Digitrax
Occupancy Detection Yet Again
About fifteen months ago work on adding occupancy detection to Sumida Crossing stalled. That was in part because I’d planned to use the BDL168 detectors to also do transponding, and a few months earlier had abandoned that plan since I was unable to get that aspect to work reliably, even on a simple test track. The number of solder joints on the BDL was also a nuisance that caused me to put off further work.
Recently I’ve been rethinking my approach. The BDL168 is an amazingly cost-effective solution. Ignoring the transponding part, you get 16 detectors on a board that includes a LocoNet bus interface for US$120 (street price). That’s $7.50 per detector (if you can use all 16). That’s really hard to beat for a bus-connected detector. I’d originally planned to install one per table on the layout, and my cost would have worked out to around $10 to $15 per detector on average.
On the other hand, I’m thinking that I might want to move to either a OpenLCB/NMRAnet bus (if I want a feature-rich bus for the future) or a really dumb serial bus (like S88 or C/MRI). The latter is attractive since I can potentially interface to it with an Arduino, opening up some room for home-brew devices. Of course I could do that with NMRAnet, but today that requires a US$45 shield to add to the Arduino (or one with it built in), which kind of takes away from the appeal of using $10 Arduinos to do things like drive signal masts.
While thinking about this, I went off and started researching what was available commercially or as home-brew circuitry and software libraries for these busses and for doing occupancy detection with them, as the latter would be a good way to get my feet wet and solve my “don’t want to solder those #$@! BDL168s any more” problem.
But in the past week I’ve been sidetracked into looking at homebrew inductive-coil detection circuits.
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Recently I’ve been rethinking my approach. The BDL168 is an amazingly cost-effective solution. Ignoring the transponding part, you get 16 detectors on a board that includes a LocoNet bus interface for US$120 (street price). That’s $7.50 per detector (if you can use all 16). That’s really hard to beat for a bus-connected detector. I’d originally planned to install one per table on the layout, and my cost would have worked out to around $10 to $15 per detector on average.
On the other hand, I’m thinking that I might want to move to either a OpenLCB/NMRAnet bus (if I want a feature-rich bus for the future) or a really dumb serial bus (like S88 or C/MRI). The latter is attractive since I can potentially interface to it with an Arduino, opening up some room for home-brew devices. Of course I could do that with NMRAnet, but today that requires a US$45 shield to add to the Arduino (or one with it built in), which kind of takes away from the appeal of using $10 Arduinos to do things like drive signal masts.
While thinking about this, I went off and started researching what was available commercially or as home-brew circuitry and software libraries for these busses and for doing occupancy detection with them, as the latter would be a good way to get my feet wet and solve my “don’t want to solder those #$@! BDL168s any more” problem.
But in the past week I’ve been sidetracked into looking at homebrew inductive-coil detection circuits.
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August 2013 Status - a Retrospective
And not only another month, but another year has passed. Not much happened in August; as I mentioned last time I’ve mostly been working on the Arduino project. So this month’s post will focus on the past, but will also look forward to the future.
This month marks the fourth anniversary of Sumida Crossing, dating things from the start of construction. Planning actually started earlier, around June of 2009 in earnest although there had been a lot of thought prior to that. And the first real train didn’t run until early 2010 (unless you count a test on a loop of temporary track). And actually, although the first post in this blog dates from September 16, it wasn’t actually online until the end of November. Prior to that I’d been working on the initial version of the website offline, and hadn’t bought the domain name or space on a server until I judged it ready. I don’t think it even had a name before November; I’m pretty sure I made that up when I bought the domain name.
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This month marks the fourth anniversary of Sumida Crossing, dating things from the start of construction. Planning actually started earlier, around June of 2009 in earnest although there had been a lot of thought prior to that. And the first real train didn’t run until early 2010 (unless you count a test on a loop of temporary track). And actually, although the first post in this blog dates from September 16, it wasn’t actually online until the end of November. Prior to that I’d been working on the initial version of the website offline, and hadn’t bought the domain name or space on a server until I judged it ready. I don’t think it even had a name before November; I’m pretty sure I made that up when I bought the domain name.
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PWM Motor Control
DC motors are controlled by varying the voltage and polarity of the DC power connected to them. In a simple DC power-pack a rheostat is used to provide a voltage to the track that varies from zero volts to the power pack’s maximum, which is often around 16 Volts. A simple switch is used to swap the positive and negative outputs to change the polarity (and thus the direction the motor turns). This tends to waste a lot of power as heat, but since that’s happening inside the power pack (and “a lot” isn’t really all that much at these voltages) that’s acceptable.
