How Cutting Edge PCB Design Has Enabled the Nest Thermostat to Transform Homes

April 7, 2017 CircuitStudio

Round dial thermostat
Not exactly the most thrilling thing in the world.

 

Growing up in the northeast, the thermostat was always a point of contention in my household. It was never set high enough - only 60 degrees in the middle of January! My parents, being the practical people they are, wanted to save energy. If everyone is out at school or work all day, then there’s no point having the heat on full blast. “Besides, you can just put on more layers” they would always say. I disagreed. The stereotypical adolescent in me saw us as civilized people, and therefore capable of paying a heating bill. Like most adolescents, I didn’t know much then. Heating an empty house isn’t cheap, even if it is warm and welcoming. I had no idea that technology, driven by advances in PCB design, would come to the rescue.

 

 

Thermostats Weren’t Always the Hottest Technology Fad

For the longest time, the humdrum thermostat was ignored by startups and hardware designers. Contemporary examples were lacking in features. Just read the thermometer and set the temperature. If you were lucky, you got a timer and a little LCD display. In fact, a 2005 thermostat was fundamentally no different from a 1965 thermostat. Sure, they graduated from analog to digital, and perhaps looked a bit nicer (harvest gold, anyone?), but the features and controls remained the same. It’s either ”on” or “off.” If you think about it, thermostats were a space overdue for disruption. It wasn’t until the late 2000’s that somebody finally gave it the attention it needed.

 

Enter Nest. As a PCB designer or developer, you’ve probably been following the emergence of the “smart home” space that Nest has come to define. Founded in 2011, Nest was created by two former Apple engineers, Tony Fadell and Matt Rogers. As the story goes, Fadell was building a vacation home when he started shopping for thermostats. Taking a page out of the Steve Jobs book, Fadell was immediately dissatisfied with the selection he found and thought he could do better. Joining Rodgers, an ambitious up-and-comer in Apple’s iPod division, they set out to make a 21st-century thermostat. The resulting product was a new idea in home controls. A thermostat that “learns” your heating and cooling habits. It notices when you turn down the heat as you leave for work, and then turn it up when you return. After reinforcing the habit, the Nest thermostat automatically does it for you. It even considers the time needed to heat or cool a room to a certain temperature. It also tracks the weather at your location, boosting your boiler when a cold front rolls in. Plus, like many other “smart home” products, the Nest thermostat links into a cloud control panel, which lets you monitor your system online.

 

Digital thermostat
Now we’re talking! The Nest thermostat even looks better than older models.
 

Without a doubt, the Nest thermostat blew away the competition, but how does it know when to blast the A/C? This is the result of its machine learning abilities. Using self-learning algorithms, the Nest thermostat “learns” the habits of the household, tracking when the heat (or air conditioning) is turned up or down. After accruing enough data, the Nest unit is able to anticipate and automatically adjust the temperature setting according to your habits and the time of day. However, it’s more than just a new way to save energy. For the PCB designer, Nest represents a new way of applying the latest and greatest in cutting-edge PCB development.

 

An Exciting Way to Apply Modern PCB Technology

 

The Nest thermostat was made possible by recent PCB advances. Had Nest attempted to rethink thermostats a decade earlier in 2001, the technology would not have been able to meet the size and performance requirements. Sure, Nest might have been able to cobble together a working prototype, but it wouldn’t have the size and packaging of a contemporary “smart home” product. Not to mention a much higher price! Techniques like high-density PCB’s, ball grid array chips, and efficiency-based design approaches were only just emerging. They weren’t ready to scale to a consumer price point. Nest turned the world of thermostats upside-down, but the technology needed to be there first.

Processor with BGAs
Compact Ball grid Array (BGA) IC’s are just one technique Nest took advantage of.
 

The thing is, all of the technology in the Nest thermostat didn’t just come together through economy-of-scale. Getting all of those IC’s to fit on a complex high-density board is no easy feat. Therefore, much credit is due to the design effort that went into the product. Though a teardown of the thermostat performed by Sparkfun, we can see what’s possible with modern PCB design techniques. The main logic board has its foundations in a multi-layer approach with an abundance of surface mounted chips, optimizing the space requirements. Several IC’s are present, each taking advantage of a ball grid array mounting to further reduce the size and maximize the number of interconnection pins. A more conventional quad flat package, for example, would be too big and inefficient. To further save space, Nest employed surface contacts on the board itself, rather than defaulting to bulky ribbon cables. In the case of one daughterboard, they used the mounting screws themselves to provide power, ground, and signal. All told, the Nest thermostat is a hallmark of high density and space efficient design. Through the techniques employed, Nest united the performance and form factor that is needed for a successful thermostat solution.

 

The techniques employed by Nest are enabling a whole new category of smart home devices. In fact, startups and independent designers everywhere are looking to recreate their success in the smart home space. Sure, you might not be developing the next category-killing thermostat, but powerful PCB design software is the key to project success. Altium’s CircuitStudio, an easy to use PCB design software, provides an intuitive interface and can handle all of the latest hardware tricks. It gives you the visibility and control that lets you meet design specifications under the most demanding of project requirements. CircuitStudio provides a professional turnkey solution that’s perfect for startups and professionals alike. With an Altium solution, you can turn up the heat on your next project.

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