→ Light Projectors:

→ Types of Light Projectors:

1. Digital Light Projector (DLP)
2. Liquid Crystal Display (LCD) Projector

→ Digital Light Projector (DLP):

● Uses a Digital Micromirror Device (DMD) chip containing millions of tiny mirrors.
● Micro mirrors tilt towards light (ON) or away (OFF) to create an image.
● Can switch on/off thousands of times per second, producing 1024 grey shades (greyscale
image).
● White light passes through a colour filter (red, green, blue).
● DLP can produce 16 million colours.

→ Advantages:
Higher contrast ratios.
More reliable and durable.
Quieter than LCD projectors.
No alignment issues due to a single DMD chip.
Lighter and smaller than LCD projectors.
Works better in dusty or smoky environments.

→ Disadvantages:
Can create "shadow" effects in moving images.
No grey components in the image.
Colour definition and saturation lower than LCD projectors.

→ Liquid Crystal Display (LCD) Projector:

● Uses a high-intensity white light source.
● Light passes through dichroic mirrors to separate red, green, and blue components.
● Light components go through three LCD screens (one for each colour).
● Each LCD screen contains thousands of tiny pixels that either block or allow light.
● Produces three monochrome images, later combined to form a full-colour image.
● The final image is projected through a lens onto the screen.

→ Advantages:
- Sharper images than DLP projectors.
- Better colour saturation.
- More energy-efficient and generates less heat.
→ Disadvantages:
- Contrast ratio is lower than DLP.
- Limited lifespan, screens degrade over time (turn yellow).
- Colour saturation reduces with age.

→ Printers:
Inkjet Printers
● Components: Print head (nozzles), ink cartridges, stepper motor & belt, paper feed.
● Printing Technologies:
1. Thermal Bubble: Resistors heat ink → bubble forms & expands → ink ejected →
vacuum pulls new ink.
2. Piezoelectric: Crystal vibrates with electric charge → ink droplets ejected.
 ● Printing Process:
1. Data sent to printer driver.
2. Printer driver formats data.
3. Printer checks ink & availability.
4. Data stored in printer buffer.
5. Paper is fed into the printer.
6. Print head moves side to side, spraying ink.
7. Paper advances after each pass.
8. Process repeats if more pages remain.
9. When the buffer is empty, CPU requests more data.
● Applications: Good for photos, color printing, low-volume prints (e.g., home use).
Laser Printers
● Uses toner powder and static electricity for printing.
● Printing Process:
1. Data sent to printer driver.
2. Printer driver formats data.
3. Printer checks availability.
4. Data stored in buffer.
5. Drum given a positive charge → Laser beam removes charge in print areas.
6. Positively charged toner sticks to negatively charged drum areas.
7. Negatively charged paper rolled over the drum.
8. Toner transfers to paper.
9. Paper's charge is removed after one rotation.
10. Fuser (heated rollers) melts toner onto the paper.
11. Discharge lamp removes all charge from the drum.
● Applications: Fast, high-quality, large-volume printing (e.g., offices, poster printing).
3D Printers
● Builds solid objects layer by layer (Additive Manufacturing).
● Types:
○ Direct 3D Printing: Uses inkjet technology; print head moves in all directions.
○ Binder 3D Printing: Powder is sprayed, then glue is added to bind layers.
○ Newer Tech: Lasers & UV light harden liquid polymers.
● Printing Process:
○ Design created using CAD software.
○ Imported into special software for 3D printers.
○ Printer setup for printing.
○ Object built layer by layer (often 0.1mm thick).
○ Object removed & processed (e.g., washed, excess material removed, cured).
● Applications:
○ Medical: Prosthetics, reconstructive surgery.
○ Aerospace: Lightweight precision parts.
○ Fashion & Art: Creative designs.
○ Manufacturing: Replacing discontinued parts (e.g., vintage car parts).

