| Topic: |
Science > Physics |
| User: |
"Rich" |
| Date: |
05 Jun 2007 04:32:08 PM |
| Object: |
Efficiency of light sources. |
Not long ago I was browsing Wallgreens while my wife was shopping
and I happened to notice some LED nightlight bulbs, screw in replacements
for the standard C7 incandescent bulb. They have 3 small LEDs inside
and the part number is C7/LED/WG. Having no idea where my old night
lights were I bought a 4-pack of the C7 model with the manual switch.
That night I plugged them in and much to my surprise, they were
very bright. So I bought another 2-pack ($3.99) and placed them
around where needed. They package says that they use less than
1W, which seemed overly vague.
At night my wife needs a room light bright enough to change diapers
by, so we had done lots of experimenting and finally settled on a
2-watt fluorescent, which was still too bright, but mostly did
the trick. Much to my surprise next morning my wife reported that
the LED nightlight was *too bright* and she had trouble sleeping.
Back to the fluorescent for the bedroom.
So navigation around the house at night is now much improved, at
little operating cost.
After this I started wondering about the potential for LEDs for
room lighting. The costs (for some devices) is getting reasonable
and the service life of LEDs is typically good, far better than
fluorescents anyway.
The two remaining problems I see is their cold blue color and
their directional nature. I can see solutions to the latter but
I'm not so sure about the former.
Opps, the biggest problem today would probably be the cost. You
can buy such bulbs today for about $65.
A recent Scientific American had an article on plasmonics, which
turned out to be very interesting. It offers two methods of
increasing the light output of LEDs, one method I recall stated
about 10X the light output and they expect from both methods combined
about 100X the light output. So, in theory at least, the intensity
problem has either been solved, or is solvable.
Anybody have any comments? if they had 100W LED bulbs today for
$20, would anybody buy them? How about $5?
The would also, I assume, work in the cold where fluorescents are
slow to start or won't start a'tall. And they start instantly.
Cheers,
Rich
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| User: "Sue..." |
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| Title: Re: Efficiency of light sources. |
05 Jun 2007 04:58:34 PM |
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On Jun 5, 6:32 pm, Rich <some...@someplace.not> wrote:
Not long ago I was browsing Wallgreens while my wife was shopping
and I happened to notice some LED nightlight bulbs, screw in replacements
for the standard C7 incandescent bulb. They have 3 small LEDs inside
and the part number is C7/LED/WG. Having no idea where my old night
lights were I bought a 4-pack of the C7 model with the manual switch.
That night I plugged them in and much to my surprise, they were
very bright. So I bought another 2-pack ($3.99) and placed them
around where needed. They package says that they use less than
1W, which seemed overly vague.
At night my wife needs a room light bright enough to change diapers
by, so we had done lots of experimenting and finally settled on a
2-watt fluorescent, which was still too bright, but mostly did
the trick. Much to my surprise next morning my wife reported that
the LED nightlight was *too bright* and she had trouble sleeping.
Back to the fluorescent for the bedroom.
So navigation around the house at night is now much improved, at
little operating cost.
After this I started wondering about the potential for LEDs for
room lighting. The costs (for some devices) is getting reasonable
and the service life of LEDs is typically good, far better than
fluorescents anyway.
The two remaining problems I see is their cold blue color and
their directional nature. I can see solutions to the latter but
I'm not so sure about the former.
Opps, the biggest problem today would probably be the cost. You
can buy such bulbs today for about $65.
Solid state lasers can be rather short lived and very
fussy about over currents. You might research that
a bit before investing in a large quantity of the LEDs.
Here is a typical driver for power LEDs with current limiting:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3532
A recent Scientific American had an article on plasmonics, which
turned out to be very interesting. It offers two methods of
increasing the light output of LEDs, one method I recall stated
about 10X the light output and they expect from both methods combined
about 100X the light output. So, in theory at least, the intensity
problem has either been solved, or is solvable.
Anybody have any comments? if they had 100W LED bulbs today for
$20, would anybody buy them? How about $5?
The would also, I assume, work in the cold where fluorescents are
slow to start or won't start a'tall. And they start instantly.
Yes... I have a few screw base type flourescents that are
getting cold natured after about 4 years.
Sue...
Cheers,
Rich
.
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| User: "tj Frazir" |
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| Title: Re: Efficiency of light sources. |
05 Jun 2007 06:02:31 PM |
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20 watt will light a tube 8000 feet long if its one tube bent 200
times.
the gas stimulated emision lamp.
A gas tube is much like a laser but without the reflecting back and
forth amplification .
Its just stimulated gas emiting light .
The resistance of the gas is how long 20 watt can be .
