Digital model railway control systems
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A number of control systems are available to operate locomotives on model railways. The earlier traditional analog systems where the speed and the direction of a train is controlled by adjusting the voltage on the track are still popular while they have recently given way to control systems based on computer technology. Digital model railway control systems are the modern alternative to control a layout and greatly simplify the wiring and add more flexibility in operations.
Digital model railway control system basics
Modern digital control systems provide the ability to independently control all aspects of operating a model railway using a minimum of wiring; often the rails themselves are the only runs of wiring required. Control is achieved by sending a digital signal down the rails. These digital signals control operation of some, or even all aspects, of the model trains and accessories, including signals, turnouts, level crossings, cranes, turntables, and so forth.
Depending on the system, it may contain the following components:
Throttle
A throttle is a unit which controls operation of a train. Throttles are also known as Cabs, particularly in the US. A throttle can control speed and direction of one train at any time. The throttle also offers some means to select one of many trains which may be operating on a layout.
Central Unit
The central unit is the heart of the digital system. The Central Unit receives commands from Throttles (and possibly other sources), and emits the appropriate digital signals onto the track, to implement the commands issued by the throttle or by other sources. Most Central Units include an integrated Booster. The throttle can also be integrated in the central unit. Central units requiring a separate throttle device are often called black box style central units. Many central units are equipped with data bus connectors for controlling accessories or receiving feedback. There are several standardized data bus types used commonly in central units.
Booster
A Booster amplifies a low-power digital signal produced by the Central Unit, to the power levels needed to operate trains. Boosters are typically limited to a power output of 3 to 4 Amps. With HO or smaller track, currents higher than 4 Amps are high enough that short-circuits caused by a derailment can spot-weld the derailed wheels to the track.
In large layouts, where the total current requirement is higher, the track will be partitioned into multiple segments, and each segment will be powered by its own digital booster. The boosters may receive digital signals via a direct cable from the Central Unit, or simply from the track of an adjacent Booster segment.
Locomotive Decoder
Locomotive decoders are small electronic devices which are fitted inside locomotives. The decoder interprets the digital signal sent from the Digital model railway control systems#Central Unit to the rails. When the Central Unit sends commands to change the speed, direction, or other aspects of this locomotive, the decoder alters the electrical feed to the motor accordingly.
Stationary Decoder
Stationary decoders are used to control operating devices which are fixed in position, such as turnouts, signals, and level crossings. Since the devices do not move, stationary decoders can be mounted under the layout, and therefore can be significantly larger than locomotive decoders. Usually stationary decoders are connected to central unit's data bus connector, but it is also possible for stationary decoders to receive their data signal from the track.
Sound and Function Decoders
Basic locomotive decoders provide control of speed and direction, and little else. Supplemental decoders can be placed into a locomotive, to control headlights, ditch lights, or movable non-traction components such as remote-controlled pantographs. These decoders are called Function Decoders.
Sound decoders are, in essence, a miniature PC sound-card with pre-recorded sounds. The sound effects are played in synchronization with the locomotive, so that as a diesel locomotive starts from standstill, the sound decoder plays sounds of a diesel engine starting up. Sound decoders for steam locomotives can play "chuff" sounds in synchrony with rotation of the driving wheels.
Some decoders have all three functions—locomotive control, sound effects, and function control—in a single device.
Feedback Bus
To automate a digitally controlled model railroad, the Central Unit needs to know when trains reach their destination, or when the train reaches a certain point. This information is detected by a sensor, such as an infrared device placed between the tracks, or a device which senses current-draw in a particular section of otherwise-isolated track.
The Feedback Bus is the device which relays an electrical signal—an "on" condition—from the sensor hardware back to the digital Central Unit. The Central Unit can then issue commands appropriate for the specific sensor, such as triggering a specific signal, or level crossing.
The advantage of feedback is that each device typically needs only two wires: one to each digital track signal.
Computer Interface
Some Central Units
Systems
Digital Command Control
Digital Command Control (DCC) systems are used to operate locomotives on a model railroad (railway). Equipped with DCC, locomotives on the same electrical section of track can be independently controlled. While DCC is only one of several alternative systems for digital model train control, it is often misinterpreted to be a generic term for such systems. Several major manufacturers offer DCC systems.
