Arduino Uno R3

Plan and verify power for a load

Distinguish USB, regulated rails, VIN, and an external load supply before connecting a motor or other higher-current component.

CSTA 2026 mapping candidatesNot reviewed by CSTA

MS-SYS-HW-30Systems & Security

Students will

Identify what each supply powers and where current returns
Explain when two circuits require common ground
Verify polarity and voltage before attaching a load

Evidence of success

A power map naming each source, load, and return path
A recorded polarity and voltage check
A written explanation of why GPIO is not a motor power supply

Hardware

Arduino Uno R3
USB cable
9 V battery snap
Teacher-approved battery or current-limited supply not included in the kit
Reviewed load circuit
Multimeter under teacher supervision

Prerequisites

Identify Uno power pins and GND
Explain the difference between a power rail and GPIO
Trace a breadboard circuit

Before class

Select and label the exact approved supply; the kit listing includes a snap but does not promise a battery
Set current limits or prepare a fuse where appropriate
Prepare a power-off inspection checklist and immediate disconnect method

Build and test

01Draw the Uno USB supply, regulated rails, external load supply, and return paths as separate labeled blocks
02Mark the 9 V snap polarity and inspect it while disconnected
03Decide whether the control and load circuits require common ground or deliberate isolation
04Measure the approved supply polarity and voltage under teacher supervision before connecting the reviewed load circuit
05Apply power briefly, observe voltage stability and heat, then disconnect before revising wiring

Optional engineering record

Record evidence from this lesson

Choose the prompts that help students explain predictions, evidence, debugging, and transfer. Saving creates a new entry in this browser’s Rudi notebook.

Record your thinking — optional4 prompts

Use these prompts if they help students capture evidence, decisions, or questions. You do not need to complete every prompt or create an entry at every step.

Predict: Before you begin, what do you expect to observe when you identify what each supply powers and where current returns?Evidence: What evidence best demonstrates this result: A power map naming each source, load, and return path?Debug: If you encounter “The Uno resets when the load starts,” what will you check first, and why?Transfer: Where could you reuse the skill from “Plan and verify power for a load” in another classroom project?

Nothing is saved until you choose this button.

Troubleshooting

The Uno resets when the load starts

Disconnect the load and review startup current, supply capacity, shared rails, grounding, and noise suppression before retesting.

The measured polarity is reversed

Do not connect the circuit; disconnect the source and correct the snap or lead orientation first.

A component becomes warm

Remove power immediately and inspect polarity, pinout, shorts, current limits, and component ratings.

2026 middle school standards

Potential CSTA connections

Not reviewed by CSTA

These are evidence-based crosswalk candidates for curriculum review—not a claim of official alignment.

MS-SYS-HW-30

Examine differences between computing systems based on user needs, system requirements, and potential societal, environmental, and ethical impacts.

Students compare logic and load power requirements and justify a system architecture for the intended hardware.

Lesson evidence: Power-path diagram and requirement check

View the official 2026 CSTA standardsStandard text: Computer Science Teachers Association (2026), CC BY-NC-SA 4.0.

Supporting concepts

power-and-signals · ohms-law · motor-control

Sources and review

Arduino Uno R3 documentation Arduino Projects Book · CC BY-NC-SA 3.0

Starting point, not verified curriculum. Review the actual hardware, circuit, code, power requirements, and classroom conditions.

After teaching this lesson