Viernes Mayo 18 , 2012
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LED Electrics Knowledge

How to Choose the Right Light Bulb

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Until recently, most of us have used the incandescent lighting, which renders the color of objects more closely to that of natural light, in our homes. Fluorescent light was harsh and cold and typically used in offices.

Light is categorized by its color rendering index, or CRI for short, and its color temperature.  CRI is how a light source, a bulb, causes the color of an object to appear to our eye and how well variations in color and shade are duplicated in comparison to natural light.

The CRI number is a rating from 0 to 100, the higher the CRI number the better the color. An incandescent bulb has a CRI of 100. Fluorescent lights can have CRIs of anywhere from 50% to 99%.

Color temperature is expressed on the Kelvin scale (K) is the color appearance of the bulb and the light it produces.

The color temperature of lamps makes them visually “warm,” “neutral” or “cool” light sources. The lower the temperature (2700-3000K) , the warmer the source, yellow-red colors. The higher the temperature(5000K) the cooler the source, green-blue color range.

How this all applies to us when we go to buy light bulbs at Home Depot is that  we generally want light that will  give us the best color rendering, a high CRI number, usually with a neutral or warm color temperature, a lower Kelvin number.

Originally these parameters’ were only met by incandescent lighting, but that is not the case anymore. The compact fluorescent bulbs available today have CRI numbers and light quality that closely matches that of incandescent bulbs. Although compact fluorescent light (CFL) bulbs tend to be more expensive they convert electricity into light much more efficiently than incandescent. The lower energy cost of the CFL can offset the higher cost of the bulb. Compared to incandescent bulbs,  fluorescent bulbs use less power for the same amount of light and usually last longer

An article in Wikipedia states that  ” In the United States, a compact fluorescent light  can save over $30 dollars in electricity costs over the bulb’s life time compared to an incandescent bulb and save 2,000 times its own weight in green house gasses. ”

Many compact fluorescents are designed to replace incandescent bulbs and can fit into most existing fixtures.

A problem with compact fluorescents bulbs is that they are made with a small amount of mercury. This mercury  requires that they be disposed through a hazardous waste disposal program, they cannot be put in the regular trash.

Another type of light is the LED. The LED appears to be the bulb of the future. Although expensive LED bulbs can produce light that is comparable to incandescent.

LED (Light Emitting Diode) last longer that compact fluorescents, they use less energy than traditional bulbs and potentially, compact fluorescents. LED lights are made in all sizes and shapes. LEDs do not contain mercury so their disposal is not a problem.

An article in the New York Times quotes Charles F. Jerabek, the president and chief executive of Osram Sylvania, a unit of Siemans as stating “In the US 78 percent of the public is completely unaware that traditional light bulbs will be phased out in 2012.”

As we all konw that light bulbs should be more energy efficient, and incandescent bulbs will be a thing of the past.

 

LED LIGHT F&Q

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1. Question: what is an LED?
Answer: a light emitting diode (LED) is a semiconductor device that emits visible light when electrical current passes through it, it is a special kind of diode.

2. Question: what color of light can LED emit?
Answer: most LEDs are monochromatic. Light color is associated with the light wavelength. LEDs made with different semiconductor materials emit lights in different wavelengths. LED light wavelengths range from 400 nanometers (blue) to 800 nanometers (red). The colors of popularly available LEDs in the market are red, orange, amber, yellow, green, blue and white. 

3. Question: Can LEDs be used to replace conventional incandescent and florescent light bulbs?
Answer: yes and no. LEDs have increasingly been used in many different applications to replace old incandescent light bulbs. Examples include LED indicator lights for all kinds of electronic devices such as cell phone, calculators, automotive dash panel, LCD back-lighting, etc., LED seasonal decoration lights for Christmas and holidays, LED traffic signs and other LED direction signs, LED flashing lights, and so on. As currently available LEDs have limited brightness, in most cases, they can not be used to replace incandescent or florescent light bulbs for general lighting purposes.

