Grade 9: Hardware

​Chapter 3: Hardware

​Important!

Your book should always be open in front of you.

Multiple Choice

What do you think a microphone (mic) is?

• Input device

• Output device

Multiple Choice

What is the difference between input and output devices?

• Input devices send data to the computer; output devices receive data from the computer.
• Input devices receive data from the computer; output devices send data to the computer.

Barcode scanner - pg 88

A barcode is a series of dark and light parallel lines of varying thickness used to represent numbers and data.

📘 Key Points:

• Each digit (0–9) is represented by a unique pattern of lines.

• Guard bars separate the left and right sides of the barcode.

• Barcodes are used to identify products using a unique number.

Multiple Choice

What do you think a barcode scannner is?

• Input device

• Output device

Multiple Choice

Which of the following best describes a barcode?

• A symbol used to store text messages

• A series of lines representing numbers and data

• A sequence of numbers printed under a product

• A picture that links to a website

​How a Barcode is Read

🧠 Barcode Scanning Process:

1. A red laser or LED light scans across the barcode.

2. Light reflects back — dark bars reflect less light.

3. Photoelectric sensors detect the pattern of reflection.

4. The pattern is converted into digital data (0s and 1s).

5. The data is matched with a product record in a database.

💡 Example:
The pattern 0111101 might represent the digit 3.

Multiple Choice

Which component detects the reflected light from the barcode?

• Microprocessor

• Laser diode

• Photoelectric sensor

Barcode in Action (Supermarket Checkout)

Multiple Choice

What happens after a barcode is successfully scanned at the checkout?

• The database creates a new product entry

• The barcode number is matched in the stock database

How the System Updates Stock

🧮 Stock Control Process

1. Barcode number is used as a key field in the database.

2. Stock item record is found → price & details retrieved.

3. Stock quantity decreases by 1.

4. If stock ≤ re-order level → automatic re-ordering.

5. A flag is added to prevent multiple re-orders.

🧠 Example:
If “Milk – Stock: 10, Reorder level: 5”
→ After 6 sales → system orders more milk automatically.

Multiple Choice

In a stock control system, the barcode number acts as:

• Serial number

• The barcode number is matched in the stock database

Advantages of Using Barcodes

✅ For Management

• Fast and easy price updates

• Automatic stock control

• Reduced labeling time

• Track customer buying habits

✅ For Customers

• Faster checkout queues

• Fewer pricing errors

• Itemized bill

• Fresher stock due to better tracking

Multiple Choice

Which of the following is an advantage for management using barcodes?

• Slower checkout process

• More labeling required

• Easier stock updates

What is a QR Code?

A Quick Response (QR) Code is a two-dimensional barcode made up of dark and light squares arranged in a grid.

📘 Key Facts:

• Can store up to 4296 characters.

• Contains web addresses, phone numbers, or text.

• Read using a smartphone or tablet camera.

🖼️ Example:
A QR code that links to your school’s website or a fun educational page.

Multiple Choice

Which device is typically used to read a QR code?

• Barcode laser scanner

• Smartphone camera

• Credit card reader

• Printer

How QR Codes Work

🔍 Process:

1. Point the camera at the QR code.

2. The app scans and converts the pattern into data.

3. The browser opens the link automatically.

💡 Common Uses:

• Advertising (links to websites)

• E-tickets or boarding passes

• Contact information

Barcodes vs QR codes

Read the advantages of QR codes

​What is a Digital Camera?

A digital camera captures and stores images electronically — unlike traditional film cameras which needed developing.

📷 Key Features:

• No film is used.

• Images are stored digitally.

• Can delete, edit, and share photos instantly.

• Connects to computers via USB or Bluetooth.

💡 Example:
Phone cameras, DSLR cameras, and webcams all work as digital input devices.

Multiple Choice

Which is an advantage of QR codes over traditional barcodes?

• Smaller storage capacity

• Requires special scanners

• Can hold more information

• Cannot store web links

Disadvantages and New Developments

⚠️ Disadvantages of QR Codes:

• Multiple QR formats exist.

• Can be used to spread malicious code (attagging).

• Some software for custom QR designs is not free.

🆕 Newer Development:

• Frame QR codes allow adding logos or images inside.
  (Useful for advertisements and branding.)

Multiple Choice

What is one potential risk of scanning a QR code from an unknown source?

