Motor direction with H-Bridge (L293D/L298N) in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the motor direction output?

Given the following Arduino code controlling an H-Bridge motor driver, what will be the motor direction output on pins IN1 and IN2?

Arduino

const int IN1 = 8;
const int IN2 = 9;

void setup() {
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
}

void loop() {
  // Motor runs forward
}

A IN1 = HIGH, IN2 = LOW (Motor rotates forward)

B IN1 = HIGH, IN2 = HIGH (Motor brake)

C IN1 = LOW, IN2 = LOW (Motor stopped)

D IN1 = LOW, IN2 = HIGH (Motor rotates backward)

💡 Hint

Check the digitalWrite values in setup for IN1 and IN2.

Setting IN1 HIGH and IN2 LOW causes the motor to rotate forward. The H-Bridge uses these signals to control motor direction.

❓ Predict Output

intermediate

What happens if both IN1 and IN2 are HIGH?

Consider this Arduino code snippet controlling an H-Bridge motor driver. What is the motor behavior when both IN1 and IN2 pins are set HIGH?

Arduino

const int IN1 = 8;
const int IN2 = 9;

void setup() {
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, HIGH);
}

void loop() {
  // Motor brake
}

A Motor rotates forward

B Motor rotates backward

C Motor runs freely (coasting)

D Motor is braking (stopped with resistance)

💡 Hint

Both inputs HIGH usually activate braking in an H-Bridge.

When both IN1 and IN2 are HIGH, the motor terminals are shorted internally causing braking effect.

🔧 Debug

advanced

Why does the motor not rotate forward?

This Arduino code is intended to rotate the motor forward using an H-Bridge, but the motor does not move. Identify the cause.

Arduino

const int IN1 = 8;
const int IN2 = 9;

void setup() {
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
}

void loop() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
}

A Motor driver requires PWM signals, not digital HIGH/LOW

B digitalWrite in loop is ignored because setup sets pins LOW

C Pins IN1 and IN2 are set LOW in setup, so motor never gets forward signal

D Pin modes are not set correctly for output

💡 Hint

Check the initial pin states in setup and how loop changes them.

Setup sets both pins LOW initially, but loop sets IN1 HIGH and IN2 LOW repeatedly, so motor should run forward. However, if loop is not running or delayed, motor stays stopped. The main issue is that setup sets pins LOW and loop sets pins HIGH/LOW but loop runs continuously so motor should run. The problem is subtle: if loop is empty or not running, motor stays stopped. But here loop sets pins correctly. The best answer is that initial LOW in setup does not prevent motor running because loop sets pins HIGH/LOW. So the actual cause is that loop runs but motor does not move because wiring or power issue, but that is outside code. Among options, A is closest cause in code context.

📝 Syntax

advanced

Which code snippet correctly sets motor to rotate backward?

Choose the correct Arduino code snippet that sets the motor to rotate backward using an H-Bridge with pins IN1 and IN2.

A

digitalWrite(IN1, LOW);
digitalWrite(IN2, HIGH);

B

digitalWrite(IN1, HIGH);
digitalWrite(IN2, LOW);

C

digitalWrite(IN1, HIGH);
digitalWrite(IN2, HIGH);

D

digitalWrite(IN1, LOW);
digitalWrite(IN2, LOW);

💡 Hint

Backward rotation is the opposite of forward: IN1 LOW and IN2 HIGH.

Setting IN1 LOW and IN2 HIGH reverses the motor direction in an H-Bridge.

🚀 Application

expert

How to implement motor stop with brake using Arduino and H-Bridge?

You want to stop the motor immediately with braking effect using an H-Bridge (L293D/L298N). Which Arduino code snippet correctly implements this braking?

A

digitalWrite(IN1, LOW);
digitalWrite(IN2, HIGH);

B

digitalWrite(IN1, HIGH);
digitalWrite(IN2, HIGH);

C

digitalWrite(IN1, LOW);
digitalWrite(IN2, LOW);

D

digitalWrite(IN1, HIGH);
digitalWrite(IN2, LOW);

💡 Hint

Braking is done by setting both inputs HIGH to short motor terminals.

Setting both IN1 and IN2 HIGH causes the motor terminals to short internally, creating a braking effect.