Session 3 — Stop at a Line

Opening concept: Sensors can trigger an action at exactly the right moment — but “exactly” is harder than it sounds.

Physical activity: PL-9 (Delay and Reaction Time) — tape a line on the floor, blindfolded student walks toward it, helper rings a bell on crossing, measure the overshoot. Run it at slow and fast speeds. Ask: “If Edison is driving fast and the sensor sees the line, what happens before the motors actually stop?” Then when Edison overshoots in the activity, students already know why.

Activity:

• EdBlocks Activity 14: sensor-triggered stop
• Build a “traffic system” — black tape lines across a course. Edison drives until it hits a line, stops.
• Teams design a two-lane course where Edisons take turns (human traffic controller starts each one)
• Challenge: can you program Edison to stop, wait 2 seconds, then continue? (combines drive + sensor + wait blocks)

Engineering connection: Sequential + event-driven programming combined

Materials: Devices, USB cables, black tape, large open floor space