-- snip --
Please tell me you had your tongue in your cheek when you said that. Please do.
Alternately, if you can name just one democracy in the world that has money that doesn't ultimately come from taxes and fees on _someone_ (with real citations, not the likes of Ralph Nader or Glenn Beck), I'd be interested to hear it.
-- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
True! But local governments take Federal grants like it came from a real rich uncle, and not the public.
But I'll take the bait... cite something that Beck said that you can prove was a lie :-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The only thing bipartisan in this country is hypocrisy
Nah. Instead I'm going to apologize RIGHT NOW for bending an 'almost political' thread to 'getting too political'.
->>>> Sorry.
Ask the horses if the health bill will pass :-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The only thing bipartisan in this country is hypocrisy
I will.
-- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
What exactly does this 70 C stand for ?
Assuming 3.3 V drop at 1 A (the maximum current specified for long life specified by Cree *) the power dissipation is 3.3 W and with junction to "solder point" thermal resistance of 6 C/W, the junction is 20 C hotter. If the solder point temperature is 70 C, the junction temperature is 90 C as in the old germanium transistor days :-).
Getting 3.3 W out of a 70 C case to a 30 C ambient temperature is comparatively easy, just requiring a heatsink with (70-30)/3.3 W or 12 C/W thermal resistance, which should be easy to achieve.
Unfortunately, in order to produce something resembling 3000 lumens at the light pole, a large number of LED devices would be required, making it impossible to produce in a confined space with LEDs+heatsinks.
*) From the Cree documentation:
About 3 to 4 times better than sodium
-- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.blogtalkradio.com/onetribe - Occult Talk Show
Really? What about the decades of incandescent street lights, and the use of other technologies I've seen. Hell, we've had gas lights at times. Both carbide and natural gas.
-- Lead free solder is Belgium's version of 'Hold my beer and watch this!'
Around here I've seen a modified bucket truck with a rear wall of flashing lights in the shape of arrows on the rear to direct traffic around the truck. They climb a short ladder from inside the truck to reach the bucket, and it can be done by one worker.
-- Lead free solder is Belgium's version of 'Hold my beer and watch this!'
Bingo! You hit the nail fight on the head" "democracy".
The USA is NOT a Democracy. It's a Republic. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The only thing bipartisan in this country is hypocrisy
No. At least not on the level of individual fixtures. It's quite possible to do, of course - but it means another stage. (or letting the LEDs flicker, which makes them less efficient.
Not quite..close to a bankrupt dictatorship (on its way to the second; already made the first). Our financial status and rigts have been whittled away since FDR stole out gold and Nixon abolished the illusion that our money was backes by gold. Look at the "Patriot" act, look at TSA, need i go further?
Photometric units (candela, lumen, lux) already take into account the photopic response of "standard average human vision".
More efficient LEDs have bandwidth around 20-25 nm FWHM for blue, around 30-35 nm for green, and maybe 20-30 nm red and orange. Significant spectral content exists for a bandwidth at least double the FWHM bandwidth.
If I needed monochromatic lighting for around an observatory, I would use low pressure sodium for:
As it turns out, the LEDs on the market with highest luminous efficacy so far are white ones with blue-emitting chips and greenish-yellow-glowing phosphor. I have heard of some green LED prototypes using a phosphor (and I assume a blue LED chip) having lumens out per watt in as high as notable recent white laboratory prototypes.
- Don Klipstein ( snipped-for-privacy@misty.com)
There are now LED manufacturers, especially Lumileds, who publish projected life expectancy of lighting class LEDs at temperatures that are very reasonable. I will have to dig back in, but I seem to recall more recent white Luxeon ones being stated by Lumileds to be projected to maintain 70% of their initial light output at 50,000 operatingh hours with (I forget which) 350 or 700 mA current and some figure of peak junction temperature that I now forget, ??? probably somewhere in the range of 100-120 C, definitely hotter than 85 C.
(The PDF datasheet only reads in versions of Acrobat higher than the one on my partition with an older operating system and the program that my PC-based e-mail program is on - so I can't get to it just now.)
I can't remember exact thermal resistance of these well now either. But I am confident that the junction temperature is sufficiently cool for this 50,000 hours life expectancy (based on accelerated testing of products invented less than 50,000 hours ago) when heatsink temperature is 60 C, probably 75 C.
