Make a Sorting Machine

Prepare
- Read through this teacher material.
- If you feel it is needed, plan a lesson using the getting started material in the EV3 Lab Software or EV3 Programming app. This will help familiarize your students with LEGO^® MINDSTORMS^® Education EV3.

Engage (30 Min.)
- Use the ideas in the Ignite a Discussion section below to engage your students in a discussion related to this project.
- Explain the project.
- Split your class into teams of two students.
- Allow your students some time to brainstorm.

Explore (30 Min.)
- Have your students create multiple prototypes.
- Encourage them to explore both building and programming.
- Have each pair of students build and test two solutions.
- Provide students with cups or other containers to hold the sorted objects.

Explain (60 Min.)
- Ask your students to test their solutions and to choose the best one.
- Make sure they can create their own testing tables.
- Allow some time for each team to finalize their project and to collect assets for documenting their work.

Elaborate (60 Min.)
- Give your students some time to produce their final reports.
- Facilitate a sharing session in which each team presents their results.

Evaluate
- Give feedback on each student’s performance.
- You can use the assessment rubrics provided to simplify the process.

Sorting machines can sort objects based on properties, such as size, weight, quality, or color. They use a variety of sensors to measure these properties and then sort each object into the correct category.

Encourage an active brainstorming process.

Ask your students to think about these questions:

• Which colors will you sort?
• What size elements will you sort?
• Which type of motorized mechanism can move those elements?
• How can the machine sense different locations?
• What design features will ensure the machine’s movements are accurate and repeatable?

Encourage students to document their initial ideas and explain why they picked the solution they will use for their first prototype. Ask them to describe how they will evaluate their ideas throughout the project. That way, when they are reviewing and revising, they will have specific information they can use to evaluate their solution and decide whether or not it was effective.

To incorporate language arts skills development, have your students:

• Use their written work, sketches, and/or photos to summarize their design process and create a final report.
• Create a video demonstrating their design process starting with their initial ideas and ending with their completed project.
• Create a presentation about their program.
• Create a presentation that connects their project with real-world applications of similar systems and describes new inventions that could be made based on what they have created.

Building Ideas
Give your students an opportunity to build some examples from the links below. Encourage them to explore how these systems work and to brainstorm how these systems could inspire a solution to the Design Brief.

• Chute
• Color Sensor 1
• Color Sensor 2
• Color Squares
• Gyro Sensor
• Touch Sensor
• Tracks
• Turntable

Testing Tips
Encourage your students to design their own test setup and procedure to select the best solution. These tips can help your students as they set up their test:

• Mark the location to show where the machine should place objects.
• Use cups or other containers to hold the sorted objects.
• Create testing tables to record your observations.
• Evaluate the precision of your machine by comparing the expected results with the actual results.
• Repeat the test at least three times.

Sample Solution
Here is a sample solution that meets the Design Brief criteria:

EV3 MicroPython Sample Program

#!/usr/bin/env pybricks-micropython

from pybricks import ev3brick as brick
from pybricks.ev3devices import Motor, TouchSensor, ColorSensor
from pybricks.parameters import (Port, Button, Color, ImageFile,
                                 SoundFile)
from pybricks.tools import wait

# The Color Squares are red, green, blue, or yellow.
POSSIBLE_COLORS = (Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW)

# Configure the belt motor with default settings.  This motor drives
# the conveyor belt.
belt_motor = Motor(Port.D)

# Configure the feed motor with default settings.  This motor ejects
# the Color Squares.
feed_motor = Motor(Port.A)

# Set up the Touch Sensor.  It is used to detect when the belt motor
# has moved the sorter module all the way to the left.
touch_sensor = TouchSensor(Port.S1)

# Set up the Color Sensor.  It is used to detect the color of the Color
# Squares.
color_sensor = ColorSensor(Port.S3)

# This is the main part of the program.  It is a loop that repeats
# endlessly.
#
# First, it moves the 2 motors to their correct starting positions.
# Second, it waits for you to scan and insert up to 8 Color Squares.
# Finally, it sorts them by color and ejects them in their correct
# positions.
#
# Then the process starts over, so you can scan and insert the next set
# of Color Squares.
while True:
    # Initialize the feed motor.  This is done by running the motor
    # forward until it stalls.  This means that it cannot move any
    # further.  From this end point, the motor rotates backward by 180
    # degrees.  This is the starting position.
    feed_motor.run_until_stalled(120)
    feed_motor.run_angle(450, -180)

