There is a bulb in a firehouse in New York that (check memory) has
been running since the early 1900s, dimly, but continuously. Reason? They
are running it at quarter voltage and it never gets that cold current spike
that will kill it.


Actually, according to http://www.snopes.com/science/lightbulb.asp it
is in a firehouse in Livermore CA, since 1901 and is still (as can be
seen on the real-time lightbulb-cam
http://www.centennialbulb.org/photos.htm ) ON!

It has been off and on a few times, and they make no mention of
reduced voltage.


- Steve



On Thu, 22 Mar 2007 09:11:44 -0700, "RST Engineering"
wrote:

Or you could do it the right way and design a switching regulator with
filtering for noise so that one output goes from x to y with control
rotation, another from w to z, and still a third (inverse) output from v to
u.

The reason you don't start at 0 and go to + supply is that most lamps will
last thousands of hours if they are prewarmed before running them up to
ratings. There is a bulb in a firehouse in New York that (check memory) has
been running since the early 1900s, dimly, but continuously. Reason? They
are running it at quarter voltage and it never gets that cold current spike
that will kill it.

The second output starts at some low warming voltage but only goes up so far
so as to not blind you when the first output goes nearly to the positive
rail.

You also need an inverse dimmer for lights that need to be bright during the
day (marker, warning, etc.) but dim at night.

Single control gets all three set correctly.

Jim


wrote in message
...
Mike Spera wrote:
The 2 VOR/ILS indicators are internally lit as is the VC compass and
clock. These are all running off the one lone factory dimmer. On full,
the indicator lights will illuminate the cabin, so I run them way down
at night.

I wonder if it would be possible to install lower-wattage lamps in the
VOR/ILS indicators, or install a (fixed) resistor or diode in series
with the existing lamps in the indicators. This would let you turn the
dimmer knob up higher and have more light on your other instruments,
without the indicators blinding you.

A fixed resistor can be sized to give you pretty much whatever voltage
drop you want. You'll probably need a "power" type rated for at least
a few watts, and it needs to be mounted where it can get hot. If you
really want to be fancy, get one of the ones that comes in a finned
aluminum case with mounting lugs so it can be bolted down.