Using mobile phone as an internet radio
Phil Hobbs wrote:
On 10/12/2012 01:38 PM, Michael A. Terrell wrote:
Phil Hobbs wrote:
On 10/11/2012 07:18 PM, Dave Plowman (News) wrote:
In ,
Jeff wrote:
The lobby and foyer lights were mounted on the ceiling, pointing down.
One would think that there would be plenty of hot air accumulating
near the ceiling, but that wasn't the case. That's where the fan
ducts were located which helped to cool the lights. Few of those
lights ever burned out.
The marquee lamps were mounted on a vertical structure, with the lamps
pointed horizontally.
Vertical mounting for a GLS lamp seems to give a better life than other
orientations. A rough service type may have had a better life in this
application.
The filament temperature goes up more slowly than the ambient, since
it's radiatively cooled, but a rise of, say, 50 degrees would probably
have a significant effect on bulb life.
The projector bulbs in the old RCA TP66 film chain were mounted in a
vertical line. If you used the bottom lamp, and let it switch the to
spare on top, they had a short life of a little over 20 hours. If you
ran the top lamp, with the spare at the bottom, the life was over five
times longer. The projector used a motorized track, with a relay in
series with the filament. When the filament opened, the relay dropped
out and turned on the motor. In either position, it would run to look
for the other bulb when the one in use failed. I would pull the bad
lamp and move the good lamp to the top at the next film change, then put
the new lamp in the bottom socket. I averaged over 130 hours per lamp,
that way.
That's interesting--just storing the bulb at higher temperature reduced
its life that badly, even if it wasn't energized? The only mechanism I
can think of for that is that they leaked and let oxygen in. Otherwise
glass and metal should be unaffected by ~100 C temperatures. But then
they should leak even worse when energized. Another mystery, Scoob.
Hot tungsten doesn't have a very high emissivity in the IR, so
probably the filament temperature is more sensitive to ambient
temperature than one would expect from the T**4 dependence from Stefan's
law for black bodies. Raising the temperature by 1 degree at 3000 K
makes the radiation go up by 1000 times more than at 300 K, so the
filament regulates its own temperature quite closely if it's really a
black body.
The glass on these projection lamps was usually distorted, by the
time they failed.
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