[Darksky][DSLF] Digest Number 416 (fwd)
Jan Hollan
Tue, 28 Aug 2001 14:38:20 +0200 (CEST)
further on traffic LED lights and on uniformity with FCO...
---------- Forwarded message ----------
Date: 28 Aug 2001 09:16:33 -0000
From: DarkSky-listAyahoogroups...
To: DarkSky-listAyahoogroups...
Subject: [DSLF] Digest Number 416
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There are 15 messages in this issue.
Topics in this digest:
1. Astro Picture of the Day re: light pollution
From: "David Penasa" <dpenasaAbplw...>
2. LP article in Newsday
From: Gary Citro <callistoAoptonline...>
3. Re: [pa-lights] [Fwd: I-99 lighting]
From: "David Penasa" <dpenasaAbplw...>
4. LD+A article: Full Cutoff Lighting: The Benefits
From: "David Penasa" <dpenasaAbplw...>
5. Re: LED Traffic Lights
From: Tim Poulsen <poulsenAnetacc...>
6. RE: [pa-lights] [Fwd: I-99 lighting]
From: "Peel, Bill D." <BPeelALithonia...>
7. LED Traffic Lights -Re: Digest Number 415
From: star splitter <starsplitter_neAyahoo...>
8. Re: [pa-lights] [Fwd: I-99 lighting]
From: Barry Johnson <johnsonbAivwnet...>
9. RE: Re: LED Traffic Lights
From: "Mark Klosinski" <klosinskiAntelos...>
10. Re: LED Traffic Lights
From: "Glendon L. Howell" <glendonhowellAcompuserve...>
11. RE: [pa-lights] [Fwd: I-99 lighting]
From: "Gerry Lynn Hamilton" <glh5Apsu...>
12. Re: Re: LED Traffic Lights
From: Scott Griswold <grizAsky...>
13. Re: LED Traffic Lights
From: ctstarwchrAaol...
14. Re: [pa-lights] [Fwd: I-99 lighting]
From: ctstarwchrAaol...
15. Re: Re: LED Traffic Lights
From: "Randy John" <skysatAhome...>
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Message: 1
Date: Mon, 27 Aug 2001 09:27:22 -0600
From: "David Penasa" <dpenasaAbplw...>
Subject: Astro Picture of the Day re: light pollution
>Sent: Monday, August 27, 2001 8:51 AM
>Subject: Astro Picture of the Day re: light pollution
> The Astronomy Picture of the Day has a little bit of interesting light
> pollution
> information (most of which is probably old hat to you). Here is the
URL,
> which
> will shift to another image tomorrow:
>
> http://antwrp.gsfc.nasa.gov/apod/
>
> Thanks,
> Pete Eschman
>
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Message: 2
Date: Mon, 27 Aug 2001 11:54:17 -0400
From: Gary Citro <callistoAoptonline...>
Subject: LP article in Newsday
A full page article appeared in Long Island Newsday today in advance of the
public hearing about the proposed Suffolk County LP law which will be held
tomorrow.
The link below has the text of the article, but it will not show you the 2
accompanying photos.
There is a large satellite photo of the US at night (the standard one in IDA
literature), and a smaller photo of Susan Harder standing between a pair of
floods and a badly aimed halogen. You can see down to the "Stars Up--The
International Dark-Sky Association" portion of her T-shirt.
http://www.newsday.com/news/local/state/ny-stlite272339740aug27.story
It's not the best article we could hope for, but it will surely raise many
eyebrows in our NY and Long Island effort!
Gary Citro
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Message: 3
Date: Mon, 27 Aug 2001 12:16:59 -0600
From: "David Penasa" <dpenasaAbplw...>
Subject: Re: [pa-lights] [Fwd: I-99 lighting]
> We need to have the manufacturers develop full cutoff luminaires for
> roadway
> lighting that can meet the uniformity requirements and match the
> pole spacing.
>>
> Not possible, due to laws of physics!
>>David
>
> ???????????????????????????????????
> Not possible, due to laws of physics!
> ???????????????????????????????????
