Arduino Masterclass — Toghrul Guluzade

01 — FOUNDATIONS

How electricity works

Before touching any component, you need to understand the three ideas that explain everything in electronics.

⚡

Voltage (V)

Voltage is the push that moves electricity. Think of it like water pressure in a pipe — higher pressure pushes more water. We measure it in Volts. Your Arduino runs on 5V.

🌊

Current (A)

Current is the flow of electrons — how much electricity is actually moving. Like the amount of water flowing through a pipe. We measure it in Amperes (A) or milliamps (mA).

🚧

Resistance (Ω)

Resistance slows down the flow of electricity. Like a narrow section in a pipe. We measure it in Ohms (Ω). This is why we use resistors to protect LEDs from burning out.

🔁

Circuits need a loop

Electricity always flows from + to − (positive to negative / from high voltage to low). If the loop is broken anywhere, nothing works. This is called an open circuit.

// LIVE DEMO — watch the electrons flow from + to −

Blue = current flowing + → Red = returning to − The resistor protects the LED

💡

Ohm's Law — one formula to rule them all

Everything in electronics comes back to: V = I × R (Voltage = Current × Resistance). Rearranged to find resistance: R = V ÷ I. This is exactly how we chose the 220Ω resistor below.

HOW WE CHOSE 220Ω FOR OUR LED

🔋

Supply voltage

Arduino gives us 5 volts

💡

LED forward voltage

LED "uses up" ~2V itself

⚡

20mA

Safe LED current

Max before LED burns out

The calculation:

Voltage across resistor = 5V − 2V = 3V

R = V ÷ I = 3V ÷ 0.02A = 150Ω minimum

✓ We use 220Ω — a bit higher = safer + dimmer is fine

🧮 TRY IT YOURSELF — RESISTOR CALCULATOR

Supply voltage (V)

LED voltage drop (V)

Desired current (mA)

Enter values above to calculate ↑

02 — YOUR KIT

Meet your components

Click each component to learn what it does and how it fits in a circuit.

ESSENTIAL

Breadboard

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A breadboard lets you build circuits without soldering. Holes in the same row are connected underneath. The red (+) and blue (−) rails run along the edges and carry power.

Rows run horizontally (A–E and F–J are separate). The center gap separates the two halves. Push component legs straight in.

💡 Fun fact: "Bread" board comes from the 1960s when people literally used wooden bread boards to prototype circuits with nails!

PROTECTOR

Resistor

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Resistors limit current to protect components. The colored bands tell you its value in Ohms (Ω). We use 220Ω resistors to protect LEDs in this project.

Unlike LEDs, resistors have no polarity — you can put them in either way round.

🎨 Reading color bands: Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Gray=8, White=9, Gold=÷10

LIGHT

LED

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Light Emitting Diode. Converts electrical current directly into light. Way more efficient than a bulb — no heat wasted.

Polarity matters! The longer leg is + (anode) and goes toward power. The shorter leg is − (cathode) and goes to GND. Put it in backwards and it won't light — but won't break either.

⚠️ Never connect an LED directly to 5V without a resistor — it will burn out in seconds!

INPUT

Push Button

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A momentary button closes a circuit only while pressed. Our 4-leg button has two pairs of legs — legs on the same side are always connected, legs across the gap connect only when pressed.

We use Arduino's internal pull-up resistor — so buttons wire to GND, and pressing reads as LOW (not HIGH).

🎮 Every gaming controller uses the same principle — millions of tiny momentary buttons!

SOUND

Buzzer

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An active buzzer makes sound when you apply voltage — no fancy code needed, just HIGH and LOW. It has a small vibrating disk inside that moves air to create sound.

Polarity matters! The + leg (longer, or marked +) goes to the Arduino pin, the − leg goes to GND.

🎵 The "remove seal" sticker covers a small hole. Remove it before use or the sound will be muffled!

🌈

CONNECT

Jumper Wires

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Jumper wires connect components on a breadboard and to Arduino pins. Use colors as a convention: red for power (+), black for ground (−), other colors for signals.

It doesn't actually matter electrically — but consistent colors help you and others read your circuit and spot mistakes.

🔴 Pro tip: always use red for + and black for GND. Future you will thank present you.

03 — THE BRAIN

The Arduino Uno

The Arduino is a tiny computer that reads inputs (buttons, sensors) and controls outputs (LEDs, buzzers) based on code you give it.

GND (Ground / −)

The negative terminal. Every component's negative leg must connect here to complete the circuit.

5V Power (+)

Supplies 5 volts. Use this to power components that need constant power (like the pull-up reference).

