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Rabs

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  1. Rabs
    To automate my layout I've been investigating sensors to accurately locate the trains so that I can run realistic operations without user intervention. I will update this post with photos when I get my camera out at the weekend.
    I've been experimenting with using hall effect sensors for detecting train position on my N gauge layout. In particular I've been trying this sensor:
     
    Honeywell Latching Hall sensor
     
     
    As I see it these sensors have a number of advantages over other sensor systems.

    Not susceptible to ambient light conditions like optical sensors Don't require dividing the track into electrical blocks like current sensors Much more sensitive than reed switches (so smaller magnets) Can differentiate N from S poles - unlike a reed switch very localised effect (initial testing suggests better than 5mm resolution - easily good enough to detect when a train is clear of a set of points for example Can be completely concealed below ballast Very cheap (~80p per sensor) Virtually no additional circuitry needed The other option that I considered was RFID, but other people report problems caused by accidentally triggering tags on adjacent, parallel tracks (of which I will have a few). I'm sure that this could be overcome with a bit of optimised antenna design to reduce the transverse axis sensitivity - but RFID tag antenna design is a complex area and I'm not all that keen to get into it just for this project. Finally, RFID is usually designed to be omnidirectional - not what you want from a positioning system!
     
    You can get Hall effect sensors without a latching effect as well. I went for the latching effect because this means that I will be able to detect both the start and the end of each loco/coach or wagon by placing a magnet of opposite polarity at each end of the car - very useful if I want to position a specific coupling over a decoupler automatically.
     
    The magnets that I'm using are 4mm diameter, 1mm thick NeBFe rare earth magnets, available from many suppliers such as:
     
    Magnet suppliers
     
     
    I found that Ebay was the cheapest source - with a pack of 50 magnets costing ~£2.50 - so you can kit out each member of your rolling stock for just 10p. The ones I have are N48 grade. (Higer grade magnets have higher surface flux densities). The difference in the range between N42 and N50 isn't all that great, so I would imagine that any of these would work ok - but I've not tested any other grades.
     
    For my first tests I just placed the magnets on the ends of the steel screws which hold the chassis of my test loco together. I put the sensor on a little bit of stripboard (PCB prototyping board) and glued it to the underside of the sleepers, with the sensor between two sleepers. With this arrangement the top of the sensor was just below the level of the top of the sleepers. Passing the loco back and forth over the sensor showed it working perfectly first time (much to my surprise!).
     
    With just two magnets the sensor is 'set' when the front of the loco passes over it and 'reset' when the back passes over it. With my current arrangement it only works with the loco travelling forward over the sensor - but I have some ideas for different arrangements of magnets on the underside of the rolling stock to overcome this.
     
    Watch this space - if you find this at all interesting that is , otherwise I'll be making some posts about the more normal bits of my modelling soon!
  2. Rabs

    MERG CBUS

    By Rabs,

    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.
  3. Rabs

    Branch Terminus Shunting

    By Rabs,

    Thanks to the very helpful comments Mike the Stationmaster (in this related thread:http://www.rmweb.co.uk/community/index.php?/topic/50382-gwr-branch-terminus-signals-and-services/page__fromsearch__1), I have now arrived at a suitably prototypical signalling and track layout for the Burwood terminus. Now, to plan my uncoupler and sensor locations I need to work out how operations will be done. My guesses below are just that, pure guesses from someone who knows nothing about real railway operations. Anyone is very welcome to put me right on these. Passenger trains are pretty straightforward and I plan to handle them like this:
     

     
    Where I am less sure is with goods and mixed traffic. My current guess is along these lines:
     

