I have never liked normal model railroad passenger car lighting because of flickering as the wheels roll though turnouts.
My first attempt at non flickering was to use a rechargeable battery in each car. I installed between two to six 3mm 1½ volt 40ma to 100 ma Grain of Wheat bulbs in all of my Daylight cars. I used a single N cell Nickel-Metal Hydride battery with a LM317 voltage regulated charger powered from track power in every car. That worked very good, no flickering.
I needed a way to turn off the lights so I installed a micro switch under each car, again that worked very good until I got tired of having to remove each car to operate the switch.
Modification #1: I installed a magnetic reed latching switch under the roof of every car. That made it possible to turn on and off each car using a magnet above the roof. That became very tiresome also. After several attempts at using a fixed over head magnet I gave up on the reed switches because the switch reliability was very bad at best.
Modification #2: By this time it was obvious that the on-board battery would work very well if the process of turning the lights on and off could be overcome. DCC to the rescue!
My Daylight passenger service as always been pulled by E7A/B locomotives, DC powered E7s. But a very small relay controlled by a DCC Accessory Function in a locomotive would work. My Daylight E7s consist of Athearn SD40-2 frames with Cary cast metal E7 bodies. The Athearns are easily converted to DCC so that was next.
I removed all the batteries and charging circuits from the individual cars and rewired them for connectors to parallel all the cars to a central power unit with a DCC decoder function for on-off control.
I built a second E7B as a dummy lighting power supply unit complete with a large 5000 mah Lithium rechargeable battery and a track powered charger, I went to a higher current LM337 regulator for the 1½ volt regulator to reduce the voltage from the 4 volt battery. I installed a mini SPST relay in the E7B to turn on and off the lighting power to the cars. I connected the relay to the DCC decoder function 3 in the powered E7B and that worked very good. Modification #2 worked very good and I can now remotely turn on and off my entire passenger car lighting from my DCC controller.
One slight problem still existed, the incandescent bulbs draw quite a bit of power. I used #28 AWG wire which is rated at 220ma, the total current leaving the E7B power unit was 1.6 amps at 1.48 volts. By the time the voltage got to the observation car the voltage was down to .91 volts. By juggling cars around I got the voltage at the observation car up to 1 volt.
Modification #3: I rewired each car from connector to connector with #20 AWG wire. I still used the same between the car jumpers with #28 wire because of size and flexibility. That mod brought the voltage at the observation car up to 1.37
Everything is looking good but after some time I decided to try LED lighting one more time.
My ¾ Dome/Lounge car is the hardest to illuminate so I set out to see if it could be done and still look realistic. Using LEDs hasn't worked out for me in the past for passenger car lighting. Incandescent GOWs always looked far more realistic to me.
Modification #4: I spent over 10 hours experimenting with several sizes and types of LEDs before I got the proper light dispersion at the proper light level for the lounge area of the car. The LEDs cast sharp and contrasting non realistic shadows that doesn't happen when using incandescent bulbs. It took three LEDs to replace one 1½ volt 100 ma incandescent GOW bulb and get the same effect.
The upper deck or Vista viewing area only took three LEDs to replace the three GOWs. The trick was in reducing the brightness of the LEDs to match the 20ma GOWs brightness. I ended up using a 470K ohm resistor in series with each LED, ending up with 2.475 volts at .01 ma on a 3mm warm white LED.
To get somewhat the same light dispersion from the LEDs I filed off the lens end as close to the internal components of the LEDs as possible, reducing the length of the LEDs also helped.
The bottom line is my ¾ Dome/Lounge car went from 1½ volts at 160 ma to 4 volts at 2.3 ma. The lighting looks very close to the way it did with incandescent lighting.
plan on redoing the lighting on my entire Daylight Passenger fleet.
The reduction of the current will be a big improvement. Over the years
I've experimented with LED lighting but I was never pleased with my
results until finished this car.
To bad my photography isn't better, the lounge area looks much better than in my pictures.
I will follow up with a post on installing the LEDs as I proceed with my project.