Digital Command System
Digital Command System (DCS) is an electronic control system developed by MTH Electric Trains and released in April, 2002. DCS controls locomotives equipped with Protosound 2, Protosound 3, or Protosound 3E+ decoders. Protosound 3 locomotives are compatible with both DCS and DCC command systems. Protosound 3E+ locomotives are compatible with DCS and Märklin Digital command systems. All DCS compatible decoders are manufactured by MTH. Factory installed decoders have been offered in HO scale, 2-rail O scale, 3-rail O gauge, Gauge 1, and 3-rail Standard Gauge models. MTH has announced their intention to install DCS compatible decoders in S scale trains beginning in 2013.[1] Separate sale decoder kits have been offered for installation in all of the above noted scales except HO and S. DCS is predominantly used in 3-rail O gauge. It's chief competitors in 3-rail O are Lionel's TMCC and Legacy systems.
DCS uses proprietary command codes and transmission technology covered under US patent 6,457,681.[2] The principle differences between DCS and DCC transmission technologies include bi-directional communications and the separation of the command signal from track power. DCS command signals are transmitted at 10.7MHz using spread spectrum technology.
DCS can operate TMCC equipped models by means of an interface cable that connects the Lionel CB-1 command base to the DCS Track Interface Unit. DCS can coexist on the same track at the same time with either Lionel TMCC or Legacy command systems. Engines with either system can be operated simultaneously as long as both command control units are installed on the track.
Märklin Digital
Märklin Digital was one of the first digital model railway control systems. It consisted of a full system including locomotive decoders (based on a Motorola chip), central control, a computer interface, turnout decoders, digital relays and s88 feedback modules. For controlling 2-rail DC locomotives, like Märklin's Z and 1 gauge rolling stock, a special variety of the system was introduced in 1988. This version was developed by Lenz jointly for Märklin and Arnold. Arnold sold the system under name Arnold Digital while Märklin called it "Märklin Digital =". This system was the pre-decessor of DCC-standard. Apart from the locomotive decoders and central units, all the other system components were identical between 3-rail and 2-rail versions.
Selectrix
Selectrix is an early digital model train command control system developed by German company Döhler & Haas for model railway manufacturer Trix in the early 1980s. Since 1999 Selectrix is an open system supported by several manufacturers and standardized by MOROP. Technically Selectrix differs from competing bus systems by being fully synchronized and bi-directional. The same data bus protocol and data buses are shared by the rolling stock, accessories and feedback information.
Trainmaster Command Control
Trainmaster Command Control (TMCC) is Lionel's original command control system. It was introduced exclusively in Lionel trains in 1995. Beginning in 2000, Lionel offered licenses to other manufacturers. Licensees that formerly or currently install TMCC decoders in their models include Atlas O, K-Line, Weaver, and Sunset Models 3rd Rail Division. Licensees that formerly or currently offer separate sale decoders include Train America Studios, Digital Dynamics, and Electric RR Co. TMCC decoders have mostly been installed in 3-rail O gauge models, but it has also been offered in 2-rail O scale and S scale.
TMCC utilizes the same command codes as Digital Command Control (DCC). However, unlike DCC, it uses a 455kHz radio transmission to carry the command codes separate from track power. The locomotive decoders are dependent on AC track power (50 or 60 Hz) to synchronize the command receiver. Thus, TMCC can only operate on AC track power. Because TMCC utilizes the DCC command codes, it is possible to control TMCC with DCC compatible software. MTH Electric Trains included support to interface and control TMCC with its DCS system. Unlike DCC, TMCC-equipped locomotives can run simultaneously with non-TMCC locomotives. Lionel ceased the sale of TMCC command systems in 2010, but continues to introduce models equipped with TMCC decoders. TMCC has been superseded by Lionel's Legacy command system.[1]
Legacy Control System
Legacy Control System (Legacy) is Lionel's current electronic control system. It was introduced as a successor to Lionel's Trainmaster Command Control (TMCC) in December, 2007. Legacy is backward compatible with all TMCC decoder equipped engines. Models with Legacy sound decoders and/or Odyssey II speed control can be operated with earlier TMCC control systems but also have addition features only accessible with Legacy. The command codes for these additional features differ from the DCC command codes. Lionel has not published or licensed access to the Legacy specific command codes.