  4. Rabs

    Hello

    By Rabs,

    Hi everyone,
    I've created this blog to document the build of my first layout - which is called Burwood. I'm an electronic engineer by profession - and I hope to incorporate a significant degree of automation in the layout. This might stretch to computer control and a scripted timetable but at the very least I hope to control operations remotely without any interference from the big pink finger in the sky.
    Having previously played with HO as a child I've chosen N scale as a compromise between model accuracy and operational interest. I wanted to use a smaller scale to allow me to model part of a railway network (rather than just a single station or junction) but thought than 2mm FS was a leap too far for a first layout. Having said this I am keen to overcome the worst deficiencies in N (like those horrible couplings!) - so will be looking to what is done by many finescale modellers for inspiration.
    My chosen subject is a fictional 1930s/40s GWR setting in the West Midlands. Given a childhood of being taken on the Severn Valley Railway every summer by my grandfather (a keen G scale modeller himself) there was never going to be a choice on which of the big 4 to model!
    I hope to cover most aspects of the layout build in this blog. One potentially interesting aspect of the layout is that, given the space constraints in our house, it has to be completely concealable when not in use - so a significant part of my effort has been to design a system to allow the railway to fold completely out of sight when not in use.
    I hope that some of what I post here will be helpful and interesting to others - particularly in avoiding the mistakes that I've made and I'm sure that I'll continue to make!
    Best wishes everyone,
    Robert
  5. Rabs
    My girlfriend and I recently moved into a new house. Something that immediately got put on the list of things to replace were the hideous internal doors. A side effect of this was that I was left with no less than 5 standard 1970x755mm doors and one slightly larger one ... I wonder what they could be used for?
    Having already done a fair bit or research on baseboards I was aware that hollow core doors tend to be very noisy as baseboards - as the cavity in the centre acts like a sounding box on a guitar or violin to amplify any sound from the rails. Some people also dislike the size of internal doors for baseboards as they are too big for one person to lift and (obviously) a tight squeeze through doorways. I'm not too bothered about this second issue though as I don't intend to be moving the layout often - as it's pretty unlikely that my first layout will be exhibition standard!
    To assess the suitability of the doors for baseboards I ran a series of experiments to investigate different roadbeds, sub-roadbeds and adhesives to minimise acoustic coupling from the track to the board.
    Using some old lengths of Peco code 80 that i'd bought by mistake on ebay (I am using code 55 on the layout) I tried the combinations described below. I used a farish mk1 coach rolled by hand initially as a rough test and later tried a farish 060 locomotive running on DC pulling 2 4 wheel wagons.
     
    Experiment:
    1) Track attached to door surface with double sided adhesive tape
    2) Track attached to door with double sided adhesive foam tape
    3) Track attached to 2mm closed cell foam roadbed with Copydex latex adhesive (the roadbed was also attached to the board with Copydex)
    4) As 3) but using double sided tape between layers
    5) as 3) but using track pins to attach the track to the roadbed (the pins also extended into the board below)
    6) As 3) but with the track loosly rested on the roadbed (as a control)
     
     
    Result:
    Rather unsuprisingly there was a huge amount of noise from the track attached directly to the door with double sided tape. I was surprised to find that 2) gave almost no improvement over 1) - this might just be the grade of foam in tape that I chose, as I would have expected similar results to 4) - which is essentially the same construction of adhesive film - foam - adhesive film just put together manually rather than on a roll. The use of track pins in 5) completely removed the benefit of the foam, as the directly couple the track to the board below.
    In order of increasing noise level: 6), 3), 4), 2), 5) and 1).
    As 6) isn't viable, as there is nothing to hold the track in place I decided to go with the Copydex solution. This also has the advantage that it is much easier to unpeel copydex than it is to unpeel the double sided tape, which was a high bond variety. Finally, with Copydex you get more time to align everything when laying the track. The disadvantage is that you need to clamp the track in place while the glue dries (or weight it down) - I suspect that laying tight curves with flexitrack might be tricky with this method, and that temporary track pins might be required to hold it in place.
     
