input / output devices Flashcards
barcode scanner
shines light / red laser at barcode // light is called an illuminator // light is reflected back - white lines reflect light, black lines absorbs light // sensors detect the light // different reflections give different binary values // microprocessor interprets the data
digital camera
the button is pushed to take a photograph.
Aperture opens at the front of the camera to allow light to stream through the lens.
captured by a sensor called a charge-coupled device.
The analogue-to-digital converter converts each pixel into a digital value.
keyboard
user presses a key // key pushes the switch on the circuit board // completes a circuit // allows current to flow // signals sent to the computer // location of key pressed is calculated // compared to a character map to find the binary value
microphone
optical mouse
shines red light from a LED underneath the mouse
Light reflects back from a surface into photoelectric cell // through a lens which magnifies the reflected light to allow detection of smaller movements // button clicked -> microswitch is pressed
converted to a value
value is transmitted to the computer
computer determines the direction and speed of the movement
USB connection is used to carry the data to the computer
QR code scanner
scanned (decoded) using app // camera is used to scan the image // corner squares are used to define the alignment, for orientation // device shines illuminator onto the QR code // Black squares reflect less light, white squares reflect more light // device captures the light that is reflected back // using sensors // app/device processes the image // each small square,pattern is converted to a binary value, digital data // QR code can be saved for future reference
link to video is stored in the QR code
2D scanner
– (Scanner) shines a light onto the surface of a document
// Light moves across document
– Reflected light is captured
– Uses mirrors and lenses
- reflections are converted to binary
– Captured image is converted into a digital file
– Produces a 2D digital image
3D scanner
– Scanners shines a laser (or light) over the surface of a 3D object
– Records measurements of the geometry/dimensions of the object
– Measurements are converted to digital file
– Produces a 3D digital model
actuator
Operated by signals to cause a physical movement
Controls the movement of a
machine
digital light processing (DLP) projector
- Uses a large number of tiny mirrors
- Mirrors are laid out in a grid/matrix
- Each mirror creates a pixel in the image
- Mirrors can tilt toward or away from light source
- The mirrors reflect light toward a (projection) lens
- Colour is produced using a colour wheel
- Can be used to display an image on a wall/screen
inkjet printer
ROLLER used to move the paper through the printer//
NOZZLES spray jet ink onto the paper//
ink jets/nozzles move across the paper to distribute ink//
different colour inks are mixed to create required colours//
INK is heated//
and expands into a bubble//
bubble is pushed through the nozzle on to the paper//
then the bubble collapses//
electrical current is applied to a crystal//
which makes it vibrate//
which forces a droplet of ink through the nozzle//
uses piezoelectric or thermal technology
laser printer
data is sent to the printer and stored temporarily in the printer buffer // printing drum is given a positive charge // printing drum rotates, a laser scans across it // removes the positive charge in certain areas // negatively-charged areas produced on the printing drum // these match exactly with the text and images to be printed // printing drum is coated in positively-charged toner // this sticks to the negatively-charged parts of the printing drum // negatively-charged sheet of paper is then rolled over the drum // toner on the drum is transferred to the paper to reproduce the required text and images // paper goes through a fuser which melts the toner, fixes permanently to the paper
uses powdered ink
uses a discharge lamp to remove static charge from the drum
light emitting diode (LED) screen
display made up of pixels // that are arranged in a matrix // LEDs are behind the screen // light shone at pixels // can have diffuser used to distribute light evenly // RGB filters used // mixed to create different colours
liquid crystal display (LCD) projector
A powerful beam of white light is generated from a bulb
This beam of light is then sent to a group of chromatic-coated mirrors; these reflect the light back at different wavelengths
When the white light hits the mirrors, the reflected light has wavelengths corresponding to red, green and blue
These three different light pass through three LCD screens; these screens show the image to be projected as millions of pixels in grayscale
When the coloured light passes through the LCD screens, a red, green and blue version of the grey image emerges
Finally, the image passes through the projector lens onto the screen
higher resolution
produces less heat
uses less power
less cost of purchase
run quieter
liquid crystal display (LCD) screen
display made up of pixels // arranged together as a matrix // each pixel has three filters (red,blue,green) // shades of colour are achieved by mixing RGB // screen is backlit // light is shone through the liquid crystals // liquid crystals can be made to turn solid or transparent // by changing the shape of the crystal
uses a flat panel display
blacklit display
with LEDs
uses light-modulating properties of liquid crystals
crystals can be turned between opaque and transparent