Digital Pins (2–13)

Can be set as INPUT or OUTPUT. Read buttons (HIGH/LOW) or control LEDs and buzzers. Our game uses pins 2, 4, 6, 7, 8, 11.

USB Port

Powers the board and transfers your code from the computer. The Arduino IDE sends code here when you click Upload.

Reset Button

Restarts the program from the beginning. Useful when you want to restart a game without unplugging.

Pin 13 — Built-in LED

There's an LED soldered onto the board connected to pin 13. Great for quick tests — no wiring needed.

04 — BUILD IT

Your two projects

Start with Blink to get confident, then build the full reaction game.

💡

Blink — LED on/off loop

The "Hello World" of electronics. Wire one LED and make it blink every half second. Once this works, you understand circuits.

CONNECTIONS

Component	From	To
LED (short leg −)	Short leg	GND rail on breadboard
220Ω Resistor	One end	Same row as LED long leg
Resistor other end	Other end	Pin 7 on Arduino
GND wire	Arduino GND	− rail on breadboard

CIRCUIT DIAGRAM

THE CODE

// Blink — makes LED on pin 7 blink every 500ms

void setup() {
  pinMode(7, OUTPUT);   // tell Arduino pin 7 is an output
}

void loop() {
  digitalWrite(7, HIGH);  // turn LED ON
  delay(500);             // wait 500 milliseconds
  digitalWrite(7, LOW);   // turn LED OFF
  delay(500);             // wait 500 milliseconds
                           // then loop() runs again!
}

🧠

setup() runs once

This is where you tell Arduino what each pin does — input or output.

🔁

loop() runs forever

After setup, loop() keeps repeating until you unplug the Arduino.

🔢

delay(500) = 0.5 seconds

delay() pauses the program. 1000 = 1 second. Try changing it!

⬆️

HIGH = 5V, LOW = 0V

HIGH turns the pin on (5V). LOW turns it off (0V). Simple!

🚀 Challenge: once it blinks, try...

Make it blink 3 times fast, then pause for 2 seconds. Or add a second LED that blinks out of sync!

🎮

Reaction Game — 2 players

A yellow LED lights up at a random moment. Whoever presses their button first wins the round. 3 rounds, best of 3 wins.

ALL CONNECTIONS

Component	Arduino Pin	Notes
Button P1	Pin 2 → GND	Uses internal pull-up. No resistor needed!
Button P2	Pin 4 → GND	Uses internal pull-up. No resistor needed!
Green LED (P1)	Pin 7	+ leg → 220Ω → pin 7. − leg → GND.
Red LED (P2)	Pin 8	+ leg → 220Ω → pin 8. − leg → GND.
Yellow LED (GO)	Pin 6	+ leg → 220Ω → pin 6. − leg → GND.
Buzzer (+)	Pin 11	+ leg to pin 11. − leg to GND. Remove seal!

CIRCUIT DIAGRAM

HOW THE GAME WORKS

01

Hold both buttons for 2 seconds — both player LEDs light up and the buzzer beeps. Game is starting!
02

Yellow LED blinks 3 times — this is your "get ready" warning. Fingers off buttons!
03

Random wait — between 2 and 5 seconds of nothing. Don't press yet!
04

Yellow LED lights solid — GO! Press your button as fast as possible.
05

Winner's LED lights up and buzzer plays a beep. Serial Monitor shows your reaction time in milliseconds.
06

3 rounds total. Whoever wins 2 rounds wins the match — and gets the victory melody! 🎵

⚠️ False start rule

Press your button before the yellow LED lights up and you automatically lose that round. Your LED flashes with a penalty buzzer. Be patient!

YOUR CIRCUIT DIAGRAMS

// Insert your printed wiring diagrams here

// PROJECT 1 — BLINK

// PROJECT 2 — REACTION GAME

Build realelectronics.Today.

How electricity works

Voltage (V)

Current (A)

Resistance (Ω)

Circuits need a loop

Ohm's Law — one formula to rule them all

Meet your components

Breadboard

Resistor

LED

Push Button

Buzzer

Jumper Wires

The Arduino Uno

GND (Ground / −)

5V Power (+)

Digital Pins (2–13)

USB Port

Reset Button

Pin 13 — Built-in LED

Your two projects

Blink — LED on/off loop

CONNECTIONS

CIRCUIT DIAGRAM

THE CODE

setup() runs once

loop() runs forever

delay(500) = 0.5 seconds

HIGH = 5V, LOW = 0V

Reaction Game — 2 players

ALL CONNECTIONS

CIRCUIT DIAGRAM

HOW THE GAME WORKS

YOUR CIRCUIT DIAGRAMS

Build real
electronics.
Today.