     
    Further experimentation showed that mounting the foam on a subroadbed of laminate flooring fibre underlay further reduced the noise. For sections of track on a gradient I use hardboard cut to the approximate track plan (60mm wide), with laminate underlay the full width of that and a top layer roadbed of the 2mm closed cell foam cut into 30mm wide strips (the width I intend to ballast to). This assembly is periodically supported by wooden blocks .
  6. Rabs
    The layout will eventually live in the sitting room, so it has to be discrete. For this reason I've designed it to fold away into a sideboard sized unit. There's still a significant amount of design work to specify the lifting mechanisms, but I'll wait until I have a feel for how heavy the boards are going to be before doing this. The importance of doing the space model shown in the pictures below was to assess what baseboard size and shape I could fit in the room. This then played chicken and egg a bit with the layout track plan until I arrived at the design shown here. There is space for approximately 250mm height for each layer (including baseboard thickness of 40mm) - so I'm not going to be having any tower blocks, but a medium sized village church should be feasible.
    From this model I was then able to finalise the track plan and to cut the doors to size.
  7. Rabs

    Track Plan

    By Rabs,

    My intention for this layout was to be able to have a good mix of operation and mainline running of decent length trains (more than 5 coaches). I'm not too concerned about continuous running - which is why the layout only has 1 loop that could be used for this.
     
    It is important for me to be able to build the layout one board at a time - so that the project can be done in bite sized chunks. the whole layout is very ambitions for a first layout (with over 50m of track) - and I'm keen to avoid the usual track of biting off too much and getting frustrated. For this reason I've designed it so that the first board that I will make can be operated as a stand alone layout - so that I've got something to show for my work even if I never finish the others!
    The pictures below show the track plan as it currently stands for Burwood. The full diagram shows all track, including all the hidden track and staging areas. The more sparse diagram shows the track visible to the observer.
    I have a minimum radius of 450mm (18") on visible track, and 270mm (10.5") in hidden areas - with one exception, which I intend to disguise with dense forest. The gradients are a maximum of 1.6% on visible areas and 3% in hidden areas.
    I will be building lift out sections of scenery for all hidden pointwork. The layout will be positioned with the top edge (as it appears in these images) against a wall. Viewing access is from the other three sides. For convenience I have decided that towards the wall (up in these images) is "North" for the layout.
     
    The village of Burwood itself is served by the small branch terminus at the south of the layout. The village extends south of the station (so most of it is off the board). The branch line to reach Burwood from the North passes under a dual track mainline viaduct, which runs East/West across the central board. To the West of the plan is the busy 4 platform terminus station and engine shed of a nearby town - which has yet to receive a name!
    The central board, as well as the viaduct has a mainline junction where trains from terminus can either carry on East or turn North-East. On the Easternmost board I am currently planning to include a coal mine - but this may be scrapped if the layout looks too crowded when I eventually get to that point.
     
    I'm hoping that, as there is a gap between the two settlements (Burwood on the South board and the town on the West board) and the track doesn't go direct from one to the other it won't look as though they are treading on each other's toes.
     
    As you can see the South board looks a lot like the traditional branch terminus 1st layout - this is quite deliberate! I'm planning to build this board first and progress it to a good degree and learn as much as I can before I start building the others. This has a number of benefits:
    1) It offers interesting modelling and operation by itself
    2) It is significantly more simple than the other boards
    3) It doesn't have any reversing loops - so the wiring and control is nice and simple for a first attempt
    4) It will be relatively inexpensive to replace the track used in this board if I stuff it up
  8. Rabs

    1st Baseboard build

    By Rabs,

    Hi everyone,
    Just catching the blog up with my progress from the last few months. Last June we finished replacing our internal doors. Salviging the old ones, I cut the baseboards for Burwood. the West board is shown below. Where cuts were made I planed the edges and reinforced the cavity of the hollow door with some 30mmx20mm pine strips.
     

     

     
    I took over our living room for a day to fit removable pin hinges which I am going to use to join the boards. (sorry, I forgot to take a picture of this step)
    Having made sure that all the boards would go together repeatably, and hold rigidly when assembled, the southern board made its way up to my 'cave' for building, with the others going into storage for the time being.
     