DCC decoders need to take a constant-voltage AC input from the rails, and control a DC motor somehow. Even if they could use a rheostat, wasting power as heat inside a plastic model is more problematic. The technique normally used instead is called Pulse-Width Modulation, and it’s a fairly simple and commonplace, and efficient, method of controlling DC motors from a digital controller. The same technique is used in many other applications. Read More...
DCC decoders need to take a constant-voltage AC input from the rails, and control a DC motor somehow. Even if they could use a rheostat, wasting power as heat inside a plastic model is more problematic. The technique normally used instead is called Pulse-Width Modulation, and it’s a fairly simple and commonplace, and efficient, method of controlling DC motors from a digital controller. The same technique is used in many other applications. Read More...
Decoder Wars II - Lightboards
Comparing decoders for cab cars is actually relatively simple. These don’t need to do very much, so it’s really about checking basic functionality. I’ve laid out the full testing details on my Decoder Comparison Testing page, and here I’m going to summarize the findings for the capabilities of interest to me.
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Decoder Wars I
Edit: see the comments for some additional notes; also, I’ve edited the text to correct some errors, but those edits are marked.
A long time ago, in a distant land, titans met to do battle...no, wait, I mean recently, on my kitchen table, I started testing DCC motor decoders for N-scale EMUs. And as with most wars, after it started I began wondering why on earth I’d thought it was a good idea. Still, I have reasons for this, and the result is important: the winning candidate will go in my (so far) 27 trains that don’t support Kato’s plug-in decoders, and some have two motor cars, so it’s closer to 30 decoders.
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A long time ago, in a distant land, titans met to do battle...no, wait, I mean recently, on my kitchen table, I started testing DCC motor decoders for N-scale EMUs. And as with most wars, after it started I began wondering why on earth I’d thought it was a good idea. Still, I have reasons for this, and the result is important: the winning candidate will go in my (so far) 27 trains that don’t support Kato’s plug-in decoders, and some have two motor cars, so it’s closer to 30 decoders.
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Configuring The EM13 Part I
Kato’s EM13 DCC decoder (29-351) is a specialized decoder used for the motor car in an EMU/DMU model or other “DCC Friendly” models made by Kato. DCC Friendly (the English term is used even in Japanese, rendered as “DCCフレンドリー” or “DCC furendorī”) isn’t the same as “DCC Ready”, and it is a phrase used by others to simply mean that a model is relatively easy to convert to DCC. But when Kato uses it, the phrase means “will accept Kato FR11, FL12 and/or EM13 decoders”. And the models that do so are primarily Kato’s N-scale Japanese prototype models: commuter trains, limited express trains and Shinkansen (bullet trains). They also use it in some steam locomotive models, including the American-prototype GS-4.
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DCC Voltage and Cab Lights
’m turning my attention to the cab car decoder install now, and a recent discussion with Don along with a question from a reader had me thinking about potential problems with DCC conversion of N-scale EMU cars with cab lighting. And the one that really worried me was overvoltage from high DCC track voltages, and its harmful (fatal) effect on LEDs. DCC decoders essentially pass track voltage (minus a small bit) through to their function outputs.
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Wire
I went off on a tangent this past week. It all started when I asked myself: what gauge wire should I use on my decoders? And the root of that question was thinking that the wire I’d used on my first install, two weeks ago, was too thick. The answer turned out to be less obvious than I thought it would be, and consumed (and is still consuming; I’m not done) a lot of time.
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November 2012 Status
November, as you may have noticed from recent posts, went largely to laying the groundwork for installing wire-in DCC decoders, and a bit of testing of same. After a few delays, most of what I was waiting for finally arrived, although a few things are still backordered. In particular, the six-pin NEM651-compatible plugs and sockets mentioned in the comments last time have arrived. For the curious, the parts list has been added to my page on DCC Decoders. Read More...
Wired Decoders II
Although the rest of my decoder order still hadn’t arrived, I decided to start work on my first wire-in motor decoder, to let me get some experience with the installation process, and to do some more experimentation. I used the Micro Ace Sobu E231 as previously planned, and to start with, a DZ125 decoder from Digitrax.
