Motor speed control with PWM in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the motor speed using PWM on pin 9.

Arduino

int motorPin = 9;
void setup() {
  pinMode(motorPin, OUTPUT);
}
void loop() {
  analogWrite(motorPin, [1]);
  delay(1000);
}

Drag options to blanks, or click blank then click option'

ALOW

BHIGH

C9

D255

Attempts:

3 left

💡 Hint

Common Mistakes

Using HIGH or LOW instead of a PWM value.

Using the pin number instead of the speed value.

The analogWrite function sets the PWM duty cycle. 255 means full speed.

2fill in blank

medium

Complete the code to gradually increase motor speed from 0 to 255.

Arduino

int motorPin = 6;
void setup() {
  pinMode(motorPin, OUTPUT);
}
void loop() {
  for (int speed = 0; speed <= 255; speed++) {
    analogWrite(motorPin, [1]);
    delay(10);
  }
}

Drag options to blanks, or click blank then click option'

Aspeed

BmotorPin

C255

Ddelay

Attempts:

3 left

💡 Hint

Common Mistakes

Using the pin number instead of the speed variable.

Using a fixed value instead of the loop variable.

The variable speed changes from 0 to 255 to increase PWM duty cycle gradually.

3fill in blank

hard

Fix the error in the code to set motor speed using PWM on pin 3.

Arduino

int motorPin = 3;
void setup() {
  pinMode(motorPin, OUTPUT);
}
void loop() {
  analogWrite([1], 128);
  delay(500);
}

Drag options to blanks, or click blank then click option'

AmotorPin

B128

COUTPUT

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using the speed value instead of the pin number.

Using the pin number directly instead of the variable.

The first argument of analogWrite must be the pin number variable motorPin.

4fill in blank

hard

Fill both blanks to create a dictionary that maps motor pins to their PWM speeds if speed is above 100.

Arduino

int motorPins[] = {5, 6, 9};
int speeds[] = {90, 150, 200};
void setup() {
  for (int i = 0; i < 3; i++) {
    pinMode(motorPins[i], OUTPUT);
    if (speeds[i] [1] 100) {
      analogWrite(motorPins[i], [2]);
    }
  }
}
void loop() {}

Drag options to blanks, or click blank then click option'

A>

BmotorPins[i]

Cspeeds[i]

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong comparison operator.

Using the pin number instead of the speed value for PWM.

The condition checks if speed is greater than 100, then writes PWM speed from speeds[i] to the motor pin.

5fill in blank

hard

Fill all three blanks to read an analog sensor, map its value to PWM range, and set motor speed.

Arduino

int sensorPin = A0;
int motorPin = 10;
void setup() {
  pinMode(motorPin, OUTPUT);
}
void loop() {
  int sensorValue = analogRead([1]);
  int motorSpeed = map(sensorValue, 0, 1023, [2], [3]);
  analogWrite(motorPin, motorSpeed);
  delay(100);
}

Drag options to blanks, or click blank then click option'

AsensorPin

B0

C255

DmotorPin

Attempts:

3 left

💡 Hint

Common Mistakes

Using the motor pin instead of sensor pin for reading.

Mapping to wrong PWM range.

The sensor is read from sensorPin. The value is mapped from 0-1023 to 0-255 for PWM.

Practice

1. What does PWM do in motor speed control on an Arduino?

easy

A. It changes the motor's voltage permanently.

B. It switches power on and off quickly to control speed.

C. It changes the motor's direction.

D. It measures the motor's speed.

Solution

1. Step 1: Understand PWM function

   PWM (Pulse Width Modulation) controls speed by rapidly switching power on and off.

2. Step 2: Compare options

   Only It switches power on and off quickly to control speed. correctly describes PWM's role in speed control, others describe different functions.

