SCI/TECH: Accidental Invention Points to End of Light Bulbs

Originally posted by St Udio

Originally posted by Regenmacher
The new quantum dot bulbs are not out yet...give them a year or so.

[edit on 23-10-2005 by Regenmacher]

i appreciate both the posts you penned.

i'm still scratching my head on this quantum nano-dots LED light source...

Q: will the cost of these lightbulbs include the price of the
Ultraviolet Laser needed to activate these nano-dots?

Q: does the reduced electricity needed to operate generic LEDs
factor in the Ultraviolet Laser needed to excite these "Exotic, LEDs"
~~~~~~~~~~~~~~

They coated an LED with the quantum dots and got white light out of it, so it doesn't require a laser.

Quantum Dots Explained: www.evidenttech.com...

Nano does tungsten too:
Tungsten photonic lattice changes heat to light

[edit on 23-10-2005 by Regenmacher]

LED flashlights should be readily available in anyones home, especially during these times when natural disasters are at their peak. I bought an LED flashlight about 5 years ago at the discovery channel store, it was a bit pricey at the time, but well worth it, it still shines as bright as the first day I bought it.

Even better if we can conserve some energy/money on replacing the old fashioned light bulb to led's around the house.

Now if we could only invent a cure for aids/cancer....

Please correct me if I'm wrong, but I believe I read that Edison's original light bulb prototype still works just fine... the only reason the ones we use at home burn out is planned obsolescence, as was discussed above.

These nano-dots sound interesting, though... I just hope I can afford some.

Heinrich Göbel built functional bulbs three decades earlier than Thomas Alva Edison did.

ive got a led light and even though its really small its too bright and give me a headache striaght away so just because they can produce 'lighter' and more efficient light does it mean my head has to suffer? a from me

Originally posted by Regenmacher

Originally posted by shaunybaby
they could make edison's bulbs last a lifetime, but that wouldn't be right in the whole grand scheme of consumerism. also if they made a lightbulb that lasted forever people would just leave their lights on all the time, this is why they make bulbs that blow, so people don't leave them on. even though the onli time a bulb blows is when u switch it on/off because of the sudden flow of electricity through there, so actually if you don't want your bulbs to blow leave them on all the time...

Wrong! By that load of erroneous info, I take you never have seen a lamp that is left on 24/7 burn out or know that turning it off/on cost less than leaving it on.

How light bulbs burn out
Due to the high temperature that a tungsten filament is operated at, some of the tungsten evaporates during use. Furthermore, since no light bulb is perfect, the filament does not evaporate evenly. Some spots will suffer greater evaporation and become thinner than the rest of the filament.

These thin spots cause problems. Their electrical resistance is greater than that of average parts of the filament. Since the current is equal in all parts of the filament, more heat is generated where the filament is thinner. The thin parts also have less surface area to radiate heat away with. This "double whammy" causes the thin spots to have a higher temperature. Now that the thin spots are hotter, they evaporate more quickly.

It becomes apparant that as soon as a part of the filament becomes significantly thinner than the rest of it, this situation compounds itself at increasing speed until a thin part of the filament either melts or becomes weak and breaks.

Why making bulbs last longer often does not pay
You may have heard that the life expectancy of a light bulb is roughly inversely proportional to the 12th or 13th power of the applied voltage. And that power consumption is roughly proportional to voltage to the 1.4 to 1.55 power, and that light output is roughly proportional to the 3.1 to 3.4 power of applied voltage. This would make the luminous efficiency roughly proportional to applied voltage to the 1.55 to 2nd power of applied voltage.

Now, if a slight reduction in applied voltage results in a slight to moderate loss of efficiency and a major increase in lifetime, how could this cost you more?

The answer is in the fact that the electricity consumed by a typical household bulb during its life usually costs many times more than the bulb does. Bulbs are so cheap compared to the electricity consumed by them during their lifetime that it pays to make them more efficient by having the filaments run hot enough to burn out after only several hundred to about a thousand hours or so.

Do the math. LEDs consume far less wattage and last 50x longer.

There's money in making a light bulb last longer

The Great Internet Light Bulb Book, Part I

[edit on 23-10-2005 by Regenmacher]

what i said was not erroneous info. when was the last time you saw a bulb blow...almost certainly when you switched it on. it's actually the switchin on and off of a bulb that weakens it. bulbs pretty much have a maxium amount of times it can be switched on and off, because it only has a certain amount of times that amount of electricity can suddenly pass through it.

if these bulds have a max. times to switch it on how when i switch my light buld to a new one it shorts out straight away? am i justbuying too dogey bulds or something?

The reason many light bulbs blow out when switched on is because of the thermal stress that comes from rapid heating of the filament. If you were to let the heat build up slowly, not many would ever burn out when turned on. They would though continue to burn out when on because of the evaporation of the filament.

To increase the life of a light bulb there are only so many things one can do. The size of the filament relative to the electrical current it will carry can be increased, which will let the filament stay cooler, but change the color temperature of the light it puts out. The quality of the partial vacuum around the filament can be improved, which essentially changes the evaportaion rate of the filament--the better the vacuum the longer the filament will last. Finally, one can reduce the current flowing through the filament, which has the same effect as increasing the relative size of the filament. I'm sure light bulb companies have experimented with different filament materials and combinations of materials to extend overally light bulb life, but I don't know what works best relative to its cost.

How the heck did we get off on this tangent anyway?

[edit on 24-10-2005 by Astronomer68]

how many psychiatrists does it take to change a "quantum dot" lightbulb?
one.....but the quantum dot lightbulb has to want to change.



i really thought someone would actually make a lightbulb joke. the suspense waiting for one was killing me so....well, here's one.

Originally posted by Astronomer68
I'm sure light bulb companies have experimented with different filament materials and combinations of materials to extend overally light bulb life, but I don't know what works best relative to its cost.

While Im sure the bulb companies have experimented with different filaments, Im not so sure they have done so with the intention of improving the lifetime of bulbs to benefit consumers. I think it is far more likely that the design of bulbs is done with a planned bulb burnout time in order to sell more lightbulbs to consumers. If we buy fewer bulbs, they make less money. This corporate mentality will make it unlikely that we will be seeing these LED lights on the shelves of Walmart anytime soon.

Originally posted by The Parallelogram
the only reason the ones we use at home burn out is planned obsolescence, as was discussed above.

Amen
.

[edit on 24-10-2005 by df1]

You're probably righ there df1, they involve nanotechnology and the U.S. might not want to let that kind of info go to China.