Introduction
In this guide, we’ll cover the basics of Arduino, as the title suggests, focusing on understanding how the board works—not how to program it. Therefore, you won’t need to install any software.
To follow this guide properly, you’ll need the following components:
- Arduino board: it can be an Elegoo board. Arduino is open-source, so many cheaper clones of the original exist. The main difference is their durability, but they function the same.
- Breadboard (testing board).
- Push button.
- Potentiometer.
- LED.
- Two resistors.
You can purchase these from any major online store.
Throughout this guide, we’ll use Tinkercad for circuit diagrams. Wires connected to 5V will be red, wires connected to GND will be black, and conditional wires (those depending on input/output or connected to a pin, analog or digital) will be blue.
With Arduino, we use three types of jumper wires: male-to-male, female-to-male, and female-to-female. A “male” connection refers to the left side (a pin), while a “female” connection refers to the right side (a socket). A male wire can be inserted into a female one.
Image from murkyrobot.com
Pins: Types and Functions
Every Arduino board has 6 analog pins and 14 digital pins.
Analog pins output numeric values from 0 to 1023, while digital pins provide boolean values: true or false, 1 or 0, HIGH or LOW.
In this image, we can see the digital pins labeled “DIGITAL (PWM),” numbered from 0 to 13.
Below “ANALOG IN,” we find the analog pins: A0 through A5.
Finally, below “POWER,” we find pins that provide 3.3V or 5V or can close a circuit through GND. We’ll cover how to use these in the next section on electrical connections.
Electrical Connections
Let’s understand how a breadboard works—an essential tool for Arduino projects.
You’ll see two rows marked – and two marked +, with columns in the middle connected vertically. The image below shows how columns are internally connected: if you connect 5V to one hole, the entire vertical column will have 5V. This also applies to the red (+) and black (–) rows.
Stop! Did you understand this diagram? It’s vital before continuing!
Typically:
- A wire goes from 5V to one of the red (+) rows to make the entire row carry 5V.
- A wire goes from GND to one of the black (–) rows to make the row act as ground.
IMPORTANT: connections only apply to the specific row they’re placed on—not both red rows, for example.
As mentioned before, columns are also internally connected, so if you connect a wire from 5V and place an LED anode in the same column, it will light up—BUT BE CAREFUL, we’ll explain how to do it safely in section 4. Otherwise, you could burn the LED or even hurt yourself.
Ohm’s Law
To understand how any circuit works, we must understand Ohm’s Law.
A circuit receives voltage, measured in volts. Components may not be able to handle high current, which is why we use resistance, measured in ohms. Resistance regulates the output current (in amperes). Think of resistance as a faucet: voltage is the water coming in, and the resistance (the faucet’s opening) determines how much water (current) flows out.
In this triangle:
- V is voltage (volts).
- R is resistance (ohms).
- I is current (amperes).
The formulas are:
- Voltage = Resistance × Current
- Resistance = Voltage ÷ Current
- Current = Voltage ÷ Resistance
The most useful formula is for resistance. For example:
Let’s say the circuit runs at 5V, and you want to connect an LED with a maximum current of 0.02A. We calculate the resistance needed:
5V ÷ 0.02A = 250 ohms
So, to power the LED at full brightness safely, use a 250-ohm resistor. This way, the LED won’t burn out or explode.
First LED Experiments
Lighting up an LED
To light up an LED, you’ll need: the LED, a resistor, the Arduino board, and a breadboard.
Here’s a breakdown of the setup:
- Wire from 5V to the red (+) rail.
- Wire from GND to the black (–) rail.
- LED connected across two columns:
- The anode column (longer leg) is connected to the red rail for power.
- The cathode column (shorter leg) is connected to the black rail to complete the circuit.
- IMPORTANT: One of these connections must include a resistor to avoid burning the LED.
Lighting the LED with a Button
To light an LED with a button, you’ll need: an LED, a resistor, a button, an Arduino, and a breadboard.
Here’s a breakdown:
- Wire from 5V to the red (+) rail.
- Wire from GND to the black (–) rail.
- Button:
- One leg connected through a resistor to the red rail (power to the button).
- The opposite leg connected to a wire going to the LED anode (sends current to the LED when pressed).
- LED:
- Anode receives current from the button.
- Cathode connected via wire to the black rail (to close the circuit).
Dimming an LED with a Potentiometer
A potentiometer works like a faucet—depending on how it’s turned, it allows more or less voltage through. Refer to Ohm’s Law in section 3 for context.
To dim an LED with a potentiometer, you’ll need: the LED, potentiometer, a resistor, an Arduino, and a breadboard.
Setup breakdown:
- Wire from 5V to red rail, and from GND to black rail.
- Potentiometer:
- Middle pin connects to a column that goes to the LED’s anode.
- One outer pin connects to the red rail.
- The other outer pin connects to the black rail.
- LED:
- Anode receives signal from the potentiometer.
- Cathode goes through a resistor to the black rail (to close the circuit).
Components: What Can You Do?
One of Arduino’s strengths is the vast number of components and project possibilities.
From games to home automation, there are countless Arduino projects. Check out this list of 46 maker projects for inspiration.
Want to explore more components? Keep an eye on section 6, where we cover where to learn more.
Where to Learn More: Reference Websites
This guide is a brief introduction to Arduino and electricity, but if you enjoyed it, there’s a lot more to explore.
A great website to learn about Arduino and its components is Luis Llamas’s Arduino tutorial section:
🔗 https://www.luisllamas.es/tutoriales-de-arduino/
