Electrical wiring

This page deals with the interior lighting wiring common to all cars. A special page will be devoted to the driver car (decoder and lanterns).

Lighting strips

There are four different types of strip: a short and a long “normal”, and a short and a long one for the driver car. Here I am only talking about the first two, but the others are very similar.

The short strip is intended for the lower level and will be stuck under the higher level fitting. The long one is for the higher level and can be stuck either directly under the roof or on spacers fixed to the chassis, each solution having its pros and cons.

For all my lighting strips, I use 0.8 mm thick epoxy, that of 1.6 being much too thick.

For LEDs, I chose 1206 size SMD LEDs, “pretty” warm white (3500 K); to me, the cold white is never usable for railway equipment, even modern (its colour temperature is very much superior to the so-called “daylight” fluorescent tubes, which are currently the most common). The ideal is 2700 K to simulate the incandescence and 3500 K for the fluorescence.

LED 1206

As already mentioned above, the lower level light strip must be as thin as possible due to the low ceiling height. Here is a diagram showing its constitution.

And here is a picture showing three aspects of this strip, front to back:

  • The bare circuit showing the holes under the LEDs (this circuit is not that of the VB2N);
  • The mounted circuit seen component side;
  • The mounted circuit seen opposite side, covered with a plastic sheet that serves both as embellisher and light diffuser (not essential).

Sectional view of the strip

Lighting strips

PCBs

Here you will find all printed circuits as a PDF document.

Note : depending on the fixing method, the longer strip may be a problem in the BD car (mixed 2nd class/luggage, the one coupled to the machine), whose roof is leaning at one end. It may be necessary to bend or even break the strip to follow the inclined plane, while maintaining the electrical connections. Personally, I did a cross saw, not copper side of course, to facilitate bending.

Wiring the lower level strip

I solder two very thin wires (2) (not insulated, extracted from flexible cables) on the provided pads. This must of course be done before gluing the strip (1) to the fitting. These wires are soldered onto self-adhesive copper tapes (3) more discrete than wires and possibly painted, stuck to the end walls.

Connection of lower level strip

Wiring the upper level strip

Four wires will lead to this strip: two soldered to the ends of the ø 0.5 mm holding bars, which are connected to the connecting wires which pass along the chassis, and two others which will feed the lower strip, thanks to the copper tapes as seen above.

Connection of upper level strip

In this picture, we clearly distinguish the two red wires (positive polarity), and less clearly one of the two black wires. The second one is at the other end of the car, soldered to the other holding bar.

You can notice that I chose the option to fix the strip on the chassis and not under the roof. Thus, all the wiring is fixed to the chassis and no wire is likely to be torn off when the body is lifted. On the other hand, this requires a slight adjustment of the spacers height. In the picture, it is too high and has been modified later. A value of 8 mm should be suitable in all cases, except once again in cars with a leant roof. Note that this spacer is glued close to a wall, to avoid bending the transparent plate.

Wiring of the conductive couplers

I have experimented rigid connectors made with printed circuit board. It is very long to make, unless you have a digital control machining table! In addition to the ridiculous cost price, the only advantage over commercial electric couplers (Viessmann in particular) is that I was able to reduce the distance between NEM boxes from 15 to 14 mm without any problem of derailment, even on very tight curves. That said, the wiring is the same. A page is being prepared to describe these connectors.

So the wires of the couplers, shortened if necessary (a length of 40 mm is sufficient), are passed through the wire guide. They are then soldered to the rigid wires of the chassis and, if necessary, to the tinned end of the holding bar. The soldering must be done into the “bean” so as not to protrude too much under the chassis. Be careful not to melt the plastic! The bar in excess can then be cut off.

Connection of coupler

Working test

Before reassembling the body, it is prudent to do a test. I do it initially with direct current, with a variable laboratory power supply. I set the current limit to a low value (eg 20 mA, the actual current should not exceed 13 mA). Then I connect the circuit, and I raise the voltage from 8 V. The strips light up from 9 V. The maximum voltage is around 14 V.

Electrical test

Note: the decoder used is a Lenz LF101XF, whose maximum current per output is 200 mA. Even taking into account cab lighting and lanterns, you could feed a good fifteen cars! There will be no difficulty in illuminating the six to eight cars that constitute a real train set.

To be continued (driver car)…

100 LEDs 1206 3500 K, 520 mcd
13.50 € per 100, price 2015
at LED-Megashop (Electron Discount).

Copper tape
5 mm x 30 m self adhesive,
3.57 € — price 2015
at amazon.fr.

Pair of conductive couplers
ref. 5048 - 11.26€ — price 2015
at modellbahnshop-lippe.