Follow the Light

Color sensors are showing up in many products and devices. They can detect the ambient and reflected light of their surroundings and nearby objects, and be programmed to trigger follow-up behavior. For instance, many color sensors detect when it gets dark and "automatically" turn on streetlamps, headlights and parking lot lights. It is common to find cameras that use color sensors to monitor buildings, stores and schools. Other color sensors are used to read the numbers from swiped credit cards.

Computer programming is a component of many modern engineering designs. As students design robot programs in this activity, they begin with a "goal" or "concept" of what the program solution needs to do, before they begin writing the code. Next, the process of working on the code and "debugging" it inherently constitutes "revising and improving their designs based on the results of testing." In that sense, the thought processes required to code programs that meet problem constraints are very similar, if not identical, to the thought processes required for traditional engineering design of physical structures and products.

After this activity, students should be able to:

• Program a LEGO robot to take input from color sensors and activate motors to follow a light source.
• Explain how the program and the color sensors work.
• Relate the program (robotic response to color sensor information) to human responses to light.

• Experience using and programming the LEGO MINDSTORMS EV3 robot and intelligent brick (computer) so that it takes input from sensors for decision making.
• An understanding of how sound sensors work, both human and robotic, as presented in the associated lesson.
• Completion of the What Is a Computer Program? (unit 3) so students have the knowledge and experience to create LEGO programs.
• Completion of previous lessons and activities in this unit, specifically the What Is a Sensor? lesson.

You have learned how light is sensed by your eyes and robotic color sensors from the previous lesson. Now, how do we implement the "stimulus-sensor-coordinator-effector-response" framework in a LEGO robot?

Today, your design challenge is to carefully program the LEGO robot to move based on sensing light. It must use information detected from its color sensor to follow a beam of light. Let's get started!

Before the Activity

• Gather materials and make copies of the Follow the Light Pre-Quiz (PDF) and Follow the Light Post-Quiz (PDF), one each per student. The quizzes are provided as separate attachments, and also embedded in the presentation so they can be presented to the class as a whole, if desired.
• Assemble the LEGO MINDSTORMS EV3 taskbots by following instructions at https://www.youtube.com/watch?v=Dhe2jXi3Fc4 or in the core set.
• Perform the activity and become familiar with it in advance of the class. For this purpose, detailed programming solutions are provided on slides 7-15. Basics related to programming can be found in What Is a Computer Program? (unit 3), which is recommended to be conducted prior to this activity.
• Use the 19-slide Follow the Light Presentation (PPTX), a PowerPoint^® file, to teach and conduct the activity. Set up a computer/projector to show the presentation to the class. Instructions for how to use each slide to teach the activity are provided below.
• Arrange for enough computers so you have one for each student group. Make sure each computer has the LEGO software loaded.

With the Students

1. Administer the pre-quiz by handing out paper copies; the quiz is also on slide 2. The answers are provided for the teacher on slide 3 for discussion after students have completed the quiz.
2. (slide 4) As a quick review, remind students of the parallels between human and robot designs. Your brain commands your hand to perform a task, depending on what it has seen. Similarly, the EV3 brick can command its motor to move the taskbot based on sensor input and its programming instructions.
3. (slide 5) Then introduce the activity's design challenge, describing the objective: Build a LEGO taskbot with a color sensor, and program it to make the robot follow a flashlight as the light beam is moved around by a person.
4. Inform (or remind) students of the engineering design process—which is a series of steps used by engineering teams to guide them as they develop new solutions, products or systems (slide 6). The basic steps of the engineering design process are: defining a problem (including its criteria and constraints), brainstorming and generating different ideas, selecting the best design solution to fit the circumstances and constraints, making and testing the solution(s), and presenting the results. For engineers, constraints are the limitations (restrictions) and requirements that must be considered when designing a workable solution to a problem. This is a cyclical process that requires engineers to test and redesign solutions or products as often necessary so they end up with reliable finished solutions or products. In your engineering challenge today, you also will be going through many of these steps, especially testing and modifying your robot program to improve so it meets the challenge objective.
5. (slide 7) Get the activity started by dividing the class into groups of three students each. Distribute the assembled LEGO taskbots and the parts necessary to attach the color sensors to them. Have students in each group attach a color sensor to its taskbot, following the instructions in the LEGO core set.
6. Direct students to work in their groups to come up with the logic of the program first, before they move to detailed programming. Then have them create the program using a computer, download it to the EV3 intelligent brick and test it, debugging and retesting as necessary. Slides 8-16 provide the programming solution for the teacher.
7. Assist students as they work through the challenge. Make sure to check each group's plans and provide encouragement and suggestions so that they develop successful programs.
8. Have each student group demonstrate that its program works successfully. Use the grading rubric provided in the Assessment section.
9. At activity end, lead a class discussion about the activity, as described in the Assessment section.
10. Administer the post-quiz by handing out paper copies; the quiz is also on slide 17. The answers are provided on slide 18. Slide 19 contains vocabulary terms and definitions.

Pre-Activity Assessment

Pre-Quiz: Before starting the activity, administer the Follow the Light Pre-Quiz (PDF) (also on slide 2) to assess students' base knowledge of color sensors and the logic behind programming a robot to follow a beam of light using a color sensor. Answers are provided on the Follow the Light Pre-Quiz Answer Key (PDF) (and slide 3).

Activity-Embedded Assessment

Programming for Success: Expect students to be able to come up with the logic for the program, and then assemble the program as shown on slides 8-16. The teacher should be familiar with the entire program and should have run it successfully previously. Students successfully meet this challenge if they are able to show that their robots are able to follow the direction that the flashlight beam of light points. Use the following rubric to assess the activity (maximum 30 points):

• The two color sensors were correctly assembled on the robot (using instructions); up to 10 points
• The logic of the program worked; up to 20 points

Post-Activity Assessment

Concluding Discussion: At activity end, lead a class discussion about the activity, asking students to share their experiences and lessons learned. Ask students:

• What did you learn about programming principles?
• Describe your experiences, including any difficulties you encountered.
• How might color sensors help real-world robots perform tasks?
• Imagine how the ability to direct movement using light could be used in real-world applications. Think about this and write down at least one idea. (Then have students share their ideas with the class.)
• What might you now want to learn about color sensors?
• BONUS: Which of the steps of the engineering design process have you been participating in during this activity? (Answer: Most of the steps of the cyclical engineering design process! They include: understand and define the problem [including criteria and constraints], brainstorming and generating ideas, selecting the best solution, making and testing the solution[s], evaluating it, revising it to improve it and presenting the results.)

Post-Quiz: Administer the Follow the Light Post-Quiz (PDF)(also on slide 17) to assess students' understanding of the stimulus-to-response framework for robotic color sensors and human eyes, and their ability to explain the logic behind the program they developed in the activity. Answers are provided in the Follow the Light Post-Quiz Answer Key (PDF) (and slide 18).

Expect students who have completed the What Is a Computer Program? (unit 3) to be able to come up with the logic and detailed programming to meet the design challenge. If they have difficulty, review relevant slides from that unit (lessons 1-3), depending on which particular concepts they find difficult.