Week 25

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4.3 Characteristics of Compact Fluorescent lamp

Compact Fluorescent lamps (CFL) are available in a variety of styles or shapes. Come have two, four or six tubes. Older models and specialty models have separate tubes and ballasts. Some CFLs have the tubes and ballast permanently connected. This allows you to change the tubes without changing the ballast. Others have circular or spiral-shaped tubes. In general, the size or total surface area of the tube determines how much light the bulb produces.

4.3.1 Efficient

CFLs are four times more efficient and last up to 10 times longer than incandescent. A 22 Watt CFL has about same light output as a 100 Watt incandescent. CFLs uses 50-80% less energy than the incandescent.

4.3.2 Versatile

CFLs can be applied nearby anywhere that incandescent lights are used. Energy efficient CFLs can be used in recessed fixtures, table lamps, track lighting, ceiling fixtures and porch lights.

Week 24

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4.2 Potential of Using LED as the Lighting Source

4.2.1 Wide Color Range

The wavelength for the LED ranges from small to large scales. As LED have different wavelength, by using a multiplexing technology to control RGB LED package, it can generate a full color scales.

4.2.2 Small Size

            The sizes of LEDs are small and it can be arranged to any pattern for different applications. The sizes for the LEDs are varying from the smallest Organic LED (OLED) of 1cm type. By such a small package size, it gives a wide area for the lighting engineers to design their own applications.

4.2.3 Easy to Control

            LED operates at low voltage with DC source. Hence, the lighting intensity can be easily driven digitally by using high frequency pulse width modulation (PWM).

4.2.4 Mercury-free

There is no mercury used in the manufacturing of LEDs.

4.2.5 Cost-effective

Although LEDs are initially expensive, the cost is recouped over time and in battery savings. LED bulb use was first adopted commercially where maintenance and replacement costs are expensive. The costs of new LED bulb have gone down considerably in the last few years and are continuing to go down. Today, there are many new LED light bulbs for use in ho mans the cost is becoming less of an issue.

Week 23

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4.1.9 Lifespan / Durability

Since LEDs do not have filament, they are not damaged under circumstances when a regular incandescent bulb would be broken. Because they are solid, LED bulbs hold up well to jarring and bumping. LED bulbs last up to 10 times as long as compact fluorescents and far longer than typical incandescent.

Week 22

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4.1.5 Color Rendering Index (CRI)

Color Rendering Index represents he quality of light and its faithfulness to render colors correctly that is to enable human to perceive colors. The ideal CRI is 100 and some bulbs approach this level. LED bulbs rating ranges from 70 to 95.

Light Source	CRI Index
Fluorescent Lamp	52-95
Incandescent Lamp	~100
HID (mercury)	15-55
LED	0-80

Table 4.2: CRI index for lighting devices

4.1.6 Correlated Color Temperature (CCT)

Correlated Color Temperature is the measure used to describe the relative color appearance of a white light source. CCT indicates whether the light source appears more yellow or gold or orange or more blue, in terms of the range of available shades of white. CCT is given in Kelvin (unit of absolute temperature). 2700K is Warm and 5000K is Cool.

4.1.7 Lumens

Lumen is a unit of standard measurement that is used to describe the amount of light contained in an area as perceived by the human eye. The more lumens, the brighter the light.

4.1.8 Luminous Flux

Luminous Flux is the flow of light measured in lumens. With light bulbs, it provides an estimate of the apparent amount of light the bulb will produce. Depending on the application, much of an incandescent light is wasted because it is emitted in every direction. LED bulbs, on the other hand, put out directional light, sending all of the light exactly where it is needed.

Week 21

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4.1.4 Dimming Options

            Originally LED lights could not be dimmed and would not work with standard dimmer switches. However, many types of Led lighting including white and RGB strip lights come in dimmable models that can be dimmed in two main ways; with LED dimmer switches or using dimmable LED drivers and standard dimmer switches. These two options offer smooth, seamless dimming from 0% to 100% brightness and that means that anyone can install conventional dimmable LEDs or even dimmable color-changing LEDs anywhere that they want LED lighting and the option to dim it.

            One of the benefits of dimmable LEDs and LED dimmers are that they use a different dimming technology than most traditional dimmers and they interact with LED technology itself in such a way that dimming LEDs has absolutely no adverse impact on the life of lights. On the other hand, dimming has little to no benefit in terms of decreased energy consumption, unlike dimming incandescent bulbs which can cut their energy usage. The other possible dimming methods for LED are by using high current rheostat or by using the PWM to control dimming.

Week 20

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4.1.3 Efficiency

LED light bulbs use only 2-17 Watts of electricity. LED bulbs used in fixtures inside the home save electricity, remain cool and save money on replacement costs since LED bulbs last so long. Small LED flashlight bulbs will extend battery life 10 to 15 times longer than with incandescent bulbs.

LEDs do not provide ultraviolet radiation and infrared radiation. The only loss for LED is the heat loss. Industry experts expect continued improvement in light output and cost effectiveness of LED lighting. LED manufacturers expect that LED efficacy will ultimately be achieving a goal of 150 to 200 lumens per watt in the future.

LEDs also have favorable operating characteristics where the light do not require any strike time which means it is instantly come on and off without effect of lifetimes.

Light Source	Loss in Radiation (%)	Heat Loss (%)
Incandescent Lamp	81-86	5-6
Fluorescent Lamp	30-32	44
HID (mercury)	62-65	16-22
LED	0-0.2	80-88

Table 4.1: Losses for different lighting devices

Week 19

* mid sem break *