Input and Output Devices (Copy)

1. Input Devices

• Definition:
  • An input device is a piece of hardware that allows a user or another system to enter data and instructions into a computer for processing.
  • They convert real-world data (text, images, sound, movement, etc.) into a format the computer can understand (usually binary data).
• Purpose:
  • Required because the computer cannot directly understand human-readable information.
  • They act as the interface between the user/environment and the computer system.

1.1 Common Input Devices

1. Barcode Scanner

• Function: Uses a laser or camera to scan barcodes and convert them into digital data.
• Use Cases: Point-of-sale systems, inventory management, ticketing.
• Process: Light is reflected off the barcode → Sensor detects reflected light → Converted into a binary pattern → Sent to computer.

2. Digital Camera

• Function: Captures still images or video in digital form.
• Use Cases: Photography, surveillance, machine vision.
• Process: Light enters through lens → Image sensor (CCD or CMOS) converts light to electrical signals → Digital processor encodes into image file.

3. Keyboard

• Function: Allows text, numbers, and commands to be input via key presses.
• Use Cases: Writing, coding, command inputs.
• Process: Pressed key sends scan code to computer → Decoded to corresponding character.

4. Microphone

• Function: Converts sound waves into electrical signals for processing.
• Use Cases: Voice input, audio recording, voice control.
• Process: Diaphragm vibrates with sound → Signal is converted into binary data by ADC.

5. Optical Mouse

• Function: Detects movement and sends coordinates to the computer.
• Use Cases: Navigating GUI, gaming, design work.
• Process: LED or laser illuminates surface → Sensor captures changes in light patterns → Movement calculated.

6. QR Code Scanner

• Function: Reads QR codes and translates patterns into digital data.
• Use Cases: Payment systems, marketing, logistics.
• Process: Camera captures image of QR → Decoding software extracts stored data.

7. Touch Screen

• Types:
  • Resistive: Two layers with a gap; touching causes layers to contact and register position.
  • Capacitive: Uses changes in electrical charge at touch points to detect position.
  • Infra-red: Uses a grid of invisible infrared beams; touch breaks beams to detect position.
• Uses: Smartphones, kiosks, ATMs.

8. 2D Scanners

• Function: Digitises flat images or documents.
• Process: Light source scans line by line → Sensor captures reflection → Image assembled digitally.

9. 3D Scanners

• Function: Captures shape and dimensions of 3D objects.
• Uses: Industrial design, 3D printing, archaeology.

2. Output Devices

• Definition:
  • An output device is hardware used to present processed data from the computer to the user in a usable form (visual, audio, physical).
• Purpose:
  • Required to display, print, project, or otherwise deliver information after processing.

2.1 Common Output Devices

1. Actuator

• Function: Converts digital signals into physical movement.
• Examples: Motors, solenoids, hydraulic pistons.
• Uses: Robotics, industrial automation, home appliances.

2. Digital Light Processing (DLP) Projector

• Function: Projects images using microscopic mirrors and a spinning colour wheel.
• Advantages: High contrast, suitable for large screens.

3. Inkjet Printer

• Function: Sprays fine droplets of liquid ink directly onto paper.
• Advantages: High-quality prints, good for images/photos.
• Disadvantages: Slower than lasers, ink cartridges costly.

4. Laser Printer

• Function: Uses a laser beam and toner powder to produce high-speed prints.
• Advantages: Fast, economical for large volumes.
• Disadvantages: Not as good for photo printing.

5. LED Screen

• Function: Uses light-emitting diodes as pixels to display images.
• Advantages: Bright, energy-efficient, long lifespan.

6. LCD Projector

• Function: Passes light through liquid crystal panels to form images.
• Advantages: Good colour reproduction.

7. LCD Screen

• Function: Uses liquid crystals between polarising filters to display images.
• Advantages: Slim, low power usage.

8. Speaker

• Function: Converts electrical audio signals into sound waves.
• Uses: Music, alerts, communication.

9. 3D Printer

• Function: Builds physical 3D objects layer by layer from a digital model.
• Uses: Prototyping, manufacturing, medical models.

3. Sensors

• Definition:
  • A sensor is a device that detects and responds to a physical property (light, heat, motion, pressure, etc.) and converts it into a signal readable by a computer.
• Purpose:
  • To automatically collect environmental data for monitoring, control, or analysis.
  • Often used with Actuators to create automated systems.

3.1 Types of Sensors, Data Captured, and Applications

1. Acoustic Sensor
   • Measures: Sound levels/vibrations.
   • Uses: Voice recognition, security alarms, sonar.
2. Accelerometer
   • Measures: Acceleration, tilt, motion.
   • Uses: Smartphones (screen rotation), vehicle crash detection.
3. Flow Sensor
   • Measures: Rate of liquid or gas movement.
   • Uses: Water systems, chemical processing.
4. Gas Sensor
   • Measures: Concentration of specific gases.
   • Uses: Air quality monitoring, safety in mines.
5. Humidity Sensor
   • Measures: Moisture content in air.
   • Uses: Climate control, agriculture.
6. Infra-red Sensor
   • Measures: IR radiation or detects heat/motion.
   • Uses: Remote controls, night vision.
7. Level Sensor
   • Measures: Level of liquids or solids in a container.
   • Uses: Fuel tanks, silos.
8. Light Sensor
   • Measures: Intensity of light.
   • Uses: Automatic streetlights, smartphones adjusting brightness.
9. Magnetic Field Sensor
   • Measures: Magnetic field strength/direction.
   • Uses: Compasses, industrial detection.
10. Moisture Sensor
    • Measures: Water content in materials.
    • Uses: Soil monitoring, building maintenance.
11. pH Sensor
    • Measures: Acidity/alkalinity of liquids.
    • Uses: Laboratories, water treatment.
12. Pressure Sensor
    • Measures: Force per unit area.
    • Uses: Tire pressure monitors, weather stations.
13. Proximity Sensor
    • Measures: Presence/absence of objects without contact.
    • Uses: Touchless switches, obstacle detection.
14. Temperature Sensor
    • Measures: Heat levels.
    • Uses: Thermostats, industrial processes.

4. Selecting the Most Suitable Sensor

• Based on:
  • Type of data required (light, sound, movement, etc.).
  • Environment (indoor/outdoor, temperature, humidity).
  • Accuracy and range required.
  • Budget and technical constraints.