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Thermostat battle: Honeywell vs Nest

15 Dec 2014  | Richard Quinnell

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 Nest and Honeywell teardown

 Nest and Honeywell teardown

The Honeywell unit's single PCB includes DC-DC converters, voltage regulators, rectifiers, an eight-channel, 12bit ADC, 128MB of SDRAM, 32M of Flash and a Broadcom Wi-Fi module (shield removed). An Atmel 926 ARM processor is the main processing unit, enclosed by the metal shield just visible underneath the flat-ribbon cable to the display. A single shield encompasses all of the Nest device's main electronics. Two add-on circuits near the bottom provide sensing functions. The PCB and the display secure together with screws, capturing the metal ring between them while leaving it free to rotate.

 Nest and Honeywell teardown

The main board of the Nest, with metal shield removed, shows a TI Sitara CPU, power management and USB chip, Flash, 32Mx16 SDRAM and a Murata Wi-Fi module. There is also a ZigBee network coprocessor, implying that the device may offer expansion options in the future.

 Nest and Honeywell teardown

 Nest and Honeywell teardown

Users rotate the outer ring of the Nest to select options. This emitter/sensor combination from an optical mouse is what detects that rotation. The inside of the outer ring shows the grooved pattern that the optical mouse element uses to sense rotation.

 Nest and Honeywell teardown

The Nest senses the presence of its operator using this IR proximity detector, automatically becoming active when approached.

It is important to remember, however, that the IoT device is only half of the story. The other half is the software that interacts with the device, receiving data and issuing commands. Both the Nest and the Honeywell thermostats have apps for smartphones with demo modes that allow you to play with virtual devices if you don't actually have one. For the Honeywell device, the demo mode is available as a link on the login page. For the Nest, you will need to log in with username: demo@nest.com and password: demo.

It's worth exploring the software to see which provides the kinds of functionality you would want from a high-end home automation device. For my money, I think the Honeywell device is simply a touchscreen thermostat with Wi-Fi bolted on. There is no new functionality here. The Nest has a learning mode that can determine your usage patterns and program itself over time, eliminating the need to page through a lot of setup screens. It also makes use of local weather forecasts to anticipate when your home will need a more aggressive response in order to achieve desired settings.

My feeling is that the Honeywell device is an old design with network connectivity added as a remote interface. There is no utilisation of the network's ability to log data, correlate with other information sources or the like. The Nest seems to be a true IoT design, with network connectivity an integral part of its operation and features.

Let me know what you think of these devices and what questions you may have on what I discovered while tearing them apart.


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