Chapter 9

In the previous chapter, you learned how Arduino reads analog values using analogRead().

You saw numbers between 0 and 1023 scrolling in the Serial Monitor.

But here’s the real question:

What do we do with those numbers?

Because raw numbers by themselves don’t mean much.

This chapter is about turning readings into control.

🔘 What Is a Potentiometer (Really)?


A potentiometer is not just a “knob”.

Electrically, it is a variable voltage divider.

It has three pins:

  • one connected to 5V

  • one connected to GND

  • the middle pin outputs a variable voltage

As you turn the knob:

  • the voltage at the middle pin changes

  • Arduino reads that voltage using analogRead()

🔌 Wiring the Potentiometer

Connect it like this:

  • One side pin → 5V
  • Other side → GND
  • Middle pin → A0

That’s it.
No extra components required.

I have an full tutorial on potentiometer, check it out to know more!

💻 Reading the Potentiometer

We have done this in our previous chapter.

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

void loop() {
  int potValue = analogRead(A0);
  Serial.println(potValue);
  delay(200);
}

Now turn the knob.

You should see values smoothly changing between:

  • 0 (near GND)
  • 1023 (near 5V)
Try rotating the potentiometer and observe how the analog value changes in the Serial Monitor.

🧠 What You Should Notice

  • The change is continuous

  • Small turns → small changes

  • Fast turns → fast changes

This is analog control in its pure form.

🔄 Why Mapping Is Needed

The problem:

  • analogRead() → 0 to 1023

But real-world outputs often need:

  • 0 to 255 (PWM)

  • 0 to 180 (servo angle)

  • specific ranges

So we need a way to convert one range into another.

That’s where map() comes in.

🔢 The map() Function

Arduino provides a helper function:

map(value, fromLow, fromHigh, toLow, toHigh)

Example:

int mappedValue = map(potValue, 0, 1023, 0, 255);

Now turning the potentiometer controls values between 0 and 255!

🧪 Hardware Time: Potentiometer → Serial Output

Same circuit, change the code to this!

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

void loop() {
  int potValue = analogRead(A0);
  int mappedValue = map(potValue, 0, 1023, 0, 255);

  Serial.print("Raw: ");
  Serial.print(potValue);
  Serial.print("  Mapped: ");
  Serial.println(mappedValue);

  delay(200);
}

This shows you both:

  • what Arduino reads

  • what Arduino uses

Now you can see how the original value is efficiently mapped into our specified range.

🎯Let's Recall!!

What happens if a digital input pin is left floating? It can randomly read HIGH or LOW It always reads LOW It becomes OUTPUT Why do we use pull-up resistors? To increase current To prevent floating inputs To protect the microcontroller Which function is used to read analog inputs? serial.Print analogRead analogReader 1. It can randomly read HIGH or LOW
2. To prevent floating inputs
3. analogRead

Check these if you got them wrong:

⚠️ Important Notes About map()

  • map() does not limit values automatically

  • If inputs exceed range, outputs can too

  • It works only with integers

🧰 Common Beginner Mistakes

  • Forgetting to connect GND

  • Wiring the middle pin incorrectly

  • Expecting perfect stability (analog is noisy)

  • Thinking map() changes voltage (it doesn’t)

map() changes numbers, not signals.

📌 What Comes Next

Now that we can:

  • read analog values

  • convert them into useful ranges

The next step is to use them to control something visible.

👉 Next Chapter — Understanding PWM & LED Fading

This is where analog input meets digital output.