Digital control

Digital control – a new dimension of railway set operation

Multiple train control was originally meant by the term digital control. Historically this control emerged from America. Here several locomotives were put in position distributed both in front of, and within, the train. Here the American railways modellers view themselves as locomotive drivers which transport a train from one station into another one whilst observing the signals. The development of a corresponding locomotive control system was necessary to realise this type of operation in line with the original model. Now technology has advanced to such an extent that accessory products can also be controlled digitally.

Using digital control systems, operating situations that are in line with the original model can be replicated much better than is possible using conventional means. Here, one possibility would be instance involve attaching a trhough carriage to a train, decoupling or coupling a group of wagons with a shunting locomotive from a local freight train that is standing in the station, or to provide a front/pushing locomotive for a heavy train and to travel in double traction. The world of computer control also opens up new prospects for (fully) automated set operation. The driving characteristics of the locomotives will be much better when using decoders with engine load control than when using conventional DC operation. Shunting operations that are much more authentic are thus possible. The conventional pulse width regulations used to date can now no longer be used with the widespread LEDs that are currently widespread due to the fact the locomotives have the front and rear lights turned on simultaneously.

An advantage of the digital system presented is the further usability of the digitised locomotives on conventional sets. Here, the locomotives do indeed lose their good slow speed characteristics, and in some cases their programmed speed characteristics, but the approach delays that have been programmed still continue to be active. The locomotives can thus also travel on a conventional set of a railway modeller who is a friend.

Through this characteristic of the digitised locomotives it is possible in principle to divide up the set into digitally operated (railway station) sections and conventionally operated block sections of track. The digital control does not require any subdivision of the track set into different track sections for the simultaneous operation of several teams. At this point an essential benefit of a digital control system becomes evident. Whilst in a conventional system, the number of existing driving current ranges and the associated power controls, determine the number of trains (and number of people using the set at the same time) a digital set is flexible at all times without adjusting the wiring.

The number of connected controllers determines the number of people using the set at the same time. The number of locomotives that can be controlled at the same time exceeds the capabilities of the personnel anyway. The digitral control system is based on an “intelligent” controller, the so-called central power controller. This controller “tells“ every locomotive how it should move on the track, or not move, as the case may be. Electronic modules, which are termed “decoders”, are built into the locomotives to ensure the locomotives also understand the language of the central power controller.

Voltage constantly runs through the track to realise this principle. This is slightly higher (approx. 18 V) than it would normally be (12 V max), but mainly constant. This constant voltage makes side effects, such as constant lighting of the train, possible. However, the bulbs installed in the vehicles must be adapted to this higher voltage, i.e. exchanged, (LEDs do not need to be replaced).

The central power controller successively activates all the locomotives on the set and issues travel commands. To this end each locomotive is assigned a so-called "address”, the number under which it is registered at the central power controller. The locomotive then only reacts to commands of the central power controller if it has heard its number at the start of the command. These travel commands include the speed, the direction of travel and the condition of any functions in the locomotive. In the majority of TILLIG locomotives this is the lighting and in some models the driving beam. These functions can also be switched independently of the movement of the locomotive – voltage is constantly supplied to the track. Due to the fact voltage on the track is constantly applied as AC voltage, "forwards" and "backwards" is no longer assigned to the track system.

The definition of the direction of travel is now performed in relation to each vehicle. This means that when a locomotive receives the instruction to travel forwards, with the smokestack (or cab 1), it will do this, regardless of how it is placed on the track. Two locomotives positioned in this way thus travel towards each other if they are placed with the smokestacks facing each other on the track. If a locomotive does not react, the decoder makes a note of the last commend until the next transmitting of a command to it and performs it. Thus it is possible to issue their commands to other locomotives in the meantime. Thus several locomotives can assume different driving states independently of one another on the same track.

The properties of the decoders installed in the vehicles of the locomotives can be set. This is described as programming. Various properties can be changed depending on the decoder type. The most important ones are the addresses of the locomotives as well as the acceleration and braking delay for the mass simulation of the train.