Re: Are Halogen Blue- Lites the best?

Yep. Remember, the Xenon is only present in an automotive HID burner to satisfy statutory and practical requirements for near-instantaneous startup. Without Xenon, automotive HIDs would have a long, slow startup time like the big Hg- or Na- arc discharge lamps you remember from your school's gymnasium. When a "Xenon" headlamp is first started, its appearance is extremely blue. This Xenon arc provides a minimal amount of light until the heat of the arc vaporizes the metal salts in the burner, which then greatly intensify the arc.

Reply to
Daniel J. Stern
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Not the gap, the *arc*. Of course the gap has higher resistance (determined by the dielectric properties of the interstitial atmosphere) before power is applied. But then, the filament also has much *lower* resistance before power is applied, too!

Well...no. The efficacy advantage of integral-reflector halogen stationary lighting at 12v rather than 120v has nothing directly to do with "raised current"; rather it is almost entirely optical. For a given level of luminous flux, a 12v filament is much more compact -- it can more closely approximate a point source, which in turn facilitates greater optical precision.

...for the same reason as discussed above: More compact filament, therefore better beam focus.

Reply to
Daniel J. Stern

I use full-spectrum fluorescent bulbs in my apartment that is located in a basement. It imitates natural light, which helps since I don't get much sunlight through my windows.

Reply to
Henry Paul

Okay. I deserve a "duh" for that: *Of course* you can have *both* a halogen *and* Xenon gas together in a bulb. Must... Engage... Brain... Before... Engaging... Keyboard...

And the cynic in me suspects that the only reason for including a tiny amount of xenon with the halogen gas in such filiment-based bulbs is to permit the manufacturer to advertize the bulbs with the name "Xenon."

Cool! Thanks for the link. As you might have guessed, it's been quite a while since I studied chemistry, as well. (Though not as far back as pre-1962. I'm starting to wonder just how good my HS chemistry classes

*were*!)

- Greg Reed

Reply to
Ignignokt

Naw, you don't. You *think* you do, and the packages they come in probably say "full spectrum", but there is no such thing as a "full-spectrum fluorescent bulb". This is in part because of the nature of fluorescent lamps, which do not have a continuous SPD. It is also because there is no agreed-upon definition of "full spectrum". It is a marketing term only.

Doesn't. And all the research on the subject shows that it's the

*quantity* of light, much more than the quality, that staves off seasonal affective disorder.

If you like the quality of light that you get from these "full spectrum" bulbs you're buying, great, keep using 'em, but don't labor under any illusions about their purported magical powers.

Reply to
Daniel J. Stern

One side point...

There is a significant trend of 12V incandescents/halogens being somewhat more efficient than 120V versions of the same wattage, and there are a couple explanations:

  1. In gas-filled incandescents (includes all halogens) there is a heat conduction loss by the fill gas. This loss is surprisingly proportional to the "apparent-visible" overall length of the filament and surprisingly independent of the width of the filament.

The explanation for this: Change the width of the filament, and the "boundary layer" of filament-heated gas has its thickness change almost proportionately and that makes the temperature gradient in this layer of gas vary almost inverse-proportionately, almost cancelling the effect of increased filament circumference.

This effect is like one in HID lamps, discussed more thoroughly in "The High Pressure Mercury Vapor Discharge" by W. Elenbaas. Heat conduction from most "linear" mercury arcs is close to 10 watts per centimeter of arc length, usually not varying much with arc diameter nor mercury vapor pressure. I mention this in

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  1. Making the filament shorter and thicker permits a slightly higher temperature for a given life expectancy.

There is a limitation on "goodness" of a lower design voltage - if the filament is very thick and very short, heat conduction through the ends of the filament becomes a significant loss.

With design voltage as a variable and design wattage and life expectancy constant, the design voltage that maximizes efficiency of an incandescent lamp is:

~3-5 volts for wattages a fraction of a watt

~5-6 volts for wattages around a watt to a couple watts

~6 volts for wattages of a couple to a few watts

~10-12 volts for wattages around 10 to a few 10's of watts

~12-15 volts for wattages around a few 10's to around 100 watts

~18-28 volts for wattages around 100-200 watts

Jump to a few/several 10's of volts for a few to several hundred watts, with coiled-coil filaments

Example:

The "100A" 100 watt A19/A21 lamps, according to the Philips "SAG-100" catalog, version "9/99":

120V/130V versions that have a life expectancy of 750 hours produce at most 1730 lumens. There is a 34V version with a life expectancy of 1000 hours and a rated light output of 1940 versions. There is a 12V version with a 1000 hour life expectancy and a rated light output of 2050 lumens.

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

Well, I don't have SAD disorder, that's not why I got them. Regular fluorescent bulbs give me headaches after a short period of time. These bulbs are brighter and whiter than any other bulb I have used. I forgot what brand they are now. I have had these for a couple years now. These bulbs are rated at 5000 Kelvin with 92 CRI. Natural sunlight is 100 CRI.

"Full Spectrum" or not, without looking at the lamps I can't tell that I am not outdoors most of the time. They could call them chocolate pudding spectrum for all I care.

Reply to
Henry Paul

Are halogen 7440s made? Would they make a significant improvement in brightness, in back-up lamp application?