• It won’t scan properly

• It may download malicious software

• It deletes stored photos

• It reduces phone brightness

Summary

✅ Barcodes represent numbers using lines of different thickness.
✅ Scanners use light reflection to read them.
✅ QR codes use grids of squares to store more data.
✅ QR codes are easier to read, hold more info, and can link to websites.
✅ Both help automate sales, stock control, and data sharing.

Multiple Choice

Which statement correctly describes a digital camera?

• Requires developing before viewing photos

• Captures and stores images in digital form

• Cannot connect to a computer

• Uses film to store photos

​Inside the Camera – The Role of Pixels

A digital camera captures and stores images electronically — unlike traditional film cameras which needed developing.

📷 Key Features:

• No film is used.

• Images are stored digitally.

• Can delete, edit, and share photos instantly.

• Connects to computers via USB or Bluetooth.

💡 Example:
Phone cameras, DSLR cameras, and webcams all work as digital input devices.

Multiple Choice

What language does a computer understand?

• Natural languages like English or Urdu

• High-level programming languages like python

• Machine language (binary code)

Videos

https://www.youtube.com/watch?v=Ey6S3rKH_o4
How Digital Cameras Work | How Things Work with Kamri Noel

https://www.youtube.com/watch?v=BNA97LaWLF0
Simple explanation of how a camera works

https://www.youtube.com/watch?v=nyKJ4KxKFso
Shutter Speed

Multiple Choice

What is the role of the ADC (Analog-to-Digital Converter) in a digital camera?

• Focuses the image

• Converts electrical signals to digital form

How does a Digital Camera work?

How Digital Cameras Work:

Step 1: Light enters the camera

How Digital Cameras Work:

Step 2: The light hits a sensor (CCD)

​“Think of the CCD as millions of tiny buckets catching water.

Each bucket collects a different amount of water depending on where it dropped most."


These millions of buckets = pixels.
Water= light

How Digital Cameras Work:

Step 3: The CCD creates an analogue signal

​Explain “analogue” like this:

“Analogue signals are smooth and continuous, like real life.

How Digital Cameras Work:

Step 4: The ADC converts analogue to digital

Analogue	Digital
Smooth and continuous	Steps and numbers
Like the real world	Like computer language

​“Computers cannot understand smooth signals. They only understand numbers (0s and 1s). So the ADC acts like a translator.”

Multiple Choice

Digital data means:

• The signal is converted into numbers

• The signal is smooth and natural

​ADC

​

Inside the Camera – The Role of Pixels

📊 Pixels (Picture Elements):

• Each pixel captures brightness and color.

• Brightness is stored as a binary value (e.g., 01110011).

• Color is stored using the RGB system (Red, Green, Blue).

• A typical camera uses 24-bit color (8 bits for each color).

🎨 Example:
An orange pixel might have values —
Red: 215, Green: 165, Blue: 60 → Binary: 11010111 10100101 00111100

Multiple Choice

Which of these describes an analogue signal?

• Only 0s and 1s

• Smooth and continuous

Multiple Choice

Why does a camera need an ADC?

• To focus the lens

• To convert electrical signals into digital data

• To store images on a memory card

Multiple Choice

What does the CCD do when light hits it?

• It changes light into electrical signals

• It displays the image

Multiple Choice

In a 24-bit color system, how many bits are used for each primary color?

• 4 bits

• 8 bits

• 16 bits

Factors Affecting Image Quality

🧮 Image Quality Depends On:

• Lens quality

• Sensor quality (CCD/CMOS)

• Number of pixels (higher resolution = clearer image)

• Lighting conditions

• File format used (JPEG, RAW, etc.)

💡 Example:

A 12-megapixel image = 12 million pixels.
More pixels = larger file size, but better detail.

Multiple Choice

Which factor does not directly affect image quality in a digital camera?

• Number of pixels

• Lens quality

• Lighting conditions

• Printer ink color

: Activity – Analyze Camera Specs

📱 Activity:
Ask students to:

1. Check the megapixels of their phone camera.

2. Compare with a friend’s device.

3. Discuss: “Does higher megapixel always mean better pictures?”

What is a Keyboard?

A keyboard is the most common text input device for computers and mobile devices.

⌨️ Key Facts:

• Can be connected via USB or wirelessly.

• Tablets and phones use virtual keyboards.

• Each key has an ASCII value (e.g., A = 65).

• Pressing a key completes a circuit that sends data to the CPU.

Multiple Choice

What happens when a key is pressed on a keyboard?

