On Fri, 22 Jul 2016, Vincent Slyngstad wrote:
Somewhere, I have Oshino's write-up about bulb rated voltage and bulb
operating voltage, but I do remember the lifespan varies as some power of
the ratio, and it makes a huge difference. (There are also formulae for
derating brightness, etc.)
I found it -- the lifespan varies as the 12th power of the ratio.
The current varies as the 0.55 power, and the brightness as the 3.5th power
(of the reciprocal).
So, a 12V bulb in a 28V circuit can expect 1/26000 the lifetime, and will
take about 1.6X the current to burn about 20X brighter than normal.
A 28V bulb in a 24V circuit would last about 6.3X it's rated lifetime, take
92% of the rated current, and about 58% as bright.
. . . and that presumably clarifies the "Livermore Firehouse Bulb".
