Servo angle positioning in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the servo angle after this code runs?

Consider this Arduino code controlling a servo motor. What angle will the servo be set to after loop() runs once?

Arduino

 #include <Servo.h>
Servo myServo;

void setup() {
  myServo.attach(9);
  myServo.write(45);
}

void loop() {
  myServo.write(90);
  delay(1000);
  myServo.write(135);
  delay(1000);
  // loop ends here
}

A 135 degrees

B 45 degrees

C 90 degrees

D 0 degrees

💡 Hint

Remember the loop() function runs repeatedly. The last write() call sets the final angle before the loop restarts.

The loop() function sets the servo to 90 degrees, waits 1 second, then sets it to 135 degrees and waits 1 second. After that, the loop restarts. So the last angle set before the loop restarts is 135 degrees.

🧠 Conceptual

intermediate

Why do we use myServo.attach(pin) in Arduino servo control?

What is the main purpose of calling myServo.attach(pin) in an Arduino program controlling a servo?

A To calibrate the servo's speed

B To set the initial angle of the servo

C To power the servo motor from the Arduino

D To specify which pin the servo signal wire is connected to

💡 Hint

Think about how the Arduino knows where to send the control signal.

The attach() function tells the Arduino which pin will send the control pulses to the servo. It does not set angle, power, or speed.

🔧 Debug

advanced

Why does this servo code cause the servo to jitter?

Look at this Arduino code snippet. The servo jitters and does not hold a steady angle. What is the cause?

Arduino

#include <Servo.h>
Servo myServo;

void setup() {
  myServo.attach(10);
}

void loop() {
  for (int angle = 0; angle <= 180; angle += 10) {
    myServo.write(angle);
    delay(15);
  }
}

A The servo is not attached to the correct pin

B The delay is too short for the servo to reach the angle before changing

C The for loop should count down from 180 to 0

D The servo library is not included properly

💡 Hint

Think about how fast the servo can physically move and how often the angle changes.

The delay of 15 milliseconds is too short for the servo to reach the new angle before the next command. This causes jitter because the servo keeps receiving new positions too quickly.

📝 Syntax

advanced

Which option fixes the syntax error in this servo control code?

Find the option that corrects the syntax error in the following Arduino code:

#include <Servo.h>
Servo myServo;

void setup() {
  myServo.attach(9)
  myServo.write(90);
}

void loop() {
  // empty
}

A Add a semicolon after <code>myServo.attach(9)</code>

B Change <code>myServo.attach(9)</code> to <code>myServo.attach(9);;</code>

C Remove the semicolon after <code>myServo.write(90);</code>

D Add parentheses to <code>setup</code> like <code>setup();</code>

💡 Hint

Check the end of each statement for proper punctuation.

In Arduino (C++), each statement must end with a semicolon. The line myServo.attach(9) is missing a semicolon, causing a syntax error.

🚀 Application

expert

How many unique angles will this servo sweep cover?

This Arduino code sweeps a servo from 0 to 180 degrees in steps of 30 degrees. How many unique angles will the servo be set to during one full sweep?

Arduino

#include <Servo.h>
Servo myServo;

void setup() {
  myServo.attach(9);
}

void loop() {
  for (int angle = 0; angle <= 180; angle += 30) {
    myServo.write(angle);
    delay(500);
  }
  while(true) {}
}

A 4

B 6

C 7

D 5

💡 Hint

Count all values from 0 to 180 stepping by 30, including both ends.

The loop sets angles at 0, 30, 60, 90, 120, 150, and 180 degrees. That's 7 unique angles in total.

Practice

1. What does the Servo.write(angle) function do in Arduino servo control?

easy

A. Reads the current angle of the servo motor

B. Sets the servo motor to the specified angle between 0 and 180 degrees

C. Attaches the servo motor to a pin

D. Stops the servo motor immediately

Solution

1. Step 1: Understand Servo.write() purpose

   The Servo.write(angle) function commands the servo to move to the angle given as a parameter, which must be between 0 and 180 degrees.

2. Step 2: Differentiate from other functions

   Servo.attach() connects the servo to a pin, Servo.read() reads the current angle, and stopping is not done by Servo.write().

