Saturday Feb 28, 2009

Experiments with a Solar-powered Sun SPOT

Environmental monitoring is proving to be a popular application for Sun SPOTs (see here, here and here). This and other similar applications require a Sun SPOT device to operate for long periods (months) using a combination of renewable energy sources (e.g. a solar panel) and duty cycling -- having the device wake up only occasionally to record and/or transmit sensor readings and sleeping for the most part.

A few months ago, I conducted an experiment that collected sensor readings from a solar-powered SPOT into a mySQL database for almost four weeks. A write-up describing the results is now available as a Sun Labs Technical Report and featured in this week's spotlight on the Labs' home page.

This experiment helped us uncover and fix several issues that caused disruptions in data collection -- the occasional inability of the device to enter deep sleep, the resulting clock reset due to premature battery exhaustion, and loss of connectivity to the database after long periods of inactivity. The report offers important lessons in the design of sensor data collection frameworks and lists both recommended best practices and potential pitfalls to avoid.

As I type this, another Solar-powered SPOT running a new version of our software has been collecting and reporting sensor readings. It has already been up for more than two weeks without any of the disruptions we saw previously leading me to believe that the fixes we incorporated in response to lessons learnt are working well. Watch this space for a follow-on post describing the latest experiment.

Saturday Mar 31, 2007

Program the World: Sun SPOTs available for purchase!

Ever wondered what might be next in the ongoing evolution of computing devices from mainframes to workstations to laptops to smart phones? Did you know that the introduction of network-enabled phones more than doubled the number of computing devices connected to the World Wide Web?

This trend towards smaller and simpler is likely to continue and the next wave of computing devices is expected to bring about another dramatic increase in the size of the Web. Several research labs, both industrial and academic, have been studying tiny, battery-powered, wireless devices with the ability to autonomically sense and respond to their environments. Potential applications for these "wireless sensor devices" range from environmental monitoring to asset tracking to proactive healthcare to intelligent agriculture to ... well ... pretty much anything you can imagine!

At Sun Labs, our research team has created a small, wireless, battery-powered device, called a Sun SPOT (Small programmable Object Technology) that provides a versatile, Java technology-based platform for developing embedded applications. Each Sun SPOT is equipped with a 32-bit ARM processor and an IEEE 802.15.4 radio. Stackable boards include application-specific sensors and actuators such as accelerometers, light detectors, temperature sensors, LEDs, push buttons and general I/O pins. These devices can be duty cycled to run for months on a single charge of their rechargeable battery. Sun SPOTs have the ability to self-organize into self-healing, multi-hop network topologies and they can be reprogrammed over-the-air (securely, of course).

Sun spotsSun SPOT device
Sunspot: Hot!Sun SPOT: Cool!

Over the last few months, Sun SPOTs have been used in several university courses -- at the Art Center College of Design (e.g., in their flocking blimps), North Carolina State University, and the University of Essex --- and have earned some very positive reviews (e.g. here and here). Other high-profile projects using Sun SPOTs have covered the gamut of applications from the expected (asset tracking/monitoring, proactive healthcare) to the unexpected (innovative art exhibits) and that is precisely the point. With current state-of-the-art, developing applications for most other embedded devices is a tedious chore -- often involving learning unfamiliar languages/tools with little or no debugging support. By supporting application development and debugging via standard IDEs such as Netbeans, our platform opens up the exciting world of embedded programming to a much broader class of developers.

After several delays (caused by legal/administrative items and some other issues that we, as researchers, don't normally have to deal with :-)), the Sun SPOTs are finally available for purchase within the US. Click here to buy a kit and check out our official web site to learn more.

Today, there are over a billion Java-enabled mobile phones world-wide but it all started out almost ten years ago as a small Sun Labs project exploring Java virtual machines for the Palm PDA. Who knows what exciting developments lie ahead for Project Sun SPOT. Join us and we'll find out together.

Program the World!

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Vipul Gupta

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