    As I've mentioned before, I'm going to develop the south board completely before starting the others. It is the least complicated design, and I did the track layout to make it a self-contained terminus layout in case I never finish the rest of the layout.
    I built the trackbed in laminated hardboard/fibre underlay - as described in a previous post. The picture below shows the board during construction.
     

     
    First action was my Peco Collett Goods up the incline with two very anachronistic BR WR Mk1 coaches. An exciting moment!
     

  9. Rabs
    I'm using Peco code 55 track for Burwood and have decided on Servo operation as this offers the realism of slow action at a much lower cost than stall type motors. My kit is as follows:
    Merg CBUS (connected to PC)
    CBUS servo module (can drive 8 servos)
    9g servo
    Adapter plate
    Peco code 55 point

    I'm not using microswitches for frog switching, as this is being done by separate relays.
     
    I've come across a number of people describing methods of mounting and aligning servos manuallys such as here:
    http://www.nscale.ne...unting-Question
    and here:
    http://www.youtube.com/watch?v=8oerWG-G2so
     
    The disadvantages of this type of assembly are:
    It requires you to be both sides of the table at the same time
    Each point needs to be adjusted individually to ensure alignment
    Many people recommend the use of double sided foam tape. I suspect (although happy to be corrected if people know better) that this will lead to motors falling off as the years go by.

    This significantly adds to the hassle of setting up servo point motors
     
    To address this I have designed a little adapter plate for N gauge Peco points.
    All Peco points have a set of holes for mounting Peco's solenoid type motors. This is standard across the whole range of n gauge points. As the same motor is sold of HO/OO and O gauges I suspect that these also have the same mounting holes, but I've not measured these. I designed the plate to fit onto these holes and hold the servo motor in the correct location for this. This allows the point and motor to be assembled and setup on the bench, before mounting to the layout. Also, by using fasteners rather than adhesive it makes replacing faulty servos much easier in future. Here is the assembly designed in Solidworks:
     

     
    The red and blue components are components of the points where the red is stationary and the blue is the sliding bar.
    The grey component is the adapter plate, which I machined on my CNC mini-mill (my other hobby project):
     

     
    And here is the first prototype:
     

     
    The plate is 5mm thick acrylic with:
    A pocket and mounting holes for a 9g servo motor.
    0.95mm holes aligned to the holes in the point. These then have small stubs of 1mm brass rod inserted which grip the hole and the 0.95mm slot in the points - ensuring consistent location of the motor relative to the points
    A hole below one of the holes in the point's throwbar
    The motor positioned so that mid-throw of the servo travel corresponds to mid-throw of the points.

    The thickness was chosen so that an N gauge point with 2mm throw is actuated correctly by a 9g servo going through 15mm horizontal travel, where the separation between the servo crank and the point slider is 30mm. The blue shim has a 1mm hole in it, for the 0.9mm brass rod. This has been temporarily attached with double sided tape for testing. When I make more of these I intend to make these in 1.6mm thick FR4 PCB material and to modify the plate design to include a locating recess for this. I added a blob of solder to the brass rod above the crank to keep it from dropping out.
     
    Some videos of it in action (sorry about the poor quality and the inadvertent zooming!):
     
    http://www.youtube.com/watch?v=K1q82f0QQXA&feature=youtu.be
     
    http://www.youtube.com/watch?v=8AfX07p9RQM&feature=youtu.be
     
     
    In conclusion:
    With the plate machined, assembly and setup of the throw of the servo (I'm using a MERG servo control board) took less than a minute.
    Nice, slow action
    I was pleasantly suprised how quiet the servos are when you run them slowly
    With the diameter of the brass rod I'm using I think that I'll leave the Peco spring in the point. It only leads to a little 'hop' as the point traverses - and it means that I can turn the servo off when not in use and be confident that the point will stay thrown.

    I'm happy to share the design of the adapter plate with anyone who is interested - it wouldn't be difficult to make manually. CNC'ing it does help to make sure that they are made consistently though.
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