    # Initialize the conveyor belt motor.  This is done by first
    # running the belt motor backward until the Touch Sensor is
    # pressed.  Then the motor stops and the angle is reset to "0."  
    # This means that when it rotates backward to "0" later on, it
    # returns to this starting position.
    belt_motor.run(-500)
    while not touch_sensor.pressed():
        pass
    belt_motor.stop()
    wait(1000)
    belt_motor.reset_angle(0)

    # Clear all the contents from the Display.
    brick.display.clear()

    # Scanning a Color Square stores the color in a list.  The list is
    # empty to start.  It will grow as colors are added to it.
    color_list = []

    # This loop scans the colors of the objects.  It repeats until 8
    # objects are scanned and placed in the chute.  This is done by
    # repeating the loop while the length of the list is less than 8.
    while len(color_list) < 8:
        # Display an arrow that points to the Color Sensor.
        brick.display.image(ImageFile.RIGHT)

        # Display how many Color Squares have been scanned so far.
        brick.display.text(len(color_list))

        # Wait until the Center Button is pressed or a Color Square is
        # scanned.
        while True:
            # Store "True" if the Center Button is pressed or "False"
            # if not.
            pressed = Button.CENTER in brick.buttons()
            # Store the color measured by the Color Sensor.
            color = color_sensor.color()
            # If the Center Button is pressed or one of the possible
            # colors is detected, break out of the loop.
            if pressed or color in POSSIBLE_COLORS:
                break

        if pressed:
            # If the button was pressed, end the loop early.  It will
            # no longer wait for any Color Squares to be scanned and
            # added to the chute.
            break
        else:
            # Otherwise, a color was scanned, so it is added (appended)
            # to the list.
            brick.sound.beep(1000, 100, 100)
            color_list.append(color)

            # It should not register the same color again if it is
            # still looking at the same Color Square.  So, before
            # continuing, wait until the sensor no longer sees the
            # Color Square.
            while color_sensor.color() in POSSIBLE_COLORS:
                pass
            brick.sound.beep(2000, 100, 100)

            # Display an arrow pointing down and wait 2 seconds to
            # allow some time to slide the Color Square into the
            # motorized chute.
            brick.display.image(ImageFile.BACKWARD)
            wait(2000)

    # Play a sound and display an image to indicate that scanning is
    # complete.
    brick.sound.file(SoundFile.READY)
    brick.display.image(ImageFile.EV3)

    # Now sort the bricks using the list of colors that have been
    # stored.  Do this by looping over each color in the list.
    for color in color_list:

        # Wait for 1 second between each sorting action.
        wait(1000)

        # Run the conveyor belt motor to the position that corresponds
        # to the stored color.
        if color == Color.BLUE:
            brick.sound.file(SoundFile.BLUE)
            belt_motor.run_target(500, 10)
        elif color == Color.GREEN:
            brick.sound.file(SoundFile.GREEN)
            belt_motor.run_target(500, 132)
        elif color == Color.YELLOW:
            brick.sound.file(SoundFile.YELLOW)
            belt_motor.run_target(500, 360)
        elif color == Color.RED:
            brick.sound.file(SoundFile.RED)
            belt_motor.run_target(500, 530)

        # Now that the conveyor belt is in the correct position, eject
        # the colored object.
        feed_motor.run_angle(1500, 90)
        feed_motor.run_angle(1500, -90)

Students who enjoyed this lesson might be interested in exploring these careers pathways:

• Agriculture and Horticulture (Agricultural Mechanics and Technology)
• Manufacturing and Engineering (Machine Technology)

Teacher Observation Checklist
Create a scale that matches your needs, for example:

1. Partially accomplished
2. Fully accomplished
3. Overachieved

Use the following success criteria to evaluate your students’ progress:

• Students can evaluate competing design solutions based on prioritized criteria and tradeoff considerations.
• Students are autonomous in developing a working and creative solution.
• Students can clearly communicate their ideas.

Self Assessment
Once your students have collected some performance data, give them time to reflect on their solutions. Help them by asking questions, like:

• Is your solution meeting the Design Brief criteria?
• Can your machine’s movement(s) be made more accurate?
• What are some ways that others have solved this problem?

Ask your students to brainstorm and document two ways they could improve their solutions.

Peer Feedback
Encourage a peer review process in which each group is responsible for evaluating their own and others’ projects. This review process can help students develop skills in giving constructive feedback as well as sharpen their analysis skills and ability to use objective data to support an argument.