Here's a simple project I made to control a group of LEDs using an Arduino. This was my first ever project that I did on an Arduino Uno, and it proved to be a fantastic way to learn how to control output devices with an Arduino. Using the same functions that I've used you can replace LEDs for any other output devices such as Buzzers, Motors, Relays, etc...

Supplies

Arduino Uno, Jumper wires, LEDs, Resistors

Step 1: Connecting LEDs

Here I've soldered together multiple LEDs in parallel to scale up the Light show, for simplicity, you can use the same program with just 8 LEDs and then scale it up easily. Use suitable resistors in series with each LED to prevent them for burning out.

Step 2: Interfacing LEDs With the Arduino

There are primarily 2 ways of interfacing LEDs with the Arduino, Source mode and Sink mode. I prefer using the sink mode as it increases the current handling capacity. Once each LED has been connected using your preferred method of interfacing, we can move on to the next step of coding. In sink mode, the current flows as follows:

+5 Vcc
LED
Resistor
Digital pin of Arduino

Step 3: Programming

Open up your Arduino IDE and feel free to use my code! It uses 2 very basic functions,

digitalWrite(), which turns any digital output pin of the Arduino either high or low and,
delay() which quite intuitively produces a delay so that we can actually see the LED glowing or turned off.

I've attached a short clip of the entire program that runs for as long as you provide the circuit with power.