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  #11  
Old Thursday, May 14, 2015
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Default Role of LEDs in our daily lives

Crop production

Most of the world’s crops are currently grown outdoors in sunlight. But some food producers are moving farming indoors to make crop production more efficient. This can improve yields throughout the year and reduce water and fertiliser use.
The cost of traditional fluorescent growing lights is high, so indoor farms are starting to use LEDs instead. This includes the world’s largest ‘plant factory’ in Japan, which uses 17,500 LEDs to harvest 10,000 heads of lettuce every day.
Along with significant energy savings, LEDs generate less heat so they can be placed closer to the plants, allowing more plants to be grown together in a tight space. Manufacturers are also trying to fine-tune the type of light emitted by the LEDs to maximise plant growth.

Home lighting

We use roughly 20% of our electricity to light our homes, so making small changes to our lights could give big energy savings. Although most UK homes still use traditional incandescent filament bulbs, the sale of these for household use has been banned by the UK government in favour of low energy alternatives.
A 60W incandescent bulb can be replaced by a 12W ‘energy-saving’ CFL (compact fluorescent lamp) bulb or a 10W LED light. As LEDs continue to improve in construction and design, their efficiency could double, compared to CFLs, in just a few years. Along with savings in electricity bills, they last longer, can produce ‘warm’ or ‘cold’ light and, unlike CFLs, don’t contain toxic mercury.

Backlit screens

TV and computer screens were among the first mass market uses of LEDs, in the 1990s. LCD screens brightened by LEDs generally use 20–30% less energy than those backlit by older CCFL (cold-cathode fluorescent lamp) technology. As LEDs are compact and lightweight, they’re ideal for this use. LEDs are used to backlight all handheld devices such as mobile phones and by 2016, all backlit screens will be illuminated by LEDs.

Car lights
Car LED headlamps

LEDs are already commonly used in rear car lights, brake lights and interior displays. Their ability to be switched on almost immediately is a great advantage when reaction times are critical. LEDs are starting to be used in car headlights too, with one manufacturer predicting that 20% of headlights will incorporate LEDs worldwide by 2020.
A typical halogen headlight might use up to 65 watts of power. An equivalent LED headlight needs around 15 watts. LEDs need replacing less frequently because of their more durable design.
But there is one drawback; the low heat of LEDs mean headlamp lenses may be more likely to frost over on cold mornings.

Street lighting
It's not just energy savings; LED street lights produce directional white light rather than the yellow glow of traditional sodium lamps. This could be more aesthetically appealing and help to reduce light pollution across the skyline and into people’s homes
Street lightning is being changed with LEDs in London and across UK with other countries hoped to follow suit


source:BBC I wonder
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  #12  
Old Thursday, May 14, 2015
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Default

Quote:
Originally Posted by IslamabadKid View Post
Being an Engineer, I must say (that) the topic itself is quite broad in nature.

If you want to have complete "information" about LED, you first need to understand the semi-conductors, doping, sort of depletion region etc.

Underlying gist is that, which I assume and firmly believe, this topic must be touched from the surface. What I really mean to say is that you need to be aware of its basic functionality - which is hardly going to be asked, its significance - which is incredibly important and vital, and how it can make a prominent, economical difference by preferring LED lighting to incandescent bulbs and compact fluorescent lamps. Some facts - real and authentic - related to LED lighting must be gathered from internet. Take the countries like US, UK etc. and take their figures for comparison, or maybe for devising the plan for the betterment of Pakistan's economy by comparing it "with" their plan of LED lighting.

I do not have my notes with me right now, but I do remember the link, which is energy.gov. Go there and explore a bit about LED lighting(for practical usage). Other than that, the basic functionality you can get about it from the wikipedia page, or you may explore YouTube and type in the search "Light emitting diode".

Regards.

I saw that energy.gov link yesterday
Today I found this and this seemed better.Not too deep or too shallow.
What do you think of this?
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Old Thursday, May 14, 2015
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Post Led

Quote:
Originally Posted by Nazish Hina Shafiq View Post

I saw that energy.gov link yesterday
Today I found this and this seemed better.Not too deep or too shallow.
What do you think of this?
I have just read the material shared in the link, making me revisit and revamp the notes that I have made earlier. It covers a lot of spheres of this topic in a broader perspective. Furthermore, it summarises it quintessentially.

