Why analog input is needed in Arduino - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read an analog value from pin A0.

Arduino

int sensorValue = analogRead([1]);

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

AA0

B13

CLED_BUILTIN

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using a digital pin number instead of an analog pin name.

Confusing analogRead with digitalRead.

The analogRead function reads the voltage on an analog pin like A0.

2fill in blank

medium

Complete the code to print the analog sensor value to the serial monitor.

Arduino

Serial.println([1]);

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

ALOW

BHIGH

CdigitalValue

DsensorValue

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to print a digital pin state instead of the analog value.

Using undefined variables.

sensorValue holds the analog reading and should be printed.

3fill in blank

hard

Fix the error in the code to correctly read and print an analog value.

Arduino

void setup() {
  Serial.begin(9600);
}

void loop() {
  int value = analogRead([1]);
  Serial.print("Value: ");
  Serial.println(value);
  delay(1000);
}

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

AA0

B13

CLED_BUILTIN

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using a digital pin number with analogRead causes wrong readings.

Confusing pin numbers with pin labels.

analogRead needs an analog pin like A0 to read the sensor value.

4fill in blank

hard

Fill both blanks to create a dictionary of sensor readings greater than 500.

Arduino

int readings[] = {450, 520, 610, 480};
for (int i = 0; i < 4; i++) {
  if (readings[i] [1] 500) {
    Serial.println(readings[[2]]);
  }
}

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

A>

B<

Ci

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' causes wrong filtering.

Using wrong index to access array elements.

The code prints readings greater than 500 using the index i.

5fill in blank

hard

Fill all three blanks to create a map of sensor names to values above 300.

Arduino

String sensors[] = {"temp", "light", "sound"};
int values[] = {250, 400, 350};
for (int [1] = 0; [1] < 3; [1]++) {
  if (values[[2]] [3] 300) {
    Serial.print(sensors[[2]]);
    Serial.print(": ");
    Serial.println(values[[2]]);
  }
}

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

Ai

Bj

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variables for indexing sensors and values.

Using '<' instead of '>' in the condition.

The loop variable i is used to check values greater than 300 and print sensor names with values.

Practice

1. Why do we need analog input pins on an Arduino board?

easy

A. To connect to the internet

B. To send digital signals to LEDs

C. To power the Arduino board

D. To read sensors that give a range of values, not just ON or OFF

Solution

1. Step 1: Understand sensor signal types

   Some sensors output values that change smoothly, like temperature or light levels, not just ON/OFF.

2. Step 2: Role of analog input pins

   Analog input pins let Arduino read these changing values as numbers between 0 and 1023.

3. Final Answer:

   To read sensors that give a range of values, not just ON or OFF -> Option D

4. Quick Check:

   Analog input reads smooth sensor values [OK]

Hint: Analog pins read smooth sensor values, digital pins do ON/OFF [OK]

Common Mistakes:

• Confusing analog input with digital output
• Thinking analog pins power the board
• Believing analog pins connect to the internet

2. Which Arduino function is used to read an analog input value from pin A0?

easy

A. digitalRead(A0)

B. readAnalog(A0)

C. analogRead(A0)

D. inputRead(A0)

Solution

1. Step 1: Recall Arduino analog input syntax

   The correct function to read analog values is analogRead().

2. Step 2: Apply function to pin A0

   Use analogRead(A0) to get the sensor value from pin A0.

3. Final Answer:

   analogRead(A0) -> Option C

4. Quick Check:

   Function to read analog input = analogRead() [OK]

Hint: Use analogRead() for analog pins, digitalRead() for digital pins [OK]

Common Mistakes:

• Using digitalRead() for analog pins
• Using wrong function names like readAnalog()
• Confusing pin names or syntax

3. What will the following Arduino code print if a light sensor connected to A0 reads a value of 512?

int sensorValue = analogRead(A0);
Serial.println(sensorValue);

medium

A. 512

B. 0

C. 1023

D. Error

Solution

1. Step 1: Understand analogRead output range

   analogRead returns a value between 0 and 1023 based on sensor input.

2. Step 2: Check code behavior with sensor value 512

   The code reads 512 and prints it directly using Serial.println.

3. Final Answer:

   512 -> Option A

4. Quick Check:

   analogRead returns sensor value = 512 [OK]

Hint: analogRead returns sensor value directly, printed as is [OK]

Common Mistakes:

• Assuming analogRead returns 0 or 1023 only
• Expecting printed value to be scaled or changed
• Thinking code causes an error

4. Identify the error in this Arduino code snippet that tries to read an analog value:

int val = analogRead(0);
Serial.print(val);

medium

A. Serial.print cannot print integers

B. No error, code is correct

C. analogRead should be analogWrite here

D. analogRead needs a pin name like A0, not just 0

Solution

1. Step 1: Check analogRead parameter

   analogRead(0) is valid because 0 corresponds to pin A0 on Arduino boards.

2. Step 2: Understand Serial.print usage

   Serial.print works fine with integers.

3. Final Answer:

   No error, code is correct -> Option B

4. Quick Check:

   analogRead(0) reads A0 correctly [OK]

Hint: analogRead(0) is valid for pin A0 [OK]

Common Mistakes:

• Thinking analogRead requires 'A0' instead of 0
• Confusing analogRead with analogWrite
• Thinking Serial.print can't print numbers

5. You want to control the brightness of an LED based on a temperature sensor connected to A0. Which approach correctly uses analog input to do this?

hard

A. Read analog value from A0, map it to 0-255, then use analogWrite on LED pin

B. Use digitalRead on A0 and turn LED fully ON or OFF

C. Use analogWrite on A0 to read temperature, then digitalWrite LED

D. Connect LED to A0 and use analogRead to control brightness

Solution

1. Step 1: Read sensor value with analogRead

   Use analogRead(A0) to get temperature sensor value between 0-1023.

2. Step 2: Map sensor value to LED brightness range

   Map 0-1023 to 0-255 to match PWM brightness levels for analogWrite.

3. Step 3: Use analogWrite to set LED brightness

   Write mapped value to LED pin using analogWrite for smooth brightness control.

4. Final Answer:

   Read analog value from A0, map it to 0-255, then use analogWrite on LED pin -> Option A

5. Quick Check:

   Analog input + map + analogWrite [OK]

Hint: Map sensor range to 0-255, then analogWrite LED brightness [OK]

Common Mistakes:

• Using digitalRead for analog sensor
• Trying analogWrite on input pin
• Connecting LED directly to analog input pin