LED2011_Pres - LED Technology Alex Alex Grozdic Connor...

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Unformatted text preview: LED Technology Alex Alex Grozdic Connor Matthews Sarah Quirk Background Background on LEDs Light Emitting Diodes – A semiconductor light source. Uses include: Indicators and Signs Illuminations Measuring and Interacting Technologies highlighted: Machine Vision Intelligent Lighting Television Backlighting Machine Machine Vision Machine Machine Vision “Analysis of images to extract data for controlling a process or activity” $1.5B industry Used for imaging (digital cameras), image processing (barcode readers), and outputs (robot guidance systems) Machine Machine Vision Why LEDs are ideal: Long life means less frequent replacement Compact and easily shaped Easily strobed for imaging fast moving parts Wide spectrum of light available Low working temperature Available in waterproof designs Barcode Barcode Scanners Barcode scanners are comprised of 3 parts: Illumination system, sensor/converter, and decoder decoder LEDs are a popular choice for illumination systems in scanners Single Single Point LED Used in contact wand or pentype scanners A single light source (an LED) is used to illuminate the barcode barcode Light is reflected back to the detector and then decoded Wand must be swiped across length of barcode Linear Linear Multiple LED Used in Passive Non-contact readers Works like a wand scanner, but uses a line of LEDs and detectors instead of a single point Does not need to be swiped, but limited in length of barcode Science Science Behind the Scanner Light emitted from the scanner reflects off the barcode and returns to the detector as an analog signal Analog signal is then converted into a digital signal and sent to computer Science Science Behind the Scanner Science Science Behind the Scanner Intelligent Intelligent Lighting Intelligent Intelligent Lighting • Lighting with automated or • • • mechanical abilities Currently used in theater Focus consumer market Save 30% home-energy usage How How It Works • Requires LED lamp-driver, rectifier, smart-supply, and radio control components How How It Works Intelligent Lighting Ckt Lab 2 Ckt • AC power supply goes into the rectifier • Rectifier is 4 diodes – only permits current in one direction • Feeds voltage into the radio control, smart supply, and LED- Lamp Driver How How It Works • Power supply is always on • Smart supply feeds radio and control a standby power • The control sends a signal when the light needs to be on/off Types Types of Smart Supplies • Used to regulate current in LED applications • Power supply voltage & LED forward voltage determine which type is best Smart Smart Supply Circuit LED LED Backlighting LED LED Backlight for LCD Displays Initially used for smaller devices such as cell phones and laptops Growing market for TVs An LED TV is an LCD TV with an LED Backlight instead of a CCFL Backlight Why Why LED Backlights? 20-30% less power consumption due to lower operating voltage (3-120 Vdc with constant current) Wider dimming range and color gamut allowing greater contrast Longer lifetime, 50,000+ hours 30-50% thinner body Compact and Flexible No warm-up period Can be switched on and off faster than CCFLs (Cold Cathode Fluorescent Lamps) and have a higher light output LED LED Backlight for LCD TVs Direct Backlighting or Edge Backlighting using either White or RGB (broadens color gamut) LEDs Direct Backlighting (Local Dimming) – Thin Illuminated Panel in the back of the LCD TV Up to 3,500 LEDs (Varying electrical and optical performance, brightness required, LCD panel performance) Local diming, 80-240 blocks Brighter and clearer Edge Backlighting – LEDs surround the edge of the LCD TV Lower cost and power consumption Thinner body Poorer picture quality How How They Work Think of Light Brite! LED Current Source A sophisticated constant current source approach is necessary to supply the right amount of power for a large amount of LEDs Choose from: (Lack of standardization!) Integrated Circuit LED Drivers (custom) Built into motherboard and integrated with LCD Complete Integrated LED Driver boards Allow for enhanced control features i.e. wide dimming range and ambient light sensing. Consider: Spatial constraints (Room on printed circuit board or motherboard?), Development costs, Life cycle support, Testing and support, Driver input voltage, Driver forward voltage capability (TVs may require multiple ICs based on # of LEDs), Interconnection of LEDs (All in series or some in parallel series?), and solution requirements (Edge or Direct?). Pulse-Width Modulation Brightness is determined by the forward current through the LED backlight Dimmed by applying pulse-width modulation to the supply current – fast strobe light Switch between supply and load is turned on and off – more on is more power Low frequency is visible and can cause eye strain Too high of a frequency creates a blurry appearance Changing brightness setting on TV effects the speed the the pulse-width modulation Questions? Thank Thank you! Sources Sources http://www.digitaltrends.com/computing/led-behind-the-lcdunderstanding-led-backlit-hdtvs/ http://www.ledsmagazine.com/features/6/8/6 http://www.ledsmagazine.com/features/7/9/9 http://www.diodes.com/datasheets/ZXSC310.pdf http://acipower.com/Documents/CMS/Considerations%20for%20 LED%20Backlight%20and%20Driver%20Solutions.pdf http://www.datasheetdir.com/Led-Backlighting-Solution-WithLm3430-And-Lm3432+Application-Notes http://www.maxim-ic.com/app-notes/index.mvp/id/1871 Sources Sources http://www.digitaltrends.com/computing/led-behind-the-lcd-understanding-led-backlit-hdtvs/ http://www.ledsmagazine.com/features/6/8/6 http://www.ledsmagazine.com/features/7/9/9 http://www.diodes.com/datasheets/ZXSC310.pdf http://acipower.com/Documents/CMS/Considerations%20for%20LED%20Backlight%20and%20Driv er%20Solutions.pdf http://www.edn.com/article/519954Intelligent_lighting_holds_promise_for_efficient_lighting_networks.php http://ww1.microchip.com/downloads/en/DeviceDoc/Adding%20Intelligence%20to%20LED%20Lig hting%2001036a.pdf Relf, Christopher G. (2004). Image Acquisition and Processing with LabVIEW 1. CRC Press ISBN 9780849314803 http://www.barcodeman.com/altek/simple/ http://www.adams1.com/readers.html http://www.carolinabarcode.com/how-barcode-scanners-work-a-69.html http://www.datasheetarchive.com/barcode%20reader-datasheet.html http://www.seekic.com/circuit_diagram/Basic_Circuit/BAR_CODE_READER.html ...
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