A Years 8–9 design project: a plant monitor with a soil sensor, an alarm at a threshold and a display, planned with a test table, prototyped on the board, built in Tinkercad and optionally on hardware, tested and evaluated against the brief.
Capstone projects · Years 8–9: sense and respond · about 180 minutes · Open the student lesson
Classroom resources
Load these into Waypoints Prepare: choose Load URL and paste the copied address, or download the file and import it. In Prepare, the worksheet's Teacher edition shows the answers; the student copy hides them.
SlidesDownload Present from the browser, or export to PowerPoint or PDF.
WorksheetDownload Print the student copy; the Teacher edition has the answers.
Students will be able to
I can turn a brief into criteria and constraints.
I can plan and run tests that check a threshold.
I can evaluate my design against each criterion with evidence.
Timing
About 3 to 4 lessons (around 180 minutes). Inquire 1 lesson part · Develop 1 lesson · Create 1–2 lessons · Test and evaluate 1 lesson
Before class
Builds on Arduino › A small system (the same alarm logic and boundary tests). Real soil sensors read differently in different soils: calibrate the threshold with real dry and wet soil, and say so in the evaluation. Resistive soil probes corrode if powered all the time; powering the sensor from a pin only while reading is a good extension.
If you assess with MYP Design, the steps line up with the criteria:
A Inquiring and analysing: the brief, its criteria and constraints, and research into parts (Inquire).
B Developing ideas: a design specification, the circuit and code plan, and the test table written before building (Develop).
C Creating the solution: building it (in the simulator, then for real), following the plan and justifying changes (Create).
D Evaluating: testing against the specification, recording failures, improvements and impact (Test, Evaluate).
Otherwise, use the same four headings as a simple rubric: each step's reflect checks are the evidence list.
Running the lesson
Inquire: ask which criterion will be hardest to test.
Develop: no wiring until the test table is written.
Evaluate: insist on a test result for every criterion.
The hard part (on purpose)
Students build first and plan never. Hold the test table as the ticket to start building.
When students get stuck
What you will see
A question to ask
The fix
The alarm triggers at the wrong time.
What does the sensor read in dry soil, and in wet?
Print the readings and recalibrate the threshold.
Answers to the checks
Inquire: the brief: Sort each line of the brief: a criterion (what it must do, which you can test) or a constraint (a limit you must work within)? Blinks the LED at a reading of 300 or below → Criterion; Stays off above 300 → Criterion; Shows the current reading → Criterion; Only parts from the kit → Constraint; Runs on 4 × AA or USB → Constraint; Fits in a pencil-case-sized box → Constraint Criteria are what you will test at the end; constraints decide what you are allowed to build with.
The test table: Which test table checks the threshold best? 0 blink, 299 blink, 300 blink, 301 off, 1023 off Both sides of the threshold, the threshold itself, and the ends.
Prototype the logic: Prototype the decision: write the sketch so all five tests pass.
if (level <= 300) blink, else off: the logic is ready before any wiring.
Which is evidence?: Which is the strongest evidence that the design meets a criterion? A test from the table that set the input and recorded the expected result A planned test with a recorded result is evidence; everything else is a feeling.
Stretch and support
Stretch: Add a second threshold (very dry: steady on) or a buzzer, and stop the alarm flickering near 300.
Support: A partly filled test table and the A small system sketch as a starting point.
Exit ticket
Name one criterion of your monitor and the test that shows whether it is met.
For example: blinks at 300 or below; test at readings 299, 300 and 301.
What each step is for
Inquire: the brief: Separating what the design must do (criteria) from the limits it works within (constraints) is the first move of any design brief.
Develop: plan before you build: Writing the test table and prototyping the decision on the board before wiring anything turns the criteria into something checkable.
Create: build it: Building in the simulator first catches wiring and code slips cheaply; the real build then tests the design against the world.
Test: run your table: Running the test table written in Develop, and recording every result including failures, is the evidence for the evaluation.
Evaluate: against the brief: Judging the design criterion by criterion, with evidence from the tests, is what separates an evaluation from a description.
Where it leads
Other Years 8–9 projects: Parking assistant, Reaction game.