Topic 45. Visual Output
Most important visual outputs are based on lamps, LEDs, and liquid crystal displays.
LEDs are probably used more widely than any other device for indicating the output of a system. They are very efficient, use little current, last much longer than filament lamps, and are less easily broken. They are made in a wide range of colours, shapes and sizes. They are also available with a built-in flashing circuit. Because they take little current, they can be driven directly from the output of a 7555 timer IC, TTL, CMOS buffer gates (4049 and 4050), microcontrollers and many other devices. This simplifies circuit design and construction. Super bright LEDs, requiring larger currents, are used in applications such as car brake and indicator lamps and in torches.