IGCSE Computer Science: Output Devices

Valves / Motors / Sirens

Give 3 examples of actuators

- The model on the CAD must be a 3D model. - There must be a direct line of sight between the laser cutter and the area of material to cut (cannot cut parts that can't be seen from the outside- no hollowed out shape). - The material is cut by a very high powered laser that follows the lines of the design. The laser removes material by burning it away. - The product is removed from the 3D cutter, and if it is a component of a larger object, it is assembled.

How does a 3D cutter work (steps)?

A bright white light source is shone onto a chip which is covered in several micro mirrors. The angles of the mirrors are controlled by the chip, and these angles affect the colour of the light. This produces an image to be projected onto a wall.

How does a digital light projector (DLP) work?

The production of an object, which is build up layer by layer, that is designed on a CAD/CAM program.

What is 3D printing?

Laser printer

Which type of printer is the fastest?

LEDs don't need to warm up, but CCFL does. LED makes for a brighter image with more vivid colours than CCFL. LED makes the image higher resolution than CCFL. LEDs are slimmer, so the screen is slimmer / lighter than one using CCFL backlighting. LEDs are more reliable and longer lasting than CCFL. LEDs use much less power and are more efficient than CCFL backlighting.

Why is LED a better backlight for an LCD screen than CCFL?

For showing enlarged computer output on a wall or large screen. Both types of projectors can display to large audiences because the projected image is much bigger than a computer monitor.

What are projectors used for?

Advantages: -Have no moving parts, so are less expensive Disadvantages: -Require constant filter maintenance -Output less colour contrast

What are the advantages and disadvantages of an LCD projector?

Computer Aided Design (CAD) Computer Aided Manufacturing (CAM) Used to create a digital model of an object, usually to later be sent to a 3D cutter or 3D printer.

What is CAD/CAM?

They work the same way, but the 3D cutter cuts the Z axis as well, as oppose to only the X and Y axis like a 2D cutter.

What is the difference between a 2D cutter and a 3D cutter?

Advantages: -Produces sharp images -Doesn't need filters -Faster response time -3D capabilities Disadvantages: -Shorter lamp life -Colour ghosting / colour banding may occur

What are the advantages and disadvantages of a DLP?

Thermal bubble (Vaporises the ink using heat, this causes bubbles, which causes the ink to spray out of the nozzle). Piezoelectric technology (Vibrating crystal causes spray of ink out of nozzle)

What are the different types of inkjet technology?

The number of conversions (from Digital to Analogue) per second.

What does "sampling rate" of a DAC mean?

A component of a machine that is responsible for moving / controlling a mechanism or system. An ACTUATOR needs both a control signal (within the control system, the control signal comes from the microprocessor) and a source of energy, in order to work.

What is an actuator?

3D printing is a constructive process, whereas 3D cutting is a destructive process. In 3D printers, the product is made up of multiple layers of material, but in 3D cutters, the product is made by removing chosen areas from a single piece of material, and is therefore structurally stronger and also has a better finish (no visible layers) than a product made by a 3D printer. 3D printing can make objects with more varied shape (flexible in terms of the shapes it can make), unlike 3D cutting- which gives the user less freedom when designing.

What is the difference between a 3D cutter and a 3D printer?

A black and white laser printer only has one toner, and goes through the process once. A colour laser printer has four toners (Cyan, Magenta, Yellow and Key - old printing term for black) that are done one after the other to build up the image.

What is the difference between a black and white & a colour laser printer?

Paper, Plastic, Wood, Metal. However not every 2D cutter is able to cut all of these materials- it depends on the design and strength of the laser. Also, some materials may be too hard or reflective for the 2D cutter to cut.

What kind of materials can a 2D cutters cut?

Melted material (melted as it prints, and sets quickly while the next layer is printed on top of it). Powder (after each layer is printed, a bonding agent is put down before the next layer is printed).

What materials do modern 3D printers use?

Hertz

What unit is the sampling rate of a DAC measured in?

LEDs are more efficient, and are also smaller (which means that the screen would be slimmer).