→LED AND LCD SCREENS:

LED Screens
● Composed of tiny LEDs (red, green, or blue).
● Brightness controlled by varying electric current.
● Used in large outdoor displays due to brilliant colors.
● OLED (Organic LED) screens are an advancement (discussed later).
● Misleading Marketing: Many TVs labeled "LED" are actually LCD screens with LED
backlighting.
LCD Screens
 ● Made of liquid crystals forming an array of pixels.
● Require backlighting (do not produce light themselves).
● Backlit using LED or CCFL (older technology).
● CCFL vs. LED Backlighting:
○ LEDs light up instantly (no warm-up time).
○ LEDs provide whiter, brighter light with better color definition.
○ LED screens are thinner and more reliable than CCFL screens.
○ LEDs consume less power and generate less heat.
OLED (Organic Light Emitting Diodes)
● Use organic semiconductors to generate light.
● No backlighting needed (self-contained system).
● Enables ultra-thin, flexible, and foldable screens.
● Future applications:
○ Bendable phone screens, wearable OLED displays (e.g., smart clothing).
Advantages of OLED over LED & LCD
● Thinner, lighter, and more flexible than LED/LCD.
● Plastic layers instead of glass (more durable & lightweight).
● Brighter than LEDs and have wider viewing angles (170°).
● No backlighting required → Lower power consumption.
● Can be made into large, thin sheets (ideal for advertisements & TVs).
● Ideal for battery-operated devices (e.g., mobile phones) due to low power use.
→ LoudSpeakers:
How Digital Sound is Converted to Audio Output:
1. Digital to Analogue Conversion (DAC):
○ Digital sound (binary data) is converted into an electric current using a DAC.
2. Amplification:
○ The electric current is weak after conversion.
○ It is amplified to create a current strong enough to drive the loudspeaker.
3. Sound Production in Loudspeakers:
○ The amplified electric current is sent to the loudspeaker.
○ Working of the Loudspeaker:
■ A coil of wire is wrapped around an iron core, forming an electromagnet.
■ A permanent magnet is placed near the electromagnet.
■ Varying electric current in the coil changes the magnetic field of the iron
core.
■ The iron core moves towards the permanent magnet, causing vibrations.
■ The cone (attached to the iron core) vibrates, producing sound waves.
Key Points:
● DAC is essential to convert digital sound into an analogue signal.
● Amplifiers increase the weak electric signal from DAC.
● Loudspeakers use electromagnets to convert electric signals into sound waves.
SENSORS:
Definition & Nature of Sensors
● Sensors are input devices that measure physical properties from their surroundings.
● Examples include temperature, pressure, acidity level, and length.
● Real data is analogue, meaning it constantly changes and does not have a single discrete value.
Conversion of Data for Computers
● Computers cannot process analogue data, so it must be converted into digital format using an
Analogue-to-Digital Converter (ADC).
● When controlling devices like motors/valves, Digital-to-Analogue Converter (DAC) is used.
● Actuators are used in control applications to trigger mechanical movements.
Feedback Mechanism
● Sensor readings can influence control actions (e.g., adjusting a valve or motor).
 ● The output of the system affects the next sensor input, forming a feedback loop.
● Sensors continuously send data, but the microprocessor analyses and takes action when
necessary.
Monitoring vs. Control Systems
● Monitoring System: The microprocessor only watches the process and sends alerts if
parameters exceed the set range.
● Control System: The microprocessor takes action by adjusting devices (motors, valves, etc.) if
values go outside the acceptable range.

MONITORING SYSTEM:
1. Security Monitoring System
● System activated using a password on a keypad.
● Infrared sensor detects intruder movement.
● Acoustic sensor detects footsteps or breaking glass.
● Pressure sensor detects intruder's weight at doors/windows.
● ADC converts analogue sensor data to digital.
● Microprocessor samples data at set intervals (e.g., every 5 seconds).
● Comparison with stored values determines if values are within range.
● If values are outside range, microprocessor sends signals to:
○ Activate a siren (alarm sound).
○ Flash warning lights.
● If devices require analogue signals, a DAC is used.
● Alarm/lights continue until reset with password.
2. Patient Monitoring in Hospitals
● Multiple sensors attached to patient (e.g., temperature, heart rate, breathing rate).
● Sensors continuously send data to the computer.
● Microprocessor samples data at frequent intervals.
● Acceptable range of values is programmed into the system.
● Comparison of sensor data with stored values:
○ If values are out of range, alarm is triggered.
○ If values are within range, they are displayed as:
■ Graphical representation on a screen.
■ Digital readout for medical staff.
● Monitoring continues until sensors are removed.
CONTROL APPLICATIONS
1. Street Lighting Control
● Light sensor detects brightness and sends data to ADC.
● ADC converts analogue data to digital and sends it to the microprocessor.
● Microprocessor samples data every minute.
● If sensor reading < stored value, microprocessor:
○ Sends signal to switch on the lamp.
○ Keeps it on for 30 minutes before resampling (prevents flickering).
● If sensor reading ≥ stored value, microprocessor:
○ Sends signal to switch off the lamp.
○ Keeps it off for 30 minutes before resampling.

