Hamilton Sensor

How to make buildings smarter

by Saemmool Lee

Detecting temperature, humidity, or occupancy can make buildings “smarter.” The information can lead to reductions in energy consumption and improve the comfort of occupants by responding to energy demands in real time. We commonly see a single thermometer or humidity sensor per room, which can only provide limited information. What about deploying many cheap and disposable sensors to capture more granular data about buildings and energy use patterns?

Berkeley researchers have developed a low-cost wireless sensor that can collect various data, including temperature, humidity, occupancy, and illumination. CITRIS researcher David Culler, professor of Electrical Engineering and Computer Sciences and former CITRIS Sustainable Infrastructures faculty director, and Therese Peffer, program director of the California Institute for Energy and Environment (CIEE) at CITRIS, initiated the project in 2016, targeting a manufacturing cost of less than $10. The project’s name, “Hamilton,” is drawn from the $10 bill that features the likeness of founding father Alexander Hamilton.

The team had noticed that the cost of manufacturing was dominated by the cost of assembly rather than materials. They lowered the assembly cost by using emerging “System-on-Chip technologies” (SoC) that integrate hardware components into a single integrated circuit (IC). Then they created the Hamilton sensor with core parts (including a microcontroller, low-power radio, flash memory, and antenna) costing less than $7.  Culler says, “Berkeley has been developing novel wireless sensor systems – motes – for over 20 years.  We launched this project when we saw that the kinds of designs we imagined all along could be so routine and so inexpensive as to be everywhere.”

There are similar products in the market, but the closest in price is around $30, says Hyung-Sin Kim, postdoctoral scholar in the team. Of course, market price includes costs as well as a profit margin, and the raw manufacture cost is rarely revealed. “The only way to unveil the cost information is to directly experience the whole design and manufacture process for a low-power sensor board, which we did,” he says, “As a research community, we unveiled that the actual cost could be less than $10.”

The Hamilton sensor has another highly competitive feature: It is battery-powered and can be deployed anywhere in buildings without needing a plug, whereas thermometers are usually attached to walls and plugged in. Thanks to software the team has developed, the sensor operates at extremely low power, and can survive for more than five years without charge or replacing batteries.

“Many software implementations out there fail to achieve the lowest power even though the hardware is supposed to provide very low power,” says Kim. “We developed a low-power software that fully utilizes the low-power potential of this hardware. We finally achieved the lowest power, which is a six μA (microampere), when the hardware does nothing.”

There are two types of Hamilton sensors: One has six types of sensors to gather six types of building information and deliver those to a router. Another has seven types of sensors, adding a “PIR (passive infrared) motion sensor” that detects human occupancy, along with the other six sensors. The PIR motion sensor is more expensive than the others, so separating them offers users more cost options.

The Hamilton team has published two papers: One is “System Architecture Directions for Post-SoC/32-bit Networked Sensors (2018),” where the researchers concluded that it’s time to change system design paradigms. The paper won the best paper runner-up award at ACM SenSys 2018. Another one is “Demo Abstract: Hamilton – A Cost-Effective, Low-Power Networked Sensor for Indoor Environment Monitoring (2017),” where researchers demonstrated how the sensor operates when users purchase the product.

Michael Anderson, doctoral EECS student and the Hamilton designer, manufactured the Hamilton sensor through a vendor in Oakland in 2016. A year later, he founded “Hamilton IoT,” a startup to sell the sensors. The sensors come with 5 years of basic cloud services, so that customers don’t have to separately set up or run a server to make the sensors work. Civil engineers and researchers are the startup’s main customers.

The Hamilton team is planning to upload their software code to “RIOT-OS,” an operating system for the IoT, so that RIOT-OS maintainers can review the code. Once the maintainers finally approve the Hamilton’s code, the code becomes part of RIOT-OS so that any researcher and developer can easily use the software that the team has built.

The team envisions the Hamilton sensors as the next generation’s data provider, deployed all over and robustly connected to the Internet. “Artificial intelligence and big data came out because we have the Internet and data,” says Kim. “What about we deploy more sensors here and there pervasively, and gather another type of data from these sensors? Then we can do more interesting things.”

Photos: Adriel Olmos

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The Center for Information Technology Research in the Interest of Society (CITRIS) and the Banatao Institute drive interdisciplinary innovation for social good with faculty researchers and students from four University of California campuses – Berkeley, Davis, Merced, and Santa Cruz – along with public and private partners.

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