OUTPUT DEVICES

1. OUTPUT DEVICES • Monitor • CRT • LCD/TFT • Printer • Impact Printer • Dot matrix • Non Impact Printer • Laser • Inkjet Printer • 3D Inkjet Printer • Plotter • Speaker • Multimedia Projector (LCD)

2. CRT Monitor • A CRT monitor screen uses a cathode ray tube. The screen is coated on the inside surface with dots of chemicals called phosphors. When a beam of electrons hits a dot, the dot will glow.  • On a color monitor these phosphor dots are in groups of three: Red, Green, and Blue. This RGB system can create all the other colors by combination.

3. CRT Monitor Advantages: • Produces a higher quality image than TFT monitor. • Angle of viewing is better than TFT. • Works with light pens in CAD and CAM applications. Disadvantages: • Heavier than TFT. • Runs very hot and can cause fire if left unattended. • Consumes considerably more power than TFT. • Can flicker, leading to headaches and eyesight problems.

4. TFT/LCD Monitor • LCD displays are made of two layers of a polarizing material with a liquid crystal solution in between, divided into tiny cells. An electrical signal to a cell makes the crystals line up in a way that keeps light from going through entirely or just partly. • To make color an LCD screen uses 3 colored subcells for each cell: Red, Green, and Blue.

5. TFT/LCD Monitor Advantages: • Light weight than CRT. • Produces less glare than CRT monitor and also emits less radiation. • Consumes much less power and does not generate as much heat as a CRT monitor. Disadvantages: • Angle of viewing a TFT is critical; unclear when viewed from side by several people. • Can’t be used with light pen.

6. Printer • The speed of a printer is measured in: • cps   = characters per second • lpm   = lines per minute • ppm   = pages per minute • The faster the printing, the more expensive the printer. Types of Impact Printers Dot Matrix Forms characters using row(s) of pins, 9, 18, or 24 which impact the ribbon on top of the paper. Also called pin printers. The more pins, the smoother-looking the characters.

7. Dot MatrixPrinter • Advantages:  • Very cheap to run and maintain. • Easy to use if continuous stationary is required. • Disadvantages: • Very noisy • Costs more than an inkjet printer. • Very slow and poor printing quality.

8. Types of Non-Impact Printers • This type of printer does not involve actually striking the paper. Instead, it uses ink spray or toner powder. • Laser Printer Uses toner and heat bar onto paper to form characters. • Advantages:  • High quality printing. • Fast printing, can handle very large print jobs. • Toner cartridges last for a long time (cost effective). • Disadvantages:  • Expensive • Produce ozone and volatile organic compounds.

9. Inkjet Printer     Sprays ink onto paper to form characters. Advantages:  • Quiet ; High quality text and graphics. • Some can do color. • Cheaper than laser printer. • Light weight and occupies less space. • Disadvantages:  • Output is slow if several copies needed, as there is little buffer capacity to store the pages. • Ink cartridges run out too quickly. • Printing can ‘smudge’ if user is not careful. • Expensive if used a lot.

10. 3D inkjet printer Produces solid 3d models using modified inkjet technology, called ‘tomography’, thin layers of fine powder (plaster, resin and starch) are bonded together as a 3D model (each layer is 0.25mm thick) Uses: To produce prototype which actually work from CAD packages, photograph images, stored drawings etc. Scale model of a train station

11. 3D inkjet printer • Advantages:  • Saves a lot of money, since making prototype by other methods is very time consuming and expensive. • Physical scale models are produced with working parts, giving an idea of end product. • Powder used can be ground up and re-used. • Disadvantages: • Expensive to buy. • Slow at producing output. • End product can sometimes be a little rough and needs further work.

12. Plotter Produces hard copies like printers, but bigger paper size with high quality Uses: To produce large drawing and often used with CAD applications and for use on billboards and giant posters. • Advantages:  • Can produce huge printouts. • Extremely high print quality. • Disadvantages: • Slow in operation. • Expensive, both to buy and to maintain.

13. Speaker • Amplifies the sound. • Uses: • To output sound from multimedia presentations. • Used in home entertainment centres. • Can help blind people through audio output of text on the screen. • Used to play downloaded sound files.

14. Multimedia Projector • Receives analogue or digital signals, though modern projectors work only with digital inputs. • Signal source is usually from a computer, television or DVD player. • Image is magnified and projected onto large screen. • Most multimedia projectors take input from various types of video format such as NTSC (National Television System Committee), PAL (Phase Alternate Line) or SECAM

15. Multimedia Projector • Advantages:  • Enable many people to see a presentation rather than all of them crowding round a small computer screen. • Avoid the need for several networked computers. • Disadvantages: • Images can sometimes be fuzzy. • Multimedia projectors are expensive to buy. • Setting up projectors can be a little difficult.

16. Control Devices Actuator Transducer, used to take signals from a computer and converts them into some form of motion. Conversion of digital to analogue using DAC. • Motor: Motor is turned on or off by the actuator. • Used in many domestic appliances, such as automatic washing machine to rotate drum, water pumps in central heating system and automatic greenhouse to open windows and switch on fans. • Used to control robot arms in industry. • In computers, they operate fans, disk drives and DVD drives.

17. Buzzer: Buzzer is switched on or off by the computer. • Used in many domestic appliances, such as microwave ovens to tell cooking process is complete. • Used in burglar alarm system. • Lights: Actuator is connected to the switch that turns lights on or off. • Used in greenhouses to control lighting conditions. • Used for security lights.

18. Heater: Actuator is connected to switches that turns heater on or off. • Used in greenhouses to control temperature. • Used in central heating systems and automatic washing machines.