Mounting of electrical circuits

There are three electrical circuits: one already mentioned for track voltage rectifying; one for the lanterns; and one for lighting the compartments.

For the latter, the question arose of the number of LEDs to use. Usually, I install a LED per compartment, plus one per access platform. Due to the three car diagrams, this number is different: 13 for 2nd class cars, 12 for AB, and less for BD, depending on the number of LEDs that we want to place in the luggage room.

The number 12 suits me well, because it allows to distribute the LEDs in four groups of three in series. On the other hand, 13 does not go at all! So I cheated to have only one circuit for all cars. There are only four LEDs for the five central compartments of the 2nd class cars.

You will find circuit diagrams and films in this PDF document.

Rectifier circuit

Unlike my usual, I did not use here surface mount devices (SMD) because the available room did not impose it.

However, the capacitors and the rectifier can be seen through the win­dows, which could have been avoided with SMDs. I used two 470 μF capaci­tors in parallel instead of a single 1000 μF which I did not have and which would have been less dis­crete. Given the currents involved, 3 to 4 mA per car, these values ​​are perfectly sufficient.

Rectifier circuit

Lighting circuit

So, the lighting circuit is the same for all cars. Only the end compartments of B cars will have a well centred LED.

As always, I fix the strips not under the ceiling, which makes their con­nection difficult, but on the layout. It is therefore necessary to provide holders for it. They are made of a plastic card between 0.5 and 1 mm thick, plus a piece of section 2 × 1 mm profile for centring and wedg­ing. The dimensions of these supports are given in the aforementioned PDF document.

Lighting strip holder

Experience showed that a holder above each access platform is sufficient. Here is its installation. Glued with CA. The small notch in the middle is to make way for a misplaced SMD resistor. This small inconvenience has been corrected on the circuit film.

Lighting strip holder

There will be no control for the lighting, because it would have required an addi­tional wire, therefore more complicated couplings between the cars. In fact, the low brightness of LEDs will make them almost invisible in daylight.

Circuit of the lanterns

Lanterns are installed at one end of the BD and the AB cars, which will be the head or tail cars, depending on the direc­tion of running. They re­quire a control, which will be performed by a bistable reed switch. LEDs are small SMDs (0603).

The circuit is soldered under the end of the strip in three points, one of which has no electri­cal function, but only re­inforcement (photo above). Since these sol­ders will be covered by the reed switch, they must be made before the installation of the latter (photo opposite). The LEDs are mounted upside down, with the lighting side facing the support plate, which therefore needs to be drilled (ideally ø 1.1).

Lantern circuit

Lantern circuit, other view

Notes:

LED 0603 red 160 mcd
ref. 179
€2.80 € per 25 — price 2019
at Electron Discount