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.

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.

In message .com,
writes
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?

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.

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.

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.

--
Clive Mitchell
http:/www.bigclive.com

In article , Clive Mitchell wrote:

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.

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).

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.

I do agree that this can also be a factor.

- Don Klipstein )

Clive Mitchell wrote:
In message .com,
writes
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?

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.

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.


As the Chinese get better at making white LEDs this should change for
the better.

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.

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.

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.


--
Clive Mitchell
http:/www.bigclive.com

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.

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.

On Sun, 30 Oct 2005 20:46:58 GMT, Clive Mitchell
wrote:

In message .com,
writes
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?

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.

I agree that the heat rise above ambient of 20ma LEDs is
minimal, but your blanket statement certainly does not apply
to high power LEDs such as any of the Luxeons. These will
all overheat if not connected to a proper heat sink.

As for the impact of ambient temperature on LED life, there
is published data from the LRC that clearly shows decreased
life for even small LEDs when they are operated in a high
ambient temperature. Data for low power LEDs was presented
at the 2002 IESNA Annual conference but I can't find the
paper any more on the LRC Web site. Here is the full
reference.

Narendran, N., and L. Deng. 2002. Performance
characteristics of light-emitting diodes. IESNA Annual
Conference. Technical Papers 157-64. New York, NY:
Illuminating Engineering Society of North America.

LRC data for high power LEDs can be found at:

http://www.lrc.rpi.edu/programs/soli...ects.asp?ID=47

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

wrote in message
ups.com...

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.


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.

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.

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.

And this is most likely your problem.

A UPS puts out a very dirty signal that will easily destroy the cheap
electronics within the LED bulb. If you can find a oscilliscope reading of a
normal outlet and one of an average UPS I bet you'd be surprised by the
difference.

Fritz Schlunder wrote:
wrote in message
ups.com...

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.


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
batteries.

Adam

On Sun, 30 Oct 2005, w_tom wrote:

In earlier days - especially after that L-1011 crashed into the
Everglades - then LEDs replaced 327 incandescent bulbs.

Eh? Come again? How does the plane crash relate to the LED retrofitment?

On 31-Oct-2005, "Adam Aglionby" wrote:

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.

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

Adam Aglionby wrote:
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

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

In message . com,
writes
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.

I wouldn't actually recommend using the lamp on a UPS, especially a
consumer level unit. Their output isn't necessarily going to be the
smooth constant voltage sinewave that the lamp is designed to work with.

--
Clive Mitchell
http:/www.bigclive.com

In message ich.edu,
Daniel J. Stern writes
Eh? Come again? How does the plane crash relate to the LED
retrofitment?

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.)

--
Clive Mitchell
http:/www.bigclive.com

In message .com,
writes
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.

Just plug your LED lamp in before the UPS and keep a torch handy for if
the power goes down.

--
Clive Mitchell
http:/www.bigclive.com

In message .com, Adam
Aglionby writes
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.

Or use the handy 5V supply from any USB port to power a small cluster of
LEDs?

--
Clive Mitchell
http:/www.bigclive.com

In message , Victor Roberts
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.

I agree that the heat rise above ambient of 20ma LEDs is minimal, but
your blanket statement certainly does not apply to high power LEDs such
as any of the Luxeons. These will all overheat if not connected to a
proper heat sink.

Most LED lamps use clusters of 5mm LEDs. There are a few Luxeon
versions, but I shudder to think what the circuitry is like inside them.

If it's the early Chinese white LEDs, then even using them in a fridge
wouldn't make them last longer.

--
Clive Mitchell
http:/www.bigclive.com

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.

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!

On Sun, 30 Oct 2005, wrote:

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.

It is a common misunderstanding that LEDs produce trivial heat. In
fact,
they produce quite a bit of heat per lumen. The primary reasons for the
misunderstanding a

1) This heat is emitted to the rear of the junction, not "out the
front" in
the same direction as the light as is the case with most other light
sources, and

2) Most people's only LED experience is with the very small, relatively
low
output items used as indicator lights on e.g. electronic equipment and
dashboards. A great deal more light is required for illumination than
for
indication.

The backside heat produced by LEDs powerful and numerous enough for
illumination is *not* trivial, and it creates two problems: There is
the
issue of thermal resistance in the materials used to build the lighting
device, its housing and surroundings -- this doesn't really differ from
the
same problem with any other light source, with the exception of the
location/direction of the heat. This is throwing obstacles into the
development, for instance, of LED vehicle headlamps. Not only is the
significant backside heat creating thermal management problems
requiring
elaborate and expensive solutions (fan-cooled headlamps!) to avoid
exceeding
temperature limits in the lamp housings themselves, but the lack of
*frontside* heat means the lens doesn't defog or thaw when the lamp is
turned on. Too much heat in back, not enough in front!

