Lesson P8 – Arrays in Arduino Programming

🎯 Learning Objectives

After completing this lesson, students will be able to:

✅ Understand what arrays are

✅ Understand why arrays are needed

✅ Create and use arrays

✅ Access array elements

✅ Use loops with arrays

✅ Store multiple values efficiently

✅ Apply arrays in real Arduino projects

1. Introduction

Suppose you want to store the marks of 5 students.

Without arrays:

int mark1 = 80;
int mark2 = 75;
int mark3 = 90;
int mark4 = 85;
int mark5 = 70;

This works for 5 values.

But what if you need:

50 values?
100 values?
1000 values?

Creating separate variables becomes difficult.

To solve this problem, programmers use:

Arrays

2. What is an Array?

An array is a collection of multiple values stored under a single variable name.

Think of an array as a row of lockers.

Example:

Locker 0 → 80
Locker 1 → 75
Locker 2 → 90
Locker 3 → 85
Locker 4 → 70

All lockers belong to one array.

Real-Life Example

Imagine a classroom attendance register.

Instead of creating a separate register for every student:

Student 1
Student 2
Student 3

All names are stored in a single list.

Arrays work similarly.

3. Why Do We Need Arrays?

Arrays help:

✅ Store multiple values

✅ Save memory

✅ Simplify programs

✅ Work efficiently with loops

✅ Manage sensor readings

Without arrays, large projects become difficult to manage.

4. Declaring an Array

Syntax:

dataType arrayName[size];

Example:

int marks[5];

This creates an array capable of storing 5 integers.

5. Array Index

Every element in an array has a position called:

Index

Important:

Array indexing starts from:

Not 1.

Example

int marks[5];

Positions:

Index	Element
0	First
1	Second
2	Third
3	Fourth
4	Fifth

Visual Representation

Index:
0    1    2    3    4

Values:
80   75   90   85   70

6. Initializing an Array

Values can be assigned during creation.

Example:

int marks[5] = {80,75,90,85,70};

Now:

marks[0] = 80
marks[1] = 75
marks[2] = 90
marks[3] = 85
marks[4] = 70

7. Accessing Array Elements

Use index numbers.

Example:

Serial.println(marks[0]);

Output:

Serial.println(marks[3]);

Output:

8. Modifying Array Values

Array values can be changed.

Example:

marks[2] = 95;

Now:

marks[2] = 95

instead of:

9. Displaying Array Values

Example:

int marks[5] = {80,75,90,85,70};

void setup()
{
   Serial.begin(9600);

   Serial.println(marks[0]);
}

Output:

10. Using Arrays with Loops

Arrays become powerful when combined with loops.

Example:

int marks[5] = {80,75,90,85,70};

void setup()
{
   Serial.begin(9600);

   for(int i=0;i<5;i++)
   {
      Serial.println(marks[i]);
   }
}

Output:

Why Use a Loop?

Without a loop:

Serial.println(marks[0]);
Serial.println(marks[1]);
Serial.println(marks[2]);
Serial.println(marks[3]);
Serial.println(marks[4]);

More code.

Less efficient.

11. Finding Sum of Array Elements

Example:

int marks[5]={80,75,90,85,70};

int sum=0;

for(int i=0;i<5;i++)
{
   sum = sum + marks[i];
}

Result:

Practical Applications

Sensor averaging
Data logging
Student marks
Robot path storage

12. Finding Maximum Value

Example:

int values[5]={10,50,20,80,30};

int maximum=values[0];

for(int i=1;i<5;i++)
{
if(values[i] > maximum)
{
maximum = values[i];
}
}

Result:

13. Arrays and LEDs

Suppose 5 LEDs are connected:

LED	Pin
LED1	2
LED2	3
LED3	4
LED4	5
LED5	6

Instead of creating separate variables:

int ledPins[5]={2,3,4,5,6};

Now LEDs can be controlled using loops.

Example

for(int i=0;i<5;i++)
{
   digitalWrite(ledPins[i],HIGH);
}

All LEDs turn ON.

14. Arrays with Sensors

Example:

Multiple IR Sensors

int sensorPins[5]={A0,A1,A2,A3,A4};

Useful in:

Line Follower Robots
Smart Monitoring Systems
Industrial Automation

15. Character Arrays

Arrays can store characters.

Example:

char grade[5]={'A','B','C','D','E'};

Output:

Serial.println(grade[0]);

Displays:

16. String Arrays

Example:

String names[3]={"Rahul","Shiv","Amit"};

Output:

Serial.println(names[1]);

Displays:

Shiv

17. Memory Considerations

Arrays use memory.

Example:

int values[100];

Consumes:

100 × 2 Bytes

200 Bytes

Arduino Uno has limited memory.

Therefore avoid unnecessarily large arrays.

18. Common Beginner Mistakes

Mistake 1

Array index starts from 0.

Wrong:

int values[100];

In a 5-element array.

Valid indexes:

0–4

Mistake 2

Accessing beyond array size.

Example:

marks[10]

when only 5 elements exist.

Can cause unexpected behavior.

Mistake 3

Forgetting loop limits.

Wrong:

for(int i=0;i<=5;i++)

Correct:

for(int i=0;i<5;i++)

19. Real-World Applications

Arrays are used in:

Line Follower Robots

Store multiple IR sensor values.

Weather Stations

Store temperature history.

LED Patterns

Store LED pin numbers.

Data Loggers

Store readings.

Automation Systems

Store device states.

20. Best Practices

✅ Use meaningful array names

sensorValues

instead of:

✅ Keep array size appropriate

✅ Always check index limits

✅ Use loops with arrays

✅ Comment large arrays

📊 Summary

In this lesson, we learned:

✅ What arrays are

✅ Array declaration

✅ Array initialization

✅ Array indexing

✅ Using arrays with loops

✅ Finding sums and maximum values

✅ LED and sensor arrays

Arrays help Arduino store and manage multiple related values efficiently, making programs shorter, cleaner, and more powerful.

📖 Key Terms

Array

A collection of multiple values stored under one variable name.

Index

Position of an element inside an array.

Element

Individual value stored in an array.

Array Size

Total number of elements.

Iteration

Repeating through array elements using loops.

🎯 Quiz

1. What is an array?

A. Function

B. Collection of values under one name ✅

C. Sensor

D. Operator

2. Array indexing starts from:

A. 1

B. 2

C. 0 ✅

D. 10

3. What is the index of the first element?

A. 0 ✅

B. 1

C. 2

D. 5

4. Which loop is commonly used with arrays?

A. if

B. switch

C. for ✅

D. else

5. In a 5-element array, the last valid index is:

A. 5

B. 4 ✅

C. 3

D. 6

🏠 Assignment

Task 1

Create an integer array containing 10 numbers and display them using a for loop.

Task 2

Find the sum of all elements in an array.

Task 3

Find the largest value in an array.

Task 4

Create an array containing 5 LED pin numbers.

Task 5

Research how arrays are used in line follower robots and explain their importance.