Thanks for sharing this bit.
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Old Thursday, May 14, 2015
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Post Crude Explanation: How LED works

Answering to the picture shared in this thread regarding light emitting diode- which is being displayed on my mobile(2 hours before loaded page), but not on my PC mysteriously(refreshed an moment ago), I am going to elaborate its functionality in a layman's jargon so as to parcel out more to the people here having no science-background. At least let me try to present it in an informal, less technical way.

Please see the picture below in this thread, as all the illustrations are messed because I did not know that this forum did not support the "wide-spaces!"(unlike stackoverflow etc)

Suppose you have two boxes, one filled with + signs(let's call it p) and the other filled with - (minus signs; bold one lol; lets call it n) as depicted below:

--------|
++++ | <--- Box "p" filled with +s
--------|

--------|
-----| <--- Box "n" filled with -s
--------|

And assume that + repels +, but attracts -(minus | bold); and -(minus | bold) repel -(minus | bold), but attracts +.

Now let's suppose that you have two rods, vertically aligned besides each other; one big(three vertical lines with + sign) and one small(one vertical line with minus sign at the top) as illustrated below(which technically is the sign/representation of a battery):

+ | -
--- | |----
|


Now let's join the p and boxes(which is an oversimplified explanation, but to get some idea, let's do it! lol)
FIGURE 1.1

|------|-------|
| ++ | - - |
|------|-------|
| | |
| v |
| B |
v v
P-BOX N-BOX

B above represents the "BOARDER" between two boxes!

You must have a question: "HEY YOU SAID THAT + attracts - and vice versa, but here both are present in their boxes, not attracted towards one and another?"

If you asked this question, you are surely going in the right direction. lol

PLOT TWIST: Assume that when + crosses the boarder, it will leave
- behind; and when - crosses the boarder, it will leave + behind.

It means upon every crossing, both will cancel each other out.

However, at the end, there may be more +s in P-box than -s in N-box; or the other way around, which is there may be more -s in N-box than +s in P-box.

Now connect the boxes(FIGURE 1.1) with the battery like:

+ | -
-----------| |----------
| | |
| |
| |
| |------|-------| |
|--| ++ | - - |-----|
|------|-------|


The + rod will push the +s in P-box towards right, and - rod will push -s in N-box in the left direction. You must be wondering how? (Silly, partially incorrect explanation is coming up) As I stated before that + repels +, but attracts -; and - repels -, but attracts +.

Are you imagining what is going to happen?
YES! - will CROSS the barrier because the smaller rod( - at the top) will push the - in the box constantly while saying, actually yelling:"HEY! HEY! I HATE YOU! STAY AWAY FROM ME! KEEP THE DISTANCE! NO? OKAY! I AM GOING TO PUSH YOU AWAY! AWAYYYYYYY!"

During this all process, -s in the N-box WILL CROSS BOARDER, and whenever a battery(which in our case are two vertically aligned rods) attached to boxes, and -s crosses the boarder, ENERGY WILL BE RELEASED IN THE FORM OF PHOTONS(in simple, less accurate terminology, LIGHT)!


That's how this whole LED works!
P-Box is made of special material; so is the N-Box.

How they are made, will be discussed later(if necessary) as my leisure time ends here, so is the little bit crude knowledge regarding LEDs and my pathetic try to teach you guys a little bit of science(in really really oversimplified way, just to give you the flavour. Obviously, there are a lot of thing I have skipped during this process, and violated many different technicalities! However, this process will at least help you remember the CIRCUIT diagram for future purposes!)

PLEASE CHECK THE SYMBOL OF LIGHT EMITTING DIODE IN THE PICTURE MENTIONED BELOW:

http://upload.wikimedia.org/wikipedi...tion-LED-E.svg
(Black one)

Dinner ends; leisure times ends; so I need to zip my lips as well.


-israr

Last edited by IslamabadKid; Thursday, May 14, 2015 at 10:09 PM. Reason: Messed up illustrations
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Old Thursday, May 14, 2015
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Post Illustrations of LED-Continuation of the last post

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Default Dear Nazish Hina!

I'll be very thankful to you if the notes in respect of "Sources of Energy (Renewable i.e. LED Energy, Solar Energy, Wind Energy)and Non-Renewable Energy conservation and its sustainable use." if prep by you be shared, plz.
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