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.

Practice

1. What is the main advantage of using a stepper motor in Arduino projects?

easy

A. It moves in precise, small steps for accurate positioning.

B. It runs faster than all other motors.

C. It uses less power than a servo motor.

D. It requires no programming to control.

Solution

1. Step 1: Understand stepper motor movement

   Stepper motors move in small, fixed steps, allowing precise control of position.

2. Step 2: Compare with other motors

   Unlike regular motors, stepper motors do not rotate freely but in exact increments.

3. Final Answer:

   It moves in precise, small steps for accurate positioning. -> Option A

4. Quick Check:

   Stepper motor precision = Accurate small steps [OK]

Hint: Stepper motors move in fixed steps for precision [OK]

Common Mistakes:

• Thinking stepper motors run faster than all motors
• Assuming no programming is needed
• Confusing power usage with motor type

2. Which of the following is the correct way to create a Stepper object in Arduino code?

easy

A. Stepper myStepper = new Stepper(pin1, pin2, pin3, pin4);

B. Stepper myStepper = Stepper(stepsPerRevolution, pin1, pin2);

C. Stepper myStepper(stepsPerRevolution);

D. Stepper myStepper(stepsPerRevolution, pin1, pin2, pin3, pin4);

Solution

1. Step 1: Recall Stepper constructor syntax

   The Stepper library requires the number of steps per revolution and four control pins.

2. Step 2: Match syntax with options

   Stepper myStepper(stepsPerRevolution, pin1, pin2, pin3, pin4); correctly uses Stepper(stepsPerRevolution, pin1, pin2, pin3, pin4) to create the object.

3. Final Answer:

   Stepper myStepper(stepsPerRevolution, pin1, pin2, pin3, pin4); -> Option D

4. Quick Check:

   Stepper constructor needs steps and 4 pins [OK]

Hint: Stepper needs steps and 4 pins in constructor [OK]

Common Mistakes:

• Using only 2 pins instead of 4
• Trying to use 'new' keyword in Arduino
• Omitting steps per revolution

3. What will be the output behavior of this Arduino code snippet controlling a stepper motor?

Stepper myStepper(200, 8, 9, 10, 11);
void setup() {
  myStepper.setSpeed(60);
}
void loop() {
  myStepper.step(100);
  delay(1000);
  myStepper.step(-100);
  delay(1000);
}

medium

A. The motor rotates 100 steps forward, pauses 1 second, then 100 steps backward, pauses 1 second, and repeats.

B. The motor rotates continuously forward without stopping.

C. The motor rotates 100 steps backward only once.

D. The code will cause a compilation error due to missing pinMode setup.

Solution

1. Step 1: Analyze step commands in loop()

   The code commands the motor to move 100 steps forward, then 100 steps backward, each followed by a 1-second delay.

2. Step 2: Understand loop repetition

   Since this is in loop(), the forward and backward steps repeat indefinitely with pauses.

3. Final Answer:

   The motor rotates 100 steps forward, pauses 1 second, then 100 steps backward, pauses 1 second, and repeats. -> Option A

4. Quick Check:

   Stepper steps forward and backward with delay [OK]

Hint: Positive steps move forward; negative steps move backward [OK]

Common Mistakes:

• Thinking motor runs continuously forward
• Assuming missing pinMode causes error
• Ignoring the delay pauses

4. Identify the error in this Arduino code controlling a stepper motor:

Stepper myStepper(200, 8, 9, 10, 11);
void setup() {
  myStepper.setSpeed(60);
}
void loop() {
  myStepper.step(50);
  delay(500);
}

medium

A. The stepper motor pins are not set as outputs using pinMode.

B. There is no error; the code will run correctly.

C. The step() function requires a negative number to move forward.

D. The setSpeed() function is called in setup(), which is incorrect.

Solution

1. Step 1: Check pinMode necessity for Stepper library

   The Stepper library internally handles pin modes, so explicit pinMode calls are not required.

2. Step 2: Verify setSpeed and step usage

   Calling setSpeed() in setup() and step() in loop() is correct usage for controlling speed and movement.

3. Final Answer:

   There is no error; the code will run correctly. -> Option B

4. Quick Check:

   Stepper library manages pins; code is valid [OK]

Hint: Stepper library sets pins automatically; no pinMode needed [OK]

Common Mistakes:

• Adding unnecessary pinMode calls
• Misunderstanding setSpeed() placement
• Confusing step() sign for direction

5. You want to rotate a stepper motor exactly one full revolution at 120 RPM using Arduino's Stepper library. The motor has 200 steps per revolution. Which code snippet correctly achieves this in the loop() function?

hard

A. myStepper.setSpeed(60);
myStepper.step(200);

B. myStepper.setSpeed(120);
myStepper.step(100);

C. myStepper.setSpeed(120);
myStepper.step(200);

D. myStepper.setSpeed(120);
myStepper.step(-200);

Solution

1. Step 1: Calculate steps for one revolution

   The motor requires 200 steps for one full revolution.

2. Step 2: Set speed and steps correctly

   To rotate at 120 RPM, setSpeed(120) is correct, and step(200) moves one full revolution forward.

3. Final Answer:

   myStepper.setSpeed(120); myStepper.step(200); -> Option C

4. Quick Check:

   200 steps = 1 revolution; speed 120 RPM [OK]

Hint: Steps = motor steps/rev; speed = desired RPM [OK]

Common Mistakes:

• Using half the steps (100) for full revolution
• Setting speed lower than desired RPM
• Using negative steps when forward rotation needed