Track laying has continued and I have now completed two boards. I have also wired up those two boards complete with all the associated point motors.
I have programmed the main CBUS module in the control panel and the modules on the two boards which control the point operation and all the section switches and which controller of two controls that section. This wasn’t without its problems as two of the modules had the wrong version of firmware in their PIC controllers and stubbornly refused to be recognised by the computer used for programming! After many trials and tribulations where I was literally pulling my hair out [useful as I can’t get a haircut at present!!] I managed to upgrade them and now have a fully working system. All with only a 4 way cable connecting the control panel to the layout. You can see a 64xx pannier and a diesel railcar which have been run all over the existing tracks.
I intend to hide the point motors at the front of the layout with a removable scenic board and the ones at the back with suitable buildings. I have mocked these up in paper and they include warehouses, a stable block and a garage for the local bus.
Also shown here is mock up to show where the platforms and station building will be sited.
In lockdown and in between all the jobs in the house and garden, work is progressing on laying the track work on Tavistowe. It’s amazing how much mess accumulates on the boards while working;
The main line at the Plymouth end is complete up to the single slip which allows access to the goods yard. This end has been wired up and all the point motors added. I have decided to mount the motors on top of the board to allow ease of adjustment if needed. This area will be covered by the local cattle market on a removable piece of scenery. The main track is the 3mm Society 14.2 plastic sleepered track with code 60 bullhead rail. The points are all handmade with a mixture of copper clad strip and 1/32” plywood strip. Cosmetic chairs will be added later using the ones produced by the 3mm Society. All the trackwork is glued to the cork base with a PVA based Tacky glue.
The motors are Hoffmann point motors which work on 15vAC and have built in switches for the frog polarity. The relay to the side of the motor is the interface between the point and the MERG CBUS modules. The relay switches the point motor and in turn is turned on or off by outputs from the CBUS. The actual CBUS module [a CANACC8 for those interested] is mounted under neath the board. One of the points seen here is servo operated as there wasn’t room for another Hoffmann.
I fear that the wiring underneath is a bit of a ‘spaghetti junction ‘. Luckily the baseboards include holes to carry wiring around the layout. I am basically trying to keep the CBUS data wiring to the front of the board and the track power and AC feeds to the rear in order to reduce any interference between the two. Here you can see the twin servo board on the left which drives the point and the intermediate starter signal when it is installed. The relays on the right switch the servos on and off in response to an output from the CBUS. In the middle is the connection of the CBUS and its associated 12vDC power
That’s enough for the moment. The grass needs cutting………
In between all the jobs around the house and garden that are being found for me I have been able to make a start on Tavistowe at this horrible time of forced isolation at home.
I have laid the cork underlay on the boards and glued point templates in position. I first printed them out on tracing paper and then stuck them in place using a copy of the whole layout printed from the Templot plan as a guide. I intend to construct the points off site ,so to speak ,on templates printed on thin card and then install them in the relevant position on the layout.
Even though I haven’t laid any track yet I have built the control panel!
I have repurposed the locking lever frame I had on Eggesford to suit Tavistowe much as most heritage railways have done. I also worked out all the sections, point motors and signals I would need. I then wired up the panel to the MERG CBUS module which will control the output from the panel. This interface is done through a diode matrix as can be seen in the picture below.
This all means that there is only a 4 way cable carrying the CBUS signals on two wires(blue and yellow) and a 12vDC power supply on the red and grey. This compares with 2 x 25way cables that would be needed if wired in the conventional way. Once the trackwork is done and all the point motors, signal servos, and section feeds have been installed then I will program the module to get it all working. Well that’s s the theory!!!
As I said in a previous post, I have decided to use the MERG[Model Electronic Railway Group] CBUS system to operate the new layout.
I purchased 2 kits to make a test board. One to accept the input from switches and the other to control relays which I intended to use to drive a point motor and a Heathcote servo board. The other intention was to program it by the ‘Slim’ method which doesn’t need a computer input. Constructing the kits was fairly straightforward and the initial testing told me they were working. I followed all the instructions to teach the relay driver to respond to the switch but alas this was where I came unstuck. The relay switched on when I closed the switch and only switched off when I closed it again…….
After lots of reading around the Merg website and the forum I discovered that there was a problem programming the relay driver using the onboard switches. I therefore decided I would have to go down the computer route to set up the modules. I purchased a USB4 kit to provide a connection to the USB port on my Laptop and also a GIZMO kit to monitor the whole system.
Now a load more reading about the program to be downloaded to set up the system- 3-4 large documents on the website-and then yet another learning curve to get to know how the program works. Eventually with a lot of trial and error the last ‘light bulb moment’ occurred and I had a working test board! I can now work a Hoffmann point motor, control a servo for operating signals and switch LED’s on and off. Whow!
Now that I have worked out how to do it, it will be relatively easy to scale it up to the rest of the new layout but there is still more learning to do…… it will have to wait until the terrible Covid 19 epidemic is over as the Merg kit shop is presently closed.
While I have been waiting for my order of Tim Horn baseboards my thoughts have turned to control and wiring of Tavistowe. I intend to have a separate control panel with a manually interlocked lever frame working the points and signals and a mimic diagram for the electrical sections as I am traditional and sticking to DC control.
Recently we took Lakebank to the Southampton show and together with my partner in crime from the Launceston and District MRC, Nigel, we got talking to some very enthusiastic guys from the local group of MERG(Model Electronic Railway Group) As a result I have become a convert to their CBUS system for layout control. This a is a bi-directional system which operates down just four wires between the control panel and local modules on the layout boards. A module in the control panel reads the switches and transmits a signal to the modules on the layout which in turn work point motors and servos for signals .
This means that I can have a control panel with one 4 way connector for the CBUS and a 15 way connector to sort out all the power sections and feed from the controllers.
As you can see from the above plan of the proposed layout, it will involve 8 sections, a common return and in addition there will be two controllers Each section will be able to use either controller.
As well as these sections the layout will need 15 point motors (Hoffmann) and 5 signals controlled by servos. With conventional wiring this would involve at least 40 wires
Having come away all enthused for the system I duly signed up to join MERG. Their website is a phenomenal store of information the majority of which I have no clue as to what it means, not having much background in electronics. My mind has been well and truly ‘boggled’, and they said it would be easy!!
My next step will be to purchase some module kits and set up a test board to learn how it all works. Watch this space……….
New Year is coming and it’s time to start a new project.
I am going to build a new, permanent home layout based on Tavistock South which was the Great Western station at Tavistock, in West Devon. I was inspired by an article in the Great Western Echo- magazine of the Great Western Society. The article included an aerial photograph of the station which shows how tight it fitted into the landscape and makes an ideal prototype for a model.
It will be interesting to make the station building with its overall roof and there are quite a few small, interesting building as well.
I have drawn the plan out using Templot and found I could fit it into the 11 feet that I have space for. It did mean some adaption of the original layout. I have excluded the turntable and locomotive works and also shortened some of the sidings. As it is not exact I have decided to call the layout ‘Tavistowe’, courtesy of an idea given to me by Iain Rice!
I have decided to buy some accurate laser cut baseboards and have plumped for those produced by Tim Horn.
The main period I am going to depict is 1948-1950, ie just after nationalisation. 1948 being my year of birth! This allows a lot of pre nationalisation stock as well as some in the early BR liveries.