>
> I DON'T UNDERSTAND THIS STATEMENT, UNLESS UNIFORMITY REQUIREMENTS
ARE
> MEASURING LIGHT ABOVE HORIZONTAL, OR MAYBE I HAVE A MISCONCEPTION
ABOUT
> FULL-CUTOFF. COULD YOU EXPOUND ON THIS A LITTLE BIT?
>
> Thanks, Ken
>snip
>David, could you explain where are physical law violated? There is no
>reason that a limitation in the light above the horizon give us a
shorter
>pole spacing.
>Clear skies,
>Fabio
>snip
Ken, Fabio and others:
I knew the minute that I sent my email that I was in trouble! When I
was talking about physical laws being violated, I was referring to the
fact that if you don't have as much light coming out of luminaires at
high angles (above nadir), i.e., in the 80-90 degrees area, then by
definition you will need closer pole spacing. And, yes, light output
above horizontal has nothing to do with it.
So, it still comes down to the question: Is it still possible to have a
luminaire that meets the FCO definition (given its limitation of light
in the 80-90 degree range to meet the definition of FCO) provide the
same uniformity and minimums as say a cutoff or SCO luminaire (given the
light output permitted in the 80-90 degree range to meet its
definition), for a given pole spacing?
David
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Message: 4
Date: Mon, 27 Aug 2001 12:49:56 -0600
From: "David Penasa" <dpenasaAbplw...>
Subject: LD+A article: Full Cutoff Lighting: The Benefits
I'm rerunning one of my past emails, based upon current discussions
about the various cutoffs and their definitions.
From: David Penasa <dpenasaAbplw...>
To: Dark Sky Mailing List <DarkSky-listAyahoogroups...>
Sent: Monday, August 06, 2001 10:59 AM
Subject: [DSLF] LD+A article: Full Cutoff Lighting: The Benefits
http://www.iesna.org/PDF/FullCutoffLighting.pdf
Douglas Paulin's article entitled "Full Cutoff Lighting: The Benefits"
originally ran on page 54 in the April 2001 edition of LD+A. The correct
illustrations were not included with the printed article. They are
included with this version.
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Message: 5
Date: Mon, 27 Aug 2001 11:21:05 -0400
From: Tim Poulsen <poulsenAnetacc...>
Subject: Re: LED Traffic Lights
In speaking with a local roadway lighting engineer, I learned that:
LED lights use 10 watts where the bulbs use as much as 135 watts. They
cannot adjust the brightness with these lamps, in fact, he seemed
puzzled when I asked if they could (as in, why would you want to?
puzzlement). I don't think he ever considered that they would need to.
Maintenance (ie bulb replacement) for the LEDs is virtually zero
My county is on a mission to replace all of the lights with LEDs in
hopes of saving lots of money.
Tim
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Message: 6
Date: Mon, 27 Aug 2001 17:34:45 -0400
From: "Peel, Bill D." <BPeelALithonia...>
Subject: RE: [pa-lights] [Fwd: I-99 lighting]
David, Fabio, and others
FCO luminaires have limited contribution at higher angles above nadir for
three reasons. First, the effective thickness of the flat glass lens
increases at higher angles. Light travels through twice as much glass at 65
degrees as it does at nadir. Transmission losses double. Second, a larger
percentage of light reflects off the inner surface of the flat lens as we
increase the angle of incidence away from nadir. These inner-reflected
components can be reduced (not eliminated) with special optical coatings on
the glass, but the incremental gains do not offset the hefty premium placed
on this coating. These two limitations are usually addressed with drop
glass lenses (and there goes FCO).
The third limitation is that the reflector opening occludes (shrinks from a
square to a skinny rectangle) at the higher angles - we simply have less
'optical real estate' through which light can be delivered. Drop glass
lenses with refractive patterns yield a luminous surface area somewhat
constant in size from nadir to 90 degrees (and above). Again, there goes
FCO.
Most any luminaire with a clear flat glass lens meets IES FCO. The
manufacturer doesn't need to worry about limiting intensity in the 80 - 90
degree range - the factors above take care of that.
Bill Peel
Lithonia Lighting
snip
>David, could you explain where are physical law violated? There is no
>reason that a limitation in the light above the horizon give us a
shorter
>pole spacing.