Reply to
CompUser

We got a learning disability here?

Let's try that again:

From: Daniel J. Stern Date: Thu, 2 Sep 2004 11:34:13 -0400 Newsgroups: rec.autos.tech, alt.autos.subaru Subject: Re: Are Halogen Blue- Lites the best?

[...]

There are all kinds of myths out there about how/why Xenon is beneficial to the performance of halogen bulbs. Without going into the picayune physics, the real reason is that it permits the filament to be "driven harder" (run at a higher surface temperature) without failing. Higher filament temperature = greater surface luminance = more/whiter light.

[...]

Excessive Xenon in the fill gas mix reduces the threshold of inter-coil arcing to unacceptably low levels, though, so it is not the case that more Xenon = always better.

Reply to
Daniel J. Stern

For years, 24v (nominal) automotive halogen forward-illumination lamps have used coiled-coil filaments of between 70 and 75 watts (nominal). These CC6 or CC8 filaments are much larger in overall wire length (your point) and filament overall dimensions (my point) and so commercial-vehicle headlamp performance has tended to lag behind performance of those same lamps fitted with 12v bulbs.

Osram has just released 24v "Truckstar" automotive halogen lamps with C6 and C8 (single coil) filaments, and is making some very lofty claims for them, which are probably mostly justified. Propaganda is at

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DS

Reply to
Daniel J. Stern

Perhaps ...

Thanks for the repeat. I actually read this the first time around: It was in another leaf on this many-branched thread, and I'd already fired off the preceding post before I read it. And my arms just aren't long enough to reach through my network cable and pull back usenet posts once they've been sent. :-)

BTW, I found your web site very helpful -- lots of great information there. Thanks.

- Greg Reed

Reply to
Ignignokt

Did not look there yet...

For wattages around 50-100 watts, I have always felt under the impression that to maximize luminous efficacy for a given wattage and life expectancy with the design voltage being variable: Have the design voltage close to (a little above) 12 volts and have the filament singly coiled.

It has apeared to me that a coiled-coil filament and design voltage

20-plus volts maximizes the luminous efficacy when the wattage is over 100 watts.

However, for wattages around or a little under 100 watts with design voltages around 24 volts, a coiled-coil filament as opposed to a singly coiled one is advantageous, although mainly for "compacting" the filament into a shorter length one that better approximates a "point source". I suspect that with design voltages around 24 volts and wattages a little under 100 watts, luminous efficacy of coiled-coil and singly-coiled filaments will be similar, and singly coiled ones may or may not win out by a small margin (probably mostly by having temperature more uniform over most of the length of the filament).

Meanwhile, I thought that "automotive" voltages around twice the usual "12-volts" was mostly for aircraft! One more thing - in most aircraft the nominal voltage is 28 volts! The voltage is only twice that of the usual land vehicles, but in 28-volt aircraft the nominal voltage is close to that of their 12-cell lead-acid batteries having charge being maintained/"topped off" by running engines, as opposed to "12 volt vehicles" having the voltage being 12V with the engine off (and closer to 14V when the engine is on and the battery is successfully having full charge being maintained).

I do know that there are a few "12 volt" (maybe 14-volt?) aircraft with

6-cell lead-acid batteries, but more are "28-volt" with 12-cell ones.

Also, I have noticed that 28V aircraft "landing lamps" and any other "sealed beam" lamps have coiled-coil filaments while lamps other than sealed-beam have singly coiled filaments in a "V" shape with a filament support - is that "C2V"? While for the few aircraft with "half voltage" the filaments are singly coiled in all lamps.

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

No.

Yes, but they're not made.

DS

Reply to
Daniel J. Stern

(Did you ever see "Field of Dreams"?)

Y'Welcome!

DS

Reply to
Daniel J. Stern

Outstanding! I'll continue on my modded, Frankensteinian creation, lol.

Reply to
CompUser

Looooong time ago. I'm assuming the James Earl Jones reference was to a line from that movie? (Sorry -- I apparently don't remember it that well. Maybe it's that learning disability...)

- Greg Reed

Reply to
Ignignokt

Once, in another vehicle, I attached aftermarket driving lights to the rear bumper and wired them (via a relay) to the reverse light circuit. Did an excellent job of illuminating my behind. I mean, illuminating behind my vehicle.

And I'm not sure I'd *want* to install higher-wattage reverse lamps in the factory circuit, because I'm not sure all the hardware would be up to the challenge.

- Greg Reed

Reply to
Ignignokt

Yeah...you want to be careful with this. In addition to needing to pick the wattage carefully for thermal and electrical compatibility with your lens-reflector and wiring, respectively, the filament(s) also need(s) to be the correct size and shape, in the correct orientation and positioned identically to those in the original bulb within the lens-reflector, or your efforts will be useless at best and dangerous at worst.

DS

Reply to
Daniel J. Stern

Awww, that's the story of my life :-P

Reply to
CompUser

If I were going to experiment with bulb retrofits, I'd dig out my NAPA Echlin Ignition/Electrical Buyer's Guide and pick up some strategically-selected sockets, then use a Dremel tool to modify the reflector of a *spare* set of taillamps to accept the sockets.

Reply to
Daniel J. Stern

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