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Discussion Starter #1
I have some passenger cars that I would like to do interiors on and light up. My main issue with this feat is figuring out what to do about the lights. Do I need a dcc decoder in the cars to illuminate them? If so would it be wise to add connectors and wire all the cars to one decoder or do I need to install a decoder in each? I attempted to try an led on the rails to see if it would work but it wouldn’t light up. I touched it to a dc power pack and it did. I’m guessing that led lights won’t activate unless there is dc due to it being an alternating current and current only flows one way through an led light?
 

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LED's will work on AC. No, you do not need a decoder in your coaches for LED lighting unless you want to control the on/off of each car. Without a decoder they are on all of the time.

LED's can use AC because they will only use half of a full wave of AC. Had you reversed the wires when you tested it on the rails it would have lit. LED's operating on AC will have 60Hz flicker, but you will not likely notice it.
 

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If you want to turn the lights off via DCC, then you need a decoder and have to decide if you want a cheap decoder in each car, separate/same address and such. If you want them to light when on any DCC powered track, then you might consider using a bridge rectifier and a CA20 to generate a constant 20 ma current. You might try putting 2 sets of LED's in parallel so each sees 10ma so their a little dimmer. By the time you cobble all this together, it might be cheaper to put a decoder in each car! Another possibility is what you implied in that you could use a single decoder and run wire between all the cars to power the lights. No matter which way you turn there are things to address, wires between the cars is a hassle, but then only one car need to pick up power so there will be less drag. Pick your poison! I like having a single car with a decoder that turns on a small power supply that sends out the power to all the other cars, just need to figure the best way to wire the cars together with small gauge flexible cable and some sort of connectors
 

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I always use a rectifier and capacitor to supply power to prevent any possible light flicker from going over dirty tracks or small dead areas. Cars, being lighter than the locos, are easier to have poor connection to the rails.
 

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Discussion Starter #5
What is the cost of a car decoder? I don’t want sound just something to turn lights on
 

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There is no DCC decoder specific to controlling the
lights on a train car. You would use any
loco decoder which can be addressed by
your DCC controller to turn on and off the lights.

Actually, though, there's no reason to do it. Just
leave the lights on. They draw very little current
and add to the night-time ambience of your layout.

As has been mentioned, you simply use the 12 V strip
LEDs powered thru a simple diode circuit to conver
the track AC to flicker free DC. Many of us use
Kadee #5 brass coupler boxes opened to rub against
the rear of truck wheels for power pickup. For best
results use them on all wheels. Warm white LED
strips produce a light that resembles florescent tubes
in the cars. More yellowish LEDs look best in
Caboose lighting.

Don

Don
 

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Actually, Digitrax makes function only decoders, for among other things, turning lights on and off in cars. They are the TL1, and the TF4. If you use a locomotive decoder, then you will need a resistor across the motor wires in order for it to work properly.
 
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