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
"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
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.
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
As the Chinese get better at making white LEDs this should change for
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.
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 ( email@example.com)
1. If I understand the warning correctly, it applies to environmental
temperature, as well as temperature rise due to heat generated by the
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.
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
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
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
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
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
(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
- Don Klipstein ( firstname.lastname@example.org)
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:
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
Scary, but exhilarating. :)
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.
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.
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
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.
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;)
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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