3. Final Answer:

   It switches power on and off quickly to control speed. -> Option B

4. Quick Check:

   PWM controls speed by switching power on/off [OK]

Hint: PWM controls speed by fast power switching [OK]

Common Mistakes:

• Thinking PWM changes voltage permanently
• Confusing speed control with direction control
• Believing PWM measures speed

2. Which Arduino function is used to set motor speed with PWM?

easy

A. pinMode(pin, OUTPUT)

B. digitalWrite(pin, value)

C. analogWrite(pin, value)

D. delay(value)

Solution

1. Step 1: Identify PWM function

   analogWrite(pin, value) sets PWM signal on a pin with value 0-255 controlling speed.

2. Step 2: Check other functions

   digitalWrite sets HIGH/LOW only, pinMode sets pin mode, delay pauses code; none control PWM speed.

3. Final Answer:

   analogWrite(pin, value) -> Option C

4. Quick Check:

   Use analogWrite for PWM speed control [OK]

Hint: Use analogWrite to set PWM speed value [OK]

Common Mistakes:

• Using digitalWrite instead of analogWrite
• Confusing pinMode with speed control
• Trying to use delay to control speed

3. What will be the motor speed if the code runs

analogWrite(9, 128);

?

medium

A. Motor runs at full speed

B. Motor is off

C. Motor runs at double speed

D. Motor runs at about half speed

Solution

1. Step 1: Understand PWM value range

   analogWrite value ranges 0 (off) to 255 (full speed). 128 is about half of 255.

2. Step 2: Interpret speed from value

   Value 128 means roughly half the power, so motor runs at about half speed.

3. Final Answer:

   Motor runs at about half speed -> Option D

4. Quick Check:

   128/255 ≈ half speed [OK]

Hint: PWM 128 means about half speed [OK]

Common Mistakes:

• Thinking 128 means full speed
• Assuming motor is off at 128
• Believing speed can be doubled

4. Identify the error in this code snippet for motor speed control:

int speed = 300;
analogWrite(6, speed);

medium

A. Speed value is out of PWM range (0-255).

B. Pin 6 cannot be used for PWM.

C. analogWrite requires three arguments.

D. Variable speed must be declared as float.

Solution

1. Step 1: Check PWM value limits

   analogWrite accepts values from 0 to 255. 300 is outside this range.

2. Step 2: Verify other options

   Pin 6 supports PWM, analogWrite takes two arguments, and int is fine for speed.

3. Final Answer:

   Speed value is out of PWM range (0-255). -> Option A

4. Quick Check:

   PWM value must be 0-255 [OK]

Hint: PWM values must be 0 to 255 only [OK]

Common Mistakes:

• Using values above 255 for PWM
• Thinking analogWrite needs 3 arguments
• Believing PWM pins are limited incorrectly

5. You want to smoothly increase motor speed from 0 to full over 5 seconds using PWM on pin 10. Which code snippet achieves this?

hard

A. for(int speed=0; speed<=255; speed++) { analogWrite(10, speed); delay(20); }

B. analogWrite(10, 255); delay(5000); analogWrite(10, 0);

C. for(int speed=255; speed>=0; speed--) { analogWrite(10, speed); delay(20); }

D. digitalWrite(10, HIGH); delay(5000); digitalWrite(10, LOW);

Solution

1. Step 1: Understand smooth speed increase

   Gradually increasing PWM value from 0 to 255 in small steps with delay creates smooth speed change.

2. Step 2: Analyze code snippets

   for(int speed=0; speed<=255; speed++) { analogWrite(10, speed); delay(20); } uses a for loop from 0 to 255 with delay(20)ms, totaling about 5 seconds. Others either jump speed or use digitalWrite which is not PWM.

3. Final Answer:

   for(int speed=0; speed<=255; speed++) { analogWrite(10, speed); delay(20); } -> Option A

4. Quick Check:

   Gradual PWM increase with delay = smooth speed [OK]

Hint: Use for loop with analogWrite and delay for smooth speed [OK]

Common Mistakes:

• Using digitalWrite instead of analogWrite
• Jumping speed without gradual steps
• Not using delay to slow speed change