The document discusses liquid crystal displays (LCDs). It provides information on: - What LCDs are, how they work using liquid crystals and polarization of light - The different types of LCD technologies including passive matrix LCDs, active matrix LCDs, and others - The basic components and functioning of a common 16x2 LCD module, including the display data RAM (DDRAM) for storing character codes, character generator ROM (CGROM) containing character bitmaps, and character generator RAM (CGRAM) for custom characters.

1. 1
TECHVILL
A
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2.  Basic information about different types of lcd
 Memory architecture of LCD.
 LCD commands www.techvilla.org.in

3.  LCD: Liquid Crystal Display is a thin, flat display device made up of any
number of thin crystals
 The crystals act like tiny shutters, opening or closing in response to
the stimulus, thereby allowing degrees of light that have passed
through specific colored pixels to illuminate the screen, creating a
picture.
 These display screens are used in televisions, computer monitors, and
cell phones
What is LCD?What is LCD?
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4. 4
Solid Liquid crystal
“fourth state of matter”
Liquid
Gas www.techvilla.org.in

5. Liquid Crystal – a stable phase of
matter characterized by anisotropic
properties without the existence of a
3-dimensional crystal lattice –
generally lying between the solid
and isotropic (“liquid”) phase. 5
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6. 2015/5/22
6
vs.
Anisotropic
Liquids and gases
(uniform properties in all
directions).
Liquid Crystals
have orientational order
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8. 8
 Consists of an array of tiny segments (called pixels) that
can be manipulated to present information.
 Using polarization of lights to display objects.
 Use only ambient light to illuminate the display.
 Common wrist watch and pocket calculator to an
advanced VGA computer screen
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9. 9
Passive Matrix LCDs (AMLCD) and Active Matrix
LCDs (AMLCD)
 Passive Twisted Nematic Displays (TNLCD)
 Super Twisted nematic LCD (STNLCD)
 Thin Film Transistor LCD (TFT LCD)
 Reflective LCD
 Rear Projection LCD
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10. 10
 The parallel arrangement of liquid crystal molecules along grooves
 When coming into contact with grooved surface in a fixed direction,
liquid crystal molecules line up parallel along the grooves.
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11. MOLECULES MOVEMENT
OFFLINE (NO VOLTAGE IS APPLIED)
ALONG THE UPPER PLATE : POINT IN DIRECTION 'A'
ALONG THE LOWER PLATE : POINT IN DIRECTION 'B‘
FORCING THE LIQUID CRYSTALS INTO A TWISTED STRUCTURAL
ARRANGEMENT. (RESULTANT FORCE)
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12. LIGHT MOVEMENT
OFFLINE (NO VOLTAGE IS APPLIED)
LIGHT TRAVELS THROUGH THE SPACING OF THE
MOLECULAR ARRANGEMENT.
THE LIGHT ALSO "TWISTS" AS IT PASSES THROUGH THE
TWISTED LIQUID CRYSTALS.
LIGHT BENDS 90 DEGREES AS IT FOLLOWS THE TWIST
OF THE MOLECULES.
POLARIZED LIGHT PASS THROUGH THE ANALYZER
(LOWER POLARIZER). 12
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13. MOLECULES MOVEMENT
ONLINE (VOLTAGE IS APPLIED)
LIQUID CRYSTAL MOLECULES STRAIGHTEN OUT
OF THEIR HELIX PATTERN
MOLECULES REARRANGE THEMSELVES
VERTICALLY (ALONG WITH THE ELECTRIC FIELD)
NO TWISTING THOUGHOUT THE MOVEMENT
FORCING THE LIQUID CRYSTALS INTO A STRAIGHT
STRUCTURAL ARRANGEMENT. (ELECTRIC FORCE)
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14. LIGHT MOVEMENT
ONLINE (VOLTAGE IS APPLIED)
TWISTED LIGHT PASSES STRAIGHT
THROUGH.
LIGHT PASSES STRAIGHT THROUGH ALONG
THE ARRANGEMENT OF MOLECULES.
POLARIZED LIGHT CANNOT PASS THROUGH
THE LOWER ANALYZER (LOWER
POLARIZER).
SCREEN DARKENS.
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15. SEQUENCES OF OFFLINE AND
ONLINE MODE
OFFLINE
1. SURROUNDING LIGHT IS POLARIZED
ON THE UPPER PLATE.
2. LIGHT MOVES ALONG WITH LIQUID
CRYSTALS AND TWISTED AT RIGHT
ANGLE.
3. MOLECULES AND LIGHTS ARE
PARALLEL TO THE LOWER ANALYZER.
4. LIGHT PASSES THROUGH THE PLATE.
5. SCREEN APPEAR TRANSPARENT.
Offline Online
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16. SEQUENCES OF OFFLINE AND ONLINE
MODE
ONLINE
1. SURROUNDING LIGHT IS POLARIZED ON
THE UPPER PLATE.
2. LIGHT MOVES ALONG WITH LIQUID
CRYSTALS WHICH MOVES STRAIGHT
ALONG THE ELECTRIC FIELD.
3. MOLECULES AND LIGHTS ARE
PERPENDICULAR TO THE LOWER
ANALYZER.
4. LIGHT CANNOT PASS THROUGH THE
PLATE.
5. SCREEN APPEAR DARK.
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Offline Online
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17. POLARIZATION OF LIGHT
WHEN UNPOLARIZED LIGHT PASSES THROUGH A POLARIZING FILTER, ONLY
ONE PLANE OF POLARIZATION IS TRANSMITTED. TWO POLARIZING
FILTERS USED TOGETHER TRANSMIT LIGHT DIFFERENTLY DEPENDING ON
THEIR RELATIVE ORIENTATION. 17
Online Offline
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18.  A 16x2 LCD display is very basic module and is very
commonly used in various devices and circuits.
 Lcd’s are very economical,easily programmable.
 Can display custom characters.
 Can display 16 characters per line and there are two lines.
 Each character is displayed in 5x7 pixel matrix.
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19.  This lcd consists of:
 DDRAM
 CGROM
 CGRAM
 DDRAM – Display Data RAM
 Stores the character code for each charater of LCD display.
 Extra locations are used for shifting locations.
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20. CGROM – Character Generator ROM
Contains font bitmap for predefined characters that LCD can display.
Character code in DDRAM equates to a location in CGROM(eg. 48H location
refers to character ‘H’)
CGRAM-Character Generator RAM
Provides space for 8 custom characters.
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