3 I/O device

• Barcode scan


  Reader uses red laser, white lines reflect and black lines absorb, sensor detects level of reflected light to read binary barcode data
• Automated stock control using barcode scan

  Barcode scan -> send product code to stock database -> remove item from stock
• QR code scan


  Camera uses position and alignment markers to scan and convert to binary data, can store more information than barcodes
• Digital camera


  • Light enters lens, charge-coupled sensor captures and splits light into pixel color values, allows preview, instant image, easy transmission
• Keyboard


  Key has peg that makes contact with conducting membrane to generate digital signal character code, connected via USB or wireless
• Microphone


  Soundwaves cause diaphragm vibrations which are converted to digital signal by wire coil
• Optical mouse


  Red laser tracks movement by detecting reflected light, converts to digital values for speed and direction to control cursor
• Capacitive touchscreen


  Conductive layer senses change in electrostatic field from user's conductive touch to calculate coordinates, high image quality, long lifespan, sensitive to light interference
• Resistive touchscreen


  User's touch pushes flexible top layer to connect with bottom layer, completing circuit, cheap to manufacture, resistant to surface contaminants, can use any object
• Infrared touchscreen


  LED shines infrared light in matrix, touch interrupts beam to detect position, high image quality, precise, durable, supports multiple touches, but requires finger/stylus
• 2D scanner


  Shines light strip and measures reflected light for each pixel to recreate digital document
• 3D scanner


  Shines light over object and records dimensions to digitally recreate the object
• Actuator


  Physically moves to perform a specific function
• DLP (Digital Light Processing) projector

  • Millions of micromirrors on a microprocessor change position to modulate light intensity, high contrast, lightweight, but can suffer from shadows and color definition issues
• LCD (Liquid Crystal Display)


  • Light-modulating properties of liquid crystals change shape to allow light to pass, creating colors by mixing RGB, flat panel backlit display, less power and heat, vivid high-resolution images, but limited lifespan
• LED (Light Emitting Diode)


  • Tiny LEDs emit light, no backlight needed so can be thin and have large screens, better image quality than LCD, long lifespan, low power
• OLED (Organic Light Emitting Diode)


  • Organic carbon compounds create semiconductors that emit light, no backlight needed so can be thin, light, and flexible
• Inkjet printer


  • Print head moves and sprays ink droplets from cartridge through fine nozzles onto paper, uses piezoelectric or thermal bubble technology, produces bright colors
• Laser printer


  • Uses toner cartridge and large paper tray, applies negative and positive charges to stick toner particles to paper then heats to bond, fast high-volume printing with sharp images but higher running costs
• 3D printer


  • Deposits layers of plastic to build 3D objects from digital models, precise and allows rapid prototyping
• Speaker


  Converts digital sound signal from DAC and amplifier into soundwaves
• Sensor types


  • Infrared, proximity, temperature, pressure, motion, level, flow
• Process in automated systems


  Input sensor data -> Digitize -> Store in system -> Compare to stored values -> If within range, actuate (e.g. spray water) -> Repeat until turned off or door closed