

Nest thermostat teardown - nabilt
http://www.sparkfun.com/tutorials/334

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tsumnia
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).

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mbell
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.

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MrEnigma
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...](http://www.marco.org/2011/12/17/nest-
incompatibility-without-c-wire)

Although it may just be for boilers.

~~~
ydant
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.

~~~
MrEnigma
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.

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colinloretz
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.

~~~
lutorm
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.

~~~
joshu
did you document any of this?

~~~
lutorm
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.

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statictype
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.

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biturd
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.

~~~
epochwolf
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)

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michaelcampbell
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.

~~~
tsumnia
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.

~~~
michaelcampbell
> 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. ;-)

~~~
tsumnia
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.

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7952
Would be great if hotels used these and let you decide the temperature of your
room before you arrive.

~~~
rscale
Or remembered your preference between stays.

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savrajsingh
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!

~~~
mbell
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.

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younata
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.

~~~
statictype
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.

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

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

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sbierwagen
Dead link?

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

~~~
stilldavid
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.

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georgieporgie
_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?

~~~
statictype
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?).

~~~
timdorr
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.

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

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