• The computer lights up the key

• The CPU checks the key’s ASCII value

• The key generates a sound signal

• The key changes color

How a Keyboard Works

⚙️ Process:

1. Each key rests on a membrane or circuit board.

2. Pressing a key (e.g., ‘H’) completes an electrical circuit.

3. The computer detects the key press.

4. The key’s ASCII code is sent to the CPU.

5. The CPU converts this into a character on the screen.

Inside a Keyboard

Video

Multiple Choice

Which of the following is true about keyboard operation?

• Each key press sends a sound wave

• Keys communicate through Wi-Fi

• A circuit is completed when a key is pressed

What is ASCII?

Full Form:
American Standard Code for Information Interchange

Simple Definition:
ASCII is a code that computers use to represent text (letters, numbers, and symbols).

Since computers only understand binary (0s and 1s), every letter or symbol you type on a keyboard is stored and processed as a binary number inside the computer.

Multiple Choice

What does ASCII stand for?

• American Symbol Code for Internet Information

• American Standard Code for Information Interchange

What is ASCII?

real-life comparison:

“Imagine you are sending a secret message using numbers instead of letters — for example, A = 1, B = 2, C = 3.



Computers do the same thing! But instead of simple numbers, they use special codes called ASCII.

What is ASCII?

So when you type “Hi”,

the computer actually stores it as:

H = 72 → 01001000
i = 105 → 01101001

Multiple Choice

Why is ASCII used in computers?

• To store pictures

• To convert text into binary codes so the computer can understand

• To connect the computer to the internet

Keyboard Types & Ergonomics

⌨️ Types:

• Standard Keyboard: Regular layout.

• Ergonomic Keyboard: Designed for comfort and reduced wrist strain.

⚠️ Risk:
Frequent use can cause RSI (Repetitive Strain Injury).

​Standard Keyboard: Regular layout.

​Ergonomic Keyboard: Designed for comfort and reduced wrist strain.

​Ergonomic Keyboard: Designed for comfort and reduced wrist strain.

Multiple Choice

What is the main purpose of using an ergonomic keyboard?

• To increase the speed of typing without any health benefits.
• To enhance the aesthetic appeal of the workspace.
• The main purpose of using an ergonomic keyboard is to improve comfort and reduce the risk of injury while typing.

⚠️ Risk:
Frequent use can cause RSI (Repetitive Strain Injury).

✅ Solution:

• Use ergonomic keyboards.

• Take breaks while typing.

• Maintain proper posture.

What is a Microphone?

🎙️ A microphone converts sound waves into electrical signals which are then converted into digital data.

📘 Used For:

• Recording sound/music

• Voice commands (e.g., Siri, Google Assistant)

• Online communication (Zoom, calls, etc.)

🔌 Connection Types:

• USB

• Bluetooth

• Built-in laptop/phone microphones

Multiple Choice

What is the function of a microphone in a computer system?

• Converts sound waves into electrical signals

• Converts light into sound

• Converts images into sound

How a Microphone Works

🎧 Process:

1. Sound waves hit the diaphragm.

2. The diaphragm vibrates a coil of wire near a magnet.

3. This produces an electric current.

4. The current is sent to an ADC → converted into digital sound.

🧠 Example:
When you say “Hello,” the microphone converts it into digital data (0s and 1s) for recording or transmission.

Multiple Choice

What part of the microphone vibrates when sound waves hit it?

• ADC converter

• Diaphragm

Summary

✅ Digital Cameras use sensors (CCD) and ADCs to capture and digitize images.
✅ Keyboards input text via electrical circuits and ASCII codes.
✅ Microphones convert sound waves into digital signals.
✅ All three are input devices that help computers receive data from the real world.

Optical Mouse – Introduction

An optical mouse is a pointing device that uses light (not a ball) to detect movement.
It works by taking 1500+ tiny pictures per second of the surface below it!

Main Components:

• Red light source (LED)

• Lens

• CMOS sensor

• DSP (Digital Signal Processor)

How an Optical Mouse Works

• Red LED shines light onto the surface.

• The light bounces back and is captured by the CMOS sensor (a tiny camera).

• The CMOS sensor converts reflected light into electrical pulses.

• These pulses go to a DSP (processor) that compares images to find movement.

• The DSP sends the movement coordinates to the computer, which moves the cursor.

Multiple Choice

What is the main role of the CMOS sensor in an optical mouse?

• To store light data

• To reflect the red light

• To detect and convert light into electrical signals

Advantages of Optical Mouse

✅ No moving parts → More reliable
✅ Dirt doesn’t get trapped
✅ Works on most surfaces
✅ Bluetooth models offer wireless convenience

⚠️ Wired mouse advantages:

• No battery needed

• No signal loss

• Cheaper and environmentally friendly

Multiple Choice

Why is an optical mouse more reliable than a mechanical mouse?

