Re: Strange problem with low energy light bulb

[Dave Plowman (News)]

You must really hate daylight then!

Most domestic lighting is used after dark and the colour temperature last
thing in the day is nothing like 4500k.

 

[Albert Manfredi]

You must really hate daylight then!

Daylight for artificial lighting is rather annoying. Maybe humans have
been conditioned to want warmer lighting at night, after 10s of
thousands of years of getting by with fire as light source at night.

I find the 3000K of my CFLs to be barely warm enough.

Bert

 

[Lostgallifreyan]

Wikipedia says 2.6% for the ubiquitous 100W tungsten filament bulb

For a 110V type at 1700 lumens, perhaps. 240V types only put 1200 lumens.

 

[Lostgallifreyan]

I've yet to see a spectrum published for those 'white' leds. I assume
it must be similar to CFLs.

?
That Cree document I cited has extensive detail. Several graphs for various
types. Also, they do a 'binning and labelling' document that shows plots of
all types on a cromaticity diagram. I had to think a bit to work out where
my LED torch was on that, but it's all there.

 

[Lostgallifreyan]

Most domestic lighting is used after dark and the colour temperature last
thing in the day is nothing like 4500k.

No. It's akmost certainly much hotter. While it's at its lowest brightness,
the light of a clear day fading is biased extremely toward blue. The rods
in the eye make use of that, it's why greens and blues look brighter than
red flower petals at twilight.

 

[Lostgallifreyan]

CFLs already include those losses in their stated power. LED fans only
ever quote the DC input power required for the 'chip'.

Talk about an uneven playing field !

Not their fault, exactly. CFL's rarely come without a supply attached now.
Also, LED of this kind are new, very few complete lamps with supplies exist
yet, compared to CFL's. Also, LED's run on a very different range of
supplies. Try running any fluorescent tube off a battery and a resistor.
LED's have a modularity that makes it sensible to specify them directly.

If you want to know the total power, it's not the LED maker's job to
specify any PSU they're not making themselves. You need to look at what
PSU's are available. It's only two specs for power conversion efficiency to
consider. Small inconvenience compared to what's gained.

 

[GregS]

Daylight for artificial lighting is rather annoying. Maybe humans have
been conditioned to want warmer lighting at night, after 10s of
thousands of years of getting by with fire as light source at night.

Not only that, but pinpoint sources of light have glare. Daylight is dispersed.

greg

 

[Lostgallifreyan]

[email protected] (GregS) wrote in

Not only that, but pinpoint sources of light have glare. Daylight is
dispersed.

Which is why LED's work so well when projecting on a white surface. I've
found an LED torch with an XR-E in it to be the best portable light source
I've ever had, If pointed at a ceiling it works better than a small
fluorescent. By 'better' I mean more usable for working with. I'd need a
lot more power to get that with longer wavelengths.

 

[msg]

Daylight for artificial lighting is rather annoying.

<snip>

For some of us in cold climates with little daylight during the winter
season, seasonal affective disorder can be a serious problem; bright
daylight wavelength lighting at night and in the morning is necessary
as a therapy.

BTW, why is this thread crossposted to so many newsgroups? I suggest
removing r.a.t., s.e.b. and s.e.t.a. at least for followups.

Regards,

Michael

 

[Arny Krueger]

In USA, plenty of 40 watt incandescents are rated to produce 445 to 500
lumens. My experience is mostly CFLs consuming 25-30% of the electricity
of "standard" incandescents of same light output.


Everyone else who wants to relamp with CFL, watch out with recessed
ceiling fixtures.

Why? The above successful conversion was in recessed ceiling fixtures.

Strangely nough, CFLs are actually more efficient at
producing heat conducted to the immediately surrounding air than
incandescents are, by producing a lot less infrared. I tried this - a 42
watt CFL heats up a fixture slightly more than a 60 watt incandeswcent
does, at least when I tried it. Make sure your fixture does not get too
hot for the CFL. Not only can excessive heat shorten their lives, but
also excessive heat can make them run dim as well as excessive cold can.

Our sucessful implmentation in recessed ceiling fixtures did not do anything
like matching the wattages. I think that the ratio was from a 150 watt
incadescent to two 32 watt CFLs.

 

[Don Klipstein]

[email protected] (Don Klipstein) wrote in


Ok. I thought more laser diodes were but never mind.. Aren't most class 3B
visible red diodes around 20% efficient or more though? That still leaves a
lot of headroom. Tungsten is often said to be 1% to 2% efficient at making
visible light. So a 100W incandescent 17 l/W at 1% to 2%

More like 6-7%. Each watt of tungsten radiation in the 400-700 nm range
is around 250 lumens.

places the Cree XR-E's 50+ l/W at 3 times that, up to 6%.

Figure around 250-300 lumens per watt of "white LED light". Looks like
those achieve about 20%.

683 lumens in a watt of light only applies for a wavelength around 555
nanometers, where the human eye's photopic sensitivity is highest. For
other wavelengths, multiply 683 by the "photopic function".

These are loose figures but they
suggest that if LED's reach efficiencies like DVD writer diodes, maybe 3 to
4 times the current efficiency can be had. (Not including phosphor losses,
but including LED driver losses). These figures are assuming Imax, 1A per
emitter, if LED's become cheap enough to double the emitter count and drive
each at 500 mA, the efficiency will go up by 50% or more.

- Don Klipstein ([email protected])

 

[Don Klipstein]

You must really hate daylight then!

At usual room illuminating levels in most rooms in most homes, lamps
that match the color of daylight tend to make things somewhat dreary - no
matter what the color rendering index, although higher CRI and any color
distortions being in the "more vivid" direction (common with triphosphor
fluorescents CRI 82-86) tend to help.

