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Input devices - Coggle Diagram
Input devices
2D Scanners
These are the most common form and are used to input hard-copy documents to be converted into an electronic form that can be stored in a computer.
Step 1: Cover is raised, document placed on glass panel, cover is closed
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Step 3: Scan head moves across the document, image of the document is produced and then sent to a lens which focuses the document image
Step 4: Focused image falls onto a charge couple device (CCD) which is made up of thousands of light-sensitive elements and each element creates an electric charge when light falls on it. The scanned image is turned into an electric form
Application: Computers that come equipped with OCR (optical character recognition) can allow the scanned text to be turned into text file, where it can be edited using a word processor. 2D scanners are used at airports to scan the image on a passport for facial recognition.
Bar code reader
A barcode is a series of dark and light parallel lines of varying thickness and the numbers 0 to 9 are represented by a unique series of lines. The bar code is separated into a left hand side and a right hand side
Each digit is represented by two dark lines and two light lines. Each digit is represented using the same width.
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The numbers on the right have an even number of dark elements and always begin with a dark bar. This arrangement allows a barcode to be scanned in any direction.
A barcode is scanned using LED or red laser and light is reflected back off the barcode, the dark areas reflect little or no light, allowing the bars to be read. This reflected light is read by sensors, allowing a pattern to be generated so the barcode can be understood.
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Pointing devices
Selecting items on a screen can be carried out by pointing devices such as mouse, tracker ball, touch pad, or touch screen.
A mouse makes use of a mechanical ball arrangement, the movement of which (along an X and Y plain) is noted and then represented on a computer connected via USB.
An optical mouse makes use of a red LED that can detect movement on a surface. They can be seen as a wireless mouse as well as connected via Bluetooth.
Instead of a mouse, tracker balls use a large ball that is moved for cursor movement. Both tracker balls and mouse have additional buttons for selection and scrolling.
Touch pads use a tactile sensor which allows the user ot move the cursor by moving a finger across the surface of the touch pad. They too have buttons for selection.
Digital cameras
Modern digital cameras link to a computer system via a USB port or by using Bluetooth (enabling wireless transfer)
These cameras are controlled by a microprocessor which can: adjust shutter speed, focus images automatically, operate flash automatically, adjust aperture size, adjust size of the image, remove red eye when the flash has been used.
When light passes through the lens it lands onto light sensitive cells made up of many pixels. The number of pixels determines the size and quality of the image. The quality is also dependent on other factors such as light and the type of lens.
Mobile phones have caught up with digital cameras, but are limited by the quality of their lens and storage size.
Microphones
Microphones are used to input sound to a computer. They are either built in or are external devices connected through the USB port or using wireless connectivity.
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 the computer.
Voice recognition systems detect a user's voice and converts it into digital values. The words spoken produce a wave pattern and if the pattern produces is the same as the pattern saved, the person can be correctly identified.
Speech recognition is more complex as it tries to recognize the words spoken so that they can be used for various computer applications. The sound card will convert the sound into digital form where it will be broken into phonemes. These phonemes are then compared to words found in the built-in dictionary.
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Keyboards
They are the most common method used for data entry. Keyboards are connected to the computer either by using a USB connection or by wireless connection. With mobile phones and tablets, the keyboard is often virtual or a type of touchscreen technology.
Each character on the keyboard is represented by an ASCII value. When a key is pressed, it causes a circuit to close resulting in a signal being sent to the processor where it is interpreted according to the ASCII value.
Using a keyboard could cause RSI (repetitive strain injury) in the hands and wrists and this can be reduced with the use of Ergonomic keyboards which have the keys arranged in a more comfortable manner.
Touchscreens
Capacitive
This touchscreen is made up of layers of glass that act like a capacitor, creating electric fields between the glass plates in layers. When the top glass layer is touched, the electric current changes and the coordinates where the screen was touched is determined by an on-board microprocessor.
Infra-red
Heat-sensitive
This type of touchscreen uses glass as the screen material and requires a warm object to carry out an input operation.
Optical
It uses glass as the screen material and uses an array of sensors (in the form of a grid). The point of contact is based on which grid coordinate is touched.
Resistive
This type of touchscreen makes use of an upper layer of polyester and a bottom layer of glass. When top layer is touched, the top layer and the bottom layer complete a circuit and signals are then sent out which are interpreted by a microprocessor. The calculations determine the coordinates of where the screen was touched.
Interactive whiteboards
Interactive whiteboards allow users to interact with images displayed on a white board. The hand-made changes can be saved in a computer for later use.
Users can use specialized smart board markers to write text on the board. With specialized software it is also possible to interact with the whiteboard using only your fingers
They are used during board room meetings where handwritten text entered during the meeting can later be reviewed. It can also be used to demonstrate a new software as well.
3D Scanners
3D scanners are used to scan 3D objects (x, y, z, coordinates) to be used in CAD (computer aided design) or to be printed
Computed Tomographic (CT) Scanners rely on a TOMOGRAPHY method in which a 3D Image is ‘built up’ using very thin 2D slices’. Each slice is built up using X-Rays, radio frequencies or gamma imaging. These slices are then stored as a ‘digital’ image.
Sensors
Analogue data means that it is constantly changing and there are no discrete values as a result of which readings generated by sensors can have an infinite number of values depending on precision, making them impossible for a computer to understand. An Analogue to Digital Converter (ADC) is used to:
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