📘 Lesson P4 – Operators in Arduino Programming

🎯 Learning Objectives

After completing this lesson, students will be able to:

✅ Understand what operators are

✅ Understand why operators are important

✅ Perform mathematical calculations

✅ Compare values using comparison operators

✅ Use logical operators for decision making

✅ Use assignment operators correctly

✅ Build logic for real-world Arduino projects

1. Introduction

Imagine you want Arduino to:

• Add two numbers
• Compare temperatures
• Check whether a button is pressed
• Control a motor based on distance

Can Arduino do this without calculations?

No.

Arduino needs special symbols to perform operations.

These symbols are called:

Operators

Operators help Arduino perform calculations and make decisions.

2. What is an Operator?

An operator is a special symbol that tells Arduino to perform a specific operation on data.

Example:

5 + 3

Here:

+

is an operator.

Result:

8

Real-Life Example

Suppose you buy:

• 2 notebooks
• 3 pens

To calculate total items:

2 + 3 = 5

The plus sign is performing an operation.

Similarly, Arduino uses operators to process data.

3. Types of Operators in Arduino

The most important operators are:

Arithmetic Operators

Comparison Operators

Logical Operators

Assignment Operators

Increment and Decrement Operators

4. Arithmetic Operators

Arithmetic operators perform mathematical calculations.

Addition Operator (+)

Example:

int a = 10;
int b = 5;

int result = a + b;

Result:

15

Subtraction Operator (-)

Example:

int a = 10;
int b = 3;

int result = a - b;

Result:

7

Multiplication Operator (*)

Example:

int result = 5 * 4;

Result:

20

Division Operator (/)

Example:

int result = 20 / 4;

Result:

5

Important Note

5 / 2

Result:

2

because integers do not store decimal values.

For decimals use:

float result = 5.0 / 2.0;

Result:

2.5

Modulus Operator (%)

Returns the remainder.

Example:

10 % 3

Result:

1

Because:

10 ÷ 3 = 3 remainder 1

Practical Use of Modulus

Checking whether a number is even or odd.

Example:

8 % 2 = 0

Even number.

7 % 2 = 1

Odd number.

5. Assignment Operators

Assignment operators store values in variables.

Basic Assignment (=)

Example:

int age = 22;

Here:

=

assigns value 22 to age.

Addition Assignment (+=)

Example:

int score = 10;

score += 5;

Equivalent to:

score = score + 5;

Result:

15

Subtraction Assignment (-=)

Example:

score -= 3;

Equivalent to:

score = score - 3;

Multiplication Assignment (*=)

Example:

score *= 2;

Equivalent to:

score = score * 2;

Division Assignment (/=)

Example:

score /= 2;

Equivalent to:

score = score / 2;

6. Comparison Operators

Comparison operators compare two values.

Result is always:

true

or

false

Equal To (==)

Example:

10 == 10

Result:

true

Not Equal To (!=)

Example:

10 != 5

Result:

true

Greater Than (>)

Example:

20 > 10

Result:

true

Less Than (<)

Example:

5 < 10

Result:

true

Greater Than or Equal To (>=)

Example:

10 >= 10

Result:

true

Less Than or Equal To (<=)

Example:

5 <= 10

Result:

true

Real Arduino Example

Temperature Monitoring System

if(temperature > 40)
{
    // Turn ON Fan
}

Arduino checks:

Is temperature greater than 40?

If yes, fan turns ON.

7. Logical Operators

Logical operators combine multiple conditions.

AND Operator (&&)

Both conditions must be true.

Example:

(age > 18 && age < 60)

Both conditions must be satisfied.

OR Operator (||)

At least one condition must be true.

Example:

(score > 90 || attendance > 95)

Only one condition is enough.

NOT Operator (!)

Reverses the result.

Example:

!true

Result:

false

Real Arduino Example

Automatic Door Lock

if(passwordCorrect && cardDetected)
{
   // Open Door
}

Door opens only if both conditions are true.

8. Increment Operator (++)

Used to increase value by 1.

Example:

int count = 5;

count++;

Result:

6

Equivalent to:

count = count + 1;

Practical Uses

• Counting button presses
• Robot lap counting
• Visitor counters

9. Decrement Operator (–)

Used to decrease value by 1.

Example:

int count = 5;

count--;

Result:

4

Equivalent to:

count = count - 1;

Practical Uses

• Countdown timer
• Remaining attempts
• Inventory reduction

10. Operator Precedence

Arduino follows mathematical rules.

Example:

2 + 3 * 4

Result:

14

Because multiplication happens first.

Using Parentheses

(2 + 3) * 4

Result:

20

Always use parentheses when logic becomes complex.

11. Real-World Project Examples

Ultrasonic Distance Meter

if(distance < 10)

Object is close.

Gas Leakage Detector

if(gasValue > 500)

Gas leakage detected.

Water Tank Monitoring

if(level >= 90)

Tank full.

Visitor Counter

count++;

Increase visitor count.

12. Common Beginner Mistakes

Mistake 1

Using:

=

instead of:

==

Wrong:

if(temp = 30)

Correct:

if(temp == 30)

Mistake 2

Forgetting parentheses.

Mistake 3

Confusing AND and OR.

Mistake 4

Dividing integers and expecting decimal results.

13. Best Practices

✅ Use meaningful variable names

✅ Use parentheses for clarity

✅ Test conditions carefully

✅ Keep calculations simple

✅ Add comments for complex logic

📊 Summary

In this lesson, we learned:

✅ Arithmetic Operators

✅ Assignment Operators

✅ Comparison Operators

✅ Logical Operators

✅ Increment Operator

✅ Decrement Operator

Operators are the tools that allow Arduino to calculate values, compare conditions, and make decisions in real-world projects.

📖 Key Terms

Operator

A symbol that performs an operation.

Arithmetic Operator

Performs calculations.

Comparison Operator

Compares values.

Logical Operator

Combines conditions.

Assignment Operator

Stores values.

Increment

Increases value by one.

Decrement

Decreases value by one.

🎯 Quiz

1. Which operator performs addition?

A. –

B. +

C. *

D. /

✅ Answer: B

2. Which operator checks equality?

A. =

B. ==

C. !=

D. >=

✅ Answer: B

3. What does && represent?

A. OR

B. NOT

C. AND

D. EQUAL

✅ Answer: C

4. What is the result of:

10 % 3

A. 3

B. 0

C. 1

D. 10

✅ Answer: C

5. What does count++ do?

A. Decrease count

B. Increase count by 1

C. Multiply count

D. Divide count

✅ Answer: B

🏠 Assignment

Task 1

Create a table of all arithmetic operators with examples.

Task 2

Write five comparison operator examples.

Task 3

Write three logical operator examples.

Task 4

Create a program that calculates the area of a rectangle using variables and arithmetic operators.

Task 5

Create a simple temperature monitoring logic using comparison operators.