Arduino Uno R3

Build and trace a breadboard circuit

Map the hidden connections inside a breadboard, assemble a protected LED circuit, and trace every electrical node before applying power.

CSTA 2026 mapping candidatesNot reviewed by CSTA

MS-PRO-TR-19Programming

Students will

Identify connected breadboard holes and the center gap
Trace a complete path from an output pin to GND
Find a misplaced component by comparing nodes rather than appearances

Evidence of success

A labeled breadboard node map
A correct current-path trace from D9 to GND
A diagnosis based on electrical connectivity rather than wire color alone

Hardware

Arduino Uno R3
Breadboard
Solid-core jumper wires
220 Ω resistor
Single-color LED
Starter Kit base

Prerequisites

Identify the Uno R3 power and ground pins
Upload, blink, and observe

Before class

Check whether the breadboard power rails are continuous or split
Mount the board and breadboard on the supplied base if appropriate
Prepare one correctly wired and one intentionally misplaced circuit

Reviewed connection map

Protected LED connection

Arduino D9Program-controlled output

220 Ω resistorLimits LED current

LEDAnode toward D9; verify the actual part

GNDShared return path

Connect D9 to one end of the 220 Ω resistor.
Connect the resistor to the LED anode and the LED cathode to GND.
Disconnect USB power before moving components or changing rows.

Build and test

01With power disconnected, mark the breadboard terminal strips, center gap, and power rails
02Use jumper wires to bring 5V and GND to clearly separated rails, then verify their locations
03Place an LED so its leads occupy different nodes and add one 220 Ω resistor in series
04Trace the path from D9 through the resistor and LED to GND before connecting USB
05Upload the test sketch, then move one unpowered connection and explain why the circuit stops working

Read before uploading

Annotated Arduino sketch

const int LED_PIN = 9;

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  delay(500);
  digitalWrite(LED_PIN, LOW);
  delay(500);
}

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 connected breadboard holes and the center gap?Evidence: What evidence best demonstrates this result: A labeled breadboard node map?Debug: If you encounter “The circuit looks correct but the LED stays dark,” what will you check first, and why?Transfer: Where could you reuse the skill from “Build and trace a breadboard circuit” in another classroom project?

Nothing is saved until you choose this button.

Troubleshooting

The circuit looks correct but the LED stays dark

Disconnect power and compare the actual connected rows, LED polarity, resistor placement, D9, and GND one node at a time.

A power rail works on only part of the board

Check whether that rail is split and bridge the sections only after confirming polarity.

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-PRO-TR-19

Use systematic strategies to test, refine, and document changes to a computing technology to meet the intended purpose.

Students isolate variables, compare observed behavior with the intended purpose, and document a revision.

Lesson evidence: Annotated node trace and fault diagnosis

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

Supporting concepts

board-tour · ohms-law · power-and-signals

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