His system, developed over the past eight months with a small team of fellow Brazilian college students, combines GPS technology with a set of wristbands to alert the user when it is time to turn.
"It works like a map for blind people," Cardim said in a telephone interview. "Through vibrating wristbands, they are given directions."
On Wednesday, the team got a chance to show their idea to Microsoft Chairman Bill Gates, and to present him with a Brazilian soccer jersey. Gates tried on the wristbands and inquired how the team had got them so small.
Cardim's team is a finalist in Microsoft's Imagine Cup, a 4-year-old invention contest that will be judged in August in Delhi, India. About 65,000 people were involved in this year's entries, and about 300 are representing their countries in the finals. Microsoft invited a handful of the finalists to show their projects to Gates on Wednesday.
All of the projects have to use Microsoft technology in some way and have to relate to health, this year's theme.
An Indian team showed Gates a different approach for helping the blind navigate, and aims to replicate the kind of echolocation that bats use to find their way. Among the other projects Gates checked out were an exercise-monitoring program from South Korea that uses a motion detector to measure the effectiveness of exercise, and another from a Japanese team whose medical information management software is designed to reduce medical errors.
For Microsoft, the Imagine Cup is a way to encourage young people to pursue technology careers and .
"It's sort of the DNA of Microsoft--young people with big ideas," said Joe Wilson, Microsoft's director of academic initiatives. "We want to continue to inspire that."
Plus, the students all use Microsoft technology. The Brazilian project, for example, used Windows' speech-recognition programming interfaces, the MapPoint mapping service and Visual Studio developer tools to help visually impaired users get where they want to go. The wristbands use GPS technology and Bluetooth wireless to communicate with a nearby cell phone or Pocket PC that can process a spoken destination request.
Cardim said he walked away very impressed with the Microsoft founder.
"He cares about what we are doing," Cardim said, noting that Gates already gets plenty of attention. "He isin a couple of years just to do social and charitable work."
And while Microsoft is giving plenty of money to the Imagine Cup winners--a total of $125,000 in cash prizes--Cardim said his interest is in making his project a reality.
"We're not just doing this for the competition, and we're not doing it for the money either," he said. "We'd love to see our project working, and there is no better way to do that than to get it to our users."
If the Brazilian team can make it to the final six, they stand a good chance. The top half-dozen teams will be flown by British telephone giant BT to England and given an opportunity to try and land business backing for their ideas.
Several past Imagine Cup finalists have commercialized their entries, including a Greek team that finished in second place with Sign2Talk, a combination of software and hardware that translates sign language to spoken words and vice versa. The inventors recently raised about 600,000 euros ($753,218) from the Greek government and private investors.
"They are going to start a whole company," Microsoft's Wilson said.