Proposal for a unified power supply with additional security functions for narrow gauge rolling stock

By Manfred Schaible and Ludwig Rommel

A power supply is certainly not a major concern with narrow gauge rolling stock, but we should always be aware of dangerous situations which occur during the more and more popular “sunset” or “night” runs, especially with guest vehicles. A good illumination and, what is even more important, a reliable emergency signal, could help make those services safer. A tail-light can help avoid collisions, the controller or passengers should be able to signal an emergency to the driver, an individually or centrally operated interior light might be welcome when entering or leaving a coach, and so is a power plug for an icebox or a battery charger Two more wires are available for auxiliary functions like speakers for announcements or – why not – an electrically operated brake.

Spare parts from the automobile branch meet the idea of a standardized system.

They are duty-proven, reliable and relatively cheap. The only thing to do is to wire them differently according to the new functions on railways:

The following explanations and wiring schemes will refer to these colours and pin numbersl

This is how to proceed:

1- Install a 7-pin vehicle socket at either end of the loco or carriage and connect them via a connector box installed at a convenient place in your carriage or loco by a 7-wire-cable according to the scheme and colour-code given above.

2 - You may now wire the the following items:

- Interior light (operated from the driver’s cab)

- Interior light (operated by switch in the carriage or compartment)

- Emergency signal (push-button)

- Power plug (12 V =)

- Tail-light

- Speakers or other device

3 - The carriages are interconnected via coupling cables. You can make them from 7-wire-cable about 80 to 100 cm long according to your coupling system with a plug on either end. Pre-fitted spiral cables wired to the scheme above are also available but rather expensive. In order to give these connecting cables enough space between the carriages and to avoid that they interfere with the couplings, the sockets should be fitted at a height of 60 to80cm, approximately above theleft rail in the running direction. Thus the cable hangs diagonally and can easily follow the lateral movements of the carriages.

1- Wiring in the cab of the locomotive

a- Loco with own power supply

Fit 2 sockets at either end of the loco as described in 1 and 2 above

Connect the supply from the battery or generator (+) via a 15A fuse to the red wire and the ground (-) to the black one. Thus the socket pins 6 and 7 provide a permanent power supply(+ and -) for the connected carriages.

A switch between the power supply and the brown wire supplies the socket pins 5 and thus operates the interior lights. The ground (-) passes via the black wire and pins 7.

The tail-light can beoperated together with the front lights as those lamps are usually used simultaneously. For this, the power supply towards the front lights is connected to the blue wire / pins 2. So when the front lights are switched on, a tail-light set between the blue wire / pin 2 and the black wire / pin 7 will work.

Note that this wiring switches on all the tail-lights. To avoid this, carriages with fitted-in tail-lights should be equipped with so-called „switch sockets“ where the built-in contact 54G turns off the rear fog-light when a trailer is plugged in. In our case this means that only the tail-light of the last carriage will work as there is no further plug in the socket (= „no trailer“).

A simple alternative is a removable tail-lantern which you connect to the rear socket of the last carriage, only the pins 2 and 7 of its plug being wired.

The emergency signal consists of an optic and acoustic warning device (light and buzzer/horn) fitted in the cab, it can be activated by a (red) push-button fitted in each carriage. In the cabin, the device is connected to the ground (-) and the yellow cable/pins 1. The push-button in each carriage is connected to the red wire (+) and closes the circuit with the yellow wire / pins 1

The two remaining wires (white and green / pins 3 and 4) can be used for auxiliary devices, for example speakers. The two wires can be connected to the Audio exit of an amplifier located in the cab or in one of the carriages. Note that the red an black wires ( + and -) are a permanent 12V DC power supply to in each carriage.

b) Loco without power supply

In the case that your engine has no own power supply, this electric system can be fed externally from a suitable battery either in the cab or in one of the carriages. Just connect the battery to the red and black wire (pin 6 and 7) in the connector box, the + pole should be protected by a 15A fuse.

Install a small control panel in the cab with at least two on-off switches and a warning device (light or buzzer) in order to turn the tail-light and the interior lights on and to be able to receive the emergency signal. The general power supply (red and black) allows operating other items like front lights, cabin light, horn etc which will considerably enhance the security when operating a loco which is normally not “equipped” at all.

Here is the wiring scheme for the locos:



Install a 15A fuse between the battery/supply and the system !

If your loco has no own power supply, a battery can be placed in the cabin or in one of the carriages, but in this case the controls will not work when the loco is uncoupled

2- Wiring of the carriages

According to the general wiring scheme a 7-wire cable, a connector box and two sockets on either end must be installed. The general power supply is operated from the loco or a battery via the red wire / pin 6 / + and the black wire / pin 7 / -.

The tail light is connected between black (-) and blue / pin 2 , the blue wire being also the supply for the headlights. Both can be operated from the cabin only.

Instead of a tail-light, a removable tail lantern can be plugged into the rear socket of the last carriage. Its plug is only wired on pin 2 and 7.

The interior light is wired between brown/pin 5 and black/pin 7 and can thus be switched on and off from the cabin.

If operating the interior lights should be possible from the carriage itself or from a compartment, a switch must be installed from red (+) to the lamps. A diode 1N4005 must be added before the lamps in order to separate this circuit from the one from the cab. Without this diode switching on the light in one carriage would also switch on the lamps in all the other carriages.

The emergency buttonis set between red (+) and yellow/pin 1. Pushing the button sends power from red (+) via yellow/pin 1 to the warning device in the cab.

A 12V power plug (for a cigarette lighter) can be set between red (+) and black (-) to allow using other devices like a cooling-box or a battery charger.

The white and green wires are off function. They can be used for auxiliary purposes like speakers etc.

Here is he wiring scheme for carriages with removable tail-light:

 

Note: the diode is necessary to separate the individual circuit from the one from the cabin. Switching on the interior lightning of the whole train should be the driver’s option only.

Here is a slightly different scheme for carriages with built-in tail-lights. The sockets are so-called “switching sockets” with the 58b contact which cuts off the fog tail-light of the car when a trailer is plugged in. Here, only the tail-lights of the rear end of the last carriage will work as no further plug is present in the socket, so 58b stays closed.

No worries: If your rolling stock is already electrically equipped you can easily make an adapter from your plug-and-socket system to the 7-way system shown here.

But in order to unify our systems it would be best to wholly adopt this system and replace all those different sockets and plugs by the already standardized 7-pin (car) sockets and plugs. There is no need to replace your existing interior wiring, just connect it according to the wiring scheme given here

Spiegelberg, September 2010