LED light bulbs - temperature sensivity

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Being disappointed with LED light bulbs that did not last a single month, I was looking for alternatives. I was surprised to find in the website http://www.superbrightleds.com/MR16_specs.htm the following warning:
"important note concerning the installation of LED products:
"Excessive heat will cause LEDs to fail prematurely. "They must be operated in an ambient temperature,not exceeding room temperature, for maximum life time. "As the temperature rises above 23 degrees C, the life time goes down.
"Active cooling, such as a small fan, may be required if they are installed in a small enclosed space without ventilation."
Since summer weather temperatures go way above 23 degrees Celsius (73-74 degrees Farenheit) does this mean that LED light bulbs are useful only as refrigerator lights or in air conditioned rooms?
About two years ago I purchased from the C. Crane Company a LED light bulb indicated in their catalogue as item #20L. It contains 20 LEDs, produces light equivalent to at least 25W incandescent bulb, and is still functioning satisfactorily even though I did not take any precautions whatsoever to keep it cool. Unfortunately, this model has been discontinued, but the fact that the bulb survived summer temperatures suggests to me that the technology for manufacturing LED light bulbs tolerant to higher temperatures does exist.
I would appreciate it if someone here can recommend and provide references for vendors selling 120V LED light bulbs with standard household screw base connection, which produce light equivalent to 25W incandescent bulbs or brighter and which can tolerate summer temperatures.
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For home use leds work but I stopped being interested in white Led when I saw lumen out put was apx 19 Lpw Lumen-per-watt, the same as incandesants. Flourescents go to 110 Lpw, unless better more efficient Leds are out now , why bother with them, plus they cost to much.
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snipped-for-privacy@altavista.com writes

I don't think this has anything to do with temperature at all since LED lamps tend to run almost cold due to their very simple capacitive power supply and low output. It's most likely that the problem that prompted that company to put the warning up was just crap quality white LEDs being used in their products. The first white LEDs from China had a terrible failure rate due to the fact the technology was basically copied badly and manufactured sloppily.
When their lamps started failing they probably made the assumption that it was for the same reason that compact fluorescent lamps fail, and blamed temperature.
As the Chinese get better at making white LEDs this should change for the better.

I'm afraid it's down to trial and error. Even the best sources can get a bad batch of LEDs, so even two lamps of the same style and brand could have a different performance.
Another thing that fries LED lamps is people operating the 12v units on electronic transformers which put out a much higher peak voltage due to their pulsed operation.
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Clive Mitchell
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My experience has been different. I notice temperature rise of the lamp housing surface above the ambient, temperature rise of the air in the lamp above that of the lamp housing surface, temperature rise of the leads and surfaces of the LEDs above that of the air in the lamp, and typically the LEDs have current on the high side - meaning a higher figure for temperature rise of the LED chips above that of the LED surfaces. At 20 mA, a usual 5 mm white LED has its junction temperature around 18 C above that of its leads (as measured 5 mm from the LED body).

I do agree that this can also be a factor.
- Don Klipstein ( snipped-for-privacy@misty.com)
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Clive Mitchell wrote:

Two points.
1. If I understand the warning correctly, it applies to environmental temperature, as well as temperature rise due to heat generated by the bulb.
2. I agree with you that the LED bulbs SHOULD NOT generate sufficient heat to explain significant temperature rise, but one still active from the batch that contains the failed bulbs warms up enough to be felt by touch of the glass bulb.

I am using the 120V LED bulb to light my computer keyboard. Since the bulb is fed by the UPS, I prefer the LED bulb in order to reduce the load on the UPS during power failure. Since I did notice a voltage peak in the UPS when it turns on, I wait for it to stabilize before turning anything else on, including the light. Still, two bulbs did not survive a month each. I believe this is due to poor workmanship. Trial and error at the prices of these bulbs is not good enough. I am hoping for someone to report good experience with some brand and/or vendor.

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Its a well established trend. As LED wattage increases, the efficiency drops. LEDs are slowly moving up the incandescent light product line as LED efficiency at higher wattage gets better. Currently, LEDs have not yet conquered the tens of watts market. However some of those incandescent lamps are replaced by LEDs when the LED's ten year plus reliability is required. And yes, those high wattage LEDs also require well designed heatsinks.
In earlier days - especially after that L-1011 crashed into the Everglades - then LEDs replaced 327 incandescent bulbs. Early LEDs to replace 327s cost maybe $100. As technology advances, the price drops and LEDs get more efficient at higher wattages. But currently the LED is not yet there to replace an incandescent room light.
It is a well establish principle of consumer electronics. The new product must provide a decade of improvement. Low wattage LEDs accomplish that. High power LEDs currently do not. Meanwhile a technology that originally predated Edison's light bulb - fluorescent - does provide that necessary advantage.
Another source of LEDs to replace any incandescent bulb - and have been doing this for decades - is LEDtronics. For further information, seek articles about LEDs from Electronic Products.
snipped-for-privacy@altavista.com wrote:

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On Sun, 30 Oct 2005, w_tom wrote:

