LED directional lighting on DC loco

[farrellaa]

I have a couple of Athearn BB GP locos that I would like to put LED lighting in. I mounted a warm white 3mm LED with resistor in one of them and when running it on my DCC layout with a Digitrax Zypher the light stays on in both directions. I want to put a rear LED in and make them directional. I thought I read somewhere that by wiring them  + to - would make them directional. Is there something I am missing? I connected my DC powerpack to the loco and it works OK. What is different about using the Digitrax address 00 and using real DC power? Do I need some kind of light board or other electronic components? I did a search for this on the forum and didn't get any results. I know this is a simple project but my mind is making it difficult??? Any suggestions. Thanks,

  -Bob

[Train Modeler]

DCC signal is like a pulsed AC if you will.  It's not plus on one side and negative on the other like DC.    So, to me, the easiest way to deal with it is to add a decoder.    That humm you're motor is making isn't real good for it, same is true for LED to a lesser extent.

Richard

[farrellaa]

Thanks Richard. I guess I should have mentioned that I don't plan to run these on a DCC layout, but set them up for use on a DC layout. I plan to sell them once they are finished with details and weathering. These are project engines (converted to GP18 by previous owner) I have had for a few years and decided to sell them now, since I have too many engines. I don't think they are worth the cost of adding decoders.

   -Bob

[Mark R.]

If you are setting them up for DC operation, do your testing with a DC power pack. You shouldn't use your DCC system for the reasons explained above.

To install directional lighting for the opposite end of the engine, install the LED the same way you did for the front, just wire the LED to the opposite rails to the one you installed in the front. I've found for using LEDs on DC, a 330 ohm resistor works really well. The LED will light at a very low voltage - usually below its rating.

Mark.