• It uses batteries

• It uses moving parts

• It uses a ball

• It has no moving parts

2D Scanners – Introduction

A 2D scanner is used to convert paper documents or photos into digital images.

How it works:

1. The document is placed on a glass panel.

2. A bright light (xenon lamp or LED) moves under it.

3. The scan head and mirrors send light to a lens.

4. The lens focuses the image onto a CCD (Charge-Coupled Device).

5. The CCD converts light into an electric current (analog signal).

6. Software converts this into a digital image (JPEG, PNG, etc.)

“It’s like taking a photo of your paper, but perfectly flat and clear.”

Multiple Choice

What device inside a scanner converts light into an electric signal?

• Lens

• Light source

• CCD sensor

• DSP processor

OCR – Optical Character Recognition

OCR software reads text from a scanned document and converts it into an editable file.

🧠 Example:
If you scan a printed essay → OCR allows you to open it in Word and edit the text.

Multiple Choice

Which technology converts scanned text into editable form?

• OCR

• CCD

• CMOS

3D Scanners

3D scanners capture solid objects to make 3D digital models.

How it works:

• Scans along x, y, z coordinates.

• Uses laser light, white light, or magnetic resonance.

• Produces a 3D digital image that can be used in CAD design or 3D printing.

Multiple Choice

Which of the following best describes a 3D scanner?

• Captures paper documents only

• Captures solid objects in three dimensions

• Captures sound waves

Introduction to Scanners

What is a Scanner?

A scanner is an input device that reads images, objects, or text and converts them into a digital format that a computer can store, display, or edit.

Types of Scanners

• 2D Scanners (Flatbed, passport scanners)

• 3D Scanners (capture solid objects)

Multiple Choice

Which scanner can capture depth (x, y, and z)?

• 2D scanner

• Barcode scanner

• OCR machine

• 3D scanner

Multiple Choice

3D scanners create digital models that can be used in:

• Databases

• CAD software

• Antivirus programs

• Word processors

Introduction to Scanners

What is a Scanner?

A scanner is an input device that reads images, objects, or text and converts them into a digital format that a computer can store, display, or edit.

Types of Scanners

• 2D Scanners (Flatbed, passport scanners)

• 3D Scanners (capture solid objects)

Application: CT (Computed Tomography) Scanning

What Are CT Scanners?

CT scanners create a 3D image of a solid object by taking multiple thin, 2D “slices”.

Process (Tomography)

1. Object/person is scanned by X-rays / gamma rays / radio waves.

2. Many thin slices are captured one by one.

3. Each slice is stored as a digital image.

4. Computer combines slices to form a 3D image.

CT VS MRI VS SPECT

CT scans show detailed 3D images of bone and organs using X-rays, MRI scans provide high-resolution images of soft tissues using magnets and radio waves, and SPECT scans show how organs and tissues are functioning by detecting a radioactive tracer. Choosing the right scan depends on whether you need a structural view (CT or MRI) or a functional view (SPECT). 

Multiple Choice

A CT scanner forms a 3D image by:

• Printing the object directly

• Combining many thin 2D images

• Using a barcode reader

• Taking only one high-resolution photo

Application: 2D Scanners at Airports

How Passport Scanners Work

Airports use 2D scanners + OCR software to read passport information.

Process

1. Scanner takes a digital image of the passport page.

2. OCR (Optical Character Recognition) identifies letters and numbers.

3. Software extracts:

   • Name

   • Passport number

   • Date of birth

   • Nationality

4. Image can be stored as ASCII text or JPEG.

Multiple Choice

What technology helps scanners convert passport text into editable characters?

• CT

• CAD

• OCR

• OMR

Facial Recognition at Airports

How Face Recognition Works

The system compares:

• The passport photo (scanned)

• The live camera image of the passenger

It Measures Key Facial Points

• Distance between eyes

• Width of nose

• Shape of cheekbones

• Length of jawline

• Shape of eyebrows

These measurements form a faceprint.

If both faceprints match → Identity confirmed.

Multiple Choice

Facial recognition identifies a person mainly by:

• Key measurements of facial features
  

• Eye colour only

Touch Screens Overview

Three Types of Touch Screens

1. Capacitive

2. Infrared

3. Resistive

These screens allow users to select items, scroll, type, or zoom.


"Who thinks their phone uses capacitive? Why?"

