AL ICT Lesson 11.3: Internet of Things (IoT) | Notes Tamil Medium Class Study Guide PDF Notes Exam Zoom Class

🚪 G.C.E. A/L ICT – Competency 11.1 | IoT Part 3

Door Detection, Reed Switch, Sensors, Actuators, Analog/Digital Signals, Physical Computing & Development Flow

Reed Switch Door Detection Sensor Actuator Analog vs Digital Physical Computing Exam Focus

⚡ Quick Answers | SEO / AEO / Featured Snippet Style Revision ▼

Reed Switch என்றால் என்ன?

Magnetic field மூலம் open/close ஆகும் switch. Door detection-ல் magnet உடன் பயன்படுத்தப்படும்.

Door Detection எப்படி வேலை செய்கிறது?

Reed switch digital input ஆக Arduino/microcontroller-க்கு செல்கிறது. Door open ஆனால் LED/Buzzer ON செய்யலாம்.

Sensor என்றால் என்ன?

Physical quantity-ஐ detect/measure செய்து electrical signal ஆக மாற்றும் input device.

Actuator என்றால் என்ன?

Control signal பெற்ற பிறகு physical action செய்யும் output device. Example: Fan, Motor, Relay.

Analog vs Digital

Analog = continuous values. Digital = discrete states, பொதுவாக 0/1.

Physical Computing என்றால் என்ன?

Software மூலம் physical electronic components-ஐ sense மற்றும் control செய்வது.

Most important exam concept:
Input → Processing → Output

Sensor → Microcontroller → Actuator

Door Detection & Reed Switch

🚪 26. Example 4 – Door Open/Close Detection ▼

Syllabus-ல்:

Detection of opening/closing a door using a reed switch / magnetic switch

NIE Teacher’s Guide-லும் “read switch” என்று குறிப்பிடப்பட்டாலும், பொதுவாக இங்கு reed switch என்பதே பொருள்.

Syllabus Term

Reed switch / magnetic switch

Use

Door open/close state detect செய்தல்

Input Type

Digital Input

Output

LED / Buzzer / Alarm / Message

🧲 27. Reed Switch என்றால் என்ன? ▼

Reed switch என்பது magnetic field மூலம் open/close ஆகும் switch.

பொதுவாக:

Magnet Reed Switch

ஆகிய இரண்டும் சேர்ந்து பயன்படுத்தப்படுகிறது.

Door-ல் அமைப்பு

Door │ │ Magnet │ └────────── Door Frame │ │ Reed Switch │ └──────────

Door மூடப்படும் போது

Magnet மற்றும் reed switch அருகில் வரும்.

Door திறக்கும்போது

Magnet மற்றும் reed switch விலகும்.

Memory Trick:
Magnet அருகில் வந்தால் reed switch நிலை மாறும்.

🔎 28. Door Detection Logic ▼

System Flow

Door ↓ Reed Switch ↓ Digital Input ↓ Microcontroller ↓ Decision ↓ Alarm / LED / Message

Example 1

Door Closed

LED OFF

Door Open

LED ON

Example 2

Door Open

Buzzer ON

Door Closed

Buzzer OFF

குறிப்பு: HIGH/LOW value எந்த நிலையில் வரும் என்பது circuit wiring-ஐப் பொறுத்தது. Pull-up / pull-down arrangement மற்றும் wiring method-ஐ பொறுத்து logic மாறலாம்.

📝 29. Door Detection – Pseudocode ▼

START Read reed switch IF door is open Turn ON LED ELSE Turn OFF LED REPEAT

Exam Answer Style:
Read digital input from reed switch → check door state → control output device → repeat continuously.

Applications & System Building Blocks

📊 30. மூன்று முக்கிய Applications – ஒரே பார்வையில் ▼

Application	Input	Processing	Output
LED control	Switch / program	Microcontroller	LED
Automatic light	LDR	Microcontroller	LED
Automatic fan	Temperature sensor	Microcontroller	Fan
Door detection	Reed switch	Microcontroller	LED / Buzzer

இதுதான் இந்த competency-யின் மிக முக்கியமான Input → Process → Output concept.

