Output Devices How many output devices can you name? – Screen (VDU) – Printers (dot-matrix, laser, ink-jet) – Plotter – Speakers – Motors The VDU • Differ by size and 1024x768 resolution Pixels 17 Inch • How is size measured? • How is resolution measured? • What are the main types? This is an old fashioned cathode ray tube (CRT) monitor Modern PCs and Laptops have flat screens with liquid crystal displays (LCD) Dot Matrix Printers • How do these work? • The printer contains a ribbon covered in ink which is located in front of the paper • The print head has a series of pins that are banged against the ribbon which transfers the ink to the Cheap but slow, noisy and poor quality paper Ink Jet Printers • How do these work? • The print head sprays ink onto the paper through a series of nozzles • Ink jet printers have good quality images, are cheap but can be slow and expensive to run Laser printers are fast, Laser Printers high quality and quiet BUT complex and expensive • How do they work? (1) Drum in printer is negatively charged (2) Laser etches a positively charged (3) Ink powder from image onto the drum the toner cartridge sticks to the positively (4) Paper passes charged part of the over the drum and drum the ink powder (5) A fuser unit heats transfers to the paper the paper and fuses on the ink Plotters • Some images need to be done on a large scale such as architects plans • Plotters have an arm with a pen that passes over the paper Sound • Sound can be output with speakers Motors or actuators • Motors are powered by electrical signals from the computer Stepper Motors – the motor is moved in a series of tiny steps Servo Motors – The motor moves continuously at high speed Tasks Use the Internet to find a picture of each of these output devices: – Screen (VDU) – Printers (dot-matrix, laser, ink-jet) – Plotter – Speakers – Motors Write about each device, using what you have learnt from the presentation Extension Exercise: Your friend wishes to buy a printer. Explain which type of printer he should buy and why.