4. Question: what are the advantages of LEDs compared with conventional incandescent lights?
Answer: there are several obvious advantages LEDs have over traditional incandescent light bulbs, they are as follows:
Low power consumption - energy saving,
Long lasting,
Cold lighting,
Ruggedness,
Small size and weight,
Fast switch times,
Simple to use.

5. Question: could you give more detailed explanations about these LED advantages?
Yes. Currently available LEDs are more energy efficient than incandescent bulbs, but less than florescent bulbs with the same light output. The power consumption of popular LEDs ranges from 30mW to 200 mW.
People can save money & energy by using LEDs instead of equivalent incandescent decorative bulbs.
The rated average working life of LED is 100,000 hours compared with 1,000 hours of incandescent bulbs.
LEDs emit cold lights as working LEDs generate very small amount of heat, so LEDs are much safer than equivalent incandescent light bulbs in terms of danger of fire. LEDs don’t have filaments to heat up in order to emit lights just like the case of incandescent bulbs. Lights are emitted from LEDs as a result of energy exchange occurring in the different semiconductor materials an LED is made of.
LEDs are usually shielded with solid transparent plastic materials so they are more rugged than incandescent and florescent bulbs that are usually sealed with glass.
LEDs can be powered by either AC voltage or DC voltage. The circuit that is required to appropriately drive LEDs is much simpler than that for florescent bulbs.

6. Question: we have seen so many advantages LEDs have over incandescent light and florescent bulbs, are there any disadvantages LEDs exhibit compared with incandescent or florescent bulbs?
Yes, the most significant disadvantage is the light output limitation of LED. Currently available LEDs emit limited amount of lights at a relatively small angle range, while incandescent and florescent light bulbs illuminate in all directions and give out much more brightness of light. And this is the reason why LEDs currently can not be used for general lighting applications.
The second significant disadvantage is the high prices of LEDs. The currently available LEDs in the market are 3 ~ 10 times more expensive than equivalent incandescent light bulbs. This is why some customers still hesitate to buy LED products even though LEDs have so many obvious advantages over incandescent bulbs and people actually can save money by using LED products in the long run.

7. Question: what LED products are currently available for general customers?
Answer: the most popular LED products available in volume at the market place are various kinds of LED decoration light products. And in fact, they are ideal for replacing conventional incandescent decoration light products, because when compared with incandescent light products, these LED products save up to 95% energy, have much longer working hours, are more rugged, and safer in terms of danger of fire and electric shock.
At present, people can buy beautiful LED light strings, LED rope lights, LED icicle strings, and individual round LED bulbs with changeable colors, LED rope lights, LED pipe lights, and more other LED products will be put into market in the near future.

8. Question: as we notice that in LED light strings, LEDs are in series connection just like incandescent light strings, how do you compare these two kinds of light strings in terms of reliability?
Answer: LEDs are more reliable. Most available LED light strings have series configuration like old incandescent light strings, where lights in the string are connected in series with each other, so a disconnection of LED light from the string will always make the entire string fail just like incandescent light strings. However, in the case of light burning, an incandescent light bulb will always burn open, namely, the filament of the incandescent bulb breaks, so the whole string will always fail, while an LED light may either burn open like an incandescent light bulb or burn short where a short circuit is formed inside the LED, so the burned LED will stop lighting but all the rest LEDs in the string still light normally. And LEDs usually burn short, therefore, LEDs are more reliable than incandescent light bulbs in that respect.

9. Question: are there any LED strings better than those in series connection?
Answer: yes, there is. Various LED string products are more reliable than those LED strings in series connection in market. OUR strings use a unique patented connection configuration that ensures an LED string will work normally even one or several LEDs are disconnected from the string while keeping the low prices and all the features of LED strings.

10. Question: why are LEDs of some colors are more expensive than LEDs of other colors?
Answer: the reason is that different semiconductor materials are used for different color LEDs, and some semiconductor materials are more expensive than others; another reason is that manufacturing costs are different. White LEDs are the most expensive because red, green and blue LEDs are combined together to make a white LED.