Servo motor control with Servo library in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output behavior of this servo control code?

Consider this Arduino code controlling a servo motor. What will the servo do when this code runs?

Arduino

 #include <Servo.h>
Servo myServo;

void setup() {
  myServo.attach(9);
  myServo.write(0);
}

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

A The servo moves continuously from 0 to 180 degrees without stopping.

B The servo stays at 0 degrees and does not move.

C The servo moves from 180 degrees to 0 degrees in steps of 30 degrees.

D The servo moves from 0 degrees to 180 degrees in steps of 30 degrees, pausing 0.5 seconds at each step, then repeats.

💡 Hint

Look at the for loop and the delay inside loop().

The for loop increases the servo position from 0 to 180 in steps of 30 degrees. Each position is held for 500 milliseconds before moving to the next. After reaching 180, the loop restarts, so the servo repeats this motion.

❓ Predict Output

intermediate

What error does this Arduino code produce?

Look at this code snippet controlling a servo. What error will it cause when compiled?

Arduino

#include <Servo.h>
Servo myServo;

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

void loop() {
  myServo.write(200);
  delay(1000);
}

A No error; the servo will move to 200 degrees.

B Compilation error: 'write' argument out of range causes error.

C Warning: servo angle should be between 0 and 180 degrees, but code compiles and runs.

D Runtime error: servo ignores the 200-degree command and stays at 90 degrees.

💡 Hint

Check the valid range for servo angles in the Servo library.

The Servo library accepts angles from 0 to 180 degrees. Writing 200 degrees does not cause a compile or runtime error, but the servo will likely ignore or clamp the value. The code compiles and runs with a warning or no error.

🔧 Debug

advanced

Why does this servo code not move the servo as expected?

This code is supposed to sweep the servo from 0 to 180 degrees and back. Why does the servo stay still?

Arduino

#include <Servo.h>
Servo myServo;

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

void loop() {
  for (int pos = 0; pos <= 180; pos++) {
    myServo.write(pos);
  }
  for (int pos = 180; pos >= 0; pos--) {
    myServo.write(pos);
  }
}

A The code lacks delay, so servo commands are sent too fast to move physically.

B Servo is not attached to pin 9 correctly, causing no movement.

C The for loops have incorrect conditions causing infinite loops.

D Servo library is not included, so write() does nothing.

💡 Hint

Think about how fast the servo can move and how the code sends commands.

The loops send position commands very quickly without delay. The servo cannot physically move that fast, so it appears stuck. Adding a delay inside the loops allows the servo to move step by step.

📝 Syntax

advanced

Which option fixes the syntax error in this servo code?

Find the option that corrects the syntax error in this Arduino sketch.

Arduino

#include <Servo.h>
Servo myServo;

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

void loop() {
  // empty loop
}

A Add a semicolon after myServo.attach(9);

B Change myServo.attach(9) to myServo.attach(9); myServo.write(90);

C Remove the myServo.write(90) line.

D Add parentheses after loop: void loop()() { }

💡 Hint

Look carefully at the end of the line with myServo.attach(9).

The line myServo.attach(9) is missing a semicolon at the end. Adding it fixes the syntax error. Other options either do not fix the syntax or introduce new errors.

🚀 Application

expert

How many distinct positions does this servo sweep cover?

This code sweeps a servo motor from 0 to 180 degrees in steps of 45 degrees, then back to 0. How many distinct positions does the servo move to in one full sweep cycle?

Arduino

#include <Servo.h>
Servo myServo;

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

void loop() {
  for (int pos = 0; pos <= 180; pos += 45) {
    myServo.write(pos);
    delay(500);
  }
  for (int pos = 135; pos >= 0; pos -= 45) {
    myServo.write(pos);
    delay(500);
  }
}

A 8 positions

B 5 positions

C 9 positions

D 10 positions

💡 Hint

Count the positions in the first loop and the second loop, then combine without duplicates.

The first loop moves to positions: 0, 45, 90, 135, 180 (5 positions). The second loop moves: 135, 90, 45, 0 (4 positions). The total distinct positions are 5: 0, 45, 90, 135, 180.