03/10/2019.

Tail lights

Having recently acquired a third VSE, with two VTUs, all in C1 livery, I undertook to put a ligh strip identical to the previous ones. But, as in some compositions, this coach is at the tail, I also wanted to equip it with tail lights.

A priori, it’s not easy, because there is very little space around the gangway. In addition, the light “glasses” protrude inside, which could promote light leaks.

The circuit board

It is therefore necessary to use the smallest possible SMD LEDs. I have some in a 0603 package, their active part measures 1 × 0.8 mm. Their luminosity is 160 mcd at rated current. As the circuit will have to be flat on the back wall of the coach, the components will have to be turned towards the inside of it, including the LEDs. So, they must be placed in the inverted position, and will illuminate through a hole drilled in the PCB. This hole will have a diameter of 1.3 mm.

The etching film is available on the attached PDF document.

Here is the circuit mounted, with a 4.7 kΩ resistor (it could be more), and a home made latching reed switch. PCB front…

View of PCB

… and back

View of PCB

The LEDs can be seen through their hole.

The branches of the circuit are covered with electrician tape. I thought about using heat-shrink tubing, but it probably would have been too thick. Here, the trouble is that the edge of the circuit is not hidden, and it lets a little light pass through. It will have to be painted.

Note: this circuit is too high and hinders the reinstallation of the roof (see below). I slightly decreased this height on the attached etching film.

Mounting the PCB into the body

To mount the circuit, we’ll have to mill an opening on each side, flush with the end wall, about 1.5 mm wide, and 3.5 mm long. It’s not too difficult, the only problem being sawdust that creeps everywhere. We see on the picture the printed circuit not yet equipped and the ø 1 milling bit which was used to machine the openings.

Milling of thr body

Let’s verify that the circuit fits well into the openings.

Inserting the PCB

It’s OK, except that I can’t get it down, because it’s blocked by the protruding “glasses” already mentioned. So, they must be shortened.

They are slightly glued. I unstick them levering with a small screwdriver; then they get off easily. Their body has a diameter of 1.6 mm. To shorten them, simply place them in a ø 1.6 hole drilled in a 1 mm thick plate, then saw or file the part that juts out. Here is their state before and after sawing. Then put them back in place with a little Kristal Klear glue.

Shortening the “glasses”

The equipped circuit is now correctly positioned.

Inserting the equipped circuit

View from below. The branches of the circuit are well centred thanks to the relieves of the coach’s body.

Inside view of the positionned circuit

For the power supply, it’s possible to use wires running along the entire coach (the power circuit being at the other end), but I preferred to use self-adhesive copper tapes. I could have made a new a PCB with an extra track — because the +VCC track (blue wire) already exists — but, for only one application, I preferred to keep the old one.

Circuit power supply

After mounting the light strip as for previous coaches, and connecting all the wires, all we have to do is to test the operation.

The edge of the roof must be milled in order to close it properly.

Milling the roof

Inset, here is the other end, intact, for comparison.

Coach good for the service.

Coach with lights

Note: although this is not very visible here, the lighting is colder than in previous coaches because the windows are less colourful. There is a regrettable lack of homogeneity.