Input & Output Devices

Input Devices

• **Input devices** are hardware components that allow users to interact with a computer system by inputting data or commands.
• **Barcode scanner**: reads barcodes to capture product information; used in supermarkets, warehouses, libraries for quick and accurate stock/checkout.
• **Digital camera**: captures photographs/videos as digital images; used in photography, smartphones, webcams for high-quality visual content.
• **Keyboard**: inputs text and commands by pressing keys; used with computers, tablets, laptops for typing, data entry, and software control.
• **Microphone**: captures analogue sound and converts it into digital signals; used in recording studios, smartphones, computers for audio recording and voice communication.
• **Optical mouse**: moves the cursor based on hand movements over a surface; used with computers and laptops for precise control and navigation.
• **QR code scanner**: reads QR codes to access stored information; used in retail shops and mobile apps for quick retrieval of website links or product info.
• **Touch screens** – three types: **resistive** (press flexible layer; ATMs, older devices), **infra-red** (interrupts IR beams; kiosks, large displays), **capacitive** (electrical charge change; modern smartphones, tablets, multi-touch).
• **2D scanner**: captures flat images of documents/photos; used in offices, libraries, schools for digitisation.
• **3D scanner**: captures detailed 3D shapes and dimensions; used in manufacturing, design, medical imaging for digital models.

Output Devices

• **Output devices** receive information from a computer system and present it to the user in an understandable form.
• **Actuator**: converts energy into motion; used to make robot arms move, open valves, rotate motors – essential in systems requiring movement.
• **DLP projector**: projects images/video by shining light through tiny mirrors; used in cinemas, classrooms, large presentations for high-quality images.
• **Inkjet printer**: prints text/images by spraying tiny ink droplets; used at home, schools, offices – low cost compared to other printers.
• **Laser printer**: heat from a laser fuses toner onto paper; used in offices and schools for high-quality, fast prints.
• **LED screen**: displays images/video using tiny LEDs; used in TVs, monitors, smartphones – bright, energy efficient, thin.
• **LCD projector**: projects images/video by shining light through liquid crystal panels; used in offices, classrooms, home cinemas – bright, good quality/affordability balance.
• **LCD screen**: displays images/video using liquid crystals with a backlight; used in TVs, monitors, smartphones, laptops – energy efficient, thin, sharp, lightweight.
• **Speaker**: converts electrical signals into analogue sound waves; used in TVs, radios, smartphones – multiple shapes and sizes.
• **3D printer**: adds thin layers of plastic to form a three-dimensional object; used in manufacturing, medicine, education, home for prototypes and custom parts.

Choosing the Right Device

• **User Needs**: consider tasks – a graphic designer may need a graphics tablet, a data entry clerk a keyboard with number pad.
• **User Skills**: touch screen may be more intuitive for some, mouse and keyboard for others.
• **Environment**: wireless mouse for clutter-free office, wired mouse for public computer lab to prevent theft.
• **Cost**: higher-end devices have more features but are more expensive; consider budget and whether extra features are worth the cost.

Sensors – Input Devices for Monitoring and Control

• **Sensors** are input devices that measure a physical property of the environment (e.g., light, temperature, movement).
• **Monitoring system**: tracks the state of a system, gathers data, may issue warning messages.
• **Control system**: controls the system based on sensor input – e.g., if water temperature in a fish tank falls below acceptable level, a heater is switched on.
• **Feedback loop**: outputs are recycled and used as inputs, creating a continuous cycle (e.g., heater switches off when temperature is within range).

Types of Sensors

• **Acoustic**: measures sound levels; used to detect changes in industrial machinery, monitor noise pollution, security systems.
• **Accelerometer**: measures acceleration rate, tilt, vibration; used in vehicles to deploy safety features, in phones to detect orientation.
• **Flow**: measures rate of gas, liquid or powder flow; used to detect changes in flow through pipes in water systems.
• **Gas**: detects presence of a gas (e.g., carbon monoxide); used in confined spaces, fixing gas leaks.
• **Humidity**: measures levels of water vapour; used to monitor humidity in greenhouses.
• **Infra-red**: detects motion or heat source; used in security systems (break beam), emergency services to detect people.
• **Level**: measures liquid levels; used in car petrol tanks, water tanks, leak detection.
• **Light**: measures light levels; used to automatically switch on street lights/headlights when dark.
• **Magnetic field**: detects presence and strength; used in anti-lock braking systems, monitoring rotating machinery.
• **Moisture**: measures presence and levels of moisture; used in soil monitoring, dampness in buildings.
• **pH**: measures acidity or alkalinity; used in soil monitoring for optimum growing conditions, chemical processes.
• **Pressure**: measures gas, liquid or physical pressure; used in tyre pressure monitoring, pipe pressure in manufacturing.
• **Proximity**: measures distance; used in robotics for object positioning, safety systems to prevent collisions.
• **Temperature**: measures temperature; used to maintain temperature in swimming pools, control chemical processes.

Worked Example – Sensors

• **Question**: What type of sensor would be used to help drivers when reversing? Options: A Motion, B Infra-red, C Light, D Proximity. **Answer**: D Proximity.
• **Question**: Is this a monitoring system or a control system? Options: A Monitoring, B Control. **Answer**: B Control.

Overview of input and output devices, including sensors.

Feedback loop in a control system: sensor → processor → actuator, with feedback.

Three types of touch screen: resistive, infra-red, and capacitive.