DCC lighting

Model Railroader General Discussion (Model Railroader)
1

Hi All,

I have installed an NCE D13SR decoder on a Athearn GP38 and want to use as headlights two 12 volt 30m bulbs into the vertical line-up above the front windows (they are a perfect fit). I know to use the white and blue wire for “front” headlights. But how can I make both bulbs work off the single white and blue wire from the decoder?

Need advice from some of you experienced electricians.

Thanks.

JRP

2

You wire them in parallel. This involves taking a lead from each lamp and connecting them to the white wire. Then take the other lead from each lamp and connect them both to the blue wire.

3

Careful!!!

12 volt bulbs in plastic bodies could mean melted plastic (I’ve done this!)

Cool white LEDs are much better!![bow]

4

Thanks for the direction on this. Will let you know how it goes.

JRP

5

I’d add a 22 Ohm resistor to each bulb to cut down on their heat buildup and protect the decoder from the voltage surge when the lights are turned on. Incandescent bulbs at full brightness can get hot enough to melt plastic.

6

Also consider the resistor in the circuit. If you are paralleling 2 bulbs, you should also parallel 2 resistors. Your DCC circuit is putting out about 12 volts, maybe a bit more, so those bulbs will likely have a short, hot life without some resistance to cut the voltage back a bit. You might want to go up to 1/4 watt resistors, too, because the 1/8th watt ones will heat up more and may even cause a melting problem themselves.

Even though the bulbs are a perfect fit, please give some thought to replacing them with LEDs now. LEDs will probably outlast the engine, will run much cooler and will give a much better beam of light than incandescents.