Eh? Come again? How does the plane crash relate to the LED retrofitment?
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The lamp in the toilet blew, and when the pilot went to find a torch the plane crashed.
Probably.
(I'm guessing it was probably a runway light that failed.)
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Clive Mitchell
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The famous plane crash into the Everglades made the newspapers as being blamed on a different cause:
A few medical type oxygen generators were in the cargo hold, and at least one was actually running. I forget whether due to malfunction or normal operation, but for either of these reasons some part or parts of one of the oxygen generators reached a temperature on the low end of being able to cause adjacent combustible materials to catch fire, and that started a fire in the cargo hold.
---------------
Runways have so many lights that I surely doubt failure of one or even a few of them or even half of them could make a plane crash. For that matter, jetliners have instruments that can guide them onto runways, good enough for any weather short of bad gale force crosswinds, downbursts, especially dense fog or blizzards or icing of the runway or height of a full-blown thunderstorm. (Planes do get scheduled to land at Orlando around 3 or 3:15 PM in Orlando in the summer, peak time of day and year in the "thunderstorm capital" of the USA, and how often do we hear news of plane crashes there?)
- Don Klipstein ( snipped-for-privacy@misty.com)
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Wrong plane crash - wrong decade. LEDs were replacing incandescent lamps in the 1970s. The technology is that old. You are confusing what I think was a 737 Valujet crash with a previous Eastern Airlines L1011 crash. The L1011 crash occurred when flight crew was distracted by what turned out to only be a burned out light bulb. Solution - replace all 327(?) light bulbs with LED equivalents. Valujet was only two people in the cockpit. The L-1011 crew was a three man cockpit crew with one down in the hell hole trying to resolve a landing gear problem when that plane crashed.
Don Klipstein wrote:

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One I was on almost crashed as it landed in Orlando. It was tornado season and the air was very turbulent. As the tyres were just about to touch the Tarmac the plane suddenly tipped sideways and I saw the tip of the wing just barely miss hitting the runway by about a foot. The pilot pulled it back over, the plane swivelled round at about 45 degrees to the runway, pulled back and slammed down.
There was no applause for the pilot as often happens with difficult landings. Everyone was gripping the arm rests of their seats with white knuckles.
Scary, but exhilarating. :)
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Ah hah! There is a fairly high probability the cause of your LED bulb failure is not due to any inherent manufacturing flaws or low quality workmanship or anything of the like really. The problem is most likely an incompatibility between your specific LED bulbs and UPS power source.
Typical LED bulbs designed for operation from 120V AC often use a capacitive ballast (with a small inrush limiting resistor) to limit the current through the LEDs. This is a very cheap, efficient, and easy to implement solution, so it is very commonly done.
The problem is, a capacitive ballast must be operated with a truly sinusoidal power source (like the mains are). The current through a capacitor is I=C*dV/dt where I is current in amps, C is capacitance in farads, and dV/dt is the time rate of change of voltage per unit time in volts per second. A clean sinusoid has a very slow maximum rate of change of voltage, so the peak current that the LEDs normally are subjected to is fairly low. In other words, the current crest factor of the capacitive ballast when powered from a sinusoidal source is fairly modest.
Your UPS most likely does not produce anything at all like a clean sinusoid (especially when powered by battery, although depending upon it's design it may never produce clean sinusoids even when the AC mains are fully energized). If you look at the output on an oscilloscope you may find that it is rather a square wave output that goes between 0V (with significant dwell time), 150V, 0V, and to -150V or something like that. Or it could be some kind of stepped square wave that more closely approximates a sine wave, but is still very much not a sine wave since it has high dV/dt edges, or at least steps. These high dV/dt edges will cause very high peak currents through the capacitive LED ballast, and the current crest factor will be outrageously high, likely much higher than the LEDs are specified to be able to handle reliably. Hence your LED lamp failed in very short order.
Had the LED lamp been operated from a truly sinusoidal power supply, they would likely have been much more reliable, quite possibly meeting the claimed life expectancy ratings.
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Fritz Schlunder wrote:

I greatly appreciate your detailed explanation, as well as Noozer's, for the reason of my problem. However, I need a solution. I do not need LED light bulbs for general lighting, since I prefer the compact fluorescent bulbs for this purpose. I need LED light to illuminate my keyboard because of its very low power consumption. Its being directional is also a boon.
Noozer points out that the electronic components within the LED bulb are cheap, implying that with better quality electronic components the bulb might last longer. Would it be possible to place between the UPS and the bulb a filter, made of quality components, that would smooth down those sharp edges? If so, where can I find a good design for such a filter and specifications for its components? I am willing to consider building one myself.
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Simple answer would appear to be to modify a desk lamp with LEDs and take 12V power from the computer PSU.Disadvantage of light shutting down with computer. Or hack the UPS to obtain low voltage D.C. source from internal batteries.
Adam
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Given the money spent so far, just get a powerful flashlight and use lithium batteries to power it. They have shelf lives of about a decade and can provide power for quite a while.
If power failures are so frequent that this is too expensive, get a backup system that uses a better quality inverter - check with the companies that sell off-grid power systems.
Mike
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Adam Aglionby wrote:

Even easier would be to get a keyboard that is rear illuminated, but those are sometimes pretty cheaply made or horribly expensive.
Also, you could get a USB powered LED light, or make your own (Clive's site has some ideas;)
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Or use the handy 5V supply from any USB port to power a small cluster of LEDs?
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writes

Yes,you could power 5 bright-white LEDs at 20 ma each for a total of 100 ma,and that would be plenty of light for using a keyboard.For that matter,you could probably draw the +5V right off the keyboard(KB) and have a little light bar on an arm over the KB.
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Jim Yanik
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snipped-for-privacy@altavista.com writes

Just plug your LED lamp in before the UPS and keep a torch handy for if the power goes down.
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Why does this need to be plugged into the UPS at all? If you need light in case of a power outage GET A FLASHLIGHT!
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