# Passenger car in reverse lighting???



## afboundguy (Jan 10, 2021)

Full disclosure I'm new to DCC and all I've done so far is wire a few decoders in a few engines and plan to do it to a few more engines... I am planning on doing an Aerotrain setup with a Bowser engine and Bowser passenger cars... In the Con Cor and other higher end set ups the observation car has the white and red lights that change depending on if the engine is pushing or pulling (and vice versa on the engine). I was curious how that is wired and programmed? Do you have to run a wire through from the engine to the last car or can you do it with a stationary decoder in the last passenger car?


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## DonR (Oct 18, 2012)

I'm not familiar with those passenger cars. However, I can
imagine their changeable lights are designed for DC...When
the loco is pulling forward the track polarity is right rail positive,
thus a white light...if loco is backing up (pushing) the right rail
is negative...thus the red light...or the other way around...
It's done with diodes in series with the bulbs. It wouldn't
work with DCC...the track is always modified AC and doesn't
change with direction of loco.

Don


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## mesenteria (Oct 29, 2015)

I'm not an expert in electronics, but what Don says above sounds right to me. If you'd like to retain the function and directionality of your cars' lighting, you'll need a simple on-board decoder with two or three-way lighting outputs, depending on price. The decoder will be assigned the same address as the locomotive, whose decoder will 'know' which way is forward and which is reverse, and controls the loco's lighting accordingly. Same for the cars. Tell the locomotive to back up, and the same-addressed cars should alter their lights just as you desire concurrently.


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## cv_acr (Oct 28, 2011)

In DC that would work with an LED or diode set up to only light in one direction based on polarity.

In DCC there's no directional polarity to the track voltage, so the lights will be always on, or you'd need a lighting function decoder to turn them on.


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## afboundguy (Jan 10, 2021)

Thanks for the info everybody. I want to have both lights on at the same time so I'll look into the lighting function decoder...


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## DonR (Oct 18, 2012)

If you want both...the red and the white lights on at the same
time you would simply remove the diodes, connect the two lights
in parallel to the car lighting.
That is, assuming all of those lights are incandescent.
No decoder needed. 

Don


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## afboundguy (Jan 10, 2021)

DonR said:


> If you want both...the red and the white lights on at the same
> time you would simply remove the diodes, connect the two lights
> in parallel to the car lighting.
> That is, assuming all of those lights are incandescent.
> ...


Don thanks that seems like an easy fix...


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## Steve Rothstein (Jan 1, 2021)

The one train I have that has that feature is a Kato model of the C&NW 400 minute trains. When running DC it used the polarity to switch. When I upgraded the engine to switch, I found that Kato was smart and designed the last passenger car to accept a single function decoder that is about .75 inches square. I assigned it the same number as the engine and it uses the engine's direction signal to determine red or white lights on.

I do not know how hard it is to get the type of decoder, but I do think you would like it better with a decoder in the last car.


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