Hornby Zero 1
Hornby Zero 1 is a forerunner to the modern digital model railway control system, developed by Hornby in the late 1970s. It was based around the TMS1000 4-bit microprocessor. The Zero 1 system offered simultaneous control of up to 16 locomotives and 99 accessories.The Hammond & Morgan digital train control system is totally compatible with the Zero One. Zero 1 was released in late 1979.
A multiple train control system named Zero 1 was introduced in late 1979. This control system was a forerunner to the Digital Command Control (DCC) system, an NMRA open standard, which appeared in the 1990s. Though an important milestone, Zero 1 was not widely successful; both the controller units and the decoder modules required for the locomotives and accessories were expensive, but with a clean track and well serviced locos the system worked more or less as advertised.
The Zero 1 system supplied the track with a 20V square wave at the local mains frequency (50Hz in the UK, 60Hz in the US) with a 32-bit control word replacing every third cycle. The decoder module in the locomotive would switch either the positive or the negative half-cycle of the square wave to the motor according to the desired direction of travel. During the transmission of the control word, it would remain switched off. Speed control was achieved by varying the width of the portion of the half-cycle which was switched, in 14 steps.
This system allowed for straightforward implementation with the semiconductor technology of the time, but had the disadvantage that the power supplied to the motor was highly discontinuous - as can be seen from the description above, it took the form of square pulses of a maximum width of 10ms, recurring at intervals which alternated between 20ms and 40ms (for a 50Hz mains supply). This caused the running of the motor to be extremely noisy and rough. Fine control of a locomotive at low speed was also difficult, partly due to the rough running, partly due to the inherent coarseness of a 14-step speed scale, and partly because there was a significant delay between operator input to the controller and response from the locomotive.
Locomotives fitted with a Zero 1 decoder according to Hornby's instructions could not be used on conventional systems, making it difficult to run one's locomotives on friends' layouts or club layouts. It was possible to include a miniature DPDT switch in the installation to enable the Zero 1 decoder to be switched out for use on a conventional system, but the official Hornby information made no mention of this, causing potential customers to perceive a significant disadvantage to the system which did not in fact exist.
Control of points and other accessories was available in a very simple manner. For solenoid-operated accessories (e.g. points, mechanical signals) or accessories involving lights (e.g. colour light signals), track-powered accessory decoder modules, each providing four outputs, were available. Each output could be configured either for burst operation or continuous output, for use with solenoids or lights respectively. Accessories were switched by entering a numeric code on the controller. Up to 99 accessories could be controlled.
Accessories based around motors rather than solenoids or lights, such as turntables, could be fitted with a locomotive module and controlled in the same manner as a locomotive.
Zero 1 had 3 'phased' introductions: Phase 1 = Master controller and basic system (Master controller, slave controller, hand held slave unit and loco modules) Phase 2 = Accessory control (Points, Signals etc.) Phase 3 = Micro Mimic display (Allowed for LEDs to represent status of points and signals on a mimic display panel)
The main master controller unit was discontinued in 1986, and the last time loco modules were listed was in the 1991 catalogue - 'Limited supplies of R955 loco module are available'. Repairs to Zero 1 units were no longer undertaken by Hornby, the reason given being 'Lack of available parts required'.
The system is very reliable, the basic 1980s keyboard design being the main problem on older badly stored master units. It is easily repaired though and can be made to work like new in a few simple steps. Loco modules were available in two types. The pre-1981 types were based on a single triac. The square-wave supply and the presence of spikes from the motor and from poor contacts rendered the dV/dt rating of the triac marginal and these units would sometimes self-trigger on the wrong polarity half-cycle, resulting in damage both to the unit itself and to the locomotive motor. The later type, made by H&M, used two SCRs, one for "forward" and one for "reverse", to avoid this problem. Again, the loco modules are easy to repair with the right skills.
