Reading a potentiometer in Arduino - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a potentiometer and how is it used in Arduino projects?

A potentiometer is a knob or dial that acts like a variable resistor. It changes the amount of electrical resistance when you turn it. In Arduino projects, it is used to give input by turning the knob, which changes the voltage read by the Arduino.

beginner

Which Arduino function reads the value from a potentiometer?

The function analogRead(pin) reads the voltage from the potentiometer connected to an analog pin and returns a number between 0 and 1023.

beginner

What is the range of values returned by analogRead() when reading a potentiometer?

The analogRead() function returns values from 0 to 1023. 0 means the lowest voltage (0 volts), and 1023 means the highest voltage (usually 5 volts).

beginner

How do you connect a potentiometer to an Arduino for reading its value?

Connect one outer pin of the potentiometer to 5V, the other outer pin to GND, and the middle pin (wiper) to an analog input pin on the Arduino (like A0).

beginner

What does the following Arduino code do?

int sensorValue = analogRead(A0);

This code reads the voltage from the potentiometer connected to analog pin A0 and stores the value (0 to 1023) in the variable sensorValue.

What does the middle pin (wiper) of a potentiometer connect to in an Arduino circuit?

A An analog input pin

B 5V power supply

C Ground (GND)

D Digital output pin

The middle pin of the potentiometer connects to an analog input pin to read the variable voltage.

What is the maximum value returned by analogRead() on Arduino?

A 255

B 5

C 1023

D 512

analogRead() returns values from 0 to 1023 representing voltage levels.

If you turn the potentiometer knob fully to one side, what value would you expect from analogRead()?

A Around 1023

B Around 0

C Around 512

D It will be random

Turning the knob fully to one side connects the wiper to ground, so the reading is near 0.

Which Arduino pin type is used to read a potentiometer value?

A Digital pin

B Power pin

C PWM pin

D Analog pin

Potentiometers output an analog voltage, so you must use an analog input pin.

What is the purpose of connecting the two outer pins of a potentiometer to 5V and GND?

A To create a voltage divider for variable voltage output

B To power the Arduino

C To ground the Arduino

D To connect sensors

Connecting the outer pins to 5V and GND creates a voltage divider, so the middle pin outputs a voltage between 0 and 5V.

Explain how to connect and read a potentiometer value using Arduino.

Think about the hardware connections and the Arduino function used.

Describe what the value returned by analogRead() means when reading a potentiometer.

Consider how voltage changes with knob position.

Practice

1. What does the analogRead(pin) function do when reading a potentiometer on Arduino?

easy

A. It reads the voltage level on the analog pin and returns a value from 0 to 1023.

B. It sets the output voltage of the pin to control the potentiometer.

C. It converts a digital signal to an analog voltage.

D. It resets the potentiometer to zero position.

Solution

1. Step 1: Understand analogRead function

   The analogRead(pin) reads the voltage on the specified analog pin and converts it to a number between 0 and 1023.

2. Step 2: Relate to potentiometer reading

   Since a potentiometer outputs a variable voltage depending on its position, analogRead returns a value representing that voltage level.

3. Final Answer:

   It reads the voltage level on the analog pin and returns a value from 0 to 1023. -> Option A

4. Quick Check:

   analogRead() returns 0-1023 value [OK]

Hint: Remember analogRead returns 0-1023 for voltage levels [OK]

Common Mistakes:

• Thinking analogRead sets voltage instead of reading it
• Confusing analogRead with digitalRead
• Assuming analogRead returns voltage in volts

2. Which of the following is the correct syntax to read a potentiometer connected to analog pin A0 and store the value in a variable named sensorValue?

easy

A. sensorValue = analogWrite(A0);

B. sensorValue = digitalRead(A0);

C. sensorValue = analogRead(A0);

D. sensorValue = readAnalog(A0);

Solution

1. Step 1: Identify correct function for analog input

   The function to read analog input is analogRead(pin), not digitalRead or analogWrite.