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DCC Speed Tables
My plans to start installing decoders were somewhat upset when a large quantity of the ones I’d ordered turned out to be out-of-stock, and a box arrived containing only a couple of decoders and some wire. I actually have a number of decoders on hand, though not enough to do a full EMU the way I want, or all of the models I wanted to experiment with. So, while I could have made a start, instead I decided to spend some time working out my standard configuration settings for the Digitrax decoders. I’m going to have a number of these even if I don’t use the DZ125 wire-in decoders, since my Kato “DCC Friendly” models use Kato’s EM13, which is essentially a Digitrax FX3-Series decoder. And I have a few models with lightboard replacement Digitrax decoders.
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Decoder Programming Prep
As noted last time, I’m going to (finally) install DCC decoders in some of my commuter (and other) trains that aren’t Kato “DCC Friendly” designs, meaning I have to use wire-in decoders. And since these are EMUs where the motor car is in the middle of the train, that means installing three decoders per train, a Motor Decoder and two “function-only” decoders for the cab cars.
But to start with, I need to set up my workspace since it’s been a while since the last decoder install, and the various elements had all moved off the bench to other uses. And the bench had filled up with important stuff (meaning junk I couldn’t stuff somewhere else), so I needed a better workspace. Besides, I’m going to want to sit down for this work, and the workbench is really better for standing work. Read More...
But to start with, I need to set up my workspace since it’s been a while since the last decoder install, and the various elements had all moved off the bench to other uses. And the bench had filled up with important stuff (meaning junk I couldn’t stuff somewhere else), so I needed a better workspace. Besides, I’m going to want to sit down for this work, and the workbench is really better for standing work. Read More...
Wired DCC Decoders I
This is the first of what I expect will be several posts about wire-in DCC decoders. Up to this point I’ve either been using the Digitrax-made Kato decoders that snap into Kato trains, or lightboard-replacement decoders for locomotives. But I have a large number of trains that don’t take either of those, many of them the commuter trains I’ll want to run on my new commuter line (once I finish the DCC wiring for that). Read More...
More Wires
After saying I was going to finish up the DCC electronics several times, I’ve finally made a start. There are two parts to this. The first is finishing up the remaining DCC power protection and occupancy detector panels. I did the first three tables last year, starting around January. The third was the first I’d done as a removable panel, which I wired up back in November. At the same time I’d begun the work of setting up a third accessory power bus, adding a switch and meter to the main panel. However at that point I’d stalled, with my attention off the layout over the holidays, and when I returned it was to work on buildings.
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Bus Wiring and November 2011 Status
DCC is often said to simplify a model railroad because it requires “only two wires”. While that’s true to an extent, most real model railroads will require quite a bit more. Or maybe I just like to over-complicate things.
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DCC Power II
The DCC Power work continues, but it’s still not done, as I have to do the power panels for the urban scene and the unsceniced return loops, but with the panel I built and tested back in September/October finally installed under the tables of the River Crossing scene, I’m at the halfway mark (having done the Riverside Station scene back in March).
To recap, the board contains a PM42 DCC circuit breaker that provides four separate circuit breakers and a BDL168 occupancy detector that can provide up to sixteen occupancy detectors and eight transponding sensors (see my pages on occupancy detection and the BDL168 for more details). This board provides occupancy detection for six electrical blocks, two each on the commuter tracks and one on each subway track where it loops below the expressway. Although I’m also wiring up the transponding sensors, as mentioned previously I’m having doubts about them due to problems in testing and the anticipated low power draw of my trains being borderline to register on them.
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To recap, the board contains a PM42 DCC circuit breaker that provides four separate circuit breakers and a BDL168 occupancy detector that can provide up to sixteen occupancy detectors and eight transponding sensors (see my pages on occupancy detection and the BDL168 for more details). This board provides occupancy detection for six electrical blocks, two each on the commuter tracks and one on each subway track where it loops below the expressway. Although I’m also wiring up the transponding sensors, as mentioned previously I’m having doubts about them due to problems in testing and the anticipated low power draw of my trains being borderline to register on them.
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Fun with JMRI
Some weeks I don’t get much done. Well, that’s not quite true, I did a lot of work on the website this week, but the railroading time suffered. I did find some time to play with the test track I’d set up last week though, configuring JMRI to report block status based on the BDL168 outputs.
If you’re not familiar with JMRI it’s a free software package that allows a computer to interact with any of several DCC command stations that support computer interfaces, including Digitrax. It’s also available for Windows, Linux and Macs. And while not the most Mac-like program, it works, even on the ten-year-old iMac I’m using for the layout controller.
So what I have is a test track that’s an oval divided into two electrical blocks, each connected to an output of the BDL168. I named them, creatively enough, “One” and “Two”. And I used the Layout Panel editor to draw a schematic of the track. When displayed, red shows occupied (it’s configurable) and green shows clear. Even on my old computer, the change is nearly instantaneous once the locomotive crosses the insulated rail joiners from one block to the other.