🧱 31. Building Blocks of a Digital / Embedded System ▼

ஒரு basic system-ஐ இவ்வாறு நினைவில் வைத்துக்கொள்ளுங்கள்:

INPUT ↓ ┌─────────────────┐ │ Microcontroller │ │ Processing │ └─────────────────┘ ↓ OUTPUT

Input Examples

LDR, Temperature sensor, Push button, Reed switch, Motion sensor

Processing

Microcontroller, Program / Decision logic

Output Examples

LED, Buzzer, Fan, Motor, Relay

Sensors, Actuators & Signals

📡 32. Sensor என்றால் என்ன? ▼

Sensor என்பது physical quantity-ஐ detect/measure செய்து electrical signal/data ஆக வழங்கும் component.

Sensor	Detects
LDR	Light
Temperature sensor	Temperature
PIR sensor	Motion
Ultrasonic sensor	Distance
Reed switch	Magnetic / door state

நினைவில் வைக்க:
Sensor = Input device

⚙️ 33. Actuator என்றால் என்ன? ▼

Actuator என்பது control signal கிடைத்த பிறகு physical action செய்யும் device.

Examples

Motor Fan Relay Servo motor Solenoid LED போன்ற output devices

Memory Trick:
Sensor → உணர்கிறது
Actuator → செயல்படுகிறது

🔄 34. Sensor + Controller + Actuator Model ▼

IoT/Embedded systems-ல் மிகவும் முக்கியமான model:

Physical World ↓ Sensor ↓ Microcontroller ↓ Decision ↓ Actuator ↓ Physical Action

Example – Smart Fan

Room Temperature ↓ Temperature Sensor ↓ Arduino ↓ Temperature > 30°C ↓ Relay ↓ Fan

Exam phrase:
Sensor reads the physical world. Microcontroller makes the decision. Actuator performs the physical action.

🎚️ 35. Analog vs Digital Input ▼

Analog Input	Digital Input
Continuous value	Discrete states
பல values	பொதுவாக 0 / 1
Light intensity	Button
Temperature	Reed switch
LDR	Digital switch
ADC மூலம் reading பெறலாம்	Digital read பயன்படுத்தலாம்

Easy Memory Trick:
Analog = அளவு மாறிக்கொண்டே இருக்கும்
Digital = நிலை 0/1

🌡️ 36. Analog vs Digital Example ▼

Temperature – Analog-type physical quantity

Temperature 25.1°C 25.2°C 25.3°C 25.4°C ...

இது போன்ற தொடர்ச்சியாக மாறக்கூடிய அளவுகள் Analog-type physical quantity ஆகும்.

Door Switch – Digital state

Door switch OPEN CLOSED

இதுபோன்ற இரண்டு தெளிவான நிலைகள் Digital state ஆகும்.

↔️ 37. Digital Input vs Digital Output ▼

Digital Input

Board தகவலைப் பெறுகிறது.

Example: Button → Arduino

Digital Output

Board control signal அனுப்புகிறது.

Example: Arduino → LED

மிக எளிதாக:
Input = உள்ளே வரும் data
Output = வெளியே செல்லும் control/data

Arduino Pins & System Comparison

📟 38. Arduino Pin Types – Exam Table ▼

Feature	Function
Analog Input	Variable analog signals read செய்ய
Digital Input	Digital state read செய்ய
Digital Output	Output device control செய்ய
RX	Serial data receive செய்ய
TX	Serial data transmit செய்ய
USB	Computer connection / program upload
Power	Electrical power வழங்க
Reset	Program execution-ஐ reset செய்ய

Arduino Uno official documentation-ல் digital I/O மற்றும் RX/TX serial pins பற்றிய details வழங்கப்பட்டுள்ளன.

