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DCC conversion

Although I have some experience with wiring, I have to say that it is not my favourite occupation. I find that the smallest distraction when doing the job can result in connection disasters so I also have to put my hand up to admit that the job also makes me very grumpy indeed! Nevertheless, I have wired up a couple of aircraft cockpits (and flown the 'plane afterwards).

I was brought up in the era of electro-mechanics. You could actually see what was happening in those days and it made sense. Electronics are wonderful but my general understanding is about that of ancient tribes observing an eclipse. Circuit boards look to me like a mad mixture of tiny Liquorice Allsorts and Dolly Mixtures and the sight of folks making up boards to their own design fills me with admiration.

In the old days, I had used a thing called 'pulse power'. All the locos ran really well at scale speeds and I felt all was right in the world. Coming back to the hobby, I found 'pulse power' was a thing of the past and 'all it used to do was burn out motors' (funny that, because it never happened to me). County Gate was therefore controlled using DC with a Gaugemaster controller.  This was not anything like pulse power and the speeds of some of my locos were close to a Boeing 747 at rotation.

By chance I met Malcolm Alberry at the Warley show. He was helping out at the Digitrax stand and very kindly spent a great deal of time explaining the systems to me in a way that even George Bush could understand!

As a result, we opted for the Digitrax system and begun a phased approach to digitalisation. We purchased the Digitrax Zephyr, a transformer and some remote operating stations. The Digitrax Zephyr manual can be downloaded here.

Our expectations of DCC were as follows:

  • Constant higher voltage applied to the track. This has got to solve some of the poor conductivity problems of DC when very slow running is required.

  • Simplified wiring as it is not necessary to isolate track to prevent the wrong locos from running.

  • Realistic stopping and starting.

  • Loco performance programmed into the chip to control top speed.

  • 'cruise control' so that the required speed is held 'up hill and down dale' whatever the load.

  • Equalisation of performance of our L&B locos to ensure easy double heading.

  • Easier automatic operation of the layout for exhibition purposes.

the reality, after living with these systems is this:

  • I do not think there is much difference in track conductivity between DCC and DC in practice

  • The wiring for a basic system is indeed simple.

  • The locos are indeed easier to control

  • Basic programming of a loco is simple but it gets very difficult if you want the best

  • 'cruise control'  (back EMF) might work if you make a life's work out of it but so far no luck for me

  • It is possible to equalise loco performance

  • Automation works very well but the system is very complicated and expensive

getting started

I had wished to replace the Peco solenoid motors at County Gate Station for some time and the changeover seemed like an ideal opportunity to get that done and also to upgrade our signals. We first of all stripped County Gate of its wiring and Peco point motors. Feed to the track was by self adhesive copper tape, and drop wires were put in place every metre. The amount of wires underneath were reduced by at least 75%. I was also unhappy with the signals at County Gate and decided to replace some of them with more typical SR models and at the same time seek better movement and the 'bounce' found on the prototype when they are operated.

I also had got really fed up with the permanent magnets fitted into the track to disconnect the Greenwich couplings during shunting operations. This had resulted in a number of involuntary disconnections at embarrassing moments. The magnets were dug out of the track and eventually I found electromagnets strong enough to replace them.

I decided to retain the manual operation of points and signals at this time. As such, the wiring is indeed very simple.

chipping the locos

The only things I have had chipped previously are my cats. Perhaps the digital control will keep them in order too!

Click here to check it out

Locomotives running on DC are about as clever as a bag of hammers. When chipped, locos are far more intelligent than George Bush!

The new chips are really very small and we were advised to choose the latest Digitrax offering. The new Digitrax DZ 125 chip is similar in size to the Lenz silver mini. This chip, despite the instructions that come with it, is enabled for back EMF (BEMF) (called 'scalable speed stabilisation' by the Yanks).

DZ 125

This offers better slow speed running and also compensates for grades (a bit like cruise control).

At long last, the chips arrived and the exacting job of fitting them to our locomotives began. It was necessary to virtually rebuild some of the older engines, and installation into the L&B units was far from easy. Great care is needed to ensure that there are no shorts in the system.

Chips can actually control other functions too such as directional lighting. We have installed this on a few units and it works very well indeed. The large amount of wiring needed to do this raises challenges when working with such tiny rolling stock. I do intend to fit sound to one unit, just for the hell of it!

The generic manual for these Digitrax chips can be found here and the specific manual for the DZ125, here

chip fitted to the chassis of 'Taw'  - click on image to enlarge

 The motor unit of the railcar converted. The part of the chassis which contacted the brushes had to be milled away and the wires then attached to the brushes - click on image to enlarge

Once the Digitrax Zephyr outfit was delivered, it was installed into the viaduct section of the model. The main control box was fitted into a recess cut into the front of the baseboard. This box is held in place with Velcro. In order to programme locos, it is necessary to have a programming track...two leads come from the control box to do this. We felt that this was another complication, so the harbour branch of the viaduct section is fed through a double pole, double throw switch to provide either track power or programming.

The leads to the UP5 remote sockets daisy chain from the main controller. It is transferred from one panel to the next using 8 pin DIN plugs/sockets. These also carry the track power.

the main control box fitted. Below is the switch to track for programming or power. The DIN socket will feed to the harbour section

The box was 'lit up' and I have to say we quite quickly got the hang of it. All the locos now had their numbers and can be programmed to perform as required up to a point.

the downside

DCC promises to offer all the characteristics that I required and there is no doubt you can programme each engine to do most things.

