Why Code is Important — Same Circuit, 5 Different Behaviours!

In my last video, I built a push button + LED circuit on Arduino. It worked perfectly! But then I started wondering…

🤔 Can the same circuit do completely different things… without changing a single wire?

The answer is YES — and the secret is code.

🦾

Components

LED, button, wires

= the body

🧠

Arduino

The board

= the brain

📝

Code

The program

= the instructions

Change the instructions → same body does different things. That's the power of programming!

🔌 What You Need

🔹

Arduino UNO

×1

📋

Breadboard

×1

💡

LED

×1

⚡

220Ω Resistor

×1

🔘

Push Button

×1

🧵

Jumper Wires

×5-6

🔌

USB Cable

×1

✅

Same for ALL demos

No changes!

🧩 Wiring Guide

Connect everything once. Same wiring for all 5 demos.

LED → Resistor → Pin 13

LED long leg (+) → 220Ω resistor → Pin 13 on Arduino
LED short leg (−) → GND rail on breadboard

Push Button → Pin 2

Button left leg → Pin 2 on Arduino
Button right leg → GND rail on breadboard
⚠️ INPUT_PULLUP = no external resistor needed

GND → Breadboard GND rail

Arduino GND pin → GND rail (blue/black line) on breadboard

⚠️

Button tip: Push buttons have 4 legs. Legs on the same side are connected inside. Use legs on opposite sides (diagonally across) for your connections.

Basic Push Button

Behavior: LED glows only while button is pressed.

🎥 Nitvi says:

"This is the code from my last video."

Arduino Code

const int buttonPin = 2;
const int ledPin = 13;
void setup() {
pinMode(buttonPin, INPUT_PULLUP);
pinMode(ledPin, OUTPUT);
}
void loop() {
if (digitalRead(buttonPin) == LOW) {
digitalWrite(ledPin, HIGH);
} else {
digitalWrite(ledPin, LOW);
}
}

Toggle Switch

Behavior: Press once → LED ON. Press again → LED OFF.

🎥 Nitvi says:

"Same button... but now it works like a light switch!"

Arduino Code

const int buttonPin = 2;
const int ledPin = 13;
bool ledState = LOW;
bool lastButton = HIGH;
void setup() {
pinMode(buttonPin, INPUT_PULLUP);
pinMode(ledPin, OUTPUT);
}
void loop() {
bool button = digitalRead(buttonPin);
if (button == LOW && lastButton == HIGH) {
ledState = !ledState;
digitalWrite(ledPin, ledState);
delay(200);
}
lastButton = button;
}

Blink While Pressing

Behavior: Hold button → LED blinks. Release → OFF.

🎥 Nitvi says:

"Now it blinks instead!"

Arduino Code

const int buttonPin = 2;
const int ledPin = 13;
void setup() {
pinMode(buttonPin, INPUT_PULLUP);
pinMode(ledPin, OUTPUT);
}
void loop() {
if (digitalRead(buttonPin) == LOW) {
digitalWrite(ledPin, HIGH);
delay(200);
digitalWrite(ledPin, LOW);
delay(200);
} else {
digitalWrite(ledPin, LOW);
}
}

SOS Signal

Behavior: Press button → LED flashes SOS in Morse code (... ――― ――― ...)

🎥 Nitvi says:

"Wow! It can even send an SOS message!"

Arduino Code

const int buttonPin = 2;
const int ledPin = 13;
void dot() {
digitalWrite(ledPin, HIGH);
delay(200);
digitalWrite(ledPin, LOW);
delay(200);
}
void dash() {
digitalWrite(ledPin, HIGH);
delay(600);
digitalWrite(ledPin, LOW);
delay(200);
}
void setup() {
pinMode(buttonPin, INPUT_PULLUP);
pinMode(ledPin, OUTPUT);
}
void loop() {
if (digitalRead(buttonPin) == LOW) {
dot(); dot(); dot();
dash(); dash(); dash();
dot(); dot(); dot();
delay(1000);
}
}

Random Blink Speed

Behavior: Every button press changes the blink speed randomly!

🎥 Nitvi says:

"Every press gives me a new blink speed!"

Arduino Code

const int buttonPin = 2;
const int ledPin = 13;
int speed = 200;
bool lastButton = HIGH;
void setup() {
pinMode(buttonPin, INPUT_PULLUP);
pinMode(ledPin, OUTPUT);
randomSeed(analogRead(A0));
}
void loop() {
bool button = digitalRead(buttonPin);
if (button == LOW && lastButton == HIGH) {
speed = random(100, 700);
delay(200);
}
lastButton = button;
digitalWrite(ledPin, HIGH);
delay(speed);
digitalWrite(ledPin, LOW);
delay(speed);
}

</ div>

🔍 What Changed Across All 5 Demos?

Feature	Demo 1	Demo 2	Demo 3	Demo 4	Demo 5
Circuit	Same	Same	Same	Same	Same
LED behavior	On while pressed	Toggle on/off	Blink while held	SOS signal	Random blink
What's new in code?	—	+ ledState + lastButton	+ delay(200) inside if	+ dot() + dash()	+ random() + analogRead

The only thing that changed: CODE. 🎯

✅ Key Takeaways

🦾

Electronics = Hardware

The physical parts — LED, button, wires, Arduino board

🧠

Arduino = Brain

It reads inputs and controls outputs

📝

Code = Instructions

Tells the Arduino brain what to do

⚡

Same Hardware + Different Code = Different Behaviour

5 demos, 5 behaviours, 0 wire changes!

🚀 What's Next?

Today I learned that changing the code can completely change how a circuit behaves. But now I have another question…

🤔 How does Arduino actually understand the code we write?

How does my program turn into actions like blinking an LED? Let's discover that in the next video!

If you're learning Arduino, electronics, coding, or STEM just like me, join me on this exciting journey. 👍 Like, 💬 Comment, 🔔 Subscribe on Nitvi Talks!