---
title: "Smart plant monitor"
subtitle: "Capstone projects · Years 8–9: sense and respond · Lesson 1"
---

# Smart plant monitor

**Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}}

> **Key question:** The garden club loses plants every holiday. Can a microcontroller tell them which pot is dry before it is too late?


:::teacher-note

**In one sentence:** 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.

**Students should be able to say:** 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.

**Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet.

:::


## Inquire: the brief


:::keep-together

**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)?**

Groups: Criterion, Constraint

- Blinks the LED at a reading of 300 or below: {{field-15}}
- Stays off above 300: {{field-15}}
- Shows the current reading: {{field-15}}
- Only parts from the kit: {{field-15}}
- Runs on 4 × AA or USB: {{field-15}}
- Fits in a pencil-case-sized box: {{field-15}}

:::


:::teacher-note

**Answer:** 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.

:::


## Develop: plan before you build


:::keep-together

### The test table

**Which test table checks the threshold best?**

☐ 150 blink, 800 off

☐ 0 blink, 1023 off

☐ 0 blink, 299 blink, 300 blink, 301 off, 1023 off

☐ 300 blink only

:::


:::teacher-note

**Answer:** 0 blink, 299 blink, 300 blink, 301 off, 1023 off

Both sides of the threshold, the threshold itself, and the ends.

:::


## Create: build it


**In the simulator.** 

**For real.** 

Work in the tutorial. Plan first: what will you change, and how will you test it?

{{box-4}}


:::wider

## Test: run your table


**Run the tests.** 

**Fix and re-test.** 

Work in the tutorial. Plan first: what will you change, and how will you test it?

{{box-4}}

:::


## Evaluate: against the brief


:::keep-together

### Which is evidence?

**Which is the strongest evidence that the design meets a criterion?**

☐ It worked when I tried it

☐ The code has no errors

☐ A test from the table that set the input and recorded the expected result

☐ My partner said it looks good

:::


:::teacher-note

**Answer:** 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.

:::


## Exit ticket

:::keep-together

**Name one criterion of your monitor and the test that shows whether it is met.**

{{lines-3}}

:::


:::teacher-note

**Answer:** For example: blinks at 300 or below; test at readings 299, 300 and 301.

:::