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Basic information about different types of lcd Memory architecture of LCD. LCD commands www.techvilla.org.in
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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Solid Liquid crystal
“fourth state of matter”
Liquid
Gas www.techvilla.org.in
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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2015/5/22
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vs.
Anisotropic
Liquids and gases(uniform properties in all
directions).
Liquid Crystals have orientational order
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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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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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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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MOLECULES MOVEMENTOFFLINE (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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LIGHT MOVEMENTOFFLINE (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).
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MOLECULES MOVEMENTONLINE (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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LIGHT MOVEMENTONLINE (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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SEQUENCES OF OFFLINE AND ONLINE MODE
OFFLINE1. 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 Online15
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SEQUENCES OF OFFLINE AND ONLINE MODE
ONLINE1. 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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POLARIZATION OF LIGHTWHEN 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.
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Online Offline
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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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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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CGROM – Character Generator ROMContains 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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