Progress has once again been slowed due to a combination of work, domestic and revision issues. One of the reason for doing this layout was as a joint project with my teenage son, sadly he is in mid-GCSE season, so is unable to do anything other than revise at the moment. So I am restricted to doing things he has no interest in and sympathising over the revision. Hence no scenic work has taken place and I have spent a little bit of time assembling the electronics that are going to run the layout.

In my original plan for the layout I wanted to use it as a means to try out some different ways of doing things, so it will have a control system rather more complex than is really needed for a simple shunting puzzle. Partly I feel justified in trying things out on a small layout rather than jumping in with some big project and then deciding I had taken the wrong approach or simply wasting large amount of time and money. However it is also a case that I enjoy the electronics side of things anyhow and want to have a use for some of the neat ideas that are around.

The trains are definitely going to be driven via DCC, but all the accessories and the interface to the DCC is going to be handled by the MERG CBus system. With such a small layout I don't really get or need, some of the advantages of having a layout control bus, but I still think it is simpler longer term. For those that do no know, CBus offers a way of sending messages between bit of electronics on the layout. This means that using the same pair of wires you can send a message to control some item on the layout, and also get status back from other items. You may think you have heard this before, when people preach the "DCC - two wires is all you need" message. But this does something different, it works both ways, allowing feedback as well as control. It does not replace DCC on the actual tracks however.

The picture below shows the things I have built already...

Starting at the back left, I have 4 block occupancy detectors, each one will support detection in 2 blocks, so this gives me 8 detection blocks. They are actually a MERG kit, DTC8, with the original circuit board cut up to give me four separate pairs. They are not CBus kits, but will provide input to a CBus module.

To the right of these are a pair of DCC distribution boards I have built. These are basically terminal blocks mounted on stripboard. The DCC bus is connected at the two ends, one for bus in and the other for bus out. This is then connected to a pair of four way terminal blocks. this allows for 4 dropper pairs to connect to the DCC bus. There is also an LED and resistor on the board, this allows an indication that the DCC bus is functional to as far as this distribution board. I have done it this way as I do like like the idea of bare wires to run the DCC bus, once is one way I have seen people tap onto the bus. The other approach I have seen, using scotch-lock connectors also seems a little hit and miss to me - other may get on with it, but I personally am not keen. Therefore I am wiring by DCC bus through a set of distribution boards that allow be to connect droppers in a "hub style" network. The LED is part of my obsession with having diagnostic aids for when things go wrong.

The next pair of boards to the right are a couple of MERG kits, CAN-ACE8 to be precise. These are general purpose input boards that will taken inputs from the block occupancy detectors and other sources and send them along the layout control bus - the CBus. This will let be sense things like point settings, train detection and possibly also switches on the front of the layout that viewers can operate. Each board allows 8 things to be sensed and will translate the state of these 8 items and send CBus messages whenever they change - e.g. a train enters or leaves a section. Other CBus modules can then act on this information.

Below these boards are a collection of RJ22 interface boards that will be used to plug the control panel and the handheld controller into the CBUS. I have yet to build the MERG hand-held, this is the most daunting kit as it requires surface mount soldering.

To the left is the MERG DCC command station, this is one of the few that I have tested out, and it works brilliantly. It is driven from the CBus and connects to the track with an inbuilt 1A booster. I have not yet got the external booster kit, I need to wait for MERG to get the kit back in stock. However I will probably not need more than the 1A from the command station anyway - this is only a shunting puzzle.

To the left of the command station, and connected to it via CBus, is a USB interface - this is how I tested the command station, I sent CBus commands over USB from JMRI - using an iPhone as a throttle, to the command station and hence drove trains from the iPhone. This will be attached to the layout to allow JMRI panels to be provided for point control and mimic diagrams etc. Also I will probably have the JMRI setup for driving trains with an iPhone as well as the dedicated handheld controller. One thought is to have a touchscreen and display the mimic diagram on that and hence set points etc directly from the touch screen.

The next board along is an LED driver - this will go into the dedicated panel and provide all the indications as to what is happening on the layout. Again connected by CBus, so just 4 wires have to go to the panel. This board is capable of driving far more LED's that I will need for such a small layout.

Next we have a simple power supply board that will give me a source of both 5 volts DC and 12 volts DC - I need to produce a few more of these, since this on will only give me 1Amp of each voltage. I need a 12 Volt DC source of 1.5 Amps to drive the uncoupling magnets. I also need an interface between the CBus output module and these magnets - so yet more circuits to design and build. Although this should be fairly simple.

To the left and below the power supply board is a CANSERVO8 board - this connects to CBus and allows 8 RC servos to be controlled. Three of the servos will be used to change the points whilst the others will be used for animation effects on the layout. I already have a setup for an animated figure and am looking into putting a moving crane of some sort on the quayside.

The last two boards to the right of the servo controller are a panel switch board and an auxiliary output board. The panel switch board, along with the LED driver, will be inside the mimic panel and will take all the inputs form the push buttons and send them out as messages on the CBus, thus forming the other part of the panel.

The aux. output board allows 8 accessories to be driven by the CBus, messages from any device on the bus can thus cause things to turn on or off on the layout. Five of these outputs will be used to control the uncoupling magnets, whilst the rest will perform functions like controlling the lights on the layout or operating other accessories.

As well as these boards I have also been building the mains power supply, it will delivery 2 x 16V AC circuits to the layout and is in a separate plastic box, well insulated with short circuit protection and supply status indication built into it. The idea is that the mains stays on the floor in an isolated box and never comes anywhere near the layout itself.

I also have some ready made frog juicers that I will use to switch frog polarity, these really are a bit of a luxury, since looking at the CBus way of doing things it would have been a lot cheaper to switch the frogs via relays that are triggered by the same CBus events that trigger the point motors (servos). However I wanted to try these out, and with only three points it is not a huge expense.

One things I have to look at is how the frog juicers will interact with the block occupancy detection, I may have to live without detection on the frog, which is a little bit of a shame.

I still have a few more circuits to build, the hand held controller, uncoupling magnet interface and probably another CBus output module. Then it is a case of wiring the layout up with this lo, once I have mounted all the boards, and building the control panel. I think the GCSE's will be over before I have done all of that and I will be chased up by Daniel to get a move on - oh well there never is enough time in this world.