Getting started

New to Arduino? This page covers the stuff every project needs: installing the app, plugging in the board, getting the code onto it, and talking to it. Every project page links back here, so you only have to learn it once.

What you need to start

• An Arduino UNO board. Most projects here use the Elegoo UNO R3 (a cheaper copy of the Arduino UNO that works exactly the same). The Wi-Fi Motion Alarm uses the Arduino UNO R4 WiFi.
• A USB cable that carries data, not just charging. The UNO R3 uses the square USB-B kind, the R4 uses USB-C.
• A computer: Windows, Mac or Linux.
• Jumper wires. Female-to-male wires (a hole on one end, a pin on the other) plug sensors straight into the Arduino without a breadboard. Male-to-male wires are for the keypad and breadboards.
• Parts. I used two kits: the Elegoo UNO R3 Super Starter Kit and the Elegoo 37 Sensor Kit. Any kit with the same parts works.

Step 1: Install the Arduino app

Download Arduino IDE 2 from arduino.cc/en/software and install it with the normal options. Say yes when Windows asks to install drivers.

Step 2: Plug in the board

Plug the board into the computer with the USB cable. A green ON light comes on, and the little L light usually starts blinking.

Step 3: Pick the board and the port

In the Arduino app:

1. Click Tools → Board → Arduino AVR Boards → Arduino Uno.
2. Click Tools → Port and pick the one that says Arduino Uno or USB-SERIAL CH340 (on Windows it's called COM-something).

Not sure which port it is? Unplug the board, look at the list, plug it back in, and pick the one that appeared.

For the UNO R4 WiFi: first click Tools → Board → Boards Manager, search for UNO R4, and install Arduino UNO R4 Boards. Then pick Arduino UNO R4 WiFi as the board.

Step 4: Get the code in

On any project page, scroll down to The code.

• Easiest: click Copy. In the Arduino app click File → New Sketch, select everything in the new window (Ctrl+A), and paste (Ctrl+V). Save it with the project's name.
• Or download it: click Download and open the .ino file. The app asks to move it into a folder with the same name; click OK.
• Projects with several files (like the Wi-Fi alarm): click Download all the code (.zip), unzip it, and open the .ino file inside the folder. The other files open as tabs next to it.

Step 5: Upload it

Click the round → Upload button at the top. The app turns the code into something the board understands and sends it over. When the bottom says Done uploading, the program is running on the board. It stays on the board even after you unplug it, until you upload something else.

Step 6: Talk to it with the Serial Monitor

Lots of projects print messages (like "Temperature: 72.5 F") and let you type commands (like ? for status).

1. Click Tools → Serial Monitor (or the magnifying glass at the top right).
2. At the bottom of the Serial Monitor, set the speed to 9600 baud (the triangle robot uses 115200).
3. Set the line ending box to Newline.
4. Type a command in the box at the top and press Enter.

Wiring tips

• Unplug the USB before changing wires. Then plug it back in.
• 5V and GND are on the bottom edge of the Arduino (the side with the power and A0-A5 pins). Never connect 5V straight to GND.
• The pin numbers (0-13) are printed along the top edge.
• Breadboards: each short row of 5 holes is joined inside. Two legs in the same row are connected; legs in different rows aren't.
• Either way round: many of these programs check which way round a part is plugged in and fix it themselves, so you don't have to get everything perfect the first time. The project pages say when that's the case.

Be safe

• Small projects powered from USB are safe to touch.
• Lithium batteries (18650 cells, drone LiPos) can get very hot or catch fire if their ends touch. Use protected cells, keep them in a holder, and never leave them charging unattended.
• If you're not sure about something, ask someone who knows, or ask an AI like Claude to check your wiring from a photo.