APT Lighting

The first train I added lighting to was my APT set. I installed head and tail lights, a cab light at each end, and interior lighting to the passenger vehicles. The prototype has three headlights (two marker lights plus a high intensity headlight as can be seen from this picture taken at Glasgow Shields depot) and twin tail lights just inboard of the marker lights.
Hornby original   Hornby fitted plastic headlight lenses with light-guide stalks for the two outer marker lights, lit by a single filament bulb. The diode for directional control can be seen here, it is fed from one wheel each side of the leading bogie.
I have removed the lenses and the track feed wires from the bogie as these are not needed here. I drilled five holes to take 2mm tower LEDs from DCCconcepts which are glued in place.   LEDs fitted
LEDs fitted   Viewed from the front, the alignment is not perfect, but this will not be noticeable once the outer lenses are replaced.
The next step is to wire everything up. Before starting, I ran a series of tests to decide how much current the LEDs needed to look right. I found that I needed the two marker lights wired in series with a 1kΩ resistor, the high intensisty light needed a separate feed through another 1kΩ resistor, and the two tail lights also needed to be wired in series with a 1kΩ resistor. Here everything is carefully sleeved with colour-coded heat-shrink and the tails led backwards ready to be connected.

I had made these judgements when powered by my NCE PowerCab on the test track and realised that everything was too bright when on the main line. This was powered from a PowerPro booster whose output was at a higher voltage. Not a lot but enough to make a difference.
  Initial wiring
Final wiring   The cab light is very unsophisticated. It comprises simply a single micro-dot LED soldered to a pair of stiff wire stalks (one is a 1kΩ resistor) pushed into the moulded sockets vacated by the original lighting and wired up to its tails. This simplicity will not be visible once the body is replaced. This shows a cab interior stub I used to get the dimensions right.
Then I built up a long thin (3-wide) stripboard to mount the interior lights and their resistors, which were series pairs of DCCconcepts daylight white micro-dot LEDs. Here are the first two vehicles lit up on test ...   On test
On test     ... and with their bodies on, a couple of lights have failed in the DTS. It is clear from this view that Hornby’s paintwork was not designed to be light-tight! As mentioned above, I am having to reduce the light levels for main line running.
The wires are fed down the train to the decoder in the TBF, using a DCCconcepts 6-way connector at each articulated bogie. This is invisible at normal viewing angles.   Articulated bogie connector

Configuring the Decoders

I have fitted separate function-only decoders in each trailer set to control the head and tail lights and the interior lights throughout the train. TCS’s FL4 decoders are rated at 200mA per function for each of four outputs so can easily handle the lighting for their half-set, they are located in the TBF vehicle which is marshalled next to the motor vehicles. I am using the Hornby Class 142 inter-car connectors to parallel the track pick-ups from both motor vehicles and a live bogie under each TBF.

The FL4 decoder’s four outputs are mapped by default to F1 to F4, there are no white and yellow directional output wires. However, TCS’s literature sets out how to reconfigure any function output to respond to almost any function button and behave in pretty much any way you might wish. After installing the first decoder, I experimented with the CV settings and eventually got the result I was looking for, two output wires remapped to F0 forward and reverse. The following table sets out the amended CVs:

354 or 8Green wire to F1 (default) or F2Driver’s cab lights
3616Purple wire to F3Passenger coach lighting
392Brown wire to F0 RevTail lights
401Pink wire to F0 FwdHeadlights
5316Brown wire on reverse onlyTail lights
540Pink wire on forwards onlyHeadlights

With all the decoders set to the same address and their direction bits set accordingly, the train behaves perfectly seamlessly as one unit, just like you’d expect. Even though the FL4 decoders are function-only, they do have a perfect sense of direction.


Footnote: DCCconcepts is an Australian firm but their products are available in the UK from Bromsgrove Models to whom I am unrelated save as a very satisfied customer.


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