DCC DCC lighting conundrum

[Buntobox]

I've got a Swiss 6-car EMU that started life as a Lima model but was extensively rebuilt by a Swiss chap, Andreas Hui of Hui Modellbau. It got a brand new power car chassis and Faulhaber motor which gets its power from pickups on the outer two driving cars, the power being transmitted to the central power car through a busbar that runs the length of the train. The head and tail lights are wired into the busbar and use the same pickups; the directional stuff is taken care of by four diodes on the circuit board in the power car. My question is this and please bear in mind this is my first DCC conversion and I know next to nothing about it...I understand how the motor gets wired into the decoder but will I have to run a separate lighting bus down the train for the head and tail lights in the driving cars and should I convert those lights from the existing1.5V incandescent bulbs to LEDs? Here's a picture of the driving car chassis to show what's there at the moment:


The solder tags on the top of each gearbox and the chassis casting have no use and I'm not sure why they're there at all. I suspect it was an attempt at current collection via the metalwork of the bogies and chassis but there is no insulation between the two.

 

[Yorkshire Dave]

I presume this is the SBB RAe TEE II 'Gottardo' / RABe EC 'Graue Maus'.

For DCC, in short, it would be best to run a 3 wire bus (blue, white and yellow) from the decoder (via a small circuit board which makes terminating and soldering easier) to each driving trailer to power the head/tail lights.

My personal preference would be to replace the bulbs with LEDs but it depends on how the bulbs are installed. I presume there will be a white and red bulb each serving their respective light guides.

Although decoders have a LED setting I still prefer to make up my own small circuit boards containing resistors and it looks like you have plenty of space in there.

This is one of two circuit boards I made up for my HO DB Br 290 (V90) using SMRs (Surface Mount Resistors) and used nano LEDs in each light (three white and two red for each end).







I hope it helps.

 

[Buntobox]

Thanks for this but I'm still not really following.
You're right, this is the TEE II RAe unit and at the moment the head and tail lights have one bulb each which illuminate light guides but the light they produce is virtually invisible unless the train is running flat out...which it never will. My feeling is that I should install two LEDs for the headlights but only one for the tail lights because of the way the light guides are laid out. Can the two white LEDs be wired in series?
On to questions about what you've shown me. Is the three wire bus to accommodate one red LED, one white LED (or two in series) and a common return?
Secondly, in your picture how do the two commoned circuit board tracks get power when the DCC blue lead is only connected to the three commoned tracks at the top of the board? (or so it appears).
Thirdly, what are the track feeds for top and bottom? I thought the lighting only received power via the decoder?
Sorry to be a bit thick but as I said I know almost nothing about DCC and electrical theory was never my strong suit.

Alan

 

[Bill Campbell]

Hi Alan

The convention for DCC decoders is that the pickup wires from the track are red (Right hand side) and black. These two wires are in effect the input to the decoder.

Outputs from the decoder are orange and grey for the motor, blue is the common return, white is front headlight and rear tail light and yellow is front tail light and rear headlight. There will probably be other function output wires as well.

Check the documentation with your decoder to verify this. If you do not have sufficiently detailed documentation you should be able to find this from the decoder manufacturer's website.

If you follow this wiring arrangement you will need 5 wires between each of the vehicles - red and black for the track supply; blue, white and yellow for the lights. It is advisable to use a separate dropper resistor for each LED unless you use 12v LED's.

An alternative approach to having another 3 wires between each vehicle is to install a function only decoder in each lighted vehicle.

There is plenty of information on the Internet about wiring for DCC so it may be worth spending a bit of time on research.

Regards.

 

[Buntobox]

Thanks Bill, that's useful.

Alan