2. Anti-Lock Braking System (ABS)

● Magnetic field sensors monitor wheel rotation speed.
● Microprocessor checks all wheels' rotation speeds.
● If one wheel rotates too slowly (locking up):
○ Microprocessor reduces braking pressure on that wheel.
 ○ Wheel speed increases to match others.
● If one wheel rotates too quickly, braking pressure is increased.
● Microprocessor checks and adjusts braking pressure multiple times per second.
● Driver feels ‘judder’ on brake pedal due to rapid adjustments.
3. Central Heating Control
● Pre-set temperature stored in microprocessor.
● Temperature sensor constantly sends data to the microprocessor (via ADC).
● Microprocessor compares sensor data with pre-set value:
○ If temperature ≥ pre-set value, no action is taken.
○ If temperature < pre-set value, signals are sent via DAC to:
■ Open gas valve to heat water.
■ Turn on the water pump to circulate heat.
● Process continues until the heating system is switched off.
4. Chemical Process Control
● Temperature and pH sensors monitor chemical conditions.
● Sensor data converted to digital (via ADC) and sent to the computer.
● Microprocessor compares data with stored values:
○ If temperature < 70°C, heater is switched on.
○ If temperature ≥ 70°C, heater is switched off.
○ If pH > 3.5, valve opens to add acid.
○ If pH ≤ 3.5, valve closes to stop adding acid.
● Signals sent to heaters and valves via DAC for adjustments.
● Process continues as long as the system is active.
5. Greenhouse Environment Control
→ Sensors Used
● Humidity, Moisture, Temperature, pH, and Light sensors monitor conditions.
● Sensor data is sent to an ADC, which converts it to digital form for the computer.
→ Computer Processing
● Compares sensor data with pre-set values.
● Decides and sends signals (if needed) via DAC to control devices.

→ Actions Based on Sensor Readings

If sensor reading = pre-set value, no action is taken.
● Process continues as long as the system is active.
Summary of Data Storage & Memory
1. Data Storage & Memory
● Memory (Primary Memory): Internal storage used for temporary data, workspace, and
system operations.
● Storage Devices (Secondary Storage): Used for permanent data storage, application files,
and media.
● Removable Storage: Allows data transfer and backup but is becoming less relevant due to
cloud storage and Bluetooth-based file sharing.
2. Types of Memory & Storage
● Primary Memory (Directly accessed by the CPU)

○ RAM (Random Access Memory) – Temporary, volatile storage

○ ROM (Read-Only Memory) – Permanent, non-volatile storage
● Secondary Storage (Not directly accessed by the CPU)

○Internal Storage: HDD (Hard Disk Drive), SSD (Solid-State Drive)

○External Storage: USB drives, DVDs, Flash memory, Blu-ray discs, Removable
HDDs
3. RAM (Random Access Memory)
 ● Stores data and program instructions currently in use.
● Features:
○ Readable & writable (temporary storage)
○ Volatile (loses data when power is off)
○ Faster access than secondary storage
○ More RAM = Better performance (prevents excessive access to slower storage)
● Two Types of RAM:
○ DRAM (Dynamic RAM)
■ Made of transistors & capacitors.
■ Requires constant refreshing (loses charge quickly).

■ Advantages:
■ Cheaper to manufacture
■ Higher memory capacity
■ Consumes less power
○ SRAM (Static RAM)
■ Uses flip-flops to store bits.
■ Faster data access than DRAM.
■ Doesn’t require refreshing.
■ Used in: CPU cache memory (for high-speed operations)
4. Differences Between DRAM & SRAM:
● DRAM uses capacitors and transistors, while SRAM uses flip-flops.
● DRAM needs refreshing; SRAM does not.
● DRAM is cheaper and has a higher capacity, but SRAM is much faster.
● DRAM is used for main memory, while SRAM is used in CPU cache.
● SRAM consumes more power than DRAM.

