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Archived from groups: comp.sys.ibm.pc.hardware.chips,comp.sys.intel (More info?)

In line comments.
Stuart

"Robert Redelmeier" <redelm@ev1.net.invalid> wrote in message news:rGBDd.12106$wi2.11128@newssvr11.news.prodigy.com...
> In comp.sys.ibm.pc.hardware.chips Stuart <xyz@hotmail.com> wrote:
>> In fact the life of a light bulb depends
>
> Of course.
>
>> In unusual conditions such as a 135 volt lamp burning
>> continuously at 115 to 120 volts several years is not unusual.
>
> 20,000 hrs? I would have thought tungsten sublimation
> would have killed a std 135V/2000h bulb long before then.
> Unusual conditions like halogen fill for redeposition?
Just standard US lamps except for the 135 volt.
In the cases I was referring to they are in difficult places to reach and are not turned off.
>
>> In more extreme circumstances such as a 230 volt lamp operated
>> at 125 volts for use as an indicator (as opposed to providing
>> illumination) with a limited number (less than 5) of on/off
>> cycles per year the life is in the twenty to thirty year range.
>
> I've run Euro bulbs. They hardly give off enough light at
> 115V to qualify as indicators except in darkened surroundings.

I can only say that my former employer used/uses them in hundreds of installations and they do the job.
>
> I didn't think cycles mattered that much on tungsten-filament
> bulbs with good design for thermal expansion & filament
> support. Las Vegas signage certainly gets hammered.

In a standard lamp operated at its design voltage lamp on/off cycles are a major factor in lamp failure.
You may have noticed that most lamps fail when you turn them off.
As to Las Vegas I have no personal knowledge but I do know that lamps used for traffic signals are of special construction.
They have limitations such as "Burn base down to horizontal" and have, relatively, a low light output, i.e., a 100 Watt traffic signal bulb lamp delivers a light output approximately equivalent to a 60-75 watt normal lamp. As a side note, the local jurisdictions are on a program to replace the lamps in traffic signals with LED arrays. They state the savings in lamp replacement labor costs and energy costs will offset the higher original cost.

>
>> In contrast a photo flood lamp under normal use is
>> rated in tens of hours.
>
> Of course. So do Japanese 100V bulbs at 115V. Voltage ratings
> are a bit of a farce. Filaments have a resistance curve and
> reach a particular temperature at a given voltage.
>

Voltage ratings are the result of a design tradeoff.
For a given physical lamp if you lower the voltage you will lower the light output and the efficiency and increase the light output because, as you state, the filament is at a lower temperature.
Conversely, if you raise the voltage the temperature increases, the light output and efficiency increase and the life decreases.
The voltage rating assigned to the physical lamp is, more or less, a marketing decision balancing the cost of manufacture, the cost to produce a lumen and customer expectations as to light output, life, and purchase price.


> -- Robert
>
 
Archived from groups: comp.sys.ibm.pc.hardware.chips,comp.sys.intel (More info?)

In comp.sys.ibm.pc.hardware.chips Stuart <xyz@hotmail.com> wrote:
> have noticed that most lamps fail when you turn them off.

I see more failures at start-up -- a short brief flash
when turned on.

> As to Las Vegas I have no personal knowledge but I do
> know that lamps used for traffic signals are of special
> construction.

I would expect so! Very expensive bulbs to replace, often
subject to high vibrations when lit (only very short, stiff
lightpoles might be immune).

> They have limitations such as "Burn base down
> to horizontal" and have, relatively, a low light output,

The yellows have higher output because they have a
shorter required life. Many places, there are two reds.

I believe the prohibition on "base up" is to reduce the area
exposed to cold (untreated?) glass or to reduce obscuring
from tungsten deposition.

> program to replace the lamps in traffic signals with LED
> arrays. They state the savings in lamp replacement labor
> costs and energy costs will offset the higher original cost.

Likely a very good move. Some trucks also have LED tail-lamps.

> The voltage rating assigned to the physical lamp is, more or
> less, a marketing decision

Yes, to meet cost, life, lumen & color specs.
No problem over/underclocking :)

-- Robert
 
Archived from groups: comp.sys.ibm.pc.hardware.chips,comp.sys.intel (More info?)

On Sun, 09 Jan 2005 18:30:46 +0000, Robert Redelmeier wrote:

> In comp.sys.ibm.pc.hardware.chips Stuart <xyz@hotmail.com> wrote:
>> have noticed that most lamps fail when you turn them off.
>
> I see more failures at start-up -- a short brief flash
> when turned on.

