Motor direction with H-Bridge (L293D/L298N) in Arduino - Step-by-Step Execution

Concept Flow - Motor direction with H-Bridge (L293D/L298N)

Set pin modes

↓

Write HIGH/LOW to pins

↓

Motor spins forward

↓

Delay

↓

Write reversed HIGH/LOW

↓

Motor spins backward

↓

Delay

↓

Repeat or stop

The program sets motor control pins, then writes signals to spin the motor forward or backward by controlling the H-Bridge inputs.

Execution Sample

Arduino

const int motorPin1 = 3;
const int motorPin2 = 4;

void setup() {
  pinMode(motorPin1, OUTPUT);
  pinMode(motorPin2, OUTPUT);
}

void loop() {
  digitalWrite(motorPin1, HIGH);
  digitalWrite(motorPin2, LOW);
  delay(2000);
  digitalWrite(motorPin1, LOW);
  digitalWrite(motorPin2, HIGH);
  delay(2000);
}

This code spins the motor forward for 2 seconds, then backward for 2 seconds repeatedly.

Execution Table

Step	Action	motorPin1	motorPin2	Motor Direction	Delay (ms)
1	Set motorPin1 HIGH, motorPin2 LOW	HIGH	LOW	Forward	2000
2	Wait for 2000 ms	HIGH	LOW	Forward	2000
3	Set motorPin1 LOW, motorPin2 HIGH	LOW	HIGH	Backward	2000
4	Wait for 2000 ms	LOW	HIGH	Backward	2000
5	Loop repeats from step 1	HIGH	LOW	Forward	2000

💡 Loop runs indefinitely, alternating motor direction every 2 seconds.

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 5 (Loop)
motorPin1	LOW (default)	HIGH	LOW	HIGH
motorPin2	LOW (default)	LOW	HIGH	LOW
Motor Direction	Stopped	Forward	Backward	Forward

Key Moments - 3 Insights

Why does setting motorPin1 HIGH and motorPin2 LOW make the motor spin forward?

Because the H-Bridge uses these pin signals to control current flow direction through the motor, making it spin forward as shown in execution_table step 1.

What happens if both motorPin1 and motorPin2 are set HIGH or LOW at the same time?

The motor will stop or brake because no voltage difference is applied; this is not shown in the current execution but is important to avoid damage.

Why do we use delay after setting the pins?

Delay keeps the motor spinning in one direction for a set time before changing direction, as seen in execution_table steps 2 and 4.

Visual Quiz - 3 Questions

Look at the execution table, what is the state of motorPin2 at step 3?

A LOW

B HIGH

C INPUT

D Not set

💡 Hint

Check the 'motorPin2' column in execution_table row for step 3.

At which step does the motor spin backward?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'Motor Direction' column in execution_table.

If delay(2000) is changed to delay(1000), how does the execution_table change?

A Delay column values become 1000 instead of 2000

B Motor direction changes to stop

C Pin states change to LOW

D No change

💡 Hint

Focus on the 'Delay (ms)' column in execution_table.

Concept Snapshot

Motor direction with H-Bridge:
- Use two pins to control motor direction
- Set one pin HIGH, other LOW for forward
- Reverse pins for backward
- Use delay to keep motor spinning
- Loop to alternate direction

Full Transcript

This example shows how to control a motor's direction using an H-Bridge like L293D or L298N with Arduino. We set two pins as outputs. Writing HIGH to one pin and LOW to the other makes the motor spin forward. Reversing these signals makes it spin backward. Delays keep the motor spinning in each direction for 2 seconds. The loop repeats this forever. The execution table tracks pin states and motor direction step-by-step. Key points include how pin signals control current flow and why delays are needed. The quiz checks understanding of pin states and timing.

Practice

1. Which of the following correctly describes how to make a motor spin forward using an H-Bridge (L293D/L298N) with two Arduino pins pinA and pinB?

easy

A. Set both pinA and pinB HIGH

B. Set pinA LOW and pinB HIGH

C. Set both pinA and pinB LOW

D. Set pinA HIGH and pinB LOW

Solution

1. Step 1: Understand motor direction control

   To spin the motor forward, one pin must be HIGH and the other LOW to create current flow in one direction.

2. Step 2: Apply pin states for forward spin

   Setting pinA HIGH and pinB LOW makes the motor spin forward.

3. Final Answer:

   Set pinA HIGH and pinB LOW -> Option D

4. Quick Check:

   Forward spin = pinA HIGH, pinB LOW [OK]

Hint: Forward spin means one pin HIGH, other LOW [OK]

Common Mistakes:

• Setting both pins HIGH or LOW thinking motor spins
• Confusing which pin should be HIGH for forward
• Assuming both pins LOW spins motor forward

2. Which Arduino code snippet correctly sets pin1 HIGH and pin2 LOW to spin a motor forward using an H-Bridge?

easy

A. digitalWrite(pin1, LOW); digitalWrite(pin2, HIGH);

B. digitalWrite(pin1, HIGH); digitalWrite(pin2, LOW);

C. digitalWrite(pin1, HIGH); digitalWrite(pin2, HIGH);

D. digitalWrite(pin1, LOW); digitalWrite(pin2, LOW);

Solution

1. Step 1: Recall correct pin states for forward

   Forward spin requires first pin HIGH and second pin LOW.