3. Final Answer:

   Sets the servo motor to the specified angle between 0 and 180 degrees -> Option B

4. Quick Check:

   Servo.write(angle) sets angle [OK]

Hint: Servo.write sets angle; attach connects servo [OK]

Common Mistakes:

• Confusing Servo.write() with Servo.attach()
• Thinking Servo.write() reads angle
• Assuming Servo.write() stops the servo

2. Which of the following is the correct way to attach a servo to pin 9 in Arduino?

easy

A. servo.connect(9);

B. servo.attachPin(9);

C. servo.attach(9);

D. servo.setPin(9);

Solution

1. Step 1: Recall correct Servo library syntax

   The correct method to connect a servo to a pin is servo.attach(pinNumber); where pinNumber is the Arduino pin number.

2. Step 2: Verify other options

   Methods like attachPin(), connect(), or setPin() do not exist in the Servo library.

3. Final Answer:

   servo.attach(9); -> Option C

4. Quick Check:

   servo.attach(pin) attaches servo [OK]

Hint: Use attach() to connect servo to pin [OK]

Common Mistakes:

• Using non-existent methods like attachPin()
• Confusing attach() with write()
• Forgetting parentheses in attach()

3. What will be the servo angle after running this code snippet?

#include <Servo.h>
Servo servo;
void setup() {
  servo.attach(10);
  servo.write(90);
  delay(1000);
  servo.write(45);
}
void loop() {}

medium

A. 45 degrees

B. 90 degrees

C. 135 degrees

D. 0 degrees

Solution

1. Step 1: Analyze servo.write() calls in setup()

   The servo is first set to 90 degrees, then after 1 second delay, it is set to 45 degrees.

2. Step 2: Determine final servo position after setup()

   The last command in setup() sets the servo to 45 degrees, so it stays there since loop() is empty.

3. Final Answer:

   45 degrees -> Option A

4. Quick Check:

   Last servo.write() angle = 45 [OK]

Hint: Last servo.write() sets final angle [OK]

Common Mistakes:

• Ignoring the second servo.write() call
• Assuming delay changes angle
• Thinking loop() affects angle here

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

#include <Servo.h>
Servo myServo;
void setup() {
  myServo.attach(5);
  myServo.write(200);
}
void loop() {}

medium

A. Servo angle 200 is out of valid range (0-180)

B. Servo not attached to pin 5 correctly

C. Missing delay after write()

D. Servo library not included

Solution

1. Step 1: Check servo angle range

   The servo angle must be between 0 and 180 degrees. Writing 200 is invalid and may cause unexpected behavior.

2. Step 2: Verify other code parts

   The servo is attached correctly to pin 5, delay is optional but recommended, and the Servo library is included.

3. Final Answer:

   Servo angle 200 is out of valid range (0-180) -> Option A

4. Quick Check:

   Servo angle must be 0-180 [OK]

Hint: Servo angles must be 0 to 180 degrees [OK]

Common Mistakes:

• Setting angle above 180
• Ignoring servo angle limits
• Assuming delay is mandatory

5. You want to sweep a servo smoothly from 0 to 180 degrees and back continuously. Which code snippet correctly implements this behavior?

hard

A. servo.write(0); delay(1000); servo.write(180); delay(1000);

B. servo.attach(9); servo.write(90);

C. while(true) { servo.write(90); delay(1000); }

D. for(int angle=0; angle<=180; angle++) { servo.write(angle); delay(15); } for(int angle=180; angle>=0; angle--) { servo.write(angle); delay(15); }

Solution

1. Step 1: Understand sweeping motion requirements

   Sweeping means moving the servo gradually from 0 to 180 degrees and back repeatedly, requiring loops and small delays for smooth movement.

2. Step 2: Analyze each option

   for(int angle=0; angle<=180; angle++) { servo.write(angle); delay(15); } for(int angle=180; angle>=0; angle--) { servo.write(angle); delay(15); } uses two for loops to increment and decrement angle with delays, creating smooth sweep. servo.write(0); delay(1000); servo.write(180); delay(1000); jumps instantly between 0 and 180. while(true) { servo.write(90); delay(1000); } holds at 90 degrees. servo.attach(9); servo.write(90); only sets servo once.

3. Final Answer:

   for(int angle=0; angle<=180; angle++) { servo.write(angle); delay(15); } for(int angle=180; angle>=0; angle--) { servo.write(angle); delay(15); } -> Option D

4. Quick Check:

   Sweep needs gradual angle changes with delay [OK]

Hint: Use loops with delay for smooth servo sweep [OK]

Common Mistakes:

• Jumping angles without gradual steps
• Missing delay causing jerky movement
• Not looping back from 180 to 0