​Capacitive Touch Screens

How They Work

• Screen has:

  • A protective glass layer

  • A conductive layer

  • A glass substrate

• Human finger changes the electrical field.

• Microcontroller calculates touch coordinates.

Types

• Surface capacitive (only bare fingers/stylus)

• Projected capacitive (multi-touch, gloves, stylus)

Multiple Choice

Which type of capacitive screen supports multi-touch?

• Surface

• Projective

• Resistive

• Infrared

Infrared Touch Screens

How They Work

• Screen surrounded by infrared LED transmitters and sensors.

• Beams form an invisible grid.

• When finger breaks a beam → Sensors detect touch.

---

Advantages

✔ Works even with gloves
✔ Very durable
✔ Good for large screens (kiosks)

Disadvantages

✘ Sensitive to moisture
✘ Can be triggered accidentally
✘ Affected by strong light

Multiple Choice

Infrared touch screens detect touch when:

• Pressure is applied

• Electrical field changes

• Infrared beams are interrupted

Resistive Touch Screens

How They Work

• Two layers:

  • Flexible plastic (top)

  • Glass (bottom)

• Both coated with resistive material.

• Touch brings layers into contact → Completes circuit.

• Voltage change → Microcontroller detects position.

Resistive Touch Screens

Advantages

✔ Works with stylus, finger, gloves
✔ Good for harsh environments
✔ Resistant to dust and moisture

Disadvantages

✘ Low sensitivity
✘ Must press harder
✘ Poor sunlight visibility
✘ Can scratch easily

Multiple Choice

Resistive touch screens work when:

• Light beams are blocked

• Two layers come into contact

Output Devices – Introduction

Output devices allow a computer to send information to the user or control machinery.

Examples:

• Screens

• Printers

• Projectors

• Actuators

Why Are They Important?

They show results, display images/videos, and operate machines (e.g., opening a valve).

Multiple Choice

Output devices are used to:

• Enter data into a computer

• Store data permanently

• Show results or control hardware

• Delete data

Conveyor Belt

Valve

Actuators

What is an Actuator?

A device that converts an electrical signal into movement.

Examples:

• Solenoid (linear movement)

• Motor (rotational movement)

• Relay (electrical switch)

Actuators

How a Solenoid Works

• Electricity flows into a coil

• Coil produces a magnetic field

• A metal rod (plunger) inside the coil moves

• This movement can open/close a valve or switch

3 devices at home that have actuators (e.g., automatic water taps, printers, car doors).

Multiple Choice

A solenoid converts electricity into:

• Sound

• Heat

• Linear motion

• Internet signals

Light Projectors – Introduction

Types of Projectors

1. DLP (Digital Light Projector)

2. LCD (Liquid Crystal Display) Projector

Use of Projectors

• Classrooms

• Presentations

• Multimedia displays

• Large events

LCD Projector – How It Works

LCD Projector (Older Technology)

How It Works

1. A strong white light is generated

2. Dichroic mirrors split light into Red, Green, Blue (RGB)

3. Each colour passes through its own LCD panel

4. LCD panels block or allow light through each pixel

5. Three coloured images (R/G/B) merge using a prism

6. Final colour image goes through lens → screen

What is a dichroic mirror?

A dichroic mirror is a type of dichroic filter that reflects certain wavelengths of light while allowing others to pass through

Multiple Choice

Q5. LCD projectors split white light into colours using:

• Motors

• Dichroic mirrors

• Solenoids

DLP Projector – How It Works

Digital Light Projector (DLP)

Uses a DMD chip containing millions of tiny mirrors.

How It Works

• Each micro-mirror = 1 pixel

• Mirrors tilt ON or OFF to reflect or block light

• Creates light or dark pixels

• Switch thousands of times per second for grey shades

• A bright light passes through a colour filter → RGB colours

• Can produce over 16 million colours

LCD Projector – How It Works

LCD Projector (Older Technology)

How It Works

1. A strong white light is generated

2. Dichroic mirrors split light into Red, Green, Blue (RGB)

3. Each colour passes through its own LCD panel

4. LCD panels block or allow light through each pixel

5. Three coloured images (R/G/B) merge using a prism

6. Final colour image goes through lens → screen

Multiple Choice

In a DLP projector, each pixel is controlled by:

• A crystal

• A liquid crystal cell

• A tiny mirror

INKJET PRINTERS

Main Components

• Print head: Contains tiny nozzles that spray ink droplets.

• Ink cartridges: Usually one black + CMY (cyan, magenta, yellow), sometimes six colours.

