The Microcontroller Idea Book - Jan Axelson's Lakeview Research

Displays
8
Displays
In addition to switches and keypads for user input, most projects also include a display to
let users know what’s going on inside. The type of display depends on the kinds of
information you want to show. For simple status indicators, discrete LEDs will do the job.
For numbers, you can use 7-segment displays. And if you need to display text or other
symbols in addition to numbers, character-based LCD modules are a good solution. This
chapter will show how to use each of these in an 8052-BASIC system.
Using LEDs
Discrete, or individual LEDs (light-emitting diodes) are an easy way to indicate status, such
as On, Ready, Mode selected, and so on. They are colorful, eye-catching, and easy to interface
to 5-volt logic. Available colors now include blue as well as red, green, and yellow. Some
individual LED packages can emit red, green, or amber light, depending on the voltages
applied.
Like other diodes, current passes through an LED in one direction only. When a positive
voltage is applied to the anode, current flows and electrons migrate across an energy gap in
the LED, causing it to emit light. The size of the energy gap determines the voltage drop
across the LED, as well as the color of light emitted. A tinted case can also vary the color.
The Microcontroller Idea Book 125