Using LEDs, LCDs and GLCDs in Microcontroller Projects

1.4 Display Devices

Display devices are output devices that can be connected to I/O ports of microcontrollers. Most electronic equipment, whether consumer related, commercial or industrial, have some form of display device, for example, mobile phones, calculators, GPS systems, printers, computers, MP3 players, microwave ovens, and so on.

In this section we are only concerned with small display devices commonly used in microcontroller based projects. In general, we can divide these display devices into three groups: LED based, OLED based and LCD based.

1.4.1 LED

Light Emitting Diode (LED) based displays are further divided into two groups: Simple LED based and 7-segment LED based. Simple LED devices (see Figure 1.3) consist of a single or an array of LEDs, commonly used in applications to indicate the status of something, for example, the on/off status of an electronic device, the selection of an item, and so on. Simple LEDs are available in various colours, such as red, green, orange, blue and white, and are directly connected to I/O ports of microcontrollers via current limiting resistors.

Figure 1.3 Simple LEDs

1.4.2 7-Segment LED

7-segment LEDs (see Figure 1.4) are generally used to display numeric data. The numbers are made up of 7 segments and the required number is displayed by turning on or off the appropriate segments. There are two types of 7-segment displays: common-anode ...