Just before Christmas I joined MERG as they offer a number of well developed electronics designs for layout automation (my interest - there are other things available too) which can be built for a tiny fraction of the cost of commercial systems.

I wavered for a while before joining - as I have to be careful with my hobby money. However, now that I've joined and have full access to the designs I'm glad I did. If anyone out there is also trying to decide whether or not to join I strongly recommend it if you want to get into layout automation and have a moderate knowledge of electronics. You certainly don't need to be an electronics expert to build the MERG kits - in fact basic soldering skills and the ability to use a multimeter appears to be sufficient. Everyone on the MERG forum is very helpful and friendly. I ordered some kits the weekend before Christmas and despite the kit building and MERG shop all being staffed entirely by volunteers I recieved them before Christmas, which is more than I can say for some 'professional' model shops! In case you hadn't noticed; I've been very impressed so far.

Of particular interest to me is the CBUS system. This is a layout bus network which can work alongside DCC or DC track control. It allows you to buy inexpensive modules which can:

• Operate motors - solenoid (with or without CDU), tortoise/stall or servo motor modules are avaialble - for points, turntables, signals, etc.
  
• detect occupancy - optical or track current
  
• read inputs - control panels buttons
  
• communicate with a PC by USB or serial
  
• control DCC locomotives and accessories
  
• Connect DCC Cabs
  

One feature which I don't think is available yet is transponding - but as far as I can see that's redundant for my design (a PC controlled layout with block detectors), because the program will already have all the necessary information. There should be no need to interrogate the decoders. Unless I've missed something about transponding?

I built a number of modules and wired them up for testing before fitting them to the south board of Burwood.

From left to right from top these modules are:

Top Left: DTC-8, an 8 way current transformer type block occupancy detector. You simply loop the track feed through one of the transformers and the device detects the current through the wire.

Top Centre: CANACE8C, an 8 way input module, which can take inputs from whatever sensors or controls you might want to have on the layout. I'm planning to use one of these for all of the block detectors on my layout.

2nd row, Left: A module with logic-level inputs and four relays, which I will be using for frog polarity switching.

2nd row, Centre: CANACC8, an 8 way output module. This can be taught to set any and all of its 8 outputs to any combination of high/lows based on an input from somewhere else in the system (such as the CANACE8C, or from the PC). I will be using this to control the frog relay board and lighting circuits in the village of Burwood

3rd row, Centre: CANSERVO8, an 8 way servo control board. Works with standard rc servos (as shown). I will be using this for slow action point control. Incidentally, using £2 9g servos from ebay, this works out at a total cost of about £3.50 per point motor - substantially cheaper than tortoises! You can easily configure the start and stop positions, as well as the speed of throw, from the PC.

Bottom left: A diode drop type occupancy detector. This uses schottky diodes, so only drops ~300mV and works with DCC. Credit to Trevor Gibson of MERG for this little design.

Bottom Centre: CANCMD, a CBUS DCC command station and mini-booster (1A). This takes commands from the PC or a Cbus CAB and outputs the correct DCC signal to the track. It supports separate main and programming tracks. For any real layouts a booster will also be required, which MERG also offer but I've not got one yet.

Bottom Right: CANUSB, the UCB to CBUS interface which allows the PC to send and receive commands onto the layout bus.

I'm currently trialing the system with JMRI, but I've been told that it works, or soon will, with RocRail and RailRoad & Co as well.