Introduction
The future of thermostats has a name, and that name is Nest. The 2nd Generation Nest Learning Thermostat is the thermostat that never stops learning. With hardware this smart, it's important for us to keep a watchful eye on it, so we naturally had to open it up!
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Tools
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Some impressive tech specs are nested in this learning thermostat, or learn-o-stat, as we lovingly call it:
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24 bit color LCD Screen with 320 x 320 pixel resolution
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Built-in rechargeable lithium-ion battery
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Various sensors (temperature, humidity, far-field activity, near-field activity, ambient light)
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802.11b/g/n and 802.15.4 Wi-Fi support (both at 2.4 Ghz)
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Compatible with 95% of 24V heating and cooling systems, including gas, electric, forced air, heat pump, radiant, oil, hot water, solar, and geothermal
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As we open up the box, we find a Nest thermostat, an installation guide, a welcome guide, a concierge card, a screwdriver, screws, and trim kit.
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The Nest is made up of two primary components: a wall-mounted base that connects to the signal lines from your HVAC system(s), and the snap-on display unit that houses the LCD and controls.
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Nest advertises ease of installation for its thermostat. According to Nest, "three out of four customers install Nest in 30 minutes or less."
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The base unit is home to ten spring-loaded connectors that let you easily route signal lines from all of your heating and cooling systems into the Nest:
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Responsible for both the wiring and the mounting of the Nest, this component is fitted with two oblong screw holes and a built-in bubble level to aid in a neat and tidy installation.
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A few screws stand between us and the base motherboard—a quick turn of the screwdriver, and we see the green.
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With only light adhesive holding the base motherboard to its case, it doesn't take us long to pull it out for a closer look.
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We rarely see circular circuit boards. It's quite refreshing and alliterates nicely.
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The base motherboard is equipped with a surprising amount of hardware for an auxiliary board:
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ST Microelectronics STM32L151VB ultra-low-power 32 MHz ARM Cortex-M3 MCU
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Sensirion SHT20 humidity and temperature sensor
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Texas Instruments LW051A 8-channel CMOS analog multiplexer/demultiplexer
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The back of the Nest display has two ports: a micro USB port that can be used for charging (and possibly hacking the Nest's software), and a proprietary 20-pin connector that fits onto the base unit's matching plug.
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Removing a few screws allows us to separate the Nest display's rear panel from the rest of the unit and continue our exploration.
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We dutifully follow the steps to remove the battery:
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Step 1: Disconnect the base connection ribbon cable.
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Step 2: Pull the battery.
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Step 3: Unplug the battery connector.
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Step 3.5: Profit???
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At the other end of the rear panel's 'Pull' tab, we have a push option.
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This ribbon cable-mounted button turns the whole display assembly into the menu navigator, allowing users to scroll with the exterior ring and select with a press of the display.
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The cable is very securely adhered to the rear panel, but can be safely peeled off with a little patience and a lot of spudger.
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This small board houses the two motion sensors (long and short range) responsible for this feature. These sensors are capable of detecting movement within a 150° field of vision.
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Through a rather clever design, the sensor board has no cable connecting it to the motherboard. Instead, it rests on four screw posts that make up its contacts.
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We took a break from our headlong rush into the Nest's innards to sneak a peek under the large EMI shield that was covering the back of the motherboard. Unfortunately, there wasn't much to be seen.
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After expelling a few more screws, we disconnect the LCD ribbon cable to free the front panel from the device.
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Our first foray into the front panel involves peeling off the small plastic plate adhered below the screen. Mild adhesive holds it securely in place, but is easily dispatched with a little patient spudgering.
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The plastic plate turns out to actually be a window for infrared light, and is fitted with an array of Fresnel lenses that are used to widen the motion sensors' field of view and increase their range.
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The LCD is sandwiched between the front glass and a plastic frame. Adhesive secures the glass to the frame and the LCD to the glass.
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It may look like the folks at Nest cut a couple of corners on the LCD, but in fact it's a rather remarkable round display, with only the visible portion populated with pixels.
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By virtue of being a curved piece of glass, the front panel is a lens, capable of magnifying and focusing all of your important documents.
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From the looks of things, we'd venture to guess that this is a plano-convex lens, designed to wrangle the light of the LCD into a focal point.
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With everything else out of the ring, we're able to pull out the motherboard for its closeup.
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A quick look at the last component hanging off the side of the motherboard reveals an Avago ADBM-A350 optical finger navigation module, responsible for detecting the position of the outer steel ring.
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With all of the I/O connections on the back, the main motherboard houses all of its important ICs on the front:
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Texas Instruments AM3703CUS Sitara ARM Cortex A8 microprocessor
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Texas Instruments TPS65921B power management and USB single chip
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Samsung K4X51163PK 512 Mb mobile DRAM
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Ember EM357 integrated ZigBee/802.15.4 system-on-chip
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Micron MT29F2G16ABBEAH4 2 Gb NAND flash memory
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Skyworks 2436L high power 2.4 GHz 802.15.4 front-end module
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And under that last EMI shield: Texas Instruments WL1270B 802.11 b/g/n Wi-Fi solution, just like the one we found in the Kindle Fire
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Nest Learning Thermostat 2nd Generation Repairability Score: 9 out of 10 (10 is easiest to repair)
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Battery is clearly intended to be user-replaceable (with built-in directions) and can be removed with the included Phillips screwdriver.
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Solid construction surrounded by a hefty steel ring makes for great durability.
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Separation of components onto two motherboards increases modularity.
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Light adhesive holds the front panel assembly together, slightly increasing difficulty of replacing the LCD or glass.
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21 comments
Have an estimate for the BOM cost to make this?
Ufixit -
You are pointing out that the ring movement is detected visually. Are there any photos of the inner side of the ring that moves past the detector? Does it have a special pattern on it to make motion detection easier, or is it just a plain metal surface?
There are no mechanical parts used inside. The inside of the aluminum ring has what looks like an etched pattern, similar in fashion to a screen. An optic transceiver, like an optical mouse, is located to register the pattern as the ring is turned.
Thermostat 2nd Generation called Nest is to me an excellent ideal object I personally believe would be a great object I would love to own. The learning Thermostat is simple to use so long as one follow step by step directions.
vck_sm55 -