Since 2014, the Illini Solar Car Team has designed, built, and raced unique solar-powered cars that are helping the world envision a zero-carbon footprint future for personal transportation. Today, more than 100 students from across the University of Illinois’ Urbana-Champaign campus run a sophisticated operation spanning disciplines including electrical, mechanical, strategy and telemetry, and business and media. The Digi XBee® PRO RF modem helps these enthusiasts keep a careful eye on their creation to optimize speed, distance, and performance.
Meeting the Solar Challenge
With a passion for redefining the future of the automobile, dozens of students — engineers, environmental advocates, and plain-ol’ car buffs alike — are collaborating every year in the OpenLab space and various garage spaces on the University of Illinois’ Urbana-Champaign campus. Their singular mission: to build the fastest, most efficient vehicle powered solely by the sun. The Illini Solar Car Team (ISC) enters its vehicles in international competitions, such as the American Solar Challenge and the Formula Sun Grand Prix, earning top-five finishes against global competitors.
ISC’s latest vehicle —Brizo — features a carbon fiber panel chassis with a double-wishbone suspension, a rear-wheel two-coil DC brushless motor, 4 square meters of silicon solar cells, and a 5.3 kWH battery pack comprised of 420 lithium-ion batteries. The 423-pound car can reach top speeds of 70 mph and has travelled over 1500 miles.
According to Alex Lymberopoulos and Nafi Osmani, two undergraduate ICS members, the electrical system is the heart of what makes the Brizo operate. “An electric car requires reliability from the overarching power system of the motor and the custom-built battery to the solar array and down to the snippets of code that activate the turn signals,” said Osmani. “Nearly every board in the Brizo is designed from scratch and runs on custom code. That’s how we’re able to create a street-legal vehicle that can reliably drive across the continent.”
The Telemetry Dilemma
When race day arrives, telemetry plays a key role in ensuring the Brizo operates at peak efficiency. “When you’re racing 1,500 miles over several days, it’s crucial to monitor all of the systems — the motor, battery consumption, temperature sensors, and electronics,” said Lymberopoulos. “We have a lead car and a chase car surrounding the Brizo during the race, so we can get timely, accurate data, analyze it, and make informed decisions. This data is crucial because, if these systems exceed their safe zones, we can experience thermal runaway that destroys the battery. We have warning cutoffs for temperature in our custom code and then a hard cutoff to prevent damage.”
How does that data reach the chase car? Through a Digi XBee PRO 900HP modem, integrated with the ISC’s custom-designed boards. Digi XBee-PRO modules provide best-in-class range wireless connectivity to devices. Supporting RF line-of-sight ranges up to 28 miles (with high-gain antennas), and data rates of up to 200 Kbps, these modules are ideal for extended-range applications requiring increased data throughput.
The Digi XBee-PRO 900HP requires no programming and can be configured easily using Digi XCTU® software or via a simplified AT command set. Digi XBee modules are pre-certified for use in multiple countries, further reducing development costs and time-to-market.
“We plug in the XBee onto our receiver board that rides along in the chase car,” said Osmani. “And that feeds us our data from all of the system’s boards and sensors which are on the Controller Area Network (CAN) bus — especially temperature and speed. From there, we compile the data in a MongoDB database, feed that to our telemetry app and strategy app, and then predict how the car and its systems will perform in different conditions.”
“We noticed that most of the competing schools use the XBee module,” said Lymberopoulos. “That speaks to its reliability and durability. These are cars being raced across the country, and we’ve never had any reliability issues.”
A Bright Road Ahead
Following miles of track racing and road tests, Brizo debuted at the 2021 American Solar Challenge. It traveled over 1000 miles, starting in Independence, Missouri, to Santa Fe, New Mexico, along the Santa Fe National Historic Trail. Brizo placed third in the Formula Sun Grand Prix qualifier race, and fourth on the road. Brizo’s next race takes place at the 2022 American Solar Challenge along the Oregon National Historic Trail starting again in Missouri and ending along the trail in Idaho.
But these sophisticated electric vehicles aren’t the only ones with a bright future. “We’re gaining a lot of valuable experience in electrical system design, manufacturing, and test” said Osmani, and demonstrating how a solar-powered electric vehicle can become a feasible, mass-market reality. Big tech companies regularly recruit our team members because these skills transfer very well to future commercial markets.”
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