• Stepper motor & belt: Moves the print head side to side.

• Paper feed: Feeds paper automatically.

​

​

How Ink Droplets Are Produced

Thermal Bubble Technology

• Tiny resistors heat ink → ink vaporises → bubble forms.

• Bubble expands → ink is pushed out.

• Bubble collapses → vacuum pulls in new ink.

  https://www.youtube.com/watch?v=JEVurb1uVFA

  Piezoelectric Technology

  • Crystal behind the ink vibrates when electricity is applied.

  • Vibration forces ink out of the nozzle.

  • Ink is refilled automatically.

  • https://www.youtube.com/watch?v=TSGfitxlkzI

Steps in Inkjet Printing

Document data sent to printer driver.

1. Driver converts data into a format the printer can read.

2. Driver checks printer status (offline/ink/paper).

3. Data stored in printer buffer.

4. Paper is fed in; sensors check paper availability.

5. Print head moves side to side, spraying exact ink dots.

6. Paper moves slightly after each pass.

7. Repeats until buffer is empty.

8. Printer requests more data from computer until printing is complete.

Inkjet Printing

Applications of Inkjet Printers

✔ Photo printing
✔ Small-volume colour printing
✔ Home use
✘ Not suitable for large-volume printing

LASER PRINTERS

Laser printers use dry toner powder and static electricity.

Key Points

• Prints whole page at once (not line-by-line).

• Uses cyan, magenta, yellow, black (CMYK) toner.

• Fast, high-quality, economical for bulk printing.

Steps in Laser Printing

1. Document sent to printer driver.

2. Driver converts data to printer language.

3. Driver checks printer status.

4. Data stored in buffer.

5. Drum receives a positive charge.

6. Laser removes charge in areas where printing is needed → forms the image.

7. Drum gets coated with positively charged toner, which sticks to negatively charged image areas.

8. Negatively charged paper rolls over drum → toner transfers to paper.

9. Paper’s charge is neutralised.

10. Fuser unit (heated rollers) melts toner onto paper permanently.

11. Drum is cleaned and neutralised for next job

Applications of Laser Printers

✔ Large volume printing
✔ Offices, schools, businesses
✔ Fast printing with consistent quality
✘ More expensive than inkjet

3D printers produce solid, 3D objects by building them layer-by-layer using additive manufacturing.

Types of Materials Used

• Powdered metal

• Powders + binder

• Resin

• Plastics (PLA, ABS)

• Ceramics

• Paper layers

3D PRINTERS

How 3D Printing Works

1. Create design using CAD software.

2. Export design to 3D printer software.

3. Printer setup.

4. Object printed layer by layer (often 0.1 mm thick).

5. Finished object is cleaned, washed, or cured.

https://www.youtube.com/watch?v=HlvK6DLwCz4

3D PRINTERS

Types of 3D Printing

1. Direct 3D Printing

   • Uses inkjet-like nozzles.

   • Moves left-right AND up-down.

2. Binder Printing

   • First pass spreads powder.

   • Second pass sprays binder (glue).

3. Laser/UV Printing

   • Lasers or UV harden liquid resin.

3D PRINTERS

Uses of 3D Printing

✔ Prosthetics
✔ Medical implants (e.g., skull reconstruction)
✔ Engineering parts
✔ Car & aircraft components
✔ Custom tools
✔ Architecture models
✔ Artistic sculptures & jewellery

What are Electronic Screens?

Electronic screens display images using thousands or millions of tiny picture elements called pixels.
Different screen technologies create light and colour in different ways.

Why We Study Them

• Used in TVs, laptops, phones, tablets, outdoor displays

• Helps choose the right display technology

• Part of modern hardware understanding

Examples

• TV displays

• Smartphones

• Large digital signboards

• Computer monitors

Introduction to LED, LCD, and OLED Screens

Multiple Choice

1. What is the basic unit of a digital screen?

• Cell
• Dot
• Frame
• Pixel

• An LED screen is made of tiny Light Emitting Diodes.

• Each LED acts as one pixel or part of a pixel.

• LEDs come in red, green, and blue (RGB).
  By changing the brightness of each colour, millions of colours can be produced.

Where LED Screens Are Used

• Large outdoor displays

• Stadium scoreboards

• Advertising billboards

• Stage event displays

Important Note

Many “LED TVs” are actually LCD screens with LED backlighting, not true LED screens.

What is an LED Screen?

Multiple Choice

Which colours do LED pixels use to create all other colours?

