CONTROLLING THE DEFLECTION• There are two separate ways to control the deflection: – Electromagnetic deflection- magnetic principle – Electrostatic deflection – depend on charges.• Electromagnetic Deflection (Remember i=current)
• A color TV screen differsColor TV Screen from a black-and-white screen in three ways: • Three electron beams (Red, Green, Blue)that move simultaneously across the screen. • The screen is coated with red, green and blue phosphors arranged in dots or stripes. • On the inside of the tube, very close to the phosphor coating, there is a thin metal screen called a shadow mask. This mask is perforated with very small holes that are aligned with the phosphor dots (or stripes) on the screen. • .
RASTER/STROKE SCANNING Honeywell GREEN YELLOW STROKE ATT 2 GSSCANNING IS RASTER USED FOR SCANNING RANGE ALL OTHER AOA DATA 20 20 DISPLAYED (BLUE) F DATA 10 10 G 40 MODE 10 10 30 (BLUE) S CMD 20 20 I M .99 20 200 DH DH 140 RA WX RED 10 • Raster Scanning for Attitude • Raster Scanning - weather Sphere return • Stroke Scan for reminder • Stroke for texts, range,
LED DISPLAY • PN diode • Doping modify the color, oxygen, nitrogen are used • 7 bar display for numbers. • Segment type display with diffuser plate or plastic deflector to increase the sizeP134
LED DISPLAYTapes and Pointers Dot Matrix Display• LEDs are also used to • LEDs are normally arranged replace the pointers or in a 9 X 5 matrix or a 4 X 7 tapes on circular scale or matrix. vertical scale displays. • requires special driver• individual diodes are circuits. arranged in groups to form • more common in fields the illuminated bars. outside aviation, with• example is the TCAS displays being produced Electronic Vertical Speed using light bulbs, metal Indicator ‘Fly-From’ and discs and electromagnetic ‘Fly-To’ indications. devices.
LCD – LIQUID CRYSTAL DISPLAY• Operating Principle – The liquid crystal is enclosed between two set of polarizes glass (p137) . – In normal situation, the light can pass, but when current is passed, the molecules of the crystal changes its alignment and control the light. – Color is obtained by color filter on top of the LCD.
PASSIVE AND ACTIVE MATRIX• Passive Matrix – Relies on grids of vertical / horizontal conductors – Scanning current through the horizontal conductors. – pixel is off controlled by vertical conductors.• Active matrix – TFT (Thin Film Transistors) – Pixels are controlled by individual transistors. – Expensive – 800x 600 resolution – 1.4 millions transistors.