>Clear skies,
>Fabio
snip
Ken, Fabio and others:
So, it still comes down to the question: Is it still possible to have a
luminaire that meets the FCO definition (given its limitation of light
in the 80-90 degree range to meet the definition of FCO) provide the
same uniformity and minimums as say a cutoff or SCO luminaire (given the
light output permitted in the 80-90 degree range to meet its
definition), for a given pole spacing?
David
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Message: 7
Date: Mon, 27 Aug 2001 15:26:30 -0700 (PDT)
From: star splitter <starsplitter_neAyahoo...>
Subject: LED Traffic Lights -Re: Digest Number 415
280 LEDs per surface. Each surface is powered by a seperate power supply. The draw is cost. Incandescents last about a year, LEDs 10 years. Incandescents burn 100w vs the LEDs which burn 12w. This cuts the power consumption considerably plus the government receives rebates from the power companies (at least in CT) which essentially pay for the changeover. (here's something I just noticed, the power bill last year was $94000, this year it was $30000. That ratio doesn't seem to jive with the reduction in power consumption if you use the wattage readings above.Hmm.)
My town (Hamden CT) has converted all the traffic lights over to LED. Although I haven't experienced the difficulty you have, several other people have complained about it. Perhaps I need to find an intersection in a darkened area, but there are so many street lights around that is difficult. Makes you wonder what's worse. :-)
The brightness of the LED is directly affected by the amount of voltage applied. I can't see why they don't modify these lights to accomodate the ambient light in the area, or better than that use a photocell to decide. If these traffic signals are this bad, it is a traffic hazard and should be brought to the attention of your local Chief of Police and whatever commission is involved with public safety.
Clear Starry Skies! RayK
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Message: 2
Date: Sun, 26 Aug 2001 10:02:28 -0400
From: "Mark Klosinski" <klosinskiAntelos...>
Subject: LED Traffic Lights
Hi all:
Has anyone in this group experienced or heard anything about the new
"lamps"
for traffic lights? (I assume they are LED Lamps. Maybe about a
hundred
little lights.) I first noticed it around Harrisonburg, VA about two
months
ago. The lights are brighter than the normal lights. (Does anyone have
any
readings?)
{Moderator Trimmed Message - Please Trim Past Messages Before Posting}
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Message: 8
Date: Mon, 27 Aug 2001 18:43:10 -0400
From: Barry Johnson <johnsonbAivwnet...>
Subject: Re: [pa-lights] [Fwd: I-99 lighting]
These are not laws of physics. They are the IESNA definitions of cutoff
categories. Such numbers are somewhat arbitrary, but based on a consensus.
They can change when the consensus changes. Laws of physics don't change
this way.
Barry Johnson
>
> So, it still comes down to the question: Is it still possible to have a
> luminaire that meets the FCO definition (given its limitation of light
> in the 80-90 degree range to meet the definition of FCO) provide the
> same uniformity and minimums as say a cutoff or SCO luminaire (given the
> light output permitted in the 80-90 degree range to meet its
> definition), for a given pole spacing?
>
> David
{Moderator Trimmed Message - Please Trim Past Messages Before Posting}
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Message: 9
Date: Mon, 27 Aug 2001 18:54:48 -0400
From: "Mark Klosinski" <klosinskiAntelos...>
Subject: RE: Re: LED Traffic Lights
Hi:
I certainly appreciate the information on the LED from this group. The
inability to adjust the brightness on these lamps brings forth one of the
basic lighting design principles. You design for the environment that the
light will be used in. You don't design the same lighting for a rural area
as you would for the city. The LED could be good for the city, but might be
deadly in the country.
clear skies,
Mark Klosinski
Astro-officers
-----Original Message-----
From: Tim Poulsen [mailto:poulsenAnetacc...]
In speaking with a local roadway lighting engineer, I learned that:
LED lights use 10 watts where the bulbs use as much as 135 watts. They
cannot adjust the brightness with these lamps, in fact, he seemed
puzzled when I asked if they could (as in, why would you want to?
puzzlement). I don't think he ever considered that they would need to.
Maintenance (ie bulb replacement) for the LEDs is virtually zero
My county is on a mission to replace all of the lights with LEDs in
hopes of saving lots of money.
