button = pressedread one of two states
Lesson / Robotics
What Question Is the Sensor Answering?
The display says 347. That might mean bright, close, tilted, or nothing useful at all. Find out what the sensor measures, collect readings, and decide where the program should change its response.
Lesson plan
Name the measurement
Identify what the input reports and the units or states it uses.
Collect readings
Record several values under different known conditions.
Choose a boundary
Compare readings and test a threshold or timing rule.
Build the reaction timer
Add waiting, a random start, button input, and an elapsed-time result.
Explain the limits
Demonstrate the reading, the program's decision, and one source of variation.
Learning goals
- Name the quantity a sensor measures.
- Record a changing value.
- Choose and test a threshold.
- Separate the measurement from the program's decision.
- Explain variation in the readings.
Small examples
distance < 15compare a reading with a threshold
light levelinspect a value that changes
read repeatedlytake several samples over time
Guided project
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 with a tested change, one repaired problem, and a clear explanation.
Teacher checkpoints
- 1The student names the measured quantity.
- 2Several readings have been recorded.
- 3A threshold is stated and tested.
- 4The output changes for a traceable reason.
- 5The student identifies one limitation of the reading.
Common mistakes
- Every reading is expected to be identical.
- A threshold is chosen from one test.
- The sensor is credited with making the decision.
- The output changes before the input values are recorded.
Optional challenges
Builder
- Display raw readings before deciding.
Inventor
- Compare two candidate thresholds.
Boss Level
- Smooth several readings before acting.
End-of-class demonstration
- 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?