• Yellow, Cyan, Magenta
• Black, White, Gray
• Red, Green, Blue
• Orange, Purple, Brown

TRUE LED screen vs. LED-backlit LCD.

• LCD = Liquid Crystal Display

• Contains thousands of tiny liquid crystal pixels.

• Liquid crystals do not produce light. They change how light passes through them.

• They MUST be backlit from behind.

Backlighting Options

1. CCFL (Cold Cathode Fluorescent Lamps)

   • Older technology

   • Slight yellowish tint

   • Bulkier screens

2. LED Backlighting

   • Modern technology

   • Brighter, thinner, clearer

   • Uses a matrix of tiny blue-white LEDs

LCD Screens – How They Work

Multiple Choice

Why do LCD screens need a backlight?

• They are too bright

• They cannot produce their own light

• They use strong crystals

Why LEDs Are Better Than CCFL

• ✔ Instant maximum brightness (no warm-up time)
  ✔ Whiter light → sharper images
  ✔ More vivid colours
  ✔ Thinner screens
  ✔ Longer lifespan
  ✔ Lower power consumption
  ✔ Less heat released

  Examples

  • Slim LED TVs

  • LED-backlit computer monitors

  • Energy-efficient screens in tablets and laptops

Advantages of LED Backlighting

Multiple Choice

Which of the following is an advantage of LED backlighting?

• Uses more electricity

• Uses less power

What is OLED?

OLED = Organic Light Emitting Diodes

• Made using organic (carbon-based) materials.

• When electricity is applied → they produce their own light.

• No backlight needed → very thin screens.

Structure of an OLED Pixel

Layered as:

• Plastic/glass top

• Metallic cathode (–)

• Organic layers (emit and conduct)

• Glass/plastic bottom

• Anode (+)

OLED Technology – The Future

Multiple Choice

Why do OLED screens not need backlighting?

• They are too thick

• They create their own light

Advantages of OLED Technology

✔ Very thin, light, and flexible
✔ Can be made of plastic instead of glass
✔ Produces brighter light than LEDs
✔ Uses less power than LCD
✔ Very wide viewing angle (~170°)
✔ Can be folded, bent, or rolled

Examples

• Foldable phones

• Curved TVs

• Wearable screens

• Smart clothing

• Flexible tablets

Features of OLED Screens

Multiple Choice

Which is a unique feature of OLED screens?

• They can bend and fold

• They must stay flat

Multiple Choice

Which screen technology is the most flexible?

• OLED

• LED

• LCD

What Are Sensors?

Sensors are input devices that detect or measure physical properties from their surroundings.
These properties include:

• Temperature

• Pressure

• Light

• Sound

• Moisture

• Acidity (pH)

• Motion, etc.

Multiple Choice

What is a sensor?

• A device that stores data

• A device that measures physical properties

• A device that displays results

Examples Sensor:

For example:

• A thermometer’s mercury rises smoothly, not in jumps.

• A room’s temperature may be 25.11°C, 25.12°C, 25.13°C… infinite possibilities.

Computers cannot understand analogue signals, so these values must be converted into digital data first.

Examples

• A thermometer measures temperature.

• A microphone measures sound levels.

• A light sensor measures brightness in a room.

Analogue vs Digital Values

Analogue data:

• Changes smoothly and continuously.

• Has unlimited possible values.

• Examples: temperature, sound, pressure.

Digital data:

• Used by computers.

• Has fixed, discrete values (0s and 1s).

• Example: 10011001.

Because computers cannot process analogue values directly, we need an ADC (Analogue-to-Digital Converter).

Example

A temperature of 25.7°C is converted to a digital value like 10111001 before entering a microprocessor.

Multiple Choice

Why do we need an ADC?

• It stores the sensor

• It converts analogue signals into digital form

• It produces analogue data

DAC and Actuators

When computers need to control devices such as:

• Motors

• Valves

• Heaters

• Speakers

They must send analogue output values to these devices.

A DAC (Digital-to-Analogue Converter) converts digital signals from the computer into analogue signals.

An Actuator physically moves or controls something. Examples:

• Motor opens a door.

• Heater warms a room.

• Valve turns water flow on/off.

Multiple Choice

What is the purpose of a DAC?

• Convert analogue to digital

• Convert digital to analogue

Microprocessor

It is the brain of computer

How a microprocessor in a sensor works

• Sensors are often used in control systems with a microprocessor.