LEDs are also highly temperature sensitive with respect to their
output.
It's common to see a swing on the order of +60% at -30°C to -40% at
+40°C,
relative to nominal output at 20°C. Most other light sources in
current use
are minimally temperature sensitive in this manner, if at all. Filament
and
arc lights generally don't know or care what the ambient temperature
is.
Fluorescent lamps tend to have low output at low temperatures (and
unreliable starting, in extremely low temperatures), but their internal
heat
tends to counteract low ambients such that this tendency amounts to
little
more than extended ramp-up time when started from cold. While thermal
direction and management issues are causing problems for headlamp
engineers,
the temperature sensitivity of LEDs' output makes problems at the other
end
of the vehicle: How do you design a brake lamp that is guaranteed to be
sufficiently intense at 40°C when its emitters are producing only 60%
of
their rated output, while not being overly intense at -40°C when the
emitters are producing 160% of their rated output? It's not as easy as
it
sounds.


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.

Unfortunately, it really is your only reliable option.

DS

wrote in
oups.com:

Fritz Schlunder wrote:
wrote in message
ups.com...

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.


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.

How much light do you NEED,as opposed to "want"?
You could use a small array of alkaline battery powered LEDS(not hi-power
Luxeon LEDs);they could run off two D cells for the time you need (and a
lot longer) to shut down your PC when the house power goes down.
Run an array of small white LEDs off a 12V gel cell,and it would last for
days,if not weeks.

It sounds like you want to light up an entire room with LED light,not just
your PC keyboard.

--
Jim Yanik
jyanik
at
kua.net

Clive Mitchell wrote in
:

In message .com, Adam
Aglionby writes
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.

Or use the handy 5V supply from any USB port to power a small cluster of
LEDs?


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.

--
Jim Yanik
jyanik
at
kua.net

Clive Mitchell wrote in
:

In message , Victor Roberts
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.

I agree that the heat rise above ambient of 20ma LEDs is minimal, but
your blanket statement certainly does not apply to high power LEDs such
as any of the Luxeons. These will all overheat if not connected to a
proper heat sink.

Most LED lamps use clusters of 5mm LEDs. There are a few Luxeon
versions, but I shudder to think what the circuitry is like inside them.

If it's the early Chinese white LEDs, then even using them in a fridge
wouldn't make them last longer.


A one watt Luxeon LED draws 300 ma at ~3.4V,all you need is a 3 terminal
regulator IC and a dropping resistor to limit the current,and properly
heat-sink the Luxeon LED.(and sufficient overhead on the supply.)
Not efficient,but it will work.

In a dark room,a 1W Lux LED is really bright,maybe too bright at close
proximity to a keyboard.

IMO,too much,I'd use a few 5mm bright-white LEDs.

--
Jim Yanik
jyanik
at
kua.net

On Mon, 31 Oct 2005 22:02:49 GMT, "Noozer"
scribbled this interesting note:

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.

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!

Or a kerosene lamp???


--
John Willis

(Remove the Primes before e-mailing me)

John Willis wrote in
:

On Mon, 31 Oct 2005 22:02:49 GMT, "Noozer"
scribbled this interesting note:

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.

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!

Or a kerosene lamp???


--
John Willis

(Remove the Primes before e-mailing me)


I have a camping 2-tube fluorescent lamp that runs on 4 D cells,runs 20 hrs
on both tubes,40 hrs on one tube.Has a nice folding lamp housing so you can
position it,and it's very compact. It cost only $12,made by Eveready,IIRC.

It came in handy last year for Hurricane Charlie.

Then I have one longer portable battery-powered single-tube
fluorescent,designed to be installed in closets with no outlets,uses 8 AA
cells,and has an external 2.5mm power jack that I made one long cable for
that alligator-clips onto my car battery for a worklight,and another cable
that goes to a 12V gel cell for inside use. That lamp cost around $9
IIRC,at WalMart,HD,or Lowes.

--
Jim Yanik
jyanik
at
kua.net

In message , Jim Yanik
writes
A one watt Luxeon LED draws 300 ma at ~3.4V,all you need is a 3
terminal regulator IC and a dropping resistor to limit the current,and
properly heat-sink the Luxeon LED.(and sufficient overhead on the
supply.) Not efficient,but it will work.

So let's assume you are using a 120V source. That's 120 - the 3.5V for
the Luxeon makes a total of 116.5V to drop at 300mA. Better make that a
big resistor for the 35W it's going to have to dissipate.

I could always build one for our 240V supply. That would dissipate 71W.

I'm guessing that the commercial Luxeon lamps contain an unregulated
switchmode circuit like the circuitry in a CFL.

