Input Devices

• Two-dimensional Scanners

  • Used to input hard-copy documents
  • The image is converted into an electronic form which can be stored in the computer
  • Optical Character Recognition (OCR): software which converts scanned documents into a text file format
  • If the original document was a photo/image, then the scanned image forms an image file such as JPEG
• Scanning process

  1. Document is placed on a glass panel
  2. Illuminated by a bright light
  3. Scanned by a scan head
  4. Image is produced and sent to a lens using mirrors
  5. Focused image is transferred to a charge couple device (CCD) with integrated circuits
  6. Software generates a digital image
• Three-dimensional Scanners

  • Can scan solid objects and produce a three-dimensional image
  • Scanners take images at several points, x, y and z (lasers, magnetic, white light)
  • The scanned images can be used in Computer Aided Design (CAD) or to a 3D printer to produce a working model
• Barcode readers/scanners

  • A series of dark and light parallel lines of varying thicknesses
  • The numbers 0 -9 are each represented by a unique series of lines
  • The left and right hand sides of the barcode are separate using guard bars
  • Allows barcode to be scanned in any direction
• Barcode Process:

  • Barcode is read by a red laser or red LED
  • Light is reflected back off the barcode; dark areas reflect little light which allows the bars to be read
  • Reflected light is read by sensors (photoelectric cells)
  • The pattern is generated, which is converted to digital
• Quick Response (QR) Codes

  • Another type of barcode is the QR codes
  • Made up of a matrix of filled-in dark squares on a light background
  • Can hold more storage (7000 digits)
• Advantages of QR codes:

  • No need for the user to write down the website address
  • QR codes can store website addresses
• Digital Cameras

  • It is controlled by a microprocessor that adjusts the shutter speed, focuses the image, etc.
  • Photo is captured when light passes through the lens onto a light sensitive cell
  • The cell is made up of pixels
  • The number of pixels determines the size of the file
• Keyboards

  • Connected to a computer with a USB connection or by wireless connection
  • Each character has an ASCII value and is converted into a digital signal
  • Slow method
  • Prone to errors
• Microphones

  • Used to input sound to a computer
  • When a microphone picks up sound, a diaphragm vibrates, producing an electric signal
  • The signal goes to a sound card and is converted into digital values and stored in a computer
  • Voice recognition, voice is detected and converted into digital
• Capacitive (touchscreen)

  • Made up of many layers of glass
  • Creating electric fields between glass plates in layers
  • When the top layer of glass is touched, electric current changes
  • Co-ordinates where the screen was touched are determined by an on-board microprocessor
• Infra-red (touchscreen)

  
  

  Heat:

  • Use glass as the screen material
  • Needs a warm object to carry an input operation

  Optical:

  • Uses glass as screen material
  • Uses an array of sensors (grid form)
  • Point of contact is based on which grid co-ordinate is touched
• Resistive (touchscreen)

  • The upper layer of polyester, the bottom layer of glass
  • When the top polyester is touched, the top layer and bottom layer complete a circuit
  • Signals are then sent out, which are interpreted by a microprocessor, determine where the screen was touched
• Acoustic sensor: measure sound
• Accelerometer sensor: measure motion
• Flow rate sensor: measure moving liquid or gas
• Gas sensor: measure oxygen or carbon dioxide
• Humidity sensor: measure water vapour
• Infra-red sensor: measure IR beam is broken
• Level sensor: measure liquid level
• Light sensor: measure birghtness
• Magnetic field: measure magnetic field
• Moisture sensor: measure water level
• pH sensor: measure acidity, alkalinity
• Pressure sensor: measure weight
• Proximity sensor: measure distance
• Temperature sensor: measure temperature