Grade 5 · Coding & Electronics · Lesson 195

Plant Moisture Indicator

Use a sealed classroom moisture sensor module to compare dry, damp and wet soil samples with an LED indicator.

Time2 × 45 minutesTeamsPairs; switch builder and safety-checker rolesEquipmentBeginner low-voltage classroom electronics

Your project in view

What you are making

Use a sealed classroom moisture sensor module to compare dry, damp and wet soil samples with an LED indicator.

This generated example illustrates one possible finished design—not actual student work. Use the lesson’s sizes, connected parts and safety steps; your colors and creative details can be different.

Finished classroom example of Plant Moisture Indicator: Use a sealed classroom moisture sensor module to compare dry, damp and wet soil samples with an LED indicator.
Plant Moisture Indicator · Generated project example

Student directions · Grade 5

What will you make and do?

You will make this specific beginner electronics project: Use a sealed classroom moisture sensor module to compare dry, damp and wet soil samples with an LED indicator. Your finished build must clearly show what the input or switch controls.

Teacher overview: Students will plan the specific object described below, make and test a first version, then use their results to improve it. Read one step together, demonstrate the unfamiliar action, and let students complete that step before moving on.

  1. 1Plan your project

    Draw the project before building. Label the safe power source, the input or switch, the output, and the complete path electricity should follow.

  2. 2Make the first parts

    Build with power disconnected. Follow this project-specific action: Use the module maker’s teacher-checked connections; students build a labeled cardboard display and keep the electronics above the spill tray. Compare every real connection with the teacher diagram.

  3. 3Put it together

    Ask an adult to check the power source, resistor or approved module, polarity, secure parts, and possible short circuits before the first powered trial.

  4. 4Test it fairly

    Use the same starting conditions and collect evidence: Teacher moves the probe among prepared dry, damp and wet cups for three rounds while students record the output and wipe the probe between samples. Record the expected output and actual output for every trial.

  5. 5Improve one part

    Disconnect power before changing one connection, position, support, switch, sensor setting, or program feature. Obtain another adult check and repeat the test.

  6. 6Show and turn in

    Show the working plant moisture indicator and turn in the labeled circuit map, complete test table, revised project, and one evidence-based improvement statement.

How will you know it works?

  • Recorded outputs distinguish at least two moisture levels
  • Electronics remain dry and the same sampling method is used
  • Explain the power source → input/control → output path

Before you move on

Explain which measurement, input or design choice you are testing. Predict the result and record what stays the same so your comparison is fair.

Machine cutting, printer setup and electrical power-on require adult approval. A basic-materials model is a valid way to demonstrate the design when equipment is unavailable.

Keep your plan, test notes and before-and-after evidence with the printable design brief below. Use the detailed teacher plan and any coding guide for tool instructions. These steps continue across the lesson’s meetings, not all in one sitting.

Beginner sequence · Step 2 of 3

Start here

Readiness check: Students can identify the power source, input or switch, and output in a picture. Before class, rehearse the exact safe build with the listed components.

Exact starter recipe

POWER OFF. Arrange and label the parts first.
Teacher-approved power (+) → input or switch → output with its required resistor/module → power (−).
For this project: Use the module maker’s teacher-checked connections; students build a labeled cardboard display and keep the electronics above the spill tray.
Teacher checks the complete path before power-on. Disconnect power before every change.

Make the simplest version work first. Then use the test and extension in this lesson.

Teacher learning resources

Preview external resources before class. The circuit reference explains the science; use this page’s specified AA kit and connection list for the build.

For teachers

Engineering standards

This shows how the lesson connects to the national NGSS engineering standards and what student work you can collect.

Assessed

3-5-ETS1-1

Define the job of the plant moisture indicator, its two success checks and the low-voltage safety limits.

What students show: Labeled input–output plan with criteria and constraints.
Practiced

3-5-ETS1-2

Compare two layouts or control ideas before choosing the easiest safe version to build and test.

What students show: Two small sketches and one criteria-based choice.
Assessed

3-5-ETS1-3

Use the same procedure for repeated trials: Teacher moves the probe among prepared dry, damp and wet cups for three rounds while students record the output and wipe the probe between samples. Change one feature and repeat.

What students show: Before-and-after test record and evidence-based explanation.

Materials

  • teacher-approved 3–5 V moisture module with insulated probe
  • battery pack
  • LED module
  • three sealed soil cups
  • tray
  • Planning pencil, circuit map, data table and printable student brief
  • Color-coded component labels and teacher-prepared insulated leads

Teacher preparation

  1. Gather and verify these exact parts: teacher-approved 3–5 V moisture module with insulated probe; battery pack; LED module; three sealed soil cups; tray.
  2. Build and test one reference circuit using the manufacturer ratings; prepare a large color-coded connection diagram.
  3. Prepare the project structure and difficult cuts, stripped leads, motor hubs or sensor modules before students arrive.
  4. Set up a clearly marked POWER OFF build area, adult-check point and short powered-test area.
  5. Print the student brief and make a troubleshooting card: battery orientation → secure clips → resistor/module → LED polarity → switch gap.