What would be the benefit of using LEDs instead of CCFL behind an LCD screen?

- The plan is made on CAD, showing the lines to be cut as several joined points on both the X and Y axis. - The plan is loaded to the software the controls the 2D cutter. - The material is cut by a very high powered laser that follows the lines of the design. The laser removes material by burning it away. - The product is removed from the 2D cutter, and if it is a component of a larger object, it is assembled.

How does a 2D cutter work (steps)?

- 3D CAD virtual model must be created in a format that the printer understands. - The printing material (eg: resin, powdered metal, paper, plastic) must be added to the printer. - Virtual model is transferred to the printer. The solid object is build up in thin layers. - Each slice of the object is printed on its x and y coordinates, and then the printer moves up one z coordinate. This repeats until the whole object is printed. - The user then must remove excess material and, if necessary, assemble the multiple components.

How does a 3D printer work (steps)?

- The printer driver ensures that the data is in a format that the laser printer understands. - The data is sent to the laser printer and temporarily stored in the printer buffer. - The printing drum is given a positive charge. - The printing drum is rotated, and a laser (discharge lamp) scans across it to remove the positive charge in certain areas, which now have negative charges. - The negatively charged areas perfectly match the text/images to be printed. - The printing drum is coated in positively charged toner, which sticks to the negatively charged areas of the printing drum. - A negatively charged piece of paper is rolled over the printing drum. - The (positively charged) toner on the printing drum is transferred to the paper to produce the required text/images. - The paper goes through a fuser, which melts the toner so that it fixes permanently to the paper. - (In a COLOUR laser printer, the process is repeated for each colour.)

How does a laser printer work (steps)?

Liquid Crystal Display (LCD) screens have a front layer that consists of many diodes, which are grouped to form many pixels. A red diode, green diode, and blue diode (and sometimes a yellow diode as well) form one pixel. Light is projected through this layer, which produces the images that the user sees on the screen. Most LCD TVs use Cold Cathode Fluorescent Lamps (CCFLs), however some TVs use Light Emitting Diodes (LEDs) behind the LCD screen instead.

How does an LCD flat panel display screen work?

A light beam is generated by a bulb or an LED. This beam is sent to chromatic coated mirrors, and when it reflects back, the light has red green and blue components. This light passes through an LCD screen, and the rays are combined by a prism. This image then passes through the projector lens onto the screen.

How does an LCD projector work?

Ordinary LED lighting uses Light Emitting Diodes (LEDs) behind the LCD screen to produce an image on screen. OR Organic Light Emitting Diodes (OLED) emit coloured light themselves (without needing backlighting).

How does an LED flat panel display screen work?

- The printer driver checks that the data (to be printed) is in a format that the inkjet printer understands. - The data is sent to the inkjet printer and temporarily stored in the printer buffer. - The paper from paper feed tray is loaded to the main body of the printer. - An error message is displayed if the tray is empty. - The sheet of paper is fed through the printer as the print head moves from side to side, printing by spraying ink out of four coloured jets. - After each row, the paper is fed slightly forward so that the next line can be printed. - Repeat until whole page printed. - Repeat until whole document printed.

How does an inkjet printer work (steps)?

- They work by converting electrical signals into sound. - The computer produces a digital signal, which then needs to go through a Digital to Analogue Convertor (DAC). - The (now analogue) signal is amplified by the amplifier and this causes the signal to produce a voltage. - The voltage causes the cone in the speaker to vibrate, which produces sound waves (which the user hears).

How to speakers / headphones work (steps)?

A Prototype from CAD/CAM (first try and something you want to make again). A Model from a blueprint (a smaller scale representation of something you want to make) A Final object/product.

Identify 3 types of things that could be made by a 3D printer?

Inkjet printer

Which type of printer has the most expensive ink?

A Laser printer. Because it can hold a whole ream of paper and can hold larger amounts of ink that the other types of printer.

Which type of printer is best for printing large volumes in an office? Why?

An Inkjet printer. Because the fact that it is slow means that produce a better quality image, and it can print on many materials, including photo paper.

Which type of printer is the best for printing good quality photos? Why?