{Moderator Trimmed Message - Please Trim Past Messages Before Posting}
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Message: 10
Date: Mon, 27 Aug 2001 19:35:43 -0400
From: "Glendon L. Howell" <glendonhowellAcompuserve...>
Subject: Re: LED Traffic Lights
Tim,
What the roadway lighting engineer told you is true from his perspective as
he is only used to purchasing the finished product --- the LED lamp.
The typical single LED only needs 2-3 volts DC to drive it and requires
some fixed resistance to drop the remaining voltage of the source. I have
not seen anything on how these new LED traffic lights are physically
constructed though, i.e. are they series connected, or parallel with series
resistance added, or a combination of these methods. In any case, the
buyer is stuck with what resistance is made into the lamp.
LEDs will change brightness substancially with just a little change in
voltage, but again it may be impractical for them to have to install some
method of changing voltage for every situation.
An easier fix that I think should be brought out to manufacturers is to
install a neutral density (ND) filter in front of the LED lamp. ND filters
do not change color but do affect intensity transmission. These may not be
available yet for traffic lighting systems, but necessity is the mother of
invention!
Glen Howell
Va-IDA
Chesapeake, VA
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Message: 11
Date: Mon, 27 Aug 2001 20:17:35 -0400
From: "Gerry Lynn Hamilton" <glh5Apsu...>
Subject: RE: [pa-lights] [Fwd: I-99 lighting]
>>>So, it still comes down to the question: Is it still possible to
have a
luminaire that meets the FCO definition (given its limitation of light
in the 80-90 degree range to meet the definition of FCO) provide the
same uniformity and minimums as say a cutoff or SCO luminaire (given
the
light output permitted in the 80-90 degree range to meet its
definition), for a given pole spacing?
David
<<<
So ... is the answer to this question "yes" or "no?"
(I have read the messages with excellent technical information on this
topic and the FCO/SCO thread. However, the answer to the question was
not clear to me.)
Gerry
Gerry Lynn Hamilton, glh5Apsu...
Member, Central Pennsylvania Observers (CPO)
Member, International Dark-Sky Association (IDA)
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Message: 12
Date: Mon, 27 Aug 2001 20:24:25 -0400
From: Scott Griswold <grizAsky...>
Subject: Re: Re: LED Traffic Lights
Decreasing the brightness using neutral density will also decrease
the brightness during the day possibly rendering lights invisible
under bright sunlight. The use of a light sensor to determine day and
night would allow the lights to be bright during the day and dim at
night.
If these lights are going up everywhere, and we get enough people to
write letters to the DOT in the local areas, we may make enough of a
stir to get something done about this problem.
Both of my parents are in their 60's and I have heard complaints from
both of them. It may appear isolated now, but they will be the
standard everywhere soon enough. Considering the savings these lights
have in dollars, it makes no sense to compromise safety at the same
time.
Pease & Dark Skies,
Scott Griswold
On Monday, August 27, 2001, at 07:35 PM, Glendon L. Howell wrote:
> An easier fix that I think should be brought out to manufacturers is to
> install a neutral density (ND) filter in front of the LED lamp. ND
> filters
> do not change color but do affect intensity transmission. These may
> not be
> available yet for traffic lighting systems, but necessity is the
> mother of
> invention!
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Message: 13
Date: Mon, 27 Aug 2001 20:22:28 EDT
From: ctstarwchrAaol...
Subject: Re: LED Traffic Lights
In a message dated 8/27/01 4:08:06 PM Eastern Daylight Time,
poulsenAnetacc... writes:
> They cannot adjust the brightness with these lamps, in fact, he seemed
> puzzled when I asked if they could (as in, why would you want to?
> puzzlement). I don't think he ever considered that they would need to.
> Maintenance (ie bulb replacement) for the LEDs is virtually zero.
Tim:
Sounds like that engineer's reaction must have been amusing to watch. ;-) Most of the designs that I have seen so far are a direct replacement that is not serviceable. Not surprising because the labor to desolder/resolder a few
LEDs in a large array would not be cost effective. Being a direct current
(DC) device that is initially supplied with alternating current (AC), an
internal rectifier bridge and voltage reduction circuit is incorporated into
many of the designs that I have seen.
