So you have an old Graham Farish N gauge diesel that you've converted
to DCC using the YouChoos guide, and perhaps even added DCC sound... now you want to bring the features of your loco right up-to-date
by adding head/tail directional lighting?!
Perhaps this is the trickiest install of all installs documented here as it involves multiple tiny LEDs, glued carefully over drilled holes
in the loco's body, with resistors added and wiring routed back to the decoder! 'Involved'? Yes, for sure, but very satisfying to see
it all working at the end!
You might also find it useful to read the related article where DCC sound AND lights are added to a Farish Class 44/45!
That's essentially it described in a nutshell... first, carefully drill out holes for the LEDs to shine through, using a very fine drill piece.
Next, wire up your LEDs with fine decoder wire. If your soldering skills are up to the job, you should go for tiny nano LEDs which are only
a mm wide and a couple of mm long! Fiddly they are, but the tiny profile makes them easier to cram in together. You are probably looking at 4 LEDs
at each end of your loco, to do the job properly... 2x red and 2x white/yellow. Some locos have headcode boards instead, which you can set a
slightly larger white SMD LED behind to great effect.
You can share a resistor between all of the LEDs at one end, assuming all of the forward lights are the same as each other, and all of the
reverse lights are the same as each other. If you have a mix of types of LEDs, such as a white LED + a yellow LED both to be
lit in forward direction, then you'll need
separate resistors for each combination, otherwise the current drawn will be mismatched and only 1 of them will actually light up!
Wires then need to be neatly routed back to the decoder somehow, which often involves filing a shallow channel in the loco's plastic body
for the wires to follow - not too deep though, or you'll go through the plastic! You might have to get a bit ingenious here to find
practical ways to place the wires!
Once the LEDs are glued in place and tested, you'll need to prevent light from escaping from the back of them and onto the track - you only
want light coming through the hole you drilled. This is usually a simple job of using some thick black acrylic paint from the inside,
smothering the back of the LEDs and their wires until no light shines through the paint.