💻 39. Traditional Computer vs Embedded System – இன்னும் தெளிவாக ▼

Traditional Computer

ஒரு student பயன்படுத்தும் laptop: Keyboard, Mouse, CPU, RAM/Storage, Operating System, Applications, Monitor. பல வகையான வேலைகளைச் செய்ய முடியும்.

Embedded System

Automatic fan: Temperature Sensor → Microcontroller → Driver → Fan. குறிப்பிட்ட control task-க்காக வடிவமைக்கப்பட்டுள்ளது.

Traditional Computer Keyboard Mouse ↓ CPU ↓ RAM / Storage ↓ Operating System ↓ Applications ↓ Monitor

Embedded System Temperature Sensor ↓ Microcontroller ↓ Driver ↓ Fan

Traditional Computer	Embedded System
General-purpose	Specific control task
Many tasks possible	One main task
User interacts through OS/apps	Direct physical control
Example: Laptop	Example: Automatic fan

Physical Computing & Development Flow

🌍 40. Physical Computing ▼

NIE Teacher’s Guide-ல் Physical Computing என்ற concept குறிப்பிடப்படுகிறது.

Physical Computing என்றால்?
Software program மற்றும் physical electronic components ஆகியவற்றை இணைத்து real-world objects-ஐ sense மற்றும் control செய்வது.

Example

Software Only

Python/Arduino code மட்டும் computer screen-ல் ஓடுவது: Software.

Physical Computing

Sensor → Program → Motor மூலம் physical world-ஐ control செய்தால்: Physical Computing.

🧠 41. Development System-ல் Software ஏன் தேவை? ▼

Board மட்டும் இருந்தால் அது நமது application logic-ஐ தானாக அறியாது. அதற்கு instructions/program கொடுக்க வேண்டும்.

Board-க்கு: “Temperature 30°C-க்கு மேல் சென்றால் fan ON செய்.” என்று program செய்ய வேண்டும்.

Conclusion:
Hardware + Software
↓
Useful Application

🛠️ 42. Program Development Flow ▼

NIE Teacher’s Guide இந்த process-ஐ flowchart-ல் ஆரம்பித்து, source code உருவாக்கி, compile செய்து, microcontroller-க்கு program செய்வதாக வழிகாட்டுகிறது.

முழு Flow

Problem ↓ Understand Requirements ↓ Algorithm ↓ Flowchart ↓ Source Code ↓ Compile ↓ Upload / Program Board ↓ Test ↓ Observe Output ↓ Debug / Improve

Exam Keywords:
Problem → Algorithm → Flowchart → Source Code → Compile → Upload → Test → Debug

Full Development Examples

💡 43. Example – Automatic Light முழு Development Process ▼

Problem

இருட்டாகும்போது LED ON ஆக வேண்டும்.

Input

LDR

Process

Arduino

Output

LED

Algorithm

Read LDR ↓ Compare with threshold ↓ Dark? ├── Yes → LED ON └── No → LED OFF

Implementation

LDR ↓ Analog Input ↓ Arduino ↓ Program ↓ Digital Output ↓ LED

🌡️ 44. Example – Automatic Fan முழு Development Process ▼

Requirement

Temperature > 30°C என்றால் fan ON.

Input

Temperature sensor

Processor

Microcontroller

Output

Fan through suitable driver/relay

Algorithm

Read temperature ↓ temperature > 30? / \ Yes No ↓ ↓ Fan ON Fan OFF

Fan/Motor-ஐ நேரடியாக microcontroller pin-க்கு இணைக்காமல் driver/relay பயன்படுத்துவது பாதுகாப்பான முறை.

🚨 45. Example – Smart Door ▼

Requirement

Door open ஆனவுடன் LED/Buzzer ON.

