Q10Microprocessor
Question
Q.10. Briefly explain working of LCD and LED.
Answer
An LCD (Liquid Crystal Display) displays alphanumeric characters by selectively polarizing liquid crystal segments/dot-matrix cells to block or pass light, driven by an onboard controller (e.g., HD44780) accepting command/data bytes from the microcontroller, while an LED (Light Emitting Diode) emits light directly when forward-biased current flows through its semiconductor junction.
An LCD (Liquid Crystal Display) works on the principle of controlling the polarization of light passing through a layer of liquid crystal material sandwiched between polarizing filters — applying a voltage across a given liquid crystal cell/segment changes its molecular alignment, altering whether it blocks or passes polarized light, thereby forming visible dark characters/segments against a lighter background; a dot-matrix character LCD module (such as the widely-used 16×2 LCD based on the HD44780 controller) contains its own onboard controller chip that accepts command bytes (to configure display mode, cursor position, clear display, etc.) and data bytes (the ASCII character codes to display) from the interfacing microcontroller over a parallel (commonly 4-bit or 8-bit) data bus along with RS (Register Select), R/W (Read/Write) and E (Enable) control lines.
An LED (Light Emitting Diode) is a semiconductor diode that emits visible (or infrared) light directly when it is forward-biased and current flows through its p-n junction, causing electron-hole recombination that releases energy in the form of photons; LEDs are simple, low-cost indicator devices requiring only a current-limiting resistor and a microcontroller I/O pin to switch on/off, in contrast to the considerably more complex LCD module and its associated command/data protocol needed to display full alphanumeric text.