Input/Output devices
How does a microphone work
- Diaphragm in the microphone vibrates when a sound is made, creating a signal - The signal passes through a sound card, and is converted into a digital signal where it is stored * In voice recognition softwares the software will store the wave patterns and check it against the stored wave patterns to verify
How does a capacitor touchscreen work
- Has many layers of glass that act as a capacitor - Electrical fields present between the layers - When an electrical conductor comes in contact with the screen the electrical field is altered - Microprocessor determines the coordinates of where it was altered and thus where the screen was touched
How does a digital camera work
- Light passes through the lens onto a light sensitive cell - Elements in the cell have pixels which convert the light into an electrical signal - Then converted into a number and stored * Microprocessor can adjust settings according to user preference (shutter speed, flash, filters)
How does a 3D printer work
- Object created in CAD then sent to printer - Object is built in layers - Printer will start on the first layer, building the x,y,z coordinates - Print head moves to the next layer - Process is repeated until object is finished - After printing excess material will have to be removed
How does a infrared touchscreen work
* Both types use glass as a screen material Heat sensitive: Needs a warm object (finger) to carry out input operations Optical: - Uses infra-red LED beams to form a grid on the screen - When the screen is touched the grid is interrupted - Sensors detect where grid was interrupted - Thus position where screen was touched is located
Cutter
* Depending on strength of the laser, some materials would be too hard or too reflective to cut - Initially planned on a CAD - Parts to be cut are highlighted - Plan is sent to the software that controls the software - Material is cut by a high powered laser that follows the path in design
Laser printer characteristics
* Discharge lamp to remove charge from drum * Powdered ink * No print head * Faster than inkjet printing * Uses a fuser * Uses a charged drum
LCD monitors
* Liquid crystal display * Font layer is made of small diodes (red, green, blue) grouped together to form a pixel * Light is projected through this layer to produce the coloured image * Usually uses CCFL (Cold Cathode Fluorescent lamps to provide the back lighting LED monitors: * Same as LCD but uses light emitting diodes to light up the screen instead of CCFL
Inkjet printer
* Movable print head, Uses liquid ink, Sprays ink in droplets - Printing poggu - Paper is fed through the printer as 4 print heads move across, spraying ink to form the text and images - Once this process finishes the paper is moved up so that the next line can be printed - Process is repeated until the whole page is printed
3D printers requirements
* Needs resin, paper, plastic and powdered metal * Needs CAD * Makes use of topography of the object * Some things (like guns!) need different components, thus the parts are printed out individually and then assembled
Why LED is better than CCFL
* Starts up almost instantly * Brighter image * Higher resolution * More efficient * Lighter
Speakers/Headphones
* Works by converting digital signal into sound * DAC has a sample measuring rate of hertz - Computer produces a digital signal which is converted to analogue signal through DAC - Amplified via an amplifier, this creates a voltage - The voltage causes a cone in the speaker to vibrate, producing sound waves
How do QR code readers work
*Stands for quick response code readers* - Light emitted from phone illuminates the QR code - Sensor on phone will detect the reflected light (black squares reflect less light than white squares) - Reflected light is interpreted processed and decoded by the app - Page is generated
Advantages of using a bar code
- Automatic stock control - Better and up to date sales (due to information/sales trends) - Faster checkouts - Errors charging customers reduced - Easier to track freshness of food
LCD Projector
- Beam of light is generated by a bulb or LED - Light is sent through chromatic coated mirrors, separating the light into red, green and blue - Light goes through LCD screens, creating red, green and blue coloured images - Images combined by a prism - Image passes through a projector lens onto the screen
How does a keyboard work
- Connected through usb or wireless - Each key has an electrical switch underneath. When a key is pressed, so is the electrical switch - the electrical circuit is completed, producing a signal which is sent to the computer - Each character also has an ASCII value, which processes the input
How does a laser printer work
- Printing poggu - Printing drum given a positive charge - Laser then scans the drum, giving certain areas a negative charge (these areas are the texts and images that are to be printed) - Drum is then covered in positive charged printing toner (will only stick to the negative regions) - Negative charged paper is then rolled onto the drum, toner transfers onto the paper - Paper is sent through a fuser, this is where the toner melts onto the paper - If it is printed in colour, the process is repeated for each colour
Advantages of QR codes
- QR codes can store much more information than bar codes (can hold 7,000 whereas bar codes can only hold 30) - Very effective for advertising as QR codes can hold the link to any website No need for the user to type in the websites URL - - Scanning the qr code will automatically take the user to the website
How do barcode readers work
- Red light is emitted from barcode reader, barcode is illuminated - Sensor on the barcode reader detects the pattern of reflected light - Analog signal is generated and interpreted by the barcode reader - Signal is converted to text - Text is sent to computer connected to scanner
How does a 3D scanner work
- Scanner head moves along the object, collecting the x,y and z coordinates - Coordinates are then used to build a 3d model of the object * If the inside is to be scanned, penetrative rays will be used * 3D object is built up slice by slice (CT scans) which is then turned into a digital model which can be viewed from different angles
How does a resistive touchscreen work
- Similar to a keyboard, when a key is pressed it connects a circuit - This sends a signal to the processor, the signal is interpreted and the processor determines which part of the screen was touched
What hardware and software is needed for the interactive whiteboard
- Stylus - A board that is sensitive to the stylus - has a grid of sensors which can determine where on the board the pen is - A connection to computer that is running an interactive whiteboard software - Proper drivers on the computer to allow communication between it and the board - Projector connected to the computer that receives output from the computer
What happens after a product with a bar code is scanned?
