test test: SMD LEDs VS VS Halogen CFL

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by Christophe » 30/10/10, 10:27

bernardd wrote:I think a small measure would bring the final touch to your test :-)

In passing, the operating voltage of the bulb is not indicated on its presentation page. It is certainly implied by the GU10 format, but for anyone who does not know these codes, like me, it would not be a luxury.


Agree on the 2 points: for the consumption, I would do it on the GU10 and the MR16 ... the 2 are stamped 3.5W in small and 3W in large but in theory the MR16 is supposed to consume less (less transformation of current required) unless the transformation circuit is really very well done ...

ps: if that tells you to test one, know that, as you have more than 300 messages on the forums, you are entitled to 10% on the store (for "life"). So contact us when your customer account is done that I apply the reduction. Explanations here: https://www.econologie.com/forums/10-de-bon- ... t4565.html
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by Obamot » 30/10/10, 10:46

Super test, happy to have learned that quality LEDs have currently acquired a certain maturity. And we are only at the beginning. I also think that LED "panels" have a bright future ...
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by Christophe » 30/10/10, 12:02

Yes now remains to be seen long-term reliability in practice ...

Because 50h has been almost 000 years 6 hours a day ... it's huge! : Shock:

But fortunately, economically the smd led bulb will be profitable long before this ...

A 9W MM compact fluorescent against 40W bulb is about 3000h (at 0.12 € / kWh + price of replacement of the classic bulb every 1000h):

Image

Here is the source file: https://www.econologie.com/calcul-du-ret ... -3659.html which allows this curve to be drawn for any eco bulb.
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by Christophe » 30/10/10, 12:35

Application to this bulb replacing a GU10 halogen of 40W of 2000h:

Image

Return point: approx.4500 h

Image
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by dedeleco » 30/10/10, 12:44

To quickly assess the lifespan of a semiconductor, such as an LED, we use the fact that the lifespan shortens exponentially with temperature. So, we measure its lifetime at two high temperatures ('a few days) and we extrapolate exponentially to ordinary T !!

In any case, the lifespan remains random like the radioactivity !!

We had better cool the LED as much as possible !!!
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by Christophe » 30/10/10, 14:37

I didn't know this method, do you have a more precise link?

According to the readings above with the IR thermometer: we do not exceed 42 ° C at the level of the smd bulb ... against more than 90 ° C for the compact fluorescent.

40 ° C seems very little to me, and therefore favorable to a good lifespan, right?

I will do a test of T ° on Luxeon soon.
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by dedeleco » 30/10/10, 17:56

What matters is the T at the semiconductor junction of the LED, much more in fact than the T of the support !!
So by reducing the current we increase the life as we decrease the T of the junction !!
The Fluo are not semiconductors, except the components of their power supply (power transistors) !!

Otherwise do on google semiconductor temperature breakdown or in English and look at the armada of scientific articles on the aging of semiconductors with temperature (diffusion of impurities, breakdown of junctions; etc ...)
See also the detailed characteristics of semiconductors where it is sometimes indicated (rare) !!
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by Obamot » 30/10/10, 20:42

I confirm, by going more to the bottom of things Dedelco, would it not be also the repeated thermal shocks, of rise and fall in temperature with each switching on that kill them, and less continuous use, much less damaging ( well it's my feeling and what remains in my memory of the evening tech ...)
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by dedeleco » 30/10/10, 22:00

Fluos have laborious start-ups, which quickly damage them (heating and evaporation of mercury, degradation of electrodes).
But the very different semiconductor LEDs, so well designed, are less sensitive to thermal shocks than to the stationary temperature which favors slow diffusions of impurities and degradations which destroy them with a laws of thermal activation typical of semiconductors, of which the The effect is proportional to the heating time.

Fluos and LEDs are very different.

Anyway I am only giving a well-known basic physical guiding framework, and you have to see the specialized articles with the industrial efforts to compensate for these basic defects !!

LEDs gain a lot of lifespan when used below their optimum intensity and avoid any possibility of an uncontrolled peak in current, such as momentary overvoltage in the mains, which very quickly shortens their life!

So if their diet is well stabilized their life will be dramatically lengthened !!
Also their price increases !!

For this reason, the LEDs in series to make the voltage are fragile because if one or more has a low voltage the others support this weakness and suffer with too much current.

In addition, the temptation to increase the current to have the brightness with less LEDs because less expensive, is very strong in China, at the expense of longevity divided by two, not so easy to control !!
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by dedeleco » 30/10/10, 23:18

Actual lifespan of LEDs depending on junction temperature (not the box) and current with a lot of other information:
http://www.mimaki-ls.com/Pdf/appnote/AN ... fetime.pdf
www.philipslumileds.com/uploads/165/WP12-pdf
http://www.etaplighting.com/uploadedFil ... LED_EN.pdf
http://www.nxp.com/acrobat_download2/ot ... fetime.pdf
http://www.edn.com/article/458479-Innov ... bility.php
http://www.edn.com/article/457776-Circu ... fetime.php



20 ° C more (115 ° C to 135 ° C) increases from 70000 hours to 20000 hours for 65% reduction in light !!
So avoid any heat stroke, such as going from 20 ° C to 40 ° C, heat wave or with a covering lampshade that cuts the drafts !!!
LEDs are better in a fridge !!

Basic knowledge of LEDs:
http://en.wikipedia.org/wiki/Light-emitting_diode
Lifetime and failure
Main article: List of LED failure modes

Solid state devices such as LEDs are subject to very limited wear and tear if operated at low currents and at low temperatures. Many of the LEDs made in the 1970s and 1980s are still in service today. Typical lifetimes quoted are 25,000 to 100,000 hours but heat and current settings can extend or shorten this time significantly. [34]

The most common symptom of LED (and diode laser) failure is the gradual lowering of light output and loss of efficiency. Sudden failures, although rare, can occur as well. Early red LEDs were notable for their short lifetime. With the development of high-power LEDs the devices are subjected to higher junction temperatures and higher current densities than traditional devices. This causes stress on the material and may cause early light output degradation. To quantitatively classify lifetime in a standardized manner it has been suggested to use the terms L75 and L50 which is the time it will take a given LED to reach 75% and 50% light output respectively. [35]

Like other lighting devices, LED performance is temperature dependent. Most manufacturers' published ratings of LEDs are for an operating temperature of 25 ° C. LEDs used outdoors, such as traffic signals or in-pavement signal lights, and that are utilized in climates where the temperature within the luminaire gets very hot, could result in low signal intensities or even failure. [36]

LED light output actually rises at colder temperatures (leveling off depending on type at around -30C [citation needed]). Consequently, LED technology may be a good replacement in uses such as supermarket freezer lighting [37] [38] [39] and will last longer than other technologies. Because LEDs emit less heat than incandescent bulbs, they are an energy-efficient technology for uses such as freezers. However, because they emit little heat, ice and snow may build up on the LED luminaire in colder climates. [36] This lack of waste heat generation has been observed to cause sometimes significant problems with street traffic signals and airport runway lighting in snow-prone areas, although some research has been done to try to develop heat sink technologies to transfer heat to other areas of the luminaire . [40]

http://www1.eere.energy.gov/buildings/s ... uring.html
http://www1.eere.energy.gov/buildings/s ... ation.html

So we can accelerate strongly by keeping warm at two different temperatures and by measuring the accelerated degradation of the light emitted over time !!
Then we extrapolate to ordinary T on an exponential graph !!
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