The segment code liquid crystal name originated from the early application of LCD screens, mainly to replace LED digital tubes (composed of 7 pen segments, used to display numbers 0-9), such as calculators, clocks, etc., the display content is all Numbers are also relatively simple, as shown in the figure below: Nowadays, non-dot-matrix LCD displays are generally called segment LCDs.
1. Classificação
O LCD é dividido em tipos: LCD tipo TN, LCD tipo HTN, LCD tipo STN, LCD tipo FSTN e muitos outros tipos.
Compared with the pixel array of dot matrix liquid crystal, the pixel of segment liquid crystal is very free in arrangement and shape. The most common is the "8" field similar to the nixie tube. An "8" is composed of 7 strokes, that is, 7 pixels. The "m" type "8" is composed of 16 pixels. Of course, the pen segment of the segment liquid crystal can be made into any shape, as long as the driving capability of the driving chip permits. Such as the company's logo, other patterns, text, and so on.
It is made of liquid crystal material, and the price is low. The drive cost of the segment code LCD is also very low, and the classic HT1621 series chip is a good choice. The HT1621 can drive 324=128 strokes, which is equivalent to 18 "8" characters. The interface of the HT1621 is serial, with CS, WR, RD (RD can also be omitted), and DATA. The HT1621 can also drive a buzzer to emit sounds with high and low frequencies.
2. Princípio de funcionamento
TN type LCD screen usually has three modes: full transmission, semi transmission and reflection. The liquid crystal will not actively emit light, and an external light source is required. The light source of the transparent liquid crystal comes from behind the liquid crystal; the light source of the reflective liquid crystal comes from the front of the liquid crystal, which is reflected by the polarizer of the liquid crystal screen to the observer's eyes; The light also has reflected forward light. Therefore, the fully transparent liquid crystal requires the use of a backlight, the reflectivity does not require a backlight, and the semi-transmissive liquid crystal can use a backlight or not. It is impossible to observe the display in the dark on an LCD screen that does not use a backlight.