→ ROM & RAM

1. Read-Only Memory (ROM)
● Non-volatile memory (retains data when power is off).
● Permanent storage (contents cannot be changed or written to).
● Read-only memory (cannot be modified by users, applications, or the system).
● Used to store boot-up instructions (BIOS) for starting the computer.
● Found in embedded systems like remote-controlled toys to store pre-set routines and factory
settings.
2. Random Access Memory (RAM)
● Volatile memory (data is lost when power is off).
● Temporary storage for data, files, and programs currently in use.
● Read and write access (data can be modified by users and applications).
● Improves computer speed as increasing RAM size reduces dependency on slower storage.
● In embedded systems like remote-controlled toys, RAM stores user-programmed routines and
temporary data received from remote control signals.
3. Key Differences Between RAM & ROM
● RAM is volatile, while ROM is non-volatile.
● RAM is temporary (stores active programs), while ROM is permanent (stores essential
system data).
● RAM can be written to and modified, while ROM is read-only.
● RAM affects performance, while ROM is essential for boot-up.
● RAM size can be increased, but ROM contents remain fixed.
●
→ Secondary and Off-line Storage
● Not directly addressable by the CPU (requires system intervention to access data).
● Non-volatile storage (retains data permanently until modified or deleted).
 ● Stores larger amounts of data than primary memory (RAM/ROM).
● Slower access time compared to RAM and ROM.
● Used for storing applications, operating system, device drivers, and general files (e.g.,
documents, photos, music).
● Includes both internal and external storage devices used in most computers.

→ Magnetic, Optical, and Solid-State Storage

Types of Secondary Storage
1. Magnetic Storage

○ Hard Disk Drives (HDD):

■ Data stored magnetically on spinning platters.
■ Read-write heads use electromagnets to access data.
■ Sectors and tracks organize data storage.
■ Latency issue: Time taken for data to be accessed due to mechanical
movement.
■ Fragmentation: Causes slow performance; can be improved using
defragmentation software.
■ Removable HDDs: External drives connected via USB, used for backups
and file transfers.
2. Solid-State Drives (SSD)

○ No moving parts → faster access, lower power consumption, more reliability.

○ Uses NAND/NOR flash memory; stores data as 0s and 1s using floating and control
gate transistors.
○ Non-volatile memory retains data due to dielectric insulation.
○ Advantages over HDDs:
■ Faster access speed.
■ Lightweight and more durable.
■ Lower power usage and heat generation.
○ Drawback: Limited write cycles (SSD endurance issue).
○ Used in laptops, servers, cloud storage.
3. Memory Sticks/Flash Memory

○ Uses solid-state storage technology.

○ Small, portable, connects via USB.
○ Used for file transfers and backups.
○ Dongles: Some software requires USB dongles for security and licensing.

→ Optical Media (CD/DVD Disks)

General Features
● Optical storage devices use laser light to read and write data.
● Data is stored on a single spiral track running from the center to the edge.
● Pits and lands on the track represent data.
● The optical head follows the spiral track as the disk spins.
● Sectors allow direct access to data, similar to HDDs.
● Outer disk regions spin faster than inner regions.
CD vs. DVD Technology
● CDs and DVDs use red lasers for reading and writing.
● Storage types:
○ CD-R/DVD-R → Write once.
○ CD-RW/DVD-RW → Rewritable multiple times.
● DVD vs. CD differences:
 ○ DVDs have smaller pits and narrower tracks → More data storage.
○ DVDs use a 650 nm laser, while CDs use a 780 nm laser.
○ Dual-layer DVDs → Two data layers increase storage, separated by a
polycarbonate spacer and thin reflector.
○ The laser adjusts focus to read the second layer.
Storage Capacity Improvement
● Shorter laser wavelengths → Higher storage capacity.
● Dual-layering in DVDs further increases storage compared to CDs.

→ Blu-ray Discs
General Features
● Blu-ray uses a blue laser instead of a red laser (as in DVDs).
● Shorter wavelength (405 nm) → Smaller pits and lands → Higher storage capacity.
● Single-layer Blu-ray disc: 1.2 mm thick polycarbonate disk with a 0.1 mm protective
coating.
● More secure system to prevent piracy and copyright infringement.
● Higher data transfer rates:
○ DVD: 10 Mbps
○ Blu-ray: 36 Mbps → Allows faster data access.
Storage Capacities & Comparison with DVDs
● Standard DVD: 4.7 GB (2 hours of standard-definition video).
● Single-layer Blu-ray: 25 GB (enough for 2 hours of HD video).
● Dual-layer Blu-ray: 50 GB (5.6 hours of HD video or 20 hours of standard video).
Advantages Over DVDs
● Higher interactivity → Blu-ray allows:
○ High-definition television playback.
○ Quick access to any part of the disc.
○ Storage of recorded movies and TV programs.
○ Automatic search for free space to avoid overwriting.
○ Access to websites & updates for interactive content.
Other Uses
● Can be used as backup storage for photos, music, and multimedia files.
● More reliable than CDs/DVDs for software distribution.
● Some manufacturers use CDs/DVDs for printer software distribution in read-only
format.

