being snarky. It at least, shows that they care enough about design to mention where it's done.

How do we know there isn't a tiny mic in the device and NEST isn't the Newly Elected Security Taskforce. In all seriousness, as wifi enabled devices become common, getting an unauthorized peek into someones home is going to be trivial, if it isn't already.

We have had IR cameras and laser mics for a long time.

http://en.wikipedia.org/wiki/Laser_microphone (if you don't know what they are)

I would love to have one of these as "self adjusting/learning" gadgets are well in my "gotta have" bucket. However, my family is in the house almost all the time so we don't have the typical out-of-the-house-back-at-the-same-time behavior this thing seems geared towards. I'm not sure what it could really "learn".

Too, at $250, it's almost a 2 year payback period in close to the best of circumstances; that seems a bit on the high side for me.

But it's just nifty as all hell, and I think I'd really like the ability to adjust it from anywhere; in case we forget when we leave for vacation or something, but the payback there would be long after I'm dead.

I mentioned in a little more detail in my other comment, but by learning/detecting your occupancy schedule, it can know when to turn the system on/off itself. Its as if someone was standing at your thermostat 24/7 micromanaging your temperature.

> Its as if someone was standing at your thermostat 24/7 micromanaging your temperature.

That'd be my wife and 11 year old, and almost never towards the "save money" end of the continuum. ;-)

You'd be surprised, constantly manually changing the thermostat can have adverse effects, but with PID-based management system, you attempt to heat/cool a little past the target temperature before occupancy. From there you occasionally cool/heat when it hits a deadband of, say, 2 degrees back to the target temperature. After analyzing bills and normalizing area weather, we've been able to show 8-15% savings.

Would be great if hotels used these and let you decide the temperature of your room before you arrive.

Or remembered your preference between stays.

Impressive teardown. They really went all out -- I was expecting more off the shelf, pre-tested modules (especially the wi-fi) but it looks like they developed a wholly new design with lots of room for growth. Including ZigBee in the thermostat means it will potentially talk directly to newer utility meters and ZigBee-enabled devices in your home. So the v1 feature set just scratches the surface of what they hope to do. Exciting!

The wifi is an off the shelf module. Its the metallic looking block to the right of the primary SoC. The metal is just an RF shield for the components underneath. If you look closely, you'll see its a separate PCB soldered to the main PCB indicating its a separately produced SiP module.

It does certainly look to be a well done design though.

and... now I want one. Nest made an excellent PR move by letting Sparkfun do a post of the teardown.

There should be more manufacturers who encourage costumers to take apart and examine their products.

Well to be fair, the Nest is really well designed, both internally and externally. I'm not sure how many companies would be comfortable with someone exposing the innards of their products and showing everyone how hacked together it is.

Does anyone know, how well the Nest is selling so far?

Their site says they sold out of their initial production run.

Dead link?

All of their tutorial pages seem to be borked right now.

We've got an issue in our application routing that redirects to non-ssl for tutorials, which sometimes breaks HTTPSEverywhere. If you're using it, whitelist sparkfun.com and give it another go.

Next, the web page told me it detected a new thermostat near by. Cool! To verify it had the right one, I needed to go over to my newly installed thermostat and hit the button to confirm that my thermostat was indeed the one attempting a connection.

Er... How does that work?

The thermostat connects over wifi to their servers, the server sees that a thermostat connected from the same IP as the browser, so it offers that as a potentially owned thermostat? Is there some in-browser magic where it's probing the local network for thermostats?

If it's the former, and you're in a condo behind a shared building IP, are you offered all the Nest thermostats of your neighbors?

I would assume it's the former, but in the case where there's multiple thermostats hooked up to the same shared IP it might show you a list of all unowned devices and then ask you for which one you want to activate, and then telling you to go over to it and confirm. So in the scenario of the apartment complex you wouldn't get everyone's thermostats, just the unowned ones, and even then you're limited to choosing only the ones you have physical access to.

I'm surprised they didn't bundle a webserver into the thermostat and let you connect directly to that (or maybe they did that as well?).

I would think for security reasons, they would not do that. It would be really bad if someone hacked your thermostat to run up your power bill or try to make your home temporarily uninhabitable.

But they can hack the Nest website/your account for the same result.

It's one place Nest has to keep updated, not $BIGNUM.

I struggle to think of a situation where you are in a condo (and can replace the thermostat) but not have your own IP address.

Well, that's easy. One where your HOA groups together to provide discounted Internet access.

Have you actually seen this happen? Whenever I've seen HOA-provided internet access, it's just been a group buy from Comcast or AT&T or whoever. The end result in this case is that everyone has the same basic access they'd have if they subscribed individually. They just don't pay a separate bill and they get a cheaper rate (and they can't decline it).

Having a building administer its own network with a single IP shared by the building sounds terrible. What happens if you want to run a server? Or open up a port that some program needs to listen on? I can't imagine a building having network technicians competent enough to make this situation work well.

But it would make you practically immune to stupid RIAA/etc. lawsuits :)

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