  Process:

  1. Sensor sends a continuous flow of analogue data.

  2. ADC converts it into digital form.

  3. Microprocessor checks if the reading is within acceptable range.

  4. If not, it sends a signal through DAC → Actuator to adjust something.

  5. New sensor reading is taken again.

  6. This repeated loop is called feedback

For example:

A greenhouse:

• Sensor detects temperature is too low.

• Computer turns on the heater.

• Sensor detects temperature rising.

• Heater turns off when temperature is ideal.

How a microprocessor in a sensor works

• Sensing: A sensor detects a physical property (e.g., light, temperature, pressure) and converts it into an electrical signal.

• Conversion: An analog-to-digital converter (ADC) converts the analog signal from the sensor into a digital format that the microprocessor can understand.

• Processing: The microprocessor receives the digital data and uses its stored program to analyze it. This can involve simple "if-then" logic or complex algorithms.

• Decision: Based on the processed data, the microprocessor determines what action to take. For example, it might compare the sensor reading to a pre-set value.

• Actuation: If an action is needed, the microprocessor sends a signal to an actuator, which is a device that performs the action (e.g., turns a motor on/off or activates a heater).

• Feedback loop: This process of sensing, processing, and actuating can repeat continuously to maintain a certain condition, such as keeping a water bowl full. 

Multiple Choice

What is feedback?

• A one-time measurement

• Repeating cycle where output affects the next input

Temperature Sensor

A temperature sensor measures the heat level in its surroundings.
Its signal changes as temperature increases or decreases.

Example Applications

• Central heating systems

• Chemical processes

• Greenhouse temperature control

Moisture Sensor
A moisture sensor measures water content, usually in soil.
It works by detecting electrical resistance—wetter soil conducts electricity more easily.

Example Applications

• Greenhouse irrigation

• Food processing factories

Humidity Sensor

Explanation

Humidity sensors measure water vapor in air, not water in soil.
Air’s electrical conductivity changes depending on moisture content.

Example Applications

• Building humidity monitoring

• Microchip manufacturing

• Greenhouses

Light Sensor

Explanation

Light sensors use photoelectric cells to detect brightness.
They produce electrical current based on light intensity.

Example Applications

• Street lights turning ON automatically

• Car headlights switching on in darkness

What is an IR Sensor?

An infrared sensor detects infrared radiation (invisible light).
It is mostly used to detect objects, motion, or distance.

How it Works

• The sensor sends out invisible IR rays.

• If these rays hit an object and come back, the sensor knows:
  “Something is in front of me.”

Common Uses

• TV remote controls

• Automatic doors in malls

• Parking systems to detect nearby cars

• Line-following robots in robotics classes

Infrared (Active) Sensor

Explanation

Active infrared sensors use an IR beam sent to a detector.
If the beam breaks → change is detected.

Example Applications

• Automatic car wipers

• Security alarms

Infrared (Passive) Sensor

Passive IR sensors detect heat radiation from objects, e.g., people.

Example Applications

• Intruder alarms

• Freezer temperature monitoringa

Multiple Choice

Active IR sensors vs Passive IR sensor

• Active IR sensors detects when The beam is broken; Passive IR sensors detect Body heat

• Active IR sensors are used for detection; Passive IR sensors are for emission.

Gas Sensor

A gas sensor detects the presence or amount of gases in the air.
It helps identify whether a gas is safe, dangerous, or too high/low for proper working conditions.

How it Works

A gas sensor has a special material inside it.
When certain gases touch this material, its electrical resistance changes.
The sensor measures this change and tells the system:

• “Gas level is safe”

• “There is a leak!”

• “Gas concentration is increasing.”

What is a Proximity Sensor?

A proximity sensor detects whether an object is close without touching it.

How it Works

Depending on the sensor type, it may use:

• Infrared waves

• Ultrasound

• Electromagnetic fields

When something comes close, the sensor notices the disturbance and activates a response.

Common Uses

• Phones turning off the screen when you hold it to your ear

• Automatic taps in public washrooms

• Parking sensors in cars

• Smart industrial machines

What is a Pressure Sensor?

A pressure sensor measures the force applied on its surface.

How it Works

Most pressure sensors have a diaphragm that bends when pressure is applied.
This bending changes electrical signals, which are used to calculate pressure.

Common Uses

• Measuring blood pressure

• Monitoring tire pressure in cars

• Weather stations (air pressure)

• Touch sensors in industrial machines

Real-Life Example

Cars show low tire pressure warnings using pressure sensors.

A sensor interface

A sensor interface is a bridge between a device and any attached sensor. The interface takes data collected by the sensor and outputs it to the attached device.