Arduino: Lesson 9 - LED Sequencing using Array Data Structure

Fig. 1 - Arduino: Lesson 9 - LED Sequencing using Array Data Structure

Welcome to Lesson 9 - Basic Arduino Course

In today's lesson, we will learn how to use 5 LEDs connected to 5 Arduino ports, which will light up in sequence and right after the cycle ends, will go out in sequence. With that, we will learn a new instruction, the Array data structure.

What is Array?

An array is a collection of variables that are accessed with an index number. However, the "array" data structure is not exactly an existing data type.

There are arrays of variables like "char", "int", "boolean", "float" and so on. This means that an array can be variables of any type mentioned above.

An array, or vector, for example, is a collection of variables of a specific type, which may even use the same nomenclature, but which will be distinguished by an indexed number.

For example: We can use a variable type "float" with a single name indexed by number, instead of different variables (VarFloat_1, VarFloat_2, VarFloat_3...) we can use a single grouped array with the same nomenclature that will allow each variable be manipulated separately by a numerical index, (VarFloat [0], VarFloat [1], VarFloat [2] ...).

Hardware Required

Arduino Board
5 - LEDs
5 - 250 ohms resistor - (brown, green, brown, gold)
Jumper Wires
Protoboard (optional)

The Circuit Connections

The circuit is a bit simple, we connect the longer "Anode" legs of the 5 LEDs to the positive 5V of the Arduino, and the other shorter leg "Cathode", we connect to the 150 ohm resistor and in series with GND, negative of the Arduino, as shown in Figure 2 below.

Fig. 2 - LED Sequencing using Array Data Structure - tinkercad.com

We use a protoboard to facilitate the connections, but you can also connect the wires directly to the Arduino.

The Code

The code can be implemented in the normal way in programming, as shown in the code below. But the code is quite large, we use 42 lines of code to create this kind of sequential LED circuit. To write less lines of code, an "optimizer" is required.

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// Arduino: Lesson 9 - LED Sequencing using Array Data Structure

const int Led1 = 2; // Select the output LED1 PIN

const int Led2 = 3; // Select the output LED2 PIN

const int Led3 = 4; // Select the output LED3 PIN

const int Led4 = 5; // Select the output LED4 PIN

const int Led5 = 6; // Select the output LED5 PIN

void setup() { // This function is called once when the program starts

pinMode(Led1, OUTPUT); // Initialize digital pin LED1 as an output.

pinMode(Led2, OUTPUT); // Initialize digital pin LED2 as an output.

pinMode(Led3, OUTPUT); // Initialize digital pin LED3 as an output.

pinMode(Led4, OUTPUT); // Initialize digital pin LED4 as an output.

pinMode(Led5, OUTPUT); // Initialize digital pin LED5 as an output.

}

void loop() { // The loop function runs over and over again as long as the Arduino has power.

// Turn ON each LED sequence in order

digitalWrite(Led1, HIGH);