Overlay/Panel Lighting?

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.

A diode will drop something like 0.6 V to 1 V; you can use a few in
series to drop more voltage. It will also get warm in use and needs to
be mounted where this isn't a problem. The most common diodes (1N400x
and 1N540x rectifiers) are just a lump with two wires sticking out like
a resistor. You can get diodes in TO-220 transistor cases with a
mounting/heatsink tab but these are not as common.

Can I glue in some bulbs to the plastic overlay and have a dimmer
controls running to the cig lighter?

I don't know if it's legal but it's electrically possible. All the
dimmer should need is 12 V and ground. You may want to make sure that
the plug you use fits the lighter really well.

If it's mechanically possible, you might consider the cig lighter plug
for your other options as well. Install the new lamp securely but
temporarily and wire it to a dimmer which then plugs into the lighter.
If you like it, you can get it wired more permanently.

Matt Roberds

Disclaimer: This is based on experience with illumination in ground
vehicles and in fixed installations. I don't have an A&P; I don't even
have a TG&Y. Some of this may not be allowable owner maintenance.
Your mileage may vary.

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.

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.

On Thu, 22 Mar 2007 09:11:44 -0700, "RST Engineering"
wrote:
wrote in message
...
[ too-bright VOR/ILS indicators]
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.

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.

Well, _you_ could do it the right way over the weekend. _I_ could do it
the right way after a couple of trips to Frank's Transistor Barn for
another 1-lb bag of MOSFETs to replace the ones I would blow up. In
the general case, IMHO, installing a lower-powered lamp is something any
repair station should be able to do, and installing an inline resistor or
diode is something that most repair stations could probably do. Also,
I know you mentioned filtering, but "switching power supply" and "AM
radio" makes me a little nervous.

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.

I know some dimmers for stage use do this, but there, I think the
"warming" current that flows even with the knob on 0 is there to get the
lamp to respond faster when you suddenly turn up the knob. On AC, lamps
also last longer if switched at the zero crossings of the waveform.

Matt Roberds