2. Step 2: Check variable assignment syntax

   Assigning the result of analogRead(A0) to sensorValue uses the syntax: sensorValue = analogRead(A0);

3. Final Answer:

   sensorValue = analogRead(A0); -> Option C

4. Quick Check:

   Use analogRead() to read analog pin [OK]

Hint: Use analogRead(pin) to read analog sensors [OK]

Common Mistakes:

• Using digitalRead instead of analogRead
• Using analogWrite which is for output
• Using a non-existent function readAnalog

3. What will be printed on the Serial Monitor when the following Arduino code runs and the potentiometer is turned to mid position?

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

void loop() {
  int sensorValue = analogRead(A0);
  Serial.println(sensorValue);
  delay(1000);
}

medium

A. A value close to 0 printed every second

B. A value close to 1023 printed every second

C. No output because Serial.begin is missing

D. A value close to 512 printed every second

Solution

1. Step 1: Understand analogRead output range

   The potentiometer at mid position outputs about half the voltage, so analogRead(A0) returns around 512 (half of 1023).

2. Step 2: Analyze Serial output

   The code prints the sensorValue every 1000 milliseconds (1 second), so the Serial Monitor shows a value near 512 each second.

3. Final Answer:

   A value close to 512 printed every second -> Option D

4. Quick Check:

   Mid potentiometer = ~512 output [OK]

Hint: Mid potentiometer gives about half max value 512 [OK]

Common Mistakes:

• Expecting 0 or 1023 at mid position
• Forgetting Serial.begin causes no output
• Confusing analogRead with digitalRead values

4. The following code is intended to read a potentiometer and print its value, but it does not work correctly. What is the error?

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

void loop() {
  int sensorValue;
  sensorValue = analogRead(0);
  Serial.print(sensorValue);
  delay(500);
}

medium

A. Missing Serial.println instead of Serial.print

B. Serial.begin baud rate is too low

C. No delay after Serial.print

D. Using analogRead(0) instead of analogRead(A0)

Solution

1. Step 1: Check Serial output method

   The code uses Serial.print(sensorValue) without a newline, causing consecutive values to print on the same line and appear garbled or unreadable.

2. Step 2: Use println for readability

   Serial.println(sensorValue) adds a newline after each value, making the output clear on the Serial Monitor.

3. Final Answer:

   Missing Serial.println instead of Serial.print -> Option A

4. Quick Check:

   Serial.print vs println for newlines [OK]

Hint: Use Serial.println() not print() for readable output [OK]

Common Mistakes:

• Using numeric 0 instead of A0 for analogRead
• Confusing Serial.print and Serial.println
• Ignoring delay causing fast output

5. You want to read a potentiometer and map its 0-1023 value to a 0-255 range to control LED brightness using PWM on pin 9. Which code snippet correctly does this?

hard

A. int sensorValue = analogRead(9);
int brightness = map(sensorValue, 0, 255, 0, 1023);
analogWrite(A0, brightness);

B. int sensorValue = analogRead(A0);
int brightness = map(sensorValue, 0, 1023, 0, 255);
analogWrite(9, brightness);

C. int sensorValue = digitalRead(A0);
int brightness = sensorValue * 255;
analogWrite(9, brightness);

D. int sensorValue = analogRead(A0);
int brightness = sensorValue / 4;
digitalWrite(9, brightness);

Solution

1. Step 1: Read potentiometer value correctly

   Use analogRead(A0) to get a value from 0 to 1023.

2. Step 2: Map value to 0-255 for PWM

   Use map(sensorValue, 0, 1023, 0, 255) to convert the range for LED brightness.

3. Step 3: Write PWM value to LED pin

   Use analogWrite(9, brightness) to set LED brightness on pin 9.

4. Final Answer:

   int sensorValue = analogRead(A0); int brightness = map(sensorValue, 0, 1023, 0, 255); analogWrite(9, brightness); -> Option B

5. Quick Check:

   Read analog, map range, write PWM [OK]

Hint: Use map() to convert 0-1023 to 0-255 for PWM [OK]

Common Mistakes:

• Using digitalRead instead of analogRead
• Writing PWM to analog pin or wrong pin
• Using digitalWrite for PWM control