On the other hand, optical characteristics of these are rated for junction temperature of 25 C. With real-world thermal conditions, expect a few to several percent less light output than indicated by the "25 C junction" figures in the datasheet for white Luxeons.
- Don Klipstein ( snipped-for-privacy@misty.com)
In , Robert Baer wrote in part:
A good 99.5%-plus of the visible spectrum content of SOX series low pressure sodium lamps is in the 589.0 and 589.6 nm lines in the orangish yellow. Both of these spectral features, like the other notable (notably around 3 orders of magnitude weaker) spectral features of low pressure sodium, have bandwidth less than .1 nm.
So, a good 99.5%-plus of the visible spectral content of low pressure sodium is in a closely spaced pair of narrow lines, where the total bandwidth of that spectral feature is somewhere around .7 nm. The visible spectrum, according to the most common definition, is 400-700 nm.
I know of one orangish-red line pair, nothing between that and 800 nm in the very near IR, and 3 overlapping series of very weak line pairs that produce the orangish-red line pair and plenty from very-yellowish-green to bluish violet. Most of this is in the orangish-red line pair, a very yellowish green line pair, and a very bluish green line pair. This whole set of 3 series accounts for only a few tenths of a percent of visible spectrum content of SOX series low pressure sodium lamps.
- Don Klipstein ( snipped-for-privacy@misty.com)
I would say more extreme than that by an order of magnitude, as in more like 99.5% of visible spectrum content of low pressur sodium being in one line pair having total bandwidtyh less than 1 nm, and the next one down probably has less than .2% of the total.
The 2nd-place visible spectrum feature of a low pressure sodium lamp is close to there, comprised of 4 lines: 567.0, 567.6, 568.2 and 568.8 nm. The first two of those are much stronger than the last two.
I saw that...
The Na entry has only one of the line pairs shown at all, the main one in the orangish yellow.
This source cites 2nd place being .7%, which sounds a goog half an order of magnitude high to me if it is a visible spectrum feature. (Likely according to a spectrometer experiencing saturation or having uncorrected non-flat spectral response or both.)
- Don Klipstein ( snipped-for-privacy@misty.com)
Lumileds does the same.
For white LEDs with reasonably accomplishable heatsinks in reasonable ambient temperatures (even 30 C), I would say dropping by more like 10%, maybe 15% if pushing for smaller heatsink size.
Lumileds states life expectancy figures with a requirement of junction temperature being cooler than the 150 C or whatever maximum, but still fairly hot in (IIRC) the 100-120 C range.
In older days, non-white LEDs were supposed to achieve 100,000 hour life expectancy if current did not substantially exceed "characterization current" and junction temperature did not exceed 85 C. Lately, 100 degrees C junction temperature or even a little more is OK, although non-phosphor LEDs of color yellow-green to red tend to have substantial negative temperature coefficient for photometric performance.
I would worry about hot nights far to the east of San Jose. I seem to think of typical July and August nighttime temperature in San Jose around
11-14 C. Philadelphia, farther north, has average nighttime *minimum* temperature (around sunrise) for July and August being 19-20 C at the official weather station location and about 21 C in Center City. This figure is probably 23-24 C in Orlando, Houston and New Orleans. Central city Phoenix in July and first half of August is also very warm at night.- Don Klipstein ( snipped-for-privacy@misty.com)
I agree that this is likely true, same as for fluorescent and germicidal low pressure mercury vapor lamps. The similarity among these is in radiation resulting from atomic electron transitions between states where the lower state is "the ground state".
- Don Klipstein ( snipped-for-privacy@misty.com)
In terms of the skywards light pollution from street lighting the dominant US component is from mercury light followed by HPS.
Notable exceptions were the Golden Gate bridge which for a long time was lit by LPS and regions surrounding world class observatories.
In the UK you can still find a few vintage gas lights in London if you know where to look, but they contribute almost nothing to light pollution. I don't recall ever seeing a UK road with incandescent streetlamps or for that matter an American one.
The worst offending private lights are wall mounted 1kW quartz halogen insecurity lights in crude tin cans so half their light goes upwards.
Regards, Martin Brown
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