"Cool White" fluorescent is 4100-4300 K, generally nominally 4100.

- Don Klipstein ([email protected])

 

[Don Klipstein]

I was asking about LED drivers not CFLs.

CFLs already include those losses in their stated power. LED fans only ever quote the DC
input power required for the 'chip'.

Talk about an uneven playing field !

Linear fluorescents also have nominal wattages not including ballast
losses. Though ballasts for 17 and 32 watt T8 ones and 20 watt T12
ones mostly tend to underpower them a little and fixtures for those tend
to draw close to nominal lamp wattage with ballast losses included.
Same is true with many 22 watt circlines. However, this is not true for
most other linear fluorescents such as most 34 and 40 watt T12 and 15 watt
T8, circlines other than 22 watts, all common wattages 13 watts or less,
30 watt 3-footers, and I think also the new T5 sizes over 13 watts.

- Don Klipstein ([email protected])

 

[Don Klipstein]

I've yet to see a spectrum published for those 'white' leds. I assume it
must be similar to CFLs.

Nichia's NSPW500BS, their longstanding 5 mm white model:
http://www.nichia.com/specification/led_lamp/NSPW500BS-E.pdf

Nichia's NS6W083, a higher power LED:
http://www.nichia.com/specification/led_smd/NS6W083T-E.pdf

Lumileds Luxeon K2:
http://www.lumileds.com/pdfs/DS51.pdf

Cree XRE:
http://www.cree.com/products/pdf/XLamp7090XR-E.pdf

- Don Klipstein ([email protected])

 

[Lostgallifreyan]

[email protected] (Don Klipstein) wrote in

More like 6-7%. Each watt of tungsten radiation in the 400-700 nm
range
is around 250 lumens.

So why do Cree, and Wikipedia, and probably many others, cite only 17 l/W?
Every time I've seen the efficiency expressed as a percentage it's been '1
to 2%'. Wikipedia state 2.6% which is a tad higher than I've ever been told
before, and even that's nowhere near 6-7%! It's not going to be easy to
learn if everywhere I turn there are figures differing by factors of three
or more. What makes all the others I've seen wrong?

 

[Don Klipstein]

[email protected] (Don Klipstein) wrote in


So why do Cree, and Wikipedia, and probably many others, cite only 17 l/W?
Every time I've seen the efficiency expressed as a percentage it's been '1
to 2%'. Wikipedia state 2.6% which is a tad higher than I've ever been told
before, and even that's nowhere near 6-7%! It's not going to be easy to
learn if everywhere I turn there are figures differing by factors of three
or more. What makes all the others I've seen wrong?

I have a homebrew BASIC program with the blackbody function and the
photopic function.

A USA-usual "Big-3" brand 100W 120V "standard frost" or clear
incandescent rated 750 hours average life and with a coiled-coil filament
is rated to produce 1710-1750 lumens, traditionally 1710. (The "Soft
White" version achieves 40 lumens less.)
The color temperature of that one is 2865 K.

My homebrew program says 16.7 lumens per watt (pretty close) and that
6.63% of the radiation is in the 400-700 nm range (the usual definition of
visible light). It assumes an ideal blackbody radiator with all energy
outgo being radiation.

The discrepancy is caused by tungsten having emissivity varying with
wavelength - generally inversely. Infrared radiation is suppressed enough
to get 17.1 lumens/watt instead of 16.7 despite the lamp having some heat
conduction loss. (For that matter, color temperature does not exactly
match filament temperature - filament temperature is slightly lower.)

So an ideal blackbody at 2865 K receiving 100 watts and radiating 100%
of this produces 6.63 watts of visible light and 1670 lumens. The ratio
of lumens to watts of visible output is 252, not 683.
683 lumens in a watt of visible light is only true for yellow-green
light of wavelength around 555-556 nanometers, where this figure is
maximized. Those saying that incandescents are only around 2% efficient
are assuming that a watt of any kind of visible light has 683 lumens.

Assuming my 252 lumens per watt figure for the visible portion of 2865K
blackbody radiation is true for a 1710 lumen 100 watt lightbulb, that
means a 1710 lumen 100 watt lightbulb is about 6.8% efficient at
converting electrical power to visible light (400-700 nm). The truth
won't be far from this.

- Don Klipstein ([email protected])

 

[James Sweet]

No. It's akmost certainly much hotter. While it's at its lowest
brightness,
the light of a clear day fading is biased extremely toward blue. The rods
in the eye make use of that, it's why greens and blues look brighter than
red flower petals at twilight.

It's really very orange in the evening, at least around here. The 5000K
fluorescent in my kitchen looks downright blue compared to evening sun.

6500K is the color of noon sun with clear sky, not something you encounter
often in urban areas.

Incandescent lamps that most people are accustomed to are very orange,
around 2700K.

 

[Mr.T]

Most domestic lighting is used after dark and the colour temperature last
thing in the day is nothing like 4500k.

By that reasoning you should really match the color temperature of
moonlight, which is greater than 4500K.

MrT.

 

[Don Pearce]

By that reasoning you should really match the color temperature of
moonlight, which is greater than 4500K.

MrT.

Nice chart here

http://www.olympusmicro.com/primer/lightandcolor/colortemp.html

d

 

[Mr.T]

Daylight for artificial lighting is rather annoying. Maybe humans have
been conditioned to want warmer lighting at night,

Conditioned, exactly!
Conditioning can be changed, I far prefer daylight lamps. But it does depend
on the application.

I find the 3000K of my CFLs to be barely warm enough.

Fine, that's why we all get a personal preference. However the spectrum
spread has as much to do with it as the stated color temperature IMO.

MrT.