That's when you see the failure, but power cycles aren't really what does
them in. Tungsten boils off the filament, over time, making it weaker.

>> As to Las Vegas I have no personal knowledge but I do know that lamps
>> used for traffic signals are of special construction.
>
> I would expect so! Very expensive bulbs to replace, often subject to
> high vibrations when lit (only very short, stiff lightpoles might be
> immune).

Most traffic lights are LEDs these days. They are expen$ive, but last
longer, are more efficient, and have a higher apparent brightness.
They're better and the TCO is lower.

>> They have limitations such as "Burn base down to horizontal" and have,
>> relatively, a low light output,
>
> The yellows have higher output because they have a shorter required
> life. Many places, there are two reds.

There are *hundreds* of reds. ;-) The reds were the first to change over
to LEDs.

> I believe the prohibition on "base up" is to reduce the area exposed to
> cold (untreated?) glass or to reduce obscuring from tungsten deposition.
>
>> program to replace the lamps in traffic signals with LED arrays. They
>> state the savings in lamp replacement labor costs and energy costs will
>> offset the higher original cost.
>
> Likely a very good move. Some trucks also have LED tail-lamps.

They've been using LEDs in traffic lights for ten years of so. ...and I
thought I lived in the sticks. ;-)

>> The voltage rating assigned to the physical lamp is, more or less, a
>> marketing decision
>
> Yes, to meet cost, life, lumen & color specs. No problem
> over/underclocking :)

--
Keith
 
Archived from groups: comp.sys.ibm.pc.hardware.chips,comp.sys.intel (More info?)

Bob & Keith
My fingers did type what my mind said!
As you both said most lamp failures are at lamp turn ON not OFF.
This, according to what I was told by GE engineers, is primarily due to the high initial current and the thermal shock when the cold filament is energized.
This is the same thing you see with vacuum tubes and is why computers using vacuum tubes were left on 24/7.
My point was, if the lamp is on continuously (no off/on cycles) it lasts until the filament actually boils away and fails mechanically.
Stuart


"Robert Redelmeier" <redelm@ev1.net.invalid> wrote in message news:qLeEd.12594$wi2.11948@newssvr11.news.prodigy.com...
> In comp.sys.ibm.pc.hardware.chips Stuart <xyz@hotmail.com> wrote:
>> have noticed that most lamps fail when you turn them off.
>
> I see more failures at start-up -- a short brief flash
> when turned on.
>
>> As to Las Vegas I have no personal knowledge but I do
>> know that lamps used for traffic signals are of special
>> construction.
>
> I would expect so! Very expensive bulbs to replace, often
> subject to high vibrations when lit (only very short, stiff
> lightpoles might be immune).
>
>> They have limitations such as "Burn base down
>> to horizontal" and have, relatively, a low light output,
>
> The yellows have higher output because they have a
> shorter required life. Many places, there are two reds.
>
> I believe the prohibition on "base up" is to reduce the area
> exposed to cold (untreated?) glass or to reduce obscuring
> from tungsten deposition.
>
>> program to replace the lamps in traffic signals with LED
>> arrays. They state the savings in lamp replacement labor
>> costs and energy costs will offset the higher original cost.
>
> Likely a very good move. Some trucks also have LED tail-lamps.
>
>> The voltage rating assigned to the physical lamp is, more or
>> less, a marketing decision
>
> Yes, to meet cost, life, lumen & color specs.
> No problem over/underclocking :)
>
> -- Robert
>
 
Archived from groups: comp.sys.ibm.pc.hardware.chips,comp.sys.intel (More info?)

On Mon, 10 Jan 2005 14:15:26 +0000, Stuart wrote:

> Bob & Keith
> My fingers did type what my mind said!

I don't think there was any doubt there...

> As you both said most lamp failures are at lamp turn ON not OFF.

Sure, the difference of opinion was *why* the failures. On/Off cycles or
hours. My understanding is that the hours boil off the Tungsten and the
thermal stress of the power-on does the bulb in. That is, the total hours
in use is the real killer, not the power cycles (forgeting vibration and
other abuse). Certainly different bulbs are designed for diffeent
environments, but I trust we're all talking about the typical "household
60W bulb" as the standard.

> This, according to what I was told by GE engineers, is primarily due to
> the high initial current and the thermal shock when the cold filament is
> energized. This is the same thing you see with vacuum tubes and is why
> computers using vacuum tubes were left on 24/7. My point was, if the
> lamp is on continuously (no off/on cycles) it lasts until the filament
> actually boils away and fails mechanically. Stuart

That's where "your people" and "mine" disagree. <shrug>

--
Keith