button = pressedread a two-state input
Public lesson / Robotics
What Question Is the Sensor Answering?
A machine reports 347. Is that bright, close, tilted, pressed, or meaningless? A sensor reading becomes useful only when we know what was measured and how the program interprets it.
Lesson rhythm
The idea moves toward a demonstration.
Story, problem, or provocation
Name the problem before opening the build.
Theory and concept
Make the hidden rule visible with small tests.
Guided build
Use the idea inside a working project system.
Modification challenge
Change one rule and predict the effect.
Demonstration and cleanup
Explain the result, save safely, and leave a known state.
Learning goals
What students should be able to do and explain.
- Identify what a sensor measures.
- Read a changing value.
- Choose and test a threshold.
- Distinguish measurement from decision.
- Explain noise or variation.
Theory kernel
Small examples before the larger build.
distance < 15compare a measurement with a threshold
light levelinspect a changing value
read repeatedlysample over time
Guided-build preview
micro:bit Reaction Timer
Wait for an unpredictable signal, press as quickly as possible, and make the timer distrust suspiciously early presses.
A waiting state, Random start delay, Visible go signal, Button response.
Input, Timing, Variables, Randomness, State.
A working version, one modification, one repaired problem, and an explanation.
Teacher checkpoints
Evidence before adding complexity.
- 1Student names the measured quantity.
- 2Several readings are observed.
- 3A threshold is stated and tested.
- 4Output changes for a clear reason.
- 5Student identifies one limitation.
Common mistakes
Pause, inspect, and test one cause.
- Treating readings as perfect.
- Choosing a threshold from one test only.
- Calling the sensor intelligent.
- Changing output without recording the input value.
Modification challenge
Three levels, one concept kept visible.
Higher levels are optional. They deepen the current idea rather than turning a beginner lesson into an unrelated advanced task.
Builder
- Display raw readings before deciding.
Inventor
- Compare two candidate thresholds.
Boss Level
- Smooth several readings before acting.
End-of-class demonstration
Explain the work while it is still visible.
- What does the sensor measure?
- What values did you observe?
- Where is the threshold?
- What does the code decide?
- When could the reading be wrong?