You have marbles made of three materials, and you need a machine to sort them. Could you build it?

That’s the challenge students in an engineering class at Albert Lea High School face.

Teacher Mike Sundblad has his students learning robotics with Fishertechnik construction toys. These are sort of like Legos, only with advanced options of motors, sensors and computers. Many students ended up programming the computers to tell light sensors to detect ranges of light sensitivity and to tell switches when to turn motors on and off.

“The machine sorts out, rather than people doing it,” Sundblad said.

The students can pick from three of five types of marbles: glass, clear plastic, wooden, steel and aluminum.

The students worked in groups of two or three. The project belonging to senior Josh Jensen, junior Carlton Stripe and sophomore Alek Struck attempted to sort aluminum, wooden and plastic marbles into three small bins.

Stripe said a photo cell sensor detects what happens when a light is shined on the object. Aluminum reflects. The clear plastic lets light through. A neither happens for wood.

Struck said the sensor tells the computer the result and the computer moves the machine so that the marble rolls down a chute into the correct bin. Jensen said they learned through trial and error the correct levels of sensitivity.

In class Thursday, Stripe said they were having problems getting the right results for aluminum and wood. The plastic marbles sorted just fine. Struck thought changing the position of the sensor might fix the problem.

Sundblad said the project not only gives them a lesson in mechanical concepts, it also teaches them how computers big and small are used in many devices these days.

The class is college-level, combining many disciplines from math to English, and is certified as three college credits from the University of Minnesota.

Sundblad said because the students know it is a University of Minnesota course he has no resistance when assigning research papers.

Sundblad’s son, sophomore Brody Sundblad, is in the class. He said he and his father played with Legos quite a bit when he was younger. He said they built a remote-control car.

Sophomores Christian Andersen and Tylor Matson employed two photo cell sensors on their contraption. The first one separates the easy-to-tell glass marble. The second one has the more-difficult job of separating aluminum from plastic. By using two, sensors, they will eliminate computer issues, they said.

Senior Liz Winkels and junior Jon Koenigs said before they built theirs they first had to sketch it. Then the redesigned their plans as they sketched the project.

Sophomore Nick Santee said he is interesting in engineering as a career and likes that the class gives him University of Minnesota credit. He and sophomore Brady Falk discussed a problem with their project. Santee suggested changing the amount of time the sensor had to detect the marble. He said seven seconds was probably too long.

Twenty-one students are in the class. There are 17 in a similar class studying bridge design using wood and glue. It, too, is for college credit.

Sophomore Aaron Woitas and freshman Roman Marinin said their bridge held up to a structural efficiency of 600 to 1. That’s the mass of the bridge compared to the pressure that can be placed on it. It can hold 600 grams for every gram in the bridge’s mass.

They said the glue is their bridge’s weakness; they used too much. To get the bridge stronger, they need to built it again with the correct amount of glue.