The system is still used today by many modellers, as is shown by the demand on sites like eBay for the items in the second hand market. The unused sockets on the rear of the Phase 3 Mimic controller hinted at the way development could have been heading - a light pen socket possibly indicating a link to a computer and control via light pen. Given that this was the era of the Sinclair Spectrum (which was launched two years after Zero 1), the system was perhaps ahead of its time. The DCC system which is today's current standard for digital control of a model railway is similar in many ways to how Zero 1 worked.
Airfix Multiple Control System
Airfix Multiple Control System(MTC) was introduced in 1980 and used 20v AC on the track with a superimposed control signal. Unfortunately it was only produced for about 18 months when Airfix went into receivership and the concept was not developed but dropped.[2][3] MTC system offered simultaneous control any 4 out of up to 16 locomotives.[4][5]
DYNATROL
DYNATROL is a 15-channel command control system from Power Systems Inc.The track voltage is 13.5 volts d.c.It was introduced late 1970s.[6]
Digitrack 1600
Digitrack 1600 is one of the first generation digital Digital model railway control system developed and marketed by Chuck Balmer and Dick Robbins in 1972.[7] CTC-16 is a second-generation design based on the Digitrack 1600, a commercial system marketed from 1972 to 1976.[8] The CTC-16 digital train control system is totally compatible with the Digitrack 1600.
Rail-Command 816
RAIL-COMMAND 816 is an 8-channel digital signal system using a 12 volts d.c.constant track voltage.It was introduced late 1970s.
CTC-16
CTC-16 system offered simultaneous control of up to 16 locomotives.[9] A series of 16 pulses is sent out to the track 125 times each second. A receiver monted in each locomotive is tuned to respond to only one of the 16 pluses. The amount of voltage appliied to the motor depends on the width of the pulse commanding that paricular locomotive. The receiver decodes the programmed channel from the command signal and extracts the speed and direction information from it.The receiver is essentially a transistor throttle built right into the locomotive. The command station is not expandable beyond 16 channels.
PROTRAC
PROTRACR/C system 9000 offers 8-channel command control.It was introduced late 1970s.
SALOTA 5300
SALOTA 5300 offers 5-channel command control with a 16-to 18-volt d.c. constant track voltage. It was introduced late 1970s.
PMP-112
PMP-112 system offered simultaneous control of up to 112 locomotives. It was based CTC-16.[10]
RFPT
RFPT offers 9-channel command control system using high-frequency control signals and a 12-volt a.c. constant track voltage.
KATO Digital
KATO Digital is KATO's electronic control system for HO scale model trains. Conceptually it is similar to Digital Command Control (DCC).It was introduced late 1980s.[11]
Software
Digital model railway control systems are often connected with an external computer where special software for controlling the train layout is running. This allows more options for operating trains from fully automatic system where the computer is in control of everything in a layout to a computer based control console for controlling signals and points on the layout and leaving the role of the train engineer to a human.
Hornby RailMaster
RailMaster is a new model railway control software package announced by Hornby, one of the world's largest model railway companies, at Christmas 2010. The software connects to the Hornby Elite DCC controller (at present) and allows for the controls of trains, points, signals, turntables and uncouplers from a single screen. Although you can use it with a normal mouse, it has been optimised for touch-screen PCs where you just touch a point, a signal or slide a locomotive throttle.
This link http://www.youtube.com/watch?v=hGfiuO2o9NQ is a video on YouTube showing the new system.
The new RailMaster software will be available to purchase during the second quarter 2011. Hornby aim to set the standard in PC model railway control software and have a comprehensive action plan to significantly enhance this area over the coming years.
Rocrail
Rocrail is an Open Source Project that can control a model train layout from one or more computers. You can run trains directly from your computer, and you can have the computer run trains automatically for you. You can even have some of the trains on your layout running automatically while you control others by hand.
References
- ^ http://www.digitdynam.com/command_control.html
- ^ Airfix_mtc
- ^ Airfix World
- ^ Airfix MTC
- ^ Airfix Railway Systems
- ^ Model Railroader November 1979 p80
- ^ Model Railroader August 1972 p37-40
- ^ Model Railroader December 1979 p64
- ^ Model Railroader December 1979-April 1980
- ^ Railroad Model Craftsman March 1986-June 1986
- ^ KATO Digital