Line Following + Showcase - 3 Hour Session

Audience: Students ages 9-14 (no coding experience needed)
Theme: “Steer in proportion to how far off you are”
Series: SPIKE Prime Robotics Camp (Day 5 of 5)

The Mission

Today’s mission: Teach your robot to follow a line — then demo everything you built this week at the showcase.

The robot has a color sensor that can read how much light bounces back off the floor. Today you’ll turn that one number into smooth steering: the farther the robot drifts off the edge of the line, the harder it steers back. That idea is called proportional control, and tuning it is the whole game. Then we celebrate the week.

1. Session Goals

By the end of this session, every student should be able to:

  • Read reflected light with line_sensor.reflection() (a number from 0 to 100)
  • Measure the BLACK (line) and WHITE (floor) readings and compute a threshold
  • Make the robot follow the edge of a line using robot.drive(speed, turn_rate)
  • Tune GAIN so the line-follow is smooth (too low = sloppy, too high = wobbly)
  • Demo their best run of the week at the showcase

2. Success Definition

A student is successful if they can say:

“My robot followed a line, and I explained how I tuned it.”

3. Environment & Prerequisites

  • Laptop: Windows or Chromebook with Chrome, Edge, or Chromium (Web Bluetooth required — iPads and Firefox won’t work)
  • Editor: code.pybricks.com — nothing to install
  • Robot: the same two-motor driving base from the week, with a color sensor mounted facing down at the front; hub already flashed with Pybricks firmware (see the Setup & Firmware Guide)
  • Surface: the line needs contrast — use black electrical tape on white poster board or a light floor

Two ways to code: You can drag blocks or type Python — same robot, same ideas. The Python is shown below; the Block Coding Guide shows the matching blocks.

4. 3-Hour Agenda (Minute-by-Minute)

9:00-9:15 — Arrival Game: Debug the Dance

Fix a movement sequence that has a deliberate bug

  • Drop-in game while everyone arrives
  • A short dance/move sequence is written down with one obvious mistake in it
  • Students spot and fix the bug — pre-teaching “the robot did exactly what the steps said”

9:15-9:25 — Mission Huddle + Catch-Up

Meet today’s mission and recap the week so far

  • Catch-up: quick recap of sensors and decisions from Day 4 so every team can read a sensor and react before we add steering
  • Today: teach the robot to follow a line using its color sensor, then showcase the week
  • Mantra: “Bugs are sensor data — the robot did what the code said”

9:25-10:25 — Robotics Block 1: Calibrate & First Follow

Read the sensor on the line and the floor, then take a first follow

  • Add the color sensor to the setup (ColorSensor(Port.D))
  • Print line_sensor.reflection() while you hold the sensor over the black tape, then over the white floor — write both numbers down
  • Set BLACK, WHITE, and the threshold (their midpoint) on the worksheet
  • Run the starter and watch the robot follow the edge of the line
  • Rotate roles ~halfway (Coder, Builder, Navigator, Tester)
  • Off-robot task: lay out and tape the line course, and predict where the robot will wobble

10:25-10:35 — Energizer

Get up and move

  • Debug the Dance (full-group version) or stretch-and-shake

10:35-10:50 — Snack Break

  • Keep food and drinks away from the kits and laptops

10:50-11:30 — Robotics Block 2: Tune the Gain

Experiment with GAIN until the line-follow is smooth

  • Change only GAIN and watch what happens — this is the whole point
  • Too low → the robot is sloppy and drifts off the line
  • Too high → the robot wobbles back and forth
  • Find the value that’s just right and record your tries on the worksheet
  • Stretch (older students, if two color sensors are free): steer from the difference between a left and right sensor

11:30-12:00 — Showcase + Cleanup

Each team demos their best run of the week — the camp finale

  • Each team shows their best run from the whole week (a drive, a maze, a gyro turn, an obstacle dodge, or today’s line-follow)
  • Explain one thing you tuned and how you knew it worked
  • Charge and pack the hubs

5. Printed Student Handouts

Handout 1: Vocabulary (Fill-in-the-Blank)

  • ColorSensor, reflection, threshold, proportional control
  • GAIN, deviation, edge of the line, calibration

Handout 2: Mission Worksheet

  • BLACK and WHITE reflection readings + computed threshold
  • GAIN tuning table (try / behavior)
  • Week-in-review reflection

6. Instructor Guardrails

  • The line needs contrast — black electrical tape on white poster board or a light floor; test it before students arrive
  • Never present BLACK=10 / WHITE=80 / GAIN=1.2 as correct answers — they’re starting guesses each team measures and tunes
  • This program follows the edge of the line, not the center — say so, or the wobble will confuse students
  • Experimenting with GAIN is the lesson — protect the time for it
  • Leave a hard stop for the showcase; it’s the payoff for the whole week

7. Showcase & What Comes Next

This is the finale. Take a minute to look back at everything your robot learned:

  1. First Drive — drove a calibrated distance, turned an angle, traced a square
  2. Maze Runner — solved a maze with named, reusable moves (functions)
  3. Gyro Precision — used the gyro for straighter, more accurate turns
  4. Obstacle Avoidance — sensed the world and changed its behavior with if/else
  5. Line Following — followed a line with proportional control (today!)

End with:

“You taught a robot to drive, solve a maze, steer by its inner compass, dodge obstacles, and follow a line — and you can explain how. That’s real robotics.”

Keep going after camp with the Learn More page.

8. Overarching Goals

  • Turn one sensor reading into smooth, continuous control (proportional steering)
  • Cement the week’s core habit: measure on the real surface, then tune — don’t memorize
  • Give every student a confident “here’s what I built and how I tuned it” showcase moment
  • End the week on a celebration of everything the robot — and the team — can do