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| User: "Rich" |
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| Title: Re: Efficiency of light sources. |
05 Jun 2007 05:37:25 PM |
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Sue... wrote:
On Jun 5, 6:32 pm, Rich <some...@someplace.not> wrote:
Not long ago I was browsing Wallgreens while my wife was shopping
and I happened to notice some LED nightlight bulbs, screw in replacements
for the standard C7 incandescent bulb. They have 3 small LEDs inside
and the part number is C7/LED/WG. Having no idea where my old night
lights were I bought a 4-pack of the C7 model with the manual switch.
That night I plugged them in and much to my surprise, they were
very bright. So I bought another 2-pack ($3.99) and placed them
around where needed. They package says that they use less than
1W, which seemed overly vague.
At night my wife needs a room light bright enough to change diapers
by, so we had done lots of experimenting and finally settled on a
2-watt fluorescent, which was still too bright, but mostly did
the trick. Much to my surprise next morning my wife reported that
the LED nightlight was *too bright* and she had trouble sleeping.
Back to the fluorescent for the bedroom.
So navigation around the house at night is now much improved, at
little operating cost.
After this I started wondering about the potential for LEDs for
room lighting. The costs (for some devices) is getting reasonable
and the service life of LEDs is typically good, far better than
fluorescents anyway.
The two remaining problems I see is their cold blue color and
their directional nature. I can see solutions to the latter but
I'm not so sure about the former.
Opps, the biggest problem today would probably be the cost. You
can buy such bulbs today for about $65.
Solid state lasers can be rather short lived and very
fussy about over currents.
While true I was not referring to solid state lasers, they tend
to be monochromatic, pinpoint and make very poor light sources.
And one low-power devices used in DVD players seem to last quite
a long time. Now if only the write lasers in DVD burners lasted
longer.
You might research that
a bit before investing in a large quantity of the LEDs.
Well, I've already invested almost $10. This will ruin me! ;^}
Typically I don't consider lighting costs as an investment, but
that's just me.
Here is a typical driver for power LEDs with current limiting:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3532
I don't think low-cost lighting typically uses ICs, although I
could be mistaken. Looking into my LED nightlight I see what looks
like 4 diodes and a resistor. No doubt there's a small transformer
underneath. Looks like a transformer, a full-wave bridge rectifier
and a pulldown resistor. Simple, seems to work.
A recent Scientific American had an article on plasmonics, which
turned out to be very interesting. It offers two methods of
increasing the light output of LEDs, one method I recall stated
about 10X the light output and they expect from both methods combined
about 100X the light output. So, in theory at least, the intensity
problem has either been solved, or is solvable.
Anybody have any comments? if they had 100W LED bulbs today for
$20, would anybody buy them? How about $5?
The would also, I assume, work in the cold where fluorescents are
slow to start or won't start a'tall. And they start instantly.
Yes... I have a few screw base type flourescents that are
getting cold natured after about 4 years.
Geez, what kind are you using? I finally started recording the
start and replace dates of compact fluorescents and with 5 replaced
already this is what I find.
Min 1.08 (years)
Max 2.08 (years)
Avg 1.60 (years)
The average went down from 1.7 years after I replaced one of
the bathroom CF's this morning. Note, I was lazy and used a
365 day year. I don't think I've ever seen a CF bulb last 4
years.
Cheers,
Rich
Sue...
Cheers,
Rich
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| User: "Sue..." |
|
| Title: Re: Efficiency of light sources. |
06 Jun 2007 03:38:08 AM |
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On Jun 5, 7:37 pm, Rich <some...@someplace.not> wrote:
[...]
Opps, the biggest problem today would probably be the cost. You
can buy such bulbs today for about $65.
Solid state lasers can be rather short lived and very
fussy about over currents.
While true I was not referring to solid state lasers, they tend
to be monochromatic, pinpoint and make very poor light sources.
Understood. My point was that the high current, often pulsed,
required to get them to ~laze~ may be comparable to that in
the high power LEDs, making them much less reliable than a
30ma panel indicator. I don't know that to be a fact. But you
can probably find out *before* you take out a second mortgage
on the family pet to relamp the house.
And one low-power devices used in DVD players seem to last quite
a long time. Now if only the write lasers in DVD burners lasted
longer.
You might research that
a bit before investing in a large quantity of the LEDs.
Well, I've already invested almost $10. This will ruin me! ;^}
Mortage your neighbor's pet. I won't tell anyone.
Typically I don't consider lighting costs as an investment, but
that's just me.
Here is a typical driver for power LEDs with current limiting:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3532
I don't think low-cost lighting typically uses ICs, although I
could be mistaken. Looking into my LED nightlight I see what looks
like 4 diodes and a resistor. No doubt there's a small transformer
underneath. Looks like a transformer, a full-wave bridge rectifier
and a pulldown resistor. Simple, seems to work.
So the more current limiting they design in,
the lower the effieciency.
Maxim might tell ya who buys their regulators and why.
