Lighting for your HO Scale Model Locomotive

Another thing that was missing from the Sante Fe model train locomotive included with the set was a Mars light on the front of the locomotive. A Mars light was a special warning light used on locomotives beginning in the 1940's. The light beam would oscillate typically in a figure eight pattern in order to catch the eye of motorists and pedestrians.

Well, I guess I can't expect all this lighting detail from a starter set, but then it made me wonder how I could:
1. Maintain the same light intensity no matter what speed the locomotive was going, note my started set is a standard DC system, this may not be a problem with DCC (Digital Command Control) systems.
2. Simulate a Mars light on the front of the locomotive.

Here is the constant intensity light circuit I used, I broke my first rule of "breadboard first" as I have built this circuit many times before and it has always worked like a charm. This circuit connects in series with the DC motor in the loco and provides a constant voltage to a LED to be used as a headlight on the locomotive. Here is a picture of the completed perf board.

And here is the circuit I used for my Mars light. This circuit was intended for a rotating beacon on a lighthouse but it worked equally well for a Mars light. I substituted the incandescent light bulb for a high intensity LED. Now I did breadboard the beacon circuit first because I have never used this circuit before and needed to know that it worked to my liking before committing it to perf board. Here is picture of me testing the Mars light circuit to be used for my Mars light on the front of the locomotive. Note: The circuit does not make the LED perform like a real Mars light; it just makes the LED vary in intensity as it is turning on and off like an incandescent light would.

Once I confirmed the Mars light circuit functioned to my liking I committed it to perf board. Notice how tightly I spaced the components together so that it would fit the body of my Sante Fe HO Scale locomotive.

I had to remove some of the steel plates used for weight in the locomotive in order to make room for the constant intensity and Mars light perf boards. I carefully weighed the locomotive on a letter scale including the upper body shell before removing the steel plates.

Here is picture of the both the constant intensity lighting perf board and the Mars light perf board mounted in the locomotive. The top light on front of the locomotive is the Mars light, it flashes on and off about once a second, the bottom light stays on at a constant intensity. As soon as the throttle on the power pack energizes the track to a couple volts both the constant intensity and Mars light circuit starts working. Note: Unlike incandescent bulbs, LEDs only light when the properly polarity of voltage is applied to them. As such the constant intensity and the Mars light are only on when the locomotive is traveling forward. The sharpie marker in the picture is keeping the drive wheels on the locomotive above the track while letting the wheels used to pickup power on the track, this allows me to test the locomotive while in place.

And now I need to add weight back to the locomotive to compensate for the steel plates I removed so that my constant intensity and Mars light perf boards would fit.

Here is a picture of the properly situated lead weights. I used stick-on weights from Amazon. These weights are typically used in the automotive industry to balance tires. Caution: These weights are made of lead, you should wash your hands after handling them and do not allow children to handle these weights. If children are going to play with the locomotive then I recommend using some other means of adding weight. Try to get the weights as close to being over the wheels as possible.

Here is the front of the locomotive; I had to slightly enlarge the headlight mounting holes to accommodate the 5mm High Intensity LEDs.

Conclusion: So with some knowledge of electronics and little hard work and you to can have authentic looking lighting on your HO Scale locomotive.