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!

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.

The change to DCC took place at the same time that we converted to Tortoise point motors and upgraded our signals. Initially, 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 was 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.

Times move on and very quickly, the advantages of DCC became obvious even to a stick-in-the-mud like me.

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.

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

• Easier automatic operation of the layout for exhibition purposes.

The only thing that has not turned out too well is 'easy double heading' . The whole thing is a complicated sequence that can result in the locos suddenly going opposite directions and wrecking coupling rods or tearing off the odd crank! After that experience, I shall probably build a free running Manning Wardle with no motor or gears to double head!

getting started

The problem was where to start. Several attempts to get information from trade stands resulted in a torrent of alien terms which very quickly glazed over my eyes. That is until 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.

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. 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 Peco electro-magnets fitted in their place.

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. Below are the differences between George Bush and a DCC model locomotive.

• they know who they are :  loco address

• they respond when called : just dial up the loco address and they respond

• they remember how to behave in an appropriate manner : The performance of the loco can be easily programmed.

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. I did not do the best job on this and finally my chassis doctor, Peter Wallace banned me from doing it and took over the task!

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 have their numbers and have had top speed programmed, acceleration, deceleration and back EMF. Despite initial fears, the system has worked perfectly 'out of the box' and did all the things claimed for it.

onwards and upwards!

I find that operating trains for two whole days during exhibitions, mind numbingly boring. Far better to be able to talk without distraction to the visitors. I also quite liked the idea of just watching trains go by. I therefore decided that the main line would be fitted with automatic train control so only the port branch will be operated by hand. See the animated schematic below.  In reality, there are six tracks behind the scenes and the automatic system will allow for four or six train operation.

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 even considered it without Malcolm's help. It must be pointed out that automatic running is useless unless you have reliable operation. We are close to this but more work is still needed.

For us, much of the problem comes from the huge difference in overhangs between some of the locos and stock which can cause coupling lock. There is still some development work to be done here. The Lynton and Barnstaple locos all have big overhangs. Of course, the problem would not arise is larger radii were employed, however, even with a larger layout such as County Gate, the trackplan would then be very restricted.

coupling lock between a Manning Wardle and coach

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.

I shall try to describe how it all works without the use of too many nerdy terms!

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 boards are able to 'talk' to each other.

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

hover over each board for explanation - do not click

All these boards are multi-functional and some require programming.

By using an interface unit, the Locobuffer, the whole network can be connected to a computer, using USB leads. Once this is done, really complex sequencing of train operation can 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.  One also has to load a Loconet programme into the laptop.

This software is well explained on this link

click on image to enlarge

click here to see wiring diagrams.

connection schematic - click on image to enlarge

fiddle yard with stock arranged for auto running