The programming of a loco depends on altering a vast number of parameters. These are called CVs and there are well over one hundred of them. These all have to fiddled with on a programming track while your supper goes cold. In my opinion, a lot more has to be devised to make the system user friendly.

DCC manuals seem to have been written by electronic nerds for electronic nerds (or USA speak). I have to say that Lenz scores slightly better in this respect, but Digitrax and NCE just make my eyes roll. Some of the information is actually wrong and there is no logic (understandable to British and French) to the way the manual is compiled.

There are a number of forums available where help is at hand and this does ease the situation.

Thanks to some good friends who are in to all of this we hope to be able to publish here the generalised programming necessary to get narrow gauge locos to run as they should.

Bitter experience has shown us that it is a very bad idea to use Peco point motors or others requiring a CDU. In 20/20 hindsight, I would have fitted Tortoise throughout.

onwards and upwards

I find that operating trains for two whole days during exhibitions, mind numbingly boring and subject to human error which quite often results in derailments and wrecks! Our little engines are very delicate and such treatment was not doing them any good. Our Desperados have been amazing doing as well as they have and have manually operated CG far better than I could in a million years but it has been very hard for them at best.

'mind numbingly boring'

Far better to be able to talk without distraction to the visitors and even have the time to visit other stands and spend time talking to old friends. I also quite liked the idea of just watching trains go by. I therefore decided that the layout would be fitted with automatic train control so only the port branch coal trains and shunting would be operated by hand.

After further discussions with Malcolm Alberry, it was decided to go the whole hog. This was a very scary decision as the equipment is not cheap and I would not have had a chance of succeeding without Malcolm's help. It must be pointed out that automatic running is useless unless you have reliable operation. This has taken a great deal of time but I can now say that we have as close to 100% train reliability as is possible.

This has been achieved by  picking up current from as many wheels as possible. Our six coupled engines are therefore plugged in to 'companion cars' which also pick up current. Many modifications have also been made to the mechanisms which must travel long distances without complaint.

I still wished to retain the potential for manual operation of the layout without depending on electronics. This means that we have double control panels and it is possible to change from one system to the other by merely swapping a few plugs.

onwards and upwards!

I shall try to describe how it all works without the use of too many nerdy terms! Apologies to those who know all of this stuff!

Apart from just controlling trains, the DCC system also includes Loconet. Loconet is a system that allows all sorts of electronics to be daisy chained together with a six wire cable using phone socket / plugs. Once connected, the various electronic boards are able to 'talk' to each other. Remember, on a DCC layout, the track remains live with a pecial DCC voltage waveform the whole time. Digital signals are passed down the rails to the locos which control their operation after they are 'read' by the chip. This is how loco lights can be switched on and off, and speed and direction control is effected. Digital signals are also passed down through the Loconet system and provided the right bits of electronics are provided, the digital stream can control point, signal and block operations as well as provide for further train control stations.

Using such systems, the DCC control board is just fitted with push buttons. The direction of point throws and signal positions are shown by LEDs.

Sections can be cut into one rail (must be the same side throughout the layout) and the system can sense where trains are, which are also shown by LEDs. It is not that dissimilar to full scale track circuiting.  The image below shows how such units fit together on County Gate.

click on image to enlarge

Parts are Digitrax, supplied by Sunningwell Command Control and CML Electronics

circuit boards explained

This is the interface between the control panel and the railway. It is connected to the panel push buttons and the indicator LEDs. It also operates the LEDs showing train position on the layout. This decodes and controls 8 points or signals and allow. They can be adjust to operate a number of different point motors. this does the same job as the DAC 10 but only for 4 points or signals. These control the sections of the layout. These are cut into a common rail and include stop, brake and detect sections. these control the operation of the signals an interface between locnet and a laptop computer
hover over each board for explanation - do not click

All these boards are multi-functional and some require programming which is rather difficult.

This facility allows us to control the entire functions of the layout through just one cable (similar to a telephone cable). The amount of wiring is thus considerably reduced.

Once this is done, by using an interface unit, the Locobuffer, the whole network can be connected to a computer, using USB leads. Really complex sequencing of train operation can then take place. The whole concept is in effect similar to sequencing and MIDI, for those familiar with modern musical keyboard systems. The controlling software is supplied by Railroad & Co.  This is a very flexible system and has an excellent 'help' forum for the sticky questions. One also has to load a Loconet programme into the laptop.

Our first show as an automated railway was at Chatham in June 2009 and I am pleased to be able to say that the system worked perfectly throughout the weekend.

We do have full wiring diagrams of County Gate. These are included for our own reference should problems arise. However, they may give some insight into the work that has gone into this project.

The software is well explained on this link

Below is shown a simplified animation of how the software operates. The route is previously set for Lyn and River Avon. The red dot shows point motors when activated. After the railcar and Yeo return to base, Exe and Halliday would be dispatched.

click on image to repeat

Here is an animation of how the ten trains operate over the main line.

the fiddle yard with stock arranged for auto running

example of 10 train operation - click on image to enlarge

A film of the completed automatic operation can be seen here