That is a cheap survey that won't even require pawing
your wedding ring. :o)
A recent Scientific American had an article on plasmonics, which
turned out to be very interesting. It offers two methods of
increasing the light output of LEDs, one method I recall stated
about 10X the light output and they expect from both methods combined
about 100X the light output. So, in theory at least, the intensity
problem has either been solved, or is solvable.
Anybody have any comments? if they had 100W LED bulbs today for
$20, would anybody buy them? How about $5?
The would also, I assume, work in the cold where fluorescents are
slow to start or won't start a'tall. And they start instantly.
Yes... I have a few screw base type flourescents that are
getting cold natured after about 4 years.
Geez, what kind are you using? I finally started recording the
start and replace dates of compact fluorescents and with 5 replaced
already this is what I find.
Min 1.08 (years)
Max 2.08 (years)
Avg 1.60 (years)
The average went down from 1.7 years after I replaced one of
the bathroom CF's this morning. Note, I was lazy and used a
365 day year. I don't think I've ever seen a CF bulb last 4
years.
No mfr on the one I just retired but I am careful to put them where
they can run continuous or nearly continuous. Besides maximising
the investment I was drawing from some studies that show building
managers where the breakpoint is to balance power savings with
shorter lamp life due to cycling. My forgetter is in turbo boost
but I was really shocked how low the threshold was. IOW if on for
6 hours you may as well leave it on all day. Particularly in an office
building where the lamps are considered part of the heaing system.
This table seems consistant with the notion:
<< Lifetime: the lifetime of fluorescent tubes and lamps
depends greatly on their mean "on-time" (i.e. how long they
are emitting light for on average). >>
http://www.epanorama.net/documents/lights/neonlamps.html
Sue...
Cheers,
Rich
Sue...
.
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| User: "Rich" |
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| Title: Re: Efficiency of light sources. |
06 Jun 2007 09:29:05 AM |
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Sue... wrote:
On Jun 5, 7:37 pm, Rich <some...@someplace.not> wrote:
[...]
Opps, the biggest problem today would probably be the cost. You
can buy such bulbs today for about $65.
Solid state lasers can be rather short lived and very
fussy about over currents.
While true I was not referring to solid state lasers, they tend
to be monochromatic, pinpoint and make very poor light sources.
Understood. My point was that the high current, often pulsed,
required to get them to ~laze~ may be comparable to that in
the high power LEDs, making them much less reliable than a
30ma panel indicator.
I have two LED flashlights with 1W and 3W Luxeon bulbs that will
blind you temporarily if you look into them. They run on D cells.
I don't know that to be a fact. But you
can probably find out *before* you take out a second mortgage
on the family pet to relamp the house.
At this point I'm just planning to use what I have till they all
burn out before buying anything new. PG&E is subsidizing CF bulbs
heavily and I've bought several 4 and 8 packs of bulbs (13W and 26W)
for only a few dollars a pack. They *are* burning out far
faster than expected, but they should last a few more years.
And the low-power devices used in DVD players seem to last quite
a long time. Now if only the write lasers in DVD burners lasted
longer.
You might research that
a bit before investing in a large quantity of the LEDs.
Well, I've already invested almost $10. This will ruin me! ;^}
Mortage your neighbor's pet. I won't tell anyone.
Hey, they are looking for a lost dog, wonder where that rascal is??
Typically I don't consider lighting costs as an investment, but
that's just me.
Here is a typical driver for power LEDs with current limiting:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3532
I don't think low-cost lighting typically uses ICs, although I
could be mistaken. Looking into my LED nightlight I see what looks
like 4 diodes and a resistor. No doubt there's a small transformer
underneath. Looks like a transformer, a full-wave bridge rectifier
and a pulldown resistor. Simple, seems to work.
So the more current limiting they design in,
the lower the effieciency.
Did you mean the less current limiting they design in?
Maxim might tell ya who buys their regulators and why.
That is a cheap survey that won't even require pawing
your wedding ring. :o)
One thing at a time, I'm still looking for that lost dog.
A recent Scientific American had an article on plasmonics, which
turned out to be very interesting. It offers two methods of
increasing the light output of LEDs, one method I recall stated
about 10X the light output and they expect from both methods combined
about 100X the light output. So, in theory at least, the intensity
problem has either been solved, or is solvable.
Anybody have any comments? if they had 100W LED bulbs today for
$20, would anybody buy them? How about $5?
The would also, I assume, work in the cold where fluorescents are
slow to start or won't start a'tall. And they start instantly.
Yes... I have a few screw base type flourescents that are
getting cold natured after about 4 years.
Geez, what kind are you using? I finally started recording the
start and replace dates of compact fluorescents and with 5 replaced
already this is what I find.
Min 1.08 (years)
Max 2.08 (years)
Avg 1.60 (years)
The average went down from 1.7 years after I replaced one of
the bathroom CF's this morning. Note, I was lazy and used a
365 day year. I don't think I've ever seen a CF bulb last 4
years.
