Reading a potentiometer in Arduino - Step-by-Step Execution

Concept Flow - Reading a potentiometer

Start

↓

Setup pin modes

↓

Loop start

↓

Read analog value from potentiometer

↓

Store value in variable

↓

Use or print value

↓

Loop repeats

The program sets up the input pin, then repeatedly reads the potentiometer's analog value, stores it, and uses or prints it.

Execution Sample

Arduino

int potPin = A0;
int val = 0;

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

void loop() {
  val = analogRead(potPin);
  Serial.println(val);
  delay(500);
}

This code reads the potentiometer value from pin A0 and prints it every half second.

Execution Table

Step	Action	Variable 'val'	Output	Notes
1	Setup serial communication	0		Serial starts at 9600 baud
2	Read analog value from A0	e.g. 512		Potentiometer middle position approx.
3	Print value to Serial	512	512	Value sent to serial monitor
4	Wait 500 ms	512		Pause before next read
5	Read analog value from A0	e.g. 600		Potentiometer moved slightly
6	Print value to Serial	600	600	Value sent to serial monitor
7	Wait 500 ms	600		Pause before next read
...	Loop continues reading and printing	varies	varies	Repeats indefinitely

💡 Arduino loop runs forever; no exit condition

Variable Tracker

Variable	Start	After Step 2	After Step 5	...final
val	0	512	600	varies with potentiometer position

Key Moments - 3 Insights

Why does 'val' change each time in the execution table?

Because the potentiometer position changes, analogRead reads a new voltage level each loop (see steps 2 and 5).

Why is there a delay after printing the value?

The delay(500) pauses the loop so the readings and prints happen every half second, making output readable (step 4).

What does analogRead actually return?

It returns a number from 0 to 1023 representing voltage from 0V to 5V on the analog pin (step 2 shows example values).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'val' after step 5?

A 600

B 512

C 0

D 1023

💡 Hint

Check the 'Variable val' column at step 5 in the execution_table.

At which step does the program print the potentiometer value to the Serial monitor?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look for the 'Print value to Serial' action in the execution_table.

If the potentiometer is turned to maximum, what is the expected range of 'val'?

A Around 0

B Around 1023

C Around 512

D Negative values

💡 Hint

Recall analogRead returns 0 to 1023 based on voltage; max position means max voltage.

Concept Snapshot

Reading a potentiometer:
- Connect potentiometer middle pin to analog input (e.g., A0).
- Use analogRead(pin) to get value 0-1023.
- Store value in variable.
- Use Serial.println() to print value.
- Use delay() to control reading speed.
- Loop repeats to update reading continuously.

Full Transcript

This Arduino program reads a potentiometer connected to analog pin A0. It starts by setting up serial communication at 9600 baud. In the loop, it reads the analog value from the potentiometer using analogRead, which returns a number between 0 and 1023 depending on the knob position. This value is stored in the variable 'val'. The program then prints this value to the serial monitor using Serial.println. After printing, it waits for 500 milliseconds before reading again. This loop repeats forever, updating the potentiometer reading continuously. The variable 'val' changes as the potentiometer is turned, reflecting the voltage level on the analog pin. The delay helps make the output readable by spacing out the readings.

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