--
Clive Mitchell
http:/www.bigclive.com

LEDs do actually produce as much heat as the same wattage lightbulb.
Here's a link http://www.patmullins.com/ledlightmyths.html#toc2 that
describes the screw in bulb replacements as doomed to fail without
adequate heat dissipating area. I think the Lumileds design guides also
show that surface area to be about 9 square inches per watt.
Here's another link for a LED lightengine
http://intencitylighting.com/IntenCity_OEM.htm with 400 square inches,
and the adjoining pages show that to be about 36 watts of LEDs.

Here's another link http://www.enluxled.com/ showing a screw in bulb
replacement that actually appears thermally viable.

LEDs with Fins! I'm impressed with that one.

Clive Mitchell wrote in
:

In message , Jim Yanik
writes
A one watt Luxeon LED draws 300 ma at ~3.4V,all you need is a 3
terminal regulator IC and a dropping resistor to limit the current,and
properly heat-sink the Luxeon LED.(and sufficient overhead on the
supply.) Not efficient,but it will work.

So let's assume you are using a 120V source. That's 120 - the 3.5V for
the Luxeon makes a total of 116.5V to drop at 300mA. Better make that a
big resistor for the 35W it's going to have to dissipate.


Why not use a plain old iron-core *transformer* (wall-wart?)to lower
voltage and boost current AND efficiency? (120VAC source)

IIRC,the OP was talking about driving them from a 5 or 12V DC source.
That's what I was responding to.


I could always build one for our 240V supply. That would dissipate 71W.

I'm guessing that the commercial Luxeon lamps contain an unregulated
switchmode circuit like the circuitry in a CFL.


More likely to be a regulated switchmode circuit.
LEDs like a constant current. CFLs are much more tolerant than LEDs.

--
Jim Yanik
jyanik
at
kua.net

John Willis wrote:

[... snip...]


Or a kerosene lamp???


--
John Willis

(Remove the Primes before e-mailing me)

Wonderful idea! What will you think of next? Bonfire?
Congratulations for your fast 'progress' towards the stone age!

wrote:
LEDs do actually produce as much heat as the same wattage lightbulb.
Here's a link http://www.patmullins.com/ledlightmyths.html#toc2 that
describes the screw in bulb replacements as doomed to fail without
adequate heat dissipating area. I think the Lumileds design guides also
show that surface area to be about 9 square inches per watt.

The MCPCB that Lumileds stars are mounted on, 1 inch square , is rated
as minimum heatsink requirement for 1W in 25 C ambient, temp of star
board in 70`s C and junction temp at the limit.

Adam

On 1 Nov 2005 16:12:03 -0800, scribbled this
interesting note:


John Willis wrote:

[... snip...]


Or a kerosene lamp???


--
John Willis

(Remove the Primes before e-mailing me)

Wonderful idea! What will you think of next? Bonfire?
Congratulations for your fast 'progress' towards the stone age!

You're very welcome!

Personally, I don't throw out old technology. We've had power outages
in this area that can last anywhere from less than a minute to several
days. In the second case, a kerosene lamp, a gas cook top, and a good
ice chest will get you through. The computer will be useless. The TV
dead. The corded telephone may or may not work, depending upon
conditions, and the roads will be impassable, although the cell phone
charger in the car can be used to keep that one working...if the
system is up.

You may not know it, but you, Sir, are addressing an individual who
owns 78 rpm, LP 33 1/3 RPM, and 45 RPM records, in addition to eight
track tapes, cassette tapes, VHS, CDs, CD ROMs, and DVDs. And I can
play them all. The oldest playback device I own is a Victrola from the
mid-1920s. The latest is a DVD player less than a year old. Just
because something is new does not, necessarily, make it better in all
circumstances. In that power outage, I could still wind up the old
Victrola and listen to a little Bach!:~)


--
John Willis

(Remove the Primes before e-mailing me)

Yes, the Lumileds parts with a dissipator will operate at room
temperature, but life time is short. For commercial applications, they
require a lot more surface area, or a lot of airflow.

In article , Clive Mitchell wrote:
In message ich.edu,
Daniel J. Stern writes
Eh? Come again? How does the plane crash relate to the LED
retrofitment?

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.)

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 )

Here in NY they've started replacing traffic light bulbs with LEDs.
They're certainly bright enough (obviously it's a cluster, not just one
LED), and they have several advantages-- longer life, they tend to fade
a bit with time rather than simply fail, and they won't all fail at the
same time which is what obviously happens with one regular bulb.

Since the outside temperature in NY can reach close to a hundred
degrees in the summer daytime, obviously some LEDs work just fine at
higher temperatures.

Shaun Eli
http://www.BrainChampagne.com
Brain Champagne: Clever Comedy for the Smart Mind (sm)

Replacing incandescent bulbs in traffic lights with LEDs was
ongoing and standard back when Enron and its peers were
robbing $billions from CA. The technology is now so old that
most traffic signals have some or all bulbs replaced by LEDs.

