Arduino Beginner Guide (Complete)

1. What is Arduino?

Arduino is a small programmable electronic board.
You write code on a computer and upload it to the board.
The board then controls electronic parts like LEDs, sensors, motors, etc.

2. Arduino Uno Pins Explained

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Digital Pins (0–13)

Used for ON / OFF
Output values:
- HIGH = 5V (ON)
- LOW = 0V (OFF)
Used for LEDs, buzzers, relays
Pin 13 has a built-in LED

Analog Pins (A0–A5)

Used to read sensor values
Value range: 0 to 1023
Example: temperature sensor, light sensor

Power Pins

Pin	Purpose
5V	5V output
3.3V	3.3V output
GND	Ground
VIN	External power input

3. Arduino Program Structure

Every Arduino program has two main functions:

void setup() {
  // runs once
}

void loop() {
  // runs forever
}

Explanation

setup() Runs one time only Used to configure pins
loop() Runs again and again Used for main logic

4. Built-in LED (Pin 13)

Arduino Uno has a built-in LED connected to pin 13. No wiring needed.

Code

void setup() {
  pinMode(13, OUTPUT);   // set pin 13 as output
}

void loop() {
  digitalWrite(13, HIGH); // LED ON
  delay(1000);            // wait 1 second
  digitalWrite(13, LOW);  // LED OFF
  delay(1000);            // wait 1 second
}

5. External LED Using Digital Pin

Components

LED
220Ω or 330Ω resistor
Breadboard
Jumper wires

Wiring

LED long leg (+) → resistor → Digital pin (D7)
LED short leg (−) → GND
Resistor protects the LED

Code (External LED)

int ledPin = 7; // LED connected to pin 7

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  digitalWrite(ledPin, HIGH); // LED ON
  delay(1000);
  digitalWrite(ledPin, LOW);  // LED OFF
  delay(1000);
}

6. Important Functions

pinMode(pin, OUTPUT);    // set pin type
digitalWrite(pin, HIGH); // ON
digitalWrite(pin, LOW);  // OFF
delay(ms);               // wait

7. How Code Runs

Arduino turns ON
setup() runs once
loop() runs forever
Code repeats continuously

Arduino Beginner Guide