Input

Reed switch

Processing

Arduino

Output

LED / Buzzer

System Flow

Door ↓ Reed Switch ↓ Digital Input ↓ Arduino ↓ Decision ↓ LED/Buzzer

Exam Answer Structure:
Input: Reed switch
Processing: Microcontroller/Arduino
Decision: Check door open/close state
Output: LED or Buzzer

🏆 Final Exam Memory Map | Sections 26–45 ▼

Door Detection

Reed switch + Magnet → Digital Input → Arduino → LED/Buzzer

Sensor

Physical quantity → Electrical signal. Input device.

Actuator

Control signal → Physical action. Output device.

Analog

Continuous values. Example: Temperature, Light intensity.

Digital

Discrete states. Example: OPEN/CLOSED, HIGH/LOW.

Physical Computing

Software + hardware இணைந்து real world-ஐ control செய்தல்.

Development Flow

Problem → Algorithm → Code → Compile → Upload → Test → Debug

Core Concept

Input → Process → Output / Sensor → Controller → Actuator

SEO / AEO Keywords:
reed switch door detection, magnetic switch, Arduino door sensor, sensor and actuator, analog vs digital input, physical computing, embedded system building blocks, GCE A/L ICT IoT notes, Competency 11.1 IoT, Arduino development flow

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Java Programming Notes - Class 2: Control Flow, Methods & OOP CSC102S3 Course Title: Computer Programming I Online Class English and Tamil Medium

☕ Java Programming – Class 2 Notes

Control Flow • Methods • OOP Fundamentals • Problem Solving Exercises

Selection (if/switch) Loops (for/while) Methods Classes & Objects Mini Project

🔀 Part A – Selection Statements (Making Decisions) ▼

Normally Java runs statements top-to-bottom (sequence). Selection statements change that order by checking a boolean condition (true/false).

A.1 The if Statement

Runs a block only when the condition is true.

int age = 20; if (age >= 18) { System.out.println("You are eligible to vote."); } System.out.println("Program finished.");

⚠️ Common Mistakes:
• if (x = 5) is an error. Use == to compare.
• Never put a semicolon after the condition: if (age >= 18); creates an empty body.

A.2 The if...else Statement

Chooses between two paths. Exactly one block always executes.

if (n % 2 == 0) { System.out.println(n + " is Even"); } else { System.out.println(n + " is Odd"); }

A.3 The else if Ladder

For more than two possibilities. Java checks top-to-bottom and runs the first true branch.

if (marks >= 75) System.out.println("A"); else if (marks >= 65) System.out.println("B"); else if (marks >= 55) System.out.println("C"); else System.out.println("Fail");

💡 Order matters! Always test the most restrictive condition first. If you wrote marks >= 55 first, a student with 90 marks would incorrectly get "C".

A.4 Nested if

An if inside another if. Used when a second decision depends on the first.

if (age >= 18) { if (hasTestPassed) { System.out.println("Licence issued."); } else { System.out.println("Please pass the driving test first."); } } else { System.out.println("You are too young to apply."); }

A.5 The switch Statement

Cleaner than else if when comparing one variable against exact constant values.

switch (day) { case 1: System.out.println("Monday"); break; case 2: System.out.println("Tuesday"); break; case 3: System.out.println("Wednesday"); break; default: System.out.println("Invalid day"); }

⚠️ Without break, execution "falls through" into the next case. Fall-through can be used intentionally to group cases (e.g., case 6 and case 7 both printing "Weekend").

💡 Ternary Operator (one-line if/else):
String result = (marks >= 40) ? "Pass" : "Fail";

🔁 Part B – Repetition (Loops) ▼

Every loop needs three things: (1) Initialisation, (2) Condition, and (3) Update. Forgetting the update causes an infinite loop.

