Wednesday, July 11, 2018

Digitizing Roco 43012 - Headlights

The model comes with bulbs that barely illuminate the headlights, even at 12 volts. If I put a 2x3mm SMD LED in place of the bulb, I get nice illumination. Good.
I think the color temperature of this LED is to white-blue'ish. A closer look at a prototype photo hopefully will help resolve that question.

When placing the same LED into the location of the bulb for the tail lights, however, enough light seeps into the headlights to illuminate everything. Looking more closely at the previous photo, the effect is visible there as well, but not as bothersome.

The reason for this behavior is that the plastic piece guiding the light from the bulb to the headlights easily picks up enough stray light. In addition, it's one piece for both head and tail lights, so it's hard to guarantee separate light paths. At the very least the top headlight in the nose must be completely dark.

One option I explored a little bit tonight was to position a LED on the chassis floor so that it lights up only a single rear light. However, it turns out that doing this naively just lights up the whole light package, i.e. both head and tail light. Even using shades or tubes doesn't help enough.

The next idea I'm going to try is to get a few tiny red SMD LEDs and glue them directly on the tail light optics in the shell. Then I just need to worry about how to connect the wires to the decoder in the chassis without causing a maintenance headache. A micro plug is likely the easiest for that, and since I have to go through the trouble for the tail lights anyways, I can use the same approach for the cab light, too.

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