# DCC loco lighting



## polex (May 10, 2008)

I'm new to dcc but I thought that it was a constant when it comes to lighting. I have a digitrax AR583 decoder in an aritso mikado. 8amp booster digitrax powered by digitrax ps2012. Problem when the loco is not moving lights will come on bright, start moving a slow speed and all the lights on the loco go dim and flicker. A faster speed the lights will be normal bright like an old analog. All on stainless track just a 10' section for testing. Digitrax said that they didn't know what might cause it, but if I thought it was a bad board I could send it back to get checked. Any ideas or thoughts?


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## bobgrosh (Jan 2, 2008)

The decoder is fine. 
Aristo has a circuit between the decoder light output and the light. This circuit attempts to run a 6 volt bulb at a constant 5 volts when used on analog or the TE's pulses. Unfortunately, it does not work very well. Follow the Digitrax Decoder manual on how to direct wire the lights to the decoder. I recommend 12 volt bulbs with a 220 ohm 1/4 watt resistor, or an 18 volt bulb with a 100 ohm resistor. You may want to try going up or down one resistor size depending on your preferences for brightness. 

Cut the old lights out. Then, wire the new lights to the blue, white and yellow wires on the small white connector on the decoder. You will be much happier. While you are at it, just read the Digitrax decoder manual and wire up the rest of the lights too. Use bulbs, not LEDs and you will really see the difference. 

Also, part of the problem is with the resistance of the stainless rail. Try it on brass. The difference is noticeable when a loco is moving around a layout. It is not a huge variation like what you see now, but it is annoying to some people. You will just have to decide for yourself how much variation you will tolerate. 

OK, so how do you know if the variations you are seeing are caused by the poor design of the loco circuit, or the stainless rail? 

Here is a simple test. 
Make a test light by connecting two 12 volt bulbs in series. ( so we don't burn them out and makes it easier to see the variations) Connect the two bulbs to one END of your 10 feet of track. 
Connect a single pair of feeders from your DCC system to THE OTHER END of your track. 
Place the loco as close to light bulb end as you can. Make sure the loco is at the opposite end of the track from the feeders. 
Select the loco and while watching the headlight, and the two test bulbs, raise the speed to the point where the loco just starts to move. Hold the loco so it cannot move. 
If the loco bulbs vary more than the two test bulbs, it's the circuit. If the headlight bulb and the two test bulbs vary by the same amount, it is the stainless rail, or, your feeders/rail joiners are suspect. 

Good luck 

B0B


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