No mfr on the one I just retired but I am careful to put them where
they can run continuous or nearly continuous.
Do you record the start and replace dates or is this just from
memory? I write the date on the ceramic with a laundry pen.
Besides maximising
the investment I was drawing from some studies that show building
managers where the breakpoint is to balance power savings with
shorter lamp life due to cycling. My forgetter is in turbo boost
but I was really shocked how low the threshold was. IOW if on for
6 hours you may as well leave it on all day. Particularly in an office
building where the lamps are considered part of the heaing system.
What with the new daylight savings hours we really don't even turn
the lights on at night right now (the kids go to bed at 8PM), only
for a short period in the morning. I woke at 3:30AM or so this morn
but the only light I used was the puter screen. Reminds me, I need
another pot of coffee.
This table seems consistant with the notion:
<< Lifetime: the lifetime of fluorescent tubes and lamps
depends greatly on their mean "on-time" (i.e. how long they
are emitting light for on average). >>
http://www.epanorama.net/documents/lights/neonlamps.html
Interesting.
Cheers,
Rich
Sue...
Cheers,
Rich
Sue...
.
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| User: "tj Frazir" |
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| Title: Re: Efficiency of light sources. |
05 Jun 2007 05:57:48 PM |
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neon florecent is 13 watt 20 inch long 1/2 inch dia. use the dime
starters .
They equal 100 watt bulb.
They stay cool. 10 year gas tube lights.
range from mercury drop in neon florecent gas grow sticks ,,to white
soft and red paint.
I like lights I can spray paint on .
Take used flrencent tubes and cut the ends off and heat bend and put in
oven to cool.
fill the tube with gasses after you solder them together all the way
around the room a few times around tables and solder 2 new lamps on the
ends .
used tubes are free .
make 1 tube 300 feet long in 1 room and light it with 20 watt at each
end.
40 watts will light a room with solid light if you solder and gas fill
2000 feet into 1 tube.
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| User: "Andy Resnick" |
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| Title: Re: Efficiency of light sources. |
06 Jun 2007 08:57:58 AM |
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Rich wrote:
<snip>.
After this I started wondering about the potential for LEDs for
room lighting. The costs (for some devices) is getting reasonable
and the service life of LEDs is typically good, far better than
fluorescents anyway.
The two remaining problems I see is their cold blue color and
their directional nature. I can see solutions to the latter but
I'm not so sure about the former.
You got it exactly- one solution that is used to color-correct "white"
LEDs is to coat the inside with a fluorescent material.
The cost ($/lumen) of an LED is still significantly higher than an
incandescent or a fluorescent. I don't have the numbers on hand, but an
LED is still 100x as expensive as the other sources, IIRC. But they are
good candidates for replacement of some bulbs (traffic lights, brake
lights on autos are good examples) and some low-power applications (I
have a LED gooseneck lamp powered by my computer's USB port), and as the
cost comes down you will see more and more LEDs. Plus, using LEDs for
light design provides a lot more flexibility:
http://www.photonicdreams.com/index.php?option=com_frontpage&Itemid=1
(never mind the cheesy pseudo-scientific babble)
<snip>
--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University
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| User: "Rich" |
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| Title: Re: Efficiency of light sources. |
06 Jun 2007 09:33:23 AM |
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Andy Resnick wrote:
Rich wrote:
<snip>.
After this I started wondering about the potential for LEDs for
room lighting. The costs (for some devices) is getting reasonable
and the service life of LEDs is typically good, far better than
fluorescents anyway.
The two remaining problems I see is their cold blue color and
their directional nature. I can see solutions to the latter but
I'm not so sure about the former.
You got it exactly- one solution that is used to color-correct "white"
LEDs is to coat the inside with a fluorescent material.
The cost ($/lumen) of an LED is still significantly higher than an
incandescent or a fluorescent. I don't have the numbers on hand, but an
LED is still 100x as expensive as the other sources, IIRC. But they are
good candidates for replacement of some bulbs (traffic lights,
I ran the numbers on those and it looks like they are paid for in short
order by power savings even after factoring in their higher cost.
brake lights on autos are good examples)
Most semis today use LED brake lights, and they can be found on some cars.
I've never seen LED replacement bulbs.
and some low-power applications (I
have a LED gooseneck lamp powered by my computer's USB port),
I bought one of those from the dollar store and my computer shut down when
I plugged it in. I threw it away, maybe if I get one from a better source?
Cheers,
Rich
and as the
cost comes down you will see more and more LEDs. Plus, using LEDs for
light design provides a lot more flexibility:
http://www.photonicdreams.com/index.php?option=com_frontpage&Itemid=1
(never mind the cheesy pseudo-scientific babble)
<snip>
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