Loop Comparison

Loop	Condition Checked	Min Runs	Best Used When
for	Before each iteration	0	Number of repetitions is known
while	Before each iteration	0	Repeat until something happens
do...while	After each iteration	1	Must run at least once (menus, validation)

B.1 The for Loop

// Print 1 to 10 for (int i = 1; i <= 10; i++) { System.out.println(i); } // Count down for (int i = 10; i >= 1; i--) { ... } // Step by 2 (even numbers) for (int i = 2; i <= 20; i += 2) { ... }

B.2 The while Loop

int i = 1; while (i <= 5) { System.out.println(i); i++; // Don't forget this! }

B.3 The do...while Loop

do { System.out.print("Enter a positive number: "); number = input.nextInt(); } while (number <= 0); // Note the semicolon!

B.4 Nested Loops

A loop inside another loop. The inner loop completes fully for each outer iteration.

// Triangle pattern for (int i = 1; i <= 5; i++) { for (int j = 1; j <= i; j++) { System.out.print("*"); } System.out.println(); } // Output: * ** *** **** *****

B.5 break vs continue

break

Immediately terminates the entire loop. Control goes to the statement after the loop.

continue

Skips the rest of the current iteration and jumps to the next one. The loop itself continues.

⚠️ Common Loop Mistakes:
• Infinite loop: forgetting i++
• Off-by-one: using < instead of <=
• Semicolon after header: for(...); creates an empty body

✏️ Problem-Solving Exercises (1–10) ▼

Combine selection and repetition. Add import java.util.Scanner; and create Scanner input = new Scanner(System.in); where needed.

Ex 1–3: Numbers, Even, Odd

// Ex 1: Print 1-100 for (int i = 1; i <= 100; i++) System.out.print(i + " "); // Ex 2: Even numbers (efficient - step by 2) for (int i = 2; i <= 100; i += 2) System.out.print(i + " "); // Ex 3: Odd numbers for (int i = 1; i <= 100; i += 2) System.out.print(i + " ");

Ex 4: Multiplication Table

int n = input.nextInt(); for (int i = 1; i <= 10; i++) { System.out.println(n + " x " + i + " = " + (n * i)); }

Ex 5: Sum of Numbers (Accumulator)

int sum = 0; for (int i = 1; i <= n; i++) sum += i; System.out.println("Sum = " + sum);

Ex 6: Factorial

long fact = 1; // Use long! int overflows after 12! for (int i = 2; i <= n; i++) fact *= i; System.out.println(n + "! = " + fact);

Ex 7: Largest of 3 Numbers

int largest = a; // Assume a is largest if (b > largest) largest = b; if (c > largest) largest = c; System.out.println("Largest = " + largest);

Ex 8: Prime Number Check

boolean isPrime = true; if (n <= 1) isPrime = false; else { for (int i = 2; i * i <= n; i++) { if (n % i == 0) { isPrime = false; break; } } }

Ex 9: Reverse a Number

int rev = 0; while (n > 0) { int digit = n % 10; // Get last digit rev = rev * 10 + digit; // Build reversed n = n / 10; // Drop last digit }

Ex 10: Palindrome Check

int original = n; // Keep a copy! // ... reverse logic from Ex 9 ... if (original == rev) System.out.println("Palindrome"); else System.out.println("NOT a Palindrome");

⚙️ Part C – Methods (Reusable Code Blocks) ▼

Methods let you reuse code, break problems into parts, and make programs easier to read and test.

Method Anatomy

public static int add(int a, int b) { return a + b; }

Part	Example	Meaning
Access modifier	public	Who can call it
static	static	Belongs to class (callable from main)
Return type	int	Type of value returned (void = nothing)
Name	add	camelCase verb
Parameters	int a, int b	Inputs (type + name)
Body	{ return a+b; }	The code that runs

Key Concepts

Parameters vs Arguments

Parameters are in the definition. Arguments are actual values passed in the call.

Pass by Value

Java passes a copy. Changing a parameter inside a method does NOT change the original variable.

void Methods

Return nothing. Just perform an action. Cannot be assigned to a variable.

Local Variables

Declared inside a method. Exist only during that method's execution. Not visible outside.

Overloading

Same name, different parameters. Java picks the right one based on arguments.

