Obstacle Avoidance Timing Guide (3 Hours)

Audience: Ages 9-14, no coding experience required.
Goal: Read a distance sensor and use if/else in a while loop so the robot reacts to obstacles.

9:00-9:15 — Arrival Game: Red Light / Green Light

Play Red Light / Green Light to prime the “watch a signal and react” mindset behind a sensor loop.

  • Objective: pre-teach “keep checking a signal and react” before anyone touches code.
  • Flow:
    1. As students arrive, call “green light” (move) and “red light” (freeze); anyone who moves on red is out.
    2. Name the pattern: you keep watching the signal and react to it — that’s exactly what a sensor loop does all day.
  • Watch for: kids who react late — that’s a fun lead-in to “the robot checks fast, over and over.”
  • Tip: keep it light; this just primes the sense-then-react mindset.

9:15-9:25 — Mission Huddle + Catch-Up

Frame the mission and confirm every robot drives and its distance sensor reads values. Verify the sensor’s actual port per robot.

  • Objective: frame today’s mission and get every robot sensing.
  • Flow:
    1. Catch-up warm-up: recap driving and turning; make sure each team’s robot still drives and the distance sensor is mounted and reads values.
    2. Today’s mission: teach your robot to sense an obstacle and change what it does.
    3. Re-state the mantra: “Bugs are sensor data.”
  • Tip: confirm the sensor’s actual port on each robot now, so Block 1 isn’t blocked.

9:25-10:25 — Robotics Block 1: Read the Sensor

Add the distance sensor and print eyes.distance() live; non-coders build the cardboard obstacle course. Milestone: a number that changes when you wave a hand (2000 = nothing in front).

  • Objective: every team adds the distance sensor and watches distance() change.
  • Flow:
    1. Add eyes = UltrasonicSensor(Port.C) (use the real port) to the Day 1 setup.
    2. Run a tiny program that prints eyes.distance().
    3. Move a hand toward the sensor and watch the number drop; note it reads 2000 when nothing is in front of it.
    4. Rotate roles ~halfway through the block.
  • Off-robot task: build the cardboard obstacle course (keeps non-coders busy and feeds Block 2).
  • Watch for:
    • Wrong sensor port — the most common early snag; verify it per robot
    • Students thinking 2000 is a bug — it’s the “no object” reading
  • Tip: a printed number that changes live is the hook — let everyone wave at it.

10:25-10:35 — Energizer

  • Quick Red Light / Green Light round two or stretch-and-shake. Get everyone up.

10:35-10:50 — Snack Break

  • Check allergies. Keep all food and drinks away from kits and laptops.

10:50-11:45 — Robotics Block 2: React with if/else + while

Wrap a while True: loop with if/else so the robot drives, then backs up and turns when an obstacle is close. Tune the trigger distance on the real course — don’t memorize 200 mm.

  • Objective: the robot drives forward, but backs up and turns when something’s close.
  • Flow:
    1. Wrap a while True: loop around a check of eyes.distance().
    2. if closer than the trigger → robot.straight(-100) then robot.turn(90); else → robot.drive(150, 0). Add wait(10).
    3. Tune the trigger distance on the real course (start near 200 mm and adjust).
    4. Challenge: don’t fall off the table — stop or turn a hair from the edge / wall.
  • Watch for:
    • Panic when the robot “won’t stop” — teach the Stop button first
    • Teams treating 200 as “the answer” — it’s a value they measure on the course
    • Sensor pointed at the floor or off to the side — aim it at the obstacles
  • Tip: masking-tape a start line and obstacles at set distances to speed up tuning.

11:45-12:00 — Demo + Cleanup

Teams demo through the course, reflect on trigger distance and surprises, then label and charge hubs for tomorrow.

  • Demo: each team (voluntarily) runs their robot through the obstacle course.
  • Prompts:
    • “What trigger distance worked best, and how did you find it?”
    • “When did the robot react in a way you didn’t expect, and what did the code say?”
  • Cleanup: label and charge hubs; keep robots intact for tomorrow.
  • Bridge: “Tomorrow we’ll teach the robot to follow a line with the color sensor — and show off everything we built all week.”

General Tips Throughout

Stop button first, calibrate rather than memorize, treat bugs as sensor data, keep everyone coding, and name the shift from fixed script to reacting to the world.

  • Stop button first: demonstrate it before the first while True: run.
  • Calibrate, don’t memorize: never hand out a “correct” trigger distance.
  • Bugs are sensor data: when the robot misbehaves, ask “what did the code say?”
  • Everyone codes: rotate roles and keep the off-robot course-building going so all four stay engaged.
  • Name the shift: from a fixed script to reacting to the world — that’s today’s win.