Home automation products are an introductory application for many consumers to access the Internet of Things (IoT), so it's a good idea to explore how suppliers can design products for this market. I chose two products as the research object for this disassembly and comparison. One of them is the Nest thermostat, which caused quite a stir in the market when it was first launched a few years ago; the other is the newly launched product, Honeywell's Wi-Fi intelligent thermostat.
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After analysis and comparison, I believe that the Honeywell thermostat is just an old design that adds a remote interface through a network connection, and does not use network connections to record data, establish associations with other sources of information, and so on. The Nest thermostat seems to have adopted a true IoT design, and network connectivity has become an integral part of its operations and features.
Next, let's start disassembling the two thermostats and see how they differ in their internal construction under different design concepts.
In the process of studying these two products, the first thing I noticed is that their packaging is very different. The Nest thermostat is packaged in a tailor-made box, with all components (including installation tools) layered in it, elegant in appearance and as jewels in the show. The Honeywell thermostat is packaged in a carton and displayed through a flip window, but the display is disappointing after the package is opened: the window display is wrapped in plastic ball cushioning, while most of the other spaces in the box are It's empty and looks like a cheap toy in a gorgeous container.
Honeywell Thermostat
Nest thermostat
In order to further compare the internal structure of the two products, I first began to observe from the outer layer. The Honeywell thermostat has a full-color touch screen that can be used to control operation. One of the characteristics of this feature is that the background color can be selected so that it can be better matched with the color scheme in the room. The Nest thermostat looks like a traditional electromechanical thermostat, with a simple color display that shows the current and set temperature, and a color scale that shows whether it is currently heating or cooling. It senses the presence of the user, automatically illuminates when someone approaches, and automatically goes out when not in use.
Unlike the Honeywell thermostat's touch screen, the Nest thermostat requires the user to rotate the outer ring of the product to confirm what they want to do, then press the appropriate unit to confirm the selection. These actions will beep as a haptic feedback.
There are no screws or other fasteners on the back of the Honeywell thermostat. Its plastic housing assembly is secured with a snap lock. On the back of the Nest thermostat, the components are screwed into the outer ring for a more secure fit.
The wall plate of the Honeywell thermostat is a simple two-layer printed circuit board (PCB) with connectors for connecting cables to the heating and ventilation air conditioning (HVAC) components. The nest thermostat's wall plate is equipped with active components, including a STMicro STM32L151 microcontroller and an 8-channel analog multiplexer. A bubble level in the middle of the wall plate can be used to assist in properly mounting the back panel to the wall.
Adopted components
The Honeywell thermostat's monolithic printed circuit board includes several DC-DC converters/regulators/rectifiers, an 8-channel 12-bit analog-to-digital converter (ADC), a 128MB synchronous dynamic random access memory (SDRAM), and a 32M flash memory. And a Broadcom Wi-Fi module (screening has been removed). The main processor is Atmel's 926 ARM processor, which has a metal casing on the outside and can only see the part under the flat cable. The main electronic components of the Nest thermostat are all covered under a single metal casing. Two additional circuits near the bottom have sensing capabilities. The printed circuit board and the display screen are screwed, and the metal ring is caught between the two, but is free to rotate.
After removing the metal case of the Nest thermostat motherboard, you can see TI's Sitara CPU, power management and USB chips, flash memory, 32Mx16 SDRAM and Murata Wi-Fi modules. In addition, there is a ZigBee network coprocessor, indicating that the product can be expanded in the future.
The user can rotate the outer ring of the Nest thermostat to select an option. The transmitter/sensor combination on this optical mouse is the device that detects the rotation operation. Inside the outer ring, a pattern of grooves used by the optical mouse assembly to sense rotation can be seen.
The Nest thermostat uses this proximity infrared detector to sense if the operator is present and automatically activates when the operator approaches.
But one thing to keep in mind is that IoT devices are just one part. The other part is that we also need software that can interact with the device to receive data and issue commands. Both Nest and Honeywell thermostats are equipped with corresponding smartphone applications and offer display modes, so virtually no thermostat users can use virtual devices to try out related applications. The display mode of the Honeywell thermostat can be downloaded directly from the login page by clicking the link. The Nest thermostat needs to be logged in first (username:;password:demo).
For high-end home automation products, in order to confirm which product provides the functions that individuals need, it is necessary to analyze the corresponding software. Personally, I think the Honeywell thermostat is nothing more than a Wi-Fi-enabled touchscreen thermostat that doesn't offer any new features. The Nest thermostat provides a learning mode that determines the consumer's usage habits and self-programs over time, eliminating the need to flip through a large number of setup pages on the screen. In addition, it leverages local weather forecasts to predict when a user's home needs a positive response to achieve the desired setting.
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