Calling Methods

Methods can call other methods. E.g., sumOfSquares() calls square() twice.

⚠️ A non-void method MUST return a value on every path. Missing return = compile error.

🏗️ Part D – OOP Fundamentals (Classes & Objects) ▼

OOP organises programs around objects that combine data (fields) and behaviour (methods).

💡 Analogy: A class is like an architect's blueprint. An object is an actual house built from that blueprint. One blueprint → many houses.

D.1 Class Definition

class Student { String name; // Field (instance variable) int age; // Field }

D.2 Creating Objects

Student s1 = new Student(); s1.name = "Kamal"; s1.age = 20; Student s2 = new Student(); // Independent object s2.name = "Nimali";

D.3 Constructors

Special method that runs automatically when new is used. Same name as class, no return type.

Student(String name, int age) { this.name = name; // 'this' refers to the field this.age = age; // Without 'this', parameter assigns to itself! }

⚠️ name = name; assigns the parameter to itself (field stays null). Always use this.name = name;

D.4 Instance vs Static Variables

Instance Variable	Static (Class) Variable
Declared without static	Declared with static
Separate copy per object	ONE copy shared by all objects
Accessed via object: s1.name	Accessed via class: Student.count
For object data (name, age)	For shared data (counters, constants)

D.5 State & Behaviour

State (Fields)

The data stored: name="Kamal", age=20

Behaviour (Methods)

What it can do: display(), isAdult(), birthday()

Calling a method can change the object's state: s1.birthday() increases age.

🎓 Mini Project – Student Management v1 ▼

A complete example combining classes, constructors, methods, and static variables.

Student.java

public class Student { String name; int age; double marks; static int count = 0; // Shared counter Student(String name, int age, double marks) { this.name = name; this.age = age; this.marks = marks; count++; } String getGrade() { if (marks >= 75) return "A"; else if (marks >= 65) return "B"; else if (marks >= 55) return "C"; else return "Fail"; } void display() { System.out.println("Name : " + name); System.out.println("Age : " + age); System.out.println("Marks: " + marks); System.out.println("Grade: " + getGrade()); System.out.println("-------------------"); } }

Main.java

public class Main { public static void main(String[] args) { Student s1 = new Student("Kamal", 20, 78.5); Student s2 = new Student("Nimali", 19, 66); Student s3 = new Student("Sunil", 21, 48); s1.display(); s2.display(); s3.display(); System.out.println("Total students: " + Student.count); } }

Expected Output

Name : Kamal Age : 20 Marks: 78.5 Grade: A ------------------- Name : Nimali Age : 19 Marks: 66.0 Grade: B ------------------- Name : Sunil Age : 21 Marks: 48.0 Grade: Fail ------------------- Total students: 3

💡 Extension Ideas: Add isAdult(), birthday(), isPass() methods. Add keyboard input with Scanner + loop. Add a second constructor.

📋 Quick Revision Summary & Practice Questions ▼

Key Takeaways

• if, else if, switch make decisions. switch needs break.
• for = known count. while = unknown (may run 0×). do...while = at least once.
• break exits loop. continue skips to next iteration.
• Method = return type + name + parameters + body. void returns nothing.
• Class = blueprint. Object = instance created with new.
• this = current object. Instance vars = per object. Static vars = shared.

Practice Questions

1. Read marks and print grade using if...else if AND using switch(marks/10).
2. Print pattern with nested loops: row 1=1, row 2=1 2, row 3=1 2 3, up to row 5.
3. What is the difference between while and do...while? Give a case where do...while is better.
4. Write static double average(int a, int b, int c) and call it from main.
5. Output of: for(int i=1; i<=5; i++){ if(i==3) continue; System.out.print(i); }?
6. Create class Book with title, price, constructor, and display(). Create 3 books.
7. Explain instance vs static variable with an example.
8. Why does name = name; in a constructor fail? How do you fix it?

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