Arduino Uno R3

Control DC motor direction

Use the kit L293D H-bridge to start, stop, and reverse a DC motor through explicit enable and direction signals.

CSTA 2026 mapping candidatesNot reviewed by CSTA

MS-SYS-HW-30Systems & SecurityMS-PRO-TR-19Programming

Students will

Distinguish motor power, logic power, enable, and direction pins
Reverse a motor by changing H-bridge input states
Stop before reversing direction

Evidence of success

The wiring record distinguishes logic and motor supply pins
The motor stops before every direction change
Forward and reverse behavior repeat without Uno resets or component heating

Hardware

Arduino Uno R3
Starter Kit DC motor
L293D H-bridge motor driver
Teacher-approved motor supply
Breadboard and jumper wires

Prerequisites

Switch a DC motor safely
Identify PWM and digital pins
Read the exact H-bridge pinout

Before class

Confirm the L293D marking, notch orientation, and datasheet pinout
Verify the motor supply and common-ground arrangement
Remove mechanical loads for the first direction test

Reviewed connection map

L293D direction control

D4 + D5Direction inputs

D9 PWMEnable and speed command

L293DSeparates logic control from motor current

Motor + reviewed supplyLoad power, return, and common reference

Wire D4, D5, and D9 to the reviewed L293D input and enable pins.
Connect logic power, motor power, grounds, and outputs using the exact IC orientation and pinout.
Stop the motor before reversing direction.

Build and test

01Map the L293D logic supply, motor supply, four ground pins, enable, inputs, and one output pair
02Connect one motor channel with power disconnected and verify the IC spans the breadboard center gap
03Run a stopped-to-forward test
04Stop the motor before commanding reverse
05Repeat forward-stop-reverse-stop while checking heat and supply stability

Read before uploading

Annotated Arduino sketch

const int ENABLE_PIN = 9;
const int INPUT_1 = 4;
const int INPUT_2 = 5;

void driveMotor(bool first, bool second, int speedValue) {
  digitalWrite(INPUT_1, first);
  digitalWrite(INPUT_2, second);
  analogWrite(ENABLE_PIN, speedValue);
}

void setup() {
  pinMode(ENABLE_PIN, OUTPUT);
  pinMode(INPUT_1, OUTPUT);
  pinMode(INPUT_2, OUTPUT);
}

void loop() {
  driveMotor(HIGH, LOW, 160);
  delay(1000);
  driveMotor(LOW, LOW, 0);
  delay(500);
  driveMotor(LOW, HIGH, 160);
  delay(1000);
  driveMotor(LOW, LOW, 0);
  delay(1000);
}

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 distinguish motor power, logic power, enable, and direction pins?Evidence: What evidence best demonstrates this result: The wiring record distinguishes logic and motor supply pins?Debug: If you encounter “Motor moves only one direction,” what will you check first, and why?Transfer: Where could you reuse the skill from “Control DC motor direction” in another classroom project?

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Troubleshooting

Motor moves only one direction

Verify both direction-input connections and print or observe their commanded states.

The H-bridge becomes warm

Disconnect power immediately and review pinout, shorts, motor stall current, supply voltage, and mechanical load.

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 examine how an H-bridge changes the computing system needed to meet a bidirectional-motion requirement.

Lesson evidence: Direction truth table

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: Stop and direction sequence test

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

Supporting concepts

motor-types · motor-control · motor-drivers · power-and-signals

Sources and review

Arduino Uno R3 documentation Arduino Projects Book · CC BY-NC-SA 3.0 Texas Instruments L293D datasheet

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

After teaching this lesson