Step by step

How to teach it

Class 1 · 0–8

Name the job

  1. Use a sealed classroom moisture sensor module to compare dry, damp and wet soil samples with an LED indicator.
  2. Point out the input or switch and output. Read the two success checks and safety limits.
Class 1 · 8–18

Model the circuit

  1. Teach sensor input and output with a large diagram.
  2. Trace one complete path from positive to negative. Model power off before touching any connection.
Class 1 · 18–35

Build with power off

  1. Use the module maker’s teacher-checked connections; students build a labeled cardboard display and keep the electronics above the spill tray.
  2. Partners compare the real build with the diagram. No pair powers on before the adult check.
Class 1 · 35–45

First safe trial

  1. Teacher checks voltage, resistor/module, polarity, secure parts and shorts.
  2. Run one brief trial, disconnect power and circle the first problem to fix.
Class 2 · 0–10

Predict and reconnect

  1. Review the diagram and safety stop signs. Predict the test result.
  2. Reconnect only after the pair can explain the intended path.
Class 2 · 10–27

Test and record

  1. Teacher moves the probe among prepared dry, damp and wet cups for three rounds while students record the output and wipe the probe between samples.
  2. One partner operates while the other records; swap roles and keep conditions the same.
Class 2 · 27–37

Troubleshoot one thing

  1. Disconnect power. Check one point at a time: source, connection, component direction, control, output.
  2. Change one feature, receive another adult check and repeat the test.
Class 2 · 37–45

Explain and pack safely

  1. Demonstrate the working input-to-output action and use one recorded result in the explanation.
  2. Disconnect power. Adult collects batteries and modules; students return remaining parts.

Assessment

  • Recorded outputs distinguish at least two moisture levels
  • Electronics remain dry and the same sampling method is used
  • Student points to and names the power source, input/control and output.
  • Build follows the teacher diagram and power-off safety routine.
  • Student records repeated results and explains one revision.

Supports & extensions

  • Provide a full-size color-coded diagram and place matching colored labels beside the real terminals.
  • Offer preconnected resistor–LED modules, larger switches or prepared structures while preserving the input–output reasoning.
  • Let students direct a partner, point to a diagram or dictate test evidence.
  • Test the smallest working circuit before attaching it to the creative project.
  • Extension after success: add one clearly labeled control or compare a second setting without changing the safe power source.

Safety & responsible use

  • Use only the exact teacher-approved covered battery pack or classroom module listed; never use wall power, lithium cells, coin/button cells, or unknown power supplies.
  • Power must be OFF before building or changing any connection. The teacher checks voltage, resistor values, polarity and possible shorts before power-on.
  • Never connect battery terminals directly. Stop immediately and disconnect power if a component becomes warm, leaks, smells unusual or behaves unpredictably.
  • Adults prepare wire ends, motor hubs and difficult holes. Cover sharp leads, secure moving parts, wear eye protection for guarded motor tests and keep liquids in a separate tray.

No-machine alternative

Use teacher-provided sensor readings to build a movable dry/damp/wet indicator and choose watering advice.

Printable student design brief

The challenge

Use a sealed classroom moisture sensor module to compare dry, damp and wet soil samples with an LED indicator.

Success criteria

  • Recorded outputs distinguish at least two moisture levels
  • Electronics remain dry and the same sampling method is used
  • Explain the power source → input/control → output path

Constraints

  • Use only the listed teacher-approved low-voltage parts
  • Power off before every connection change; adult approval before power-on
  • No soldering, wall power, lithium cells or coin/button batteries
  • Complete the working system and test record before decoration

Engineer’s notes

Draw the object students will make. Label the power source, input or switch, output and complete circuit path.
What should happen when the input changes? Write your prediction.
Copy the teacher-approved connection order in your own words.
Adult check: voltage / resistor or module / polarity / secure parts / no short.
Trial 1 / 2 / 3: starting condition, input, expected output, actual output.
Where did the result first differ from the prediction?
Power off. What ONE feature will you change?
Retest result: what evidence shows the change helped or did not help?

Printable beginner test record

Predict. Try. Improve.

Name ____________________ Partner ____________________

Our success rule: __________________________________________________

TrialInput / actionExpected resultFirst resultResult after one change
1
2
3
4
5
6
7
8
9
10

Use three rows for the introductory tests or all ten for switch reliability. Write the held, released, or other-key state for each sensing test.

One thing we changed: ______________________________________________

Things we kept the same: ____________________________________________

Our evidence shows: _________________________________________________

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