→ Virtual Memory
What is Virtual Memory?
● Virtual memory is used when RAM is full, allowing a part of the hard drive (HDD/SSD) to act
as temporary RAM.
● Prevents system crashes due to insufficient RAM.
● Slower than physical RAM but enables larger programs to run.

Without Virtual Memory

● If all programs in use exceed available RAM, the system crashes.
● No backup memory space to store excess data.
With Virtual Memory
● Older, unused data is moved from RAM to HDD/SSD to make space for active programs.
● Programs swap between RAM and virtual memory as needed.
Key Benefits
● Allows execution of programs larger than physical RAM.
● Prevents wastage of memory by swapping inactive data.
 ● Reduces need to install additional RAM.
Main Drawback: Disk Thrashing
● Excessive swapping between RAM and HDD leads to slow performance.
● Causes high read/write activity, reducing system efficiency.
● Can shorten HDD lifespan due to constant movement.
● Solution: Use SSD instead of HDD or increase RAM to minimize swapping.

→ Cloud Storage
What is Cloud Storage?
● Cloud storage allows data to be stored on remote servers instead of local storage.
● Data is often stored on multiple servers for redundancy and reliability.
● Managed by hosting companies with servers in various locations.
Types of Cloud Storage
1. Public Cloud – Storage provided by third-party companies, accessible over the internet.
2. Private Cloud – Dedicated storage within a company’s own network for security and control.
3. Hybrid Cloud – Combination of public and private cloud solutions.
Benefits of Cloud Storage
● Remote Access – Data is accessible from any device with an internet connection.
● Automatic Backup – Reduces risk of data loss from hardware failure.
● Scalability – Users can increase storage space as needed.
● Collaboration – Multiple users can access and edit shared files in real time.
● Cost-Efficiency – Eliminates the need for expensive local storage infrastructure.
Drawbacks of Cloud Storage
● Internet Dependency – Requires a stable connection to access data.
● Security Risks – Data stored on third-party servers may be vulnerable to breaches.
● Ongoing Costs – Monthly or annual fees for cloud services can be expensive.
● Limited Control – Users rely on service providers for data security and availability.
● Downtime Issues – Cloud services may face outages, restricting access to data.
Data Security in Cloud Storage
● Encryption and security protocols protect data transfers.
● Risks include data breaches, unauthorized access, and hacking incidents.
● Users should verify where data is stored and the security policies of providers.
Potential Data Loss Risks
● Cloud failures, software bugs, or cyberattacks can lead to data loss.
● Examples of cloud data loss incidents:
○ Xen hypervisor bug caused service outages.
○ Adobe cloud failure resulted in loss of permanently deleted data.
○ Celebrity photo leaks exposed private data from compromised cloud accounts.
○ Mexican voter database breach led to public exposure of sensitive personal records.
Solutions for Safer Cloud Storage
● Use strong encryption for sensitive data.
● Regularly back up important files locally.
● Choose cloud providers with strong security measures.
● Be cautious about sharing confidential data in the cloud.

→ Network Hardware

3.4.1 Network Interface Card (NIC)

● Definition: A hardware component that allows a device to connect to a network (wired or
wireless).
● Function: Generates the Media Access Control (MAC) address.
● Connectivity:
○ Wired NICs use Ethernet cables.
 ○ Wireless NICs use radio waves for communication.
○ External NICs can connect via USB.
3.4.2 Media Access Control (MAC)
● Definition: A unique 48-bit address assigned to a device’s NIC.
● Format: Six groups of hexadecimal digits (e.g., 00-1B-63-4F-2A-FF).
● Uniqueness:
○ First six digits identify the manufacturer.
○ Last six digits are the device’s serial number.
○ If NIC is replaced, a new MAC address is assigned.
Types of MAC Addresses
1. Universally Administered MAC Address (UAA)
○ Default MAC address set by the manufacturer.
○ Most commonly used.
2. Locally Administered MAC Address (LAA)
○ Can be manually changed if needed.
○ Used in cases where software requires specific MAC addresses (e.g., network
access filters).
Why Change a MAC Address?
● Some network software or security settings require a specific MAC address.
● MAC address filtering:
○ Used in firewalls, routers, and switches for security.
○ Only approved MAC addresses can connect.
○ If a MAC address isn’t allowed, the device will be blocked.
● Helps in network restrictions and access control.