Output Devices

• Capacitive Touchscreens rely on fingers touching the screen to cause a change in the electrostatic field. Microprocessors calculate the exact point of contact.
• Infrared Touchscreens use a glass screen, sensors and infrared transmitters. When a beam is broken by a finger, sensors allow a microprocessor to calculate the point of contact
• Resistive touchscreens ads made up of two layers of conductive material. When a finger touches the top screen, the layers connect, allowing an electrical current to flow, which the microprocessor uses fo calculate the point of contact
• Actuators are used by computers or microprocessors to control a process. They are mechanical or electromechanical devices
• Light Projectors convert digital output into projected light
• DLP projectors use micro mirrors on a DMD chip, which move to produce a greyscale image which is passed through an RGB filter to add colour
• LCD projectors pass a beam of light through a chromatic coated mirror which splits the image into its RGB components. The images are recombined using a prism
• Inkjet printers spray liquid ink droplets from a reservoir onto paper, using either thermal bubble or piezoelectric technology to create the droplets. Stepper motors move paper line by line and the print head moves across the page horizontally
• Laser printers use dry powder ink (toner) which is melted onto the page by a fuser. Negative charge is applied to sections of paper and positive charge is applied to the ink, so that when the drum with the ink rolls over the paper, the ink sticks to the correct sections
• 3D printers produce 3D objects by building up very thin layers of material with printing medium. Direct 3D printing uses a moving print head, and Binder 3D printing passes the print head twice for each layer, first with a dry powder and second with a binding agent
• LED Screens are made up of many RGB LEDs. By varying the current to each diode, brightness is controlled, producing many different colours. Used in large displays and scoreboards.
• LCD screens are made up of millions of liquid crustal arranged as a matrix of pixels, whose properties change as the electric field is changed. They need to be backlit with LEDs to make them visible
• OLED screens generate their own light and provide brighter colours than LCD, have very thin screens of 2mm or less and consume very little power. They also allow for true black
• Loudspeakers produce sound from varying electric currents. If sound is stored on a computer, it is passed through a digital to analogue converter. They are make up of a paper cone, permanent magnet and an electromagnet. As the current causes the coil to vibrate, the cone vibrates too - producing sound