Stepper motor basics in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Stepper Motor Step Sequence Output

What will be the output on the serial monitor when this Arduino code runs?

Arduino

int step = 0;
void setup() {
  Serial.begin(9600);
}
void loop() {
  Serial.print("Step: ");
  Serial.println(step);
  step = (step + 1) % 4;
  delay(500);
}

A Step: 0\nStep: 1\nStep: 2\nStep: 3\nStep: 0\n...

B Step: 1\nStep: 2\nStep: 3\nStep: 4\nStep: 1\n...

C Step: 0\nStep: 2\nStep: 4\nStep: 6\nStep: 0\n...

D Step: 1\nStep: 3\nStep: 5\nStep: 7\nStep: 1\n...

💡 Hint

Look at how the step variable changes and resets using modulo.

The step variable increases by 1 each loop and resets to 0 after reaching 3 because of the modulo 4 operation. So the output cycles through 0,1,2,3 repeatedly.

🧠 Conceptual

intermediate

Understanding Stepper Motor Coil Activation

In a 4-step sequence for a unipolar stepper motor, which coil activation pattern correctly represents the sequence?

A B+, A+, B-, A-

B A+, B+, A-, B-

C A+, B-, A-, B+

D A+, A-, B+, B-

💡 Hint

Think about the order coils are energized to rotate the motor smoothly.

The correct sequence energizes coils in order A+, B+, A-, B- to create a smooth rotation.

🔧 Debug

advanced

Identify the Error in Stepper Motor Wiring Code

What error will this Arduino code cause when controlling a stepper motor?

Arduino

int motorPin1 = 8;
int motorPin2 = 9;
int motorPin3 = 10;
int motorPin4 = 11;

void setup() {
  pinMode(motorPin1, OUTPUT);
  pinMode(motorPin2, OUTPUT);
  pinMode(motorPin3, OUTPUT);
  pinMode(motorPin4, OUTPUT);
}

void loop() {
  digitalWrite(motorPin1, HIGH);
  digitalWrite(motorPin2, HIGH);
  digitalWrite(motorPin3, HIGH);
  digitalWrite(motorPin4, HIGH);
  delay(1000);
}

A The motor will rotate backwards continuously.

B The code will not compile due to missing semicolons.

C The motor coils are all energized at once, causing no rotation and possible overheating.

D The Arduino will reset due to pin conflict.

💡 Hint

Consider what happens if all coils are powered simultaneously.

Energizing all coils at once prevents the motor from stepping and can cause overheating or damage.

📝 Syntax

advanced

Find the Syntax Error in Stepper Motor Control Code

Which option contains the correct syntax to set pin 8 HIGH and pin 9 LOW in Arduino?

A

digitalWrite(8, HIGH);
digitalWrite(9, LOW);

B

digitalWrite(8 HIGH);
digitalWrite(9 LOW);

C

digitalWrite(8, HIGH)
digitalWrite(9, LOW);

D

digitalWrite(8, HIGH);
digitalWrite(9, LOW)

💡 Hint

Check for missing commas, semicolons, and parentheses.

Option A has correct syntax with commas separating arguments and semicolons ending statements.

🚀 Application

expert

Calculate Steps for Desired Rotation Angle

A stepper motor has 200 steps per full revolution (360 degrees). How many steps are needed to rotate the motor shaft by 90 degrees?

A 90

B 45

C 100

D 50

💡 Hint

Calculate steps by proportion: (desired angle / 360) * total steps.

90 degrees is one quarter of 360 degrees, so steps = 200 * (90/360) = 50 steps.