Eight Hart Career Center students will travel next week to Louisville, Kentucky for the national leadership and skills conference of the SkillsUSA organization. Each of the students earned their way into nationals after winning first place for their projects at the state competition earlier this year.

Three of the students presented engineering projects to the Mexico school board Tuesday night.

Ryan Pemberton, Jacy Graham and Zach Quinlan were introduced by Project Lead the Way engineering program instructor Hester Russell. "SkillsUSA is a technical organization that supports students as they learn about their chosen skill or trade," she said. "These students compete against other students. Only first place at state gets to move onto nationals. These boys have shown they are the best in Missouri."

Pemberton developed a way to indicate when a grocery store cart return is full. His project used ultrasonic rangefinders, which he learned about in his engineering course. Graham and Quinlan's project seeks to solve a real-world problem by creating a new piece of technology.

Pemberton's project is known as the Cart Return Occupancy Status System, or CROSS. It was developed when Pemberton learned about the job Russell's son had as a cart collector.

"He had to walk to each of those racks and check on each one of them and that was really time consuming," Pemberton said.

He developed a system to notify grocery store employees when a cart rack was in need of emptying by using the rangefinders and LED lights.

"The ultrasonic rangefinder uses sound waves to detect how far away an object is. The three parts of the rangefinder are the speaker, the receiver and the timer," Pemberton said.

The speaker sends out sound waves to the nearest object. The waves bounce back to the receiver, and the timer measures how long the sound waves took to return, which indicates its distance to the nearest object.

"If I put in one shopping cart, it will cover one sensor, so it's partially filled," he said.

A green light will turn on when one cart is in the rack. As the rack fills, it will change to a yellow light and finally a red light, which signals to employees a rack is full.

Graham and Quinlan, along with Gage Worley, who was not present Tuesday due to work responsibilities, were part of the senior engineering design team.

"We spent all year developing and creating a project focused on reading disabilities," Graham said.

Those with dyslexia, for example, often will have trouble reading black text on a white background due to the high color contrast, Graham said.

"All the ways people have tried to solve that problem have been really inefficient," he said.

Past solutions have included colored, clear plastic sheets or tinted glasses. The sheets can be impractical, because the student has to shuffle, remove and replace the sheet to write answers in an exam situation. Tinted glasses are expensive, and a color that works for one student may not work for another.

The students developed a device with three dials for red, green and blue light. An earlier prototype cycled through LED colors and could only be turned on and off by removing the battery. Their updated version uses an on/off switch.

"We did this by using an arduino, which is a programmable chip, so we put it on our computer and programmed it using the C-language to control the light [that] we have, which is a pixie light," Graham said.

C is a general-purpose computer programming language.

The product also had to be affordable for schools, as well as portable, Quinlan said. It also needs to be versatile, so it can be used for books or individual pieces of paper, he said.

The group developed the light because a team member's brother has difficulty taking standardized tests. "He has dyslexia, and so it's very hard for him to manage putting on a colored sheet to read and then taking it off and working back and forth," Graham said. "We found that green is most easy on the eyes, and it modifies the page in the best way to make it easy to read."