Original page created on 19/04/2018.
Mounting of electrical circuits
There are three electrical circuits: one already mentioned for track voltage rectifying; one for the lamps; 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 coach diagrams, this number is different: 13 for 2nd class coaches, 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 coaches. There are only four LEDs for the five central compartments of the 2nd class coaches.
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 coach, these values are perfectly sufficient.
Lighting circuit
So, the lighting circuit is the same for all coaches. Only the end compartments of B coaches 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 also given in the aforementioned PDF document.
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.
There will be no control for lighting (yes, there will be! See last page!), because it would have required an extra wire (no, no!), so more complicated electric couplings between coaches. In fact, the low brightness of the LEDs will make them almost invisible in daylight.
Circuit of the lamps
Lamps are installed at one end of the BD and the AB coaches, which will be the head or tail coaches, 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 ⌀ 1.1).
Notes:
- all sides were painted black (Humbrol acryl matte # 33) to prevent light leakage;
- the bottom of the circuit should be flush with the bottom of the layout and should be glued perfectly centred so that the LEDs are well in front of the lamps.
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