- The bar code number is looked up in the database - Then the number is found, the stock for the product is looked up - The stock number for that product is reduced by one every time the bar code is read - Once the stock number has been reduced, it will be compared to a re-order level. If it is equal or less than this value, new stock are automatically reordered - The stock number will be updated when the new stock arrives
DLP Projector
- Uses a bright white light source, micro mirrors and a colour filter - White light is separated into green, red and blue via the colour filter - The micro mirrors rapidly turn on and off to generate the different shades of colour required for the image
Mice
- Uses red LED's to detect the mouses movement along the x,y coordinates - Coordinates are sent to computer to move the cursor - Most mice have other buttons, such as to open a menu, or for scrolling * Using a mouse requires desk space, also puts user at risk of injuries such as RSI * Touchpad is another pointing device, it's a tactile sensor that allows the user to control the cursor by moving their fingers on the surface of the pad * Trackballs are seen more in the industrial environment, such as a control room. They do not require space and users are less likely to get injured using them
What does a bar code store?
- Weight - Manufacturer number - Check digit - Product code
3D Cutter
- Works similarly to the 2D cutter - Design on the CAD needs to be a 3D model - Impossible to cut anything that cannot be seen from the outside (no hollow objects) - Because it is removal of material in layers, instead of building up an object in layers. Often stronger than 3D printing * Plan is made on a CAD, outlining where on the object to cut * The laser cuts along the x,y coordinates specified by the CAD, then it will move to the next layer and do the same thing
How does a 2D scanner work
- Xenon lamp illuminates the document - Scan head moves across the document, creating a scanned copy - Scanned copy is passed through a series of mirrors and lenses until it land on a charge couples device (CCD) - CCD produces a charge for each pixel when light falls on it - Charge is used to create a digital copy of the physical image in electrical form
How does an interactive whiteboard work
Allows user to write on a surface using a pen. Texts and images can be electronically captured by the software and stored - Has an array of sensors that locate where the board has been pressed - Corresponding image is displayed
How does a barcode reader work?
Bar code reader will illuminate the bar code with a red light. A sensor in the reader will then detect the pattern of reflected light (black bars will not reflect the light as well) then the decoder will interpret the pattern and convert it into digital data.
Advantages/Disadvantages of LCD of DLP
LCD: + Cheap - Less contrast and more maintenance DLP + Sharper images + Better response time + No filters needed - Lamp life relatively short
Printing poggu
Mnemonic for the following steps - Printer driver ensures data is in a form printer can understand - Data sent to printer is stored in the printer buffer
Types of inkjet printing
Piezoelectric: - Vibrating crystals which cause the ink to spray out the nozzle Thermal bubble - Ink is heated causing it to form tiny bubbles, as the bubble expands ink is ejected out from the nozzle onto the paper
Drawbacks for each touchscreen
Resistive: - Shit visibility in sunlight - Screen is easily scratched - No multi-touch Capacitor - Can only carry out input operations with bare fingers. However some have specialised styluses which can be used Infra-red - Expensive af - Heat system will only allow input operations to be carried out with bare fingers
Benefits of each touchscreen
Resistive: - Cheap - Can carry out input operations with bare fingers, stylus or with gloves Capacitor: - Durable - Multi-touch - Screen has good visibility even in sunlight - Medium cost technology Infra-red: - Multi-touch - Durable - Optical allows for input operations even if wearing gloves or with a stylus
How do QR codes work?
The users phone in the QR code reader. Using the QR code reader app the phone will illuminate the QR code. A sensor will then detect the reflected light and the decoder will convert the reflected light patterns into digital data.