You are confusing a trivial temperature increase - 100
degree F - with serious temperature increases. Even properly
designed PCs work just fine in a 100 degree room with only one
cooling fan in the power supply.

As LED lumens output increases, then LED's efficiency
decreases - which is why LED replacement for incandescent
bulbs in the tens of watts range are so expensive and require
heatsinks.

Do not assume efficiencies of a conventional LED also apply
to LEDs designed to replace a room light incandescents. As
lumens increase, so does inefficiency and heat dissipation.
This was discussed even in IEEE Spectrum sometime in maybe
2001.

Shaun Eli wrote:
Here in NY they've started replacing traffic light bulbs with LEDs.
They're certainly bright enough (obviously it's a cluster, not just one
LED), and they have several advantages-- longer life, they tend to fade
a bit with time rather than simply fail, and they won't all fail at the
same time which is what obviously happens with one regular bulb.

Since the outside temperature in NY can reach close to a hundred
degrees in the summer daytime, obviously some LEDs work just fine at
higher temperatures.

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:
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.
...

On 6 Nov 2005 07:43:26 -0800, "Shaun Eli"
wrote:

Here in NY they've started replacing traffic light bulbs with LEDs.
They're certainly bright enough (obviously it's a cluster, not just one
LED), and they have several advantages-- longer life, they tend to fade
a bit with time rather than simply fail, and they won't all fail at the
same time which is what obviously happens with one regular bulb.

Since the outside temperature in NY can reach close to a hundred
degrees in the summer daytime, obviously some LEDs work just fine at
higher temperatures.

The existence of LED-based traffic signals that work in
summer time temperatures does not contradict what has been
said earlier about the effect of high temperatures on LED
performance and life. Data sheets available from any
reputable LED manufacturer, such as Lumileds, include data
on the decrease in light output with increasing ambient or
junction temperature. The better data sheets use junction
temperature and also include data on the thermal resistance
of the LED package between junction and case. While few
manufacturers have data on LED life as a function of
junction temperature, some data is now available from
various independent lighting product evaluation
organizations.

100F, the temperature you quote is less than 38C, which is
not a very high temperature as far as an LED is concerned.
The issue in the design of LED systems is to insure that the
junction can dissipate its waste power, where the ultimate
heat sink is 25C or 38C.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

On 6-Nov-2005, Victor Roberts wrote:

100F, the temperature you quote is less than 38C

By 0.4F. FAIAP, they are the same.

Mike

John Willis wrote:
On 1 Nov 2005 16:12:03 -0800, scribbled this
interesting note:


John Willis wrote:

[... snip...]


Or a kerosene lamp???


--
John Willis

(Remove the Primes before e-mailing me)

Wonderful idea! What will you think of next? Bonfire?
Congratulations for your fast 'progress' towards the stone age!

You're very welcome!

Personally, I don't throw out old technology. We've had power outages
in this area that can last anywhere from less than a minute to several
days. In the second case, a kerosene lamp, a gas cook top, and a good
ice chest will get you through. The computer will be useless. The TV
dead. The corded telephone may or may not work, depending upon
conditions, and the roads will be impassable, although the cell phone
charger in the car can be used to keep that one working...if the
system is up.

You may not know it, but you, Sir, are addressing an individual who
owns 78 rpm, LP 33 1/3 RPM, and 45 RPM records, in addition to eight
track tapes, cassette tapes, VHS, CDs, CD ROMs, and DVDs. And I can
play them all. The oldest playback device I own is a Victrola from the
mid-1920s. The latest is a DVD player less than a year old. Just
because something is new does not, necessarily, make it better in all
circumstances. In that power outage, I could still wind up the old
Victrola and listen to a little Bach!:~)


--
John Willis

(Remove the Primes before e-mailing me)

I agree with you that old technologoly has its merits - some of it is
even superior to its newer counterpart - and I myself enjoy using it on
many occasions. But like everything else, it has its place and time.
Let us assume that the advice you gave me is good enough for you to
take it yourself. If so, I am amused with the idea that every time when
you turn your computer on, you also light your kerosene lamp and keep
it burning beside the keyboard until it is time to turn your computer
off.

Disappointed as I am with the response which I got in this thread to my
inquiry about building a filter, I took it with good humour, amused
myself with the various comments (even the uncalled for rebuke by Jim
Yanik on Oct 31, 8:50 pm, where he clearly demonstrated that he did not
pay sufficient attention to the passage he was quoting), but while I
decided not to respond to any of those postings, it was too much for me
to hold back my reaction when your idea showed up. O.K., if you are
happy with a kerosene lamp burning beside your computer, who am I to
object.

As a byproduct to my disappointment, I still got a pay off in two ways.
First, a lot of laughter, and laughter, so they say, is good for
health. Second, I found here a fellow, namely yourself, who, like me,
enjoys classical music. It is nice to meet people with something in
common to share.

All the best,

Aharon