Luminance can indeed be varied with the voltage that is applied to an LED as
Ray has stated. In order to attenuate LED traffic lighting, an external tap
between the current supply and the parallel circuitry that connects to the
array would be required in order to connect a photosensor switch circuit that
would match the LED array luminous output to the ambient brightness in the
surrounding area. This is very similar to the opto-sensor circuitry used in
many television sets that senses the lighting in the room and attenuates the
brightness of the picture tube accordingly. It is 30 year old technology
(first introduced by Quasar I think).
No traffic signal products that I have seen offer this option yet, but it
definitely has a need and is a CAN DO. More people need to complain about
the high luminance of traffic signals in dark areas and suggest attenuating
the brightness in relation to the surrounding area. From that, a
one-size-fits-all solution can be developed that provides the correct
illuminance for any situation. Are any manufacturers listening?
Clear skies,
Cliff Haas
[Non-text portions of this message have been removed]
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Message: 14
Date: Tue, 28 Aug 2001 01:51:24 -0000
From: ctstarwchrAaol...
Subject: Re: [pa-lights] [Fwd: I-99 lighting]
--- In DarkSky-listAy....., "David Penasa" <dpenasaAb.....> wrote:
>
> When I was talking about physical laws being violated, I was
> referring to the fact that if you don't have as much light
> coming out of luminaires at high angles (above nadir), i.e.,
> in the 80-90 degrees area, then by definition you will need
> closer pole spacing.
>
Hi David:
I've pondered your statement and wish to propose the following
questions/observations to consider. Light leaving any luminaire at
80 degrees from nadir will always travel exactly 5.67 times the
mounting height, provided the distance is measured along a flat
horizontal plane representing the surface of the ground (task area).
This is determined by simple Geometry.
Would you agree that when talking about roadway lighting, that our
only relevant task area is the space appearing between the guardrails
or shoulders framing the lanes of traffic? If so, it would be
logical to only assess this area's properties when determining
average illuminance and uniformity ratios. By using that logic, I
have not had difficulty exceeding IES recomendations for uniformity
of residential roadways using FCO lighting, but I have not run models
on freeway class applications yet. I'm wondering if this is the
approach that is used by other roadway lighting designers?
Wasn't it Peter Talmage, P.E., who first determined several years ago
that the threshold of *usable light* falling on the ground with
enough illuminance to benefit visual acuity occurred at ~3 times the
luminaire mounting height with most fixtures? I believe this figure
has also been written into a few ordinances since that time. It has
been quite a while since I have seen this and my memory is a bit
fuzzy. The 3x rule might have been the criteria established for
minimum distance to mount luminaires from an abutting property line.
If the 3x rule is true in regard to pole spacing (translates to 6x
mounting height between adjacent poles), the optimum angle for
maximum luminous flux emission would be 72 degrees above nadir,
again, per the rules of Geometry. Any illuminance falling beyond
that distance deteriorates by the square of the distance from the
source to a point where it eventually becomes moot (light meter-
wise). This 3x figure is puzzling, however, because IES states that
luminaires with long throw properties can be mounted up to 12 times
the mounting height or double the figure mentioned above.
The 72 degree maximum flux emission is is very close to what KIM
Lighting recommends for their FCO luminaires, too. I have seen many
manufacturers recommend spacing luminaires at 6x the mounting height
in their literature as well. It was also my impression that flux
emission above the 80 degree figure was a determination to be the
*glare zone* where horizontal illumination did more harm than good to
visual acuity. This also appears in the KIM Theory of (lighting)
Relativity.
I'm interested in everyone's thoughts on these issues.
Cheers,
Cliff Haas
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Message: 15
Date: Tue, 28 Aug 2001 06:07:34 -0000
From: "Randy John" <skysatAhome...>
Subject: Re: Re: LED Traffic Lights
Tim,
When I spoke to our traffic engineer he told me that he had asked about
night-time dimmers. They were not 'yet' available.
To everyone else remember, as the use of these LED lamps increases, the
surrounds will have to ratchet up accordingly.
Randy
----- Original Message -----
From: "Tim Poulsen" <poulsenAnetacc...>
To: "Darksky list" <darksky-listAyahoogroups...>
Sent: Monday, August 27, 2001 3:21 PM
Subject: [DSLF] Re: LED Traffic Lights
> They cannot adjust the brightness with these lamps, ...
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