2. Step 2: Match code to pin states

   Code in digitalWrite(pin1, HIGH); digitalWrite(pin2, LOW); sets pin1 HIGH and pin2 LOW correctly.

3. Final Answer:

   digitalWrite(pin1, HIGH); digitalWrite(pin2, LOW); -> Option B

4. Quick Check:

   Pin1 HIGH, Pin2 LOW = forward spin [OK]

Hint: HIGH then LOW means forward spin [OK]

Common Mistakes:

• Swapping HIGH and LOW values
• Setting both pins HIGH or LOW
• Using analogWrite instead of digitalWrite

3. What will be the motor behavior when the following Arduino code runs?

digitalWrite(3, LOW);
digitalWrite(4, HIGH);

medium

A. Motor spins backward

B. Motor spins forward

C. Motor stops

D. Motor speed changes but direction stays same

Solution

1. Step 1: Identify pin states and their meaning

   Pin 3 is LOW and pin 4 is HIGH, which reverses the current flow compared to forward spin.

2. Step 2: Determine motor direction

   This pin combination makes the motor spin backward.

3. Final Answer:

   Motor spins backward -> Option A

4. Quick Check:

   LOW then HIGH = backward spin [OK]

Hint: LOW then HIGH means backward spin [OK]

Common Mistakes:

• Assuming LOW then HIGH is forward spin
• Thinking motor stops when pins differ
• Confusing speed control with direction

4. The following code is intended to stop the motor, but it does not. What is the error?

digitalWrite(5, HIGH);
digitalWrite(6, HIGH);

medium

A. Pins must be set to LOW and HIGH to stop

B. Pins should be set to INPUT to stop motor

C. Both pins HIGH causes motor to brake, not stop

D. digitalWrite cannot be used to stop motor

Solution

1. Step 1: Understand stopping motor with H-Bridge

   To stop the motor, both pins should be LOW to cut power and stop current flow.

2. Step 2: Analyze given pin states

   Both pins are set HIGH, which causes the motor to brake but not coast to a stop.

3. Final Answer:

   Both pins HIGH causes motor to brake, not stop -> Option C

4. Quick Check:

   Stop motor = both pins LOW, not HIGH [OK]

Hint: Stop motor by setting both pins LOW [OK]

Common Mistakes:

• Setting both pins HIGH thinking motor stops
• Using INPUT mode instead of LOW
• Confusing brake with stop

5. You want to write Arduino code to spin a motor forward for 3 seconds, then stop for 2 seconds, then spin backward for 3 seconds using pins 7 and 8 with an L298N. Which code snippet correctly implements this?

hard

A. digitalWrite(7, HIGH); digitalWrite(8, LOW); delay(3000); digitalWrite(7, LOW); digitalWrite(8, LOW); delay(2000); digitalWrite(7, LOW); digitalWrite(8, HIGH); delay(3000);

B. digitalWrite(7, LOW); digitalWrite(8, HIGH); delay(3000); digitalWrite(7, LOW); digitalWrite(8, LOW); delay(2000); digitalWrite(7, HIGH); digitalWrite(8, LOW); delay(3000);

C. digitalWrite(7, HIGH); digitalWrite(8, HIGH); delay(3000); digitalWrite(7, LOW); digitalWrite(8, LOW); delay(2000); digitalWrite(7, LOW); digitalWrite(8, LOW); delay(3000);

D. digitalWrite(7, LOW); digitalWrite(8, LOW); delay(3000); digitalWrite(7, HIGH); digitalWrite(8, LOW); delay(2000); digitalWrite(7, LOW); digitalWrite(8, HIGH); delay(3000);

Solution

1. Step 1: Set pins for forward spin and delay

   Forward spin requires pin 7 HIGH and pin 8 LOW, then delay 3000 ms (3 seconds).

2. Step 2: Stop motor by setting both pins LOW and delay

   Both pins LOW stops motor, delay 2000 ms (2 seconds).

3. Step 3: Set pins for backward spin and delay

   Backward spin requires pin 7 LOW and pin 8 HIGH, delay 3000 ms.

4. Final Answer:

   digitalWrite(7, HIGH); digitalWrite(8, LOW); delay(3000); digitalWrite(7, LOW); digitalWrite(8, LOW); delay(2000); digitalWrite(7, LOW); digitalWrite(8, HIGH); delay(3000); -> Option A

5. Quick Check:

   Forward, stop, backward with correct pins and delays [OK]

Hint: Forward=HIGH-LOW, Stop=LOW-LOW, Backward=LOW-HIGH [OK]

Common Mistakes:

• Swapping forward and backward pin states
• Not stopping motor between directions
• Using HIGH-HIGH which brakes but doesn't stop