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If you’re not familiar with JMRI it’s a free software package that allows a computer to interact with any of several DCC command stations that support computer interfaces, including Digitrax. It’s also available for Windows, Linux and Macs. And while not the most Mac-like program, it works, even on the ten-year-old iMac I’m using for the layout controller.
So what I have is a test track that’s an oval divided into two electrical blocks, each connected to an output of the BDL168. I named them, creatively enough, “One” and “Two”. And I used the Layout Panel editor to draw a schematic of the track. When displayed, red shows occupied (it’s configurable) and green shows clear. Even on my old computer, the change is nearly instantaneous once the locomotive crosses the insulated rail joiners from one block to the other.
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DCC Power I
After assembling the first of my DCC protection and Occupancy Detection boards, I decided I wanted to test it and get some experience with using it. So I set up my loop of test track with insulated rail joiners separating it into two halves, and connected the feeder to outputs 1 and 2 of the BDL168, which correspond to RX4 A, detectors A & B. All of these are powered by PM42 section 1. For DCC, I used my Zephyr, and for the DC supply I used the 2 Amp, 12 Volt supply I plan to use for these systems (it’s the black box just above the Zephyr in the photo above). Powering it up, nothing went “Zap!”, which I count as a success.
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Back On Track
11 September 2011 22:24 Filed in: Electronics,Administrivia
After two months spent working on the website move, I’m back to working on (and playing with!) the railroad. That doesn’t mean I’m done with the website stuff. There are still pages left to convert, and a few problems to solve, and I’ll have more to say on that down below. But the new one is up and running, and relatively problem-free. And I’d budgeted this weekend to model railroad work in case there were problems, so I had some free time on my hands. I celebrated by getting the outer loop wired up and running a couple of trains. Then I turned my attention to working on the DCC protection and occupancy detection circuits so I can get the other two loops up and running.
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How I learned to stop worrying and love the BDL168
Well, perhaps that’s a bit strong, but I’m coming to terms with its design flaws and the poor state of the documentation surrounding it and the PM42. I now have the first set of PM42 circuit breakers and BDL168 occupancy detectors (with two sets of RX4 “transponding receivers”) installed, and have done a bit more reading over the weekend. I’ve discovered a few things and come to a few conclusions as a result of that work, and that’s making me feel that I have a handle on this now. But I had to work through a number of issues to get to this point.
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February 2011 Status - Occupancy Detection Revisited
Work has progressed slowly this month, partly from distractions, and partly because I’ve been reluctant to finish up the block occupancy detector wiring. I finally realized that the reason for this was that I wasn’t happy with my hybrid approach to occupancy detection and transponding.
To recap, my Subway and Commuter loop tracks were to be divided into blocks, with Digitrax BDL168 occupancy detectors and PM42 circuit breakers (circuit breakers are typically one per track per table, whereas there may be two, three or even four detectable track sections on a single track on one table, and more in a couple of cases). The PM42 provides for four circuit breakers, which is a nice fit for the four tracks, and the BDL168 is divided into four independent quadrants (so each can be wired to a separate circuit breaker), each with four block detectors. I’d originally planned one PM42/BDL168 per scene, meaning that wires would have to cross a table boundary in the Urban and Riverside Station scenes.
And that was a problem, for several reasons. First, running wires between tables violates my “keep all wires except bus wires local” design goal (it makes the layout harder to disassemble), second while the BDL168 can support 16 occupancy detectors, in some places I needed more than four on one track, which broke the association of the PM42 circuit breaker element to a single track, meaning a short would shut down a second line. And finally, I wanted to do Transponding, and the BDL168 only supports 8 transponding sensors (using a pair of RX4 sets), meaning some blocks would be able to report which train was in them, and some would only be able to report that some train was present, but not which. None of these were fatal flaws, but they were eating at me. And I finally realized that I only needed two more sets (seven instead of five) to fix these problems.
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To recap, my Subway and Commuter loop tracks were to be divided into blocks, with Digitrax BDL168 occupancy detectors and PM42 circuit breakers (circuit breakers are typically one per track per table, whereas there may be two, three or even four detectable track sections on a single track on one table, and more in a couple of cases). The PM42 provides for four circuit breakers, which is a nice fit for the four tracks, and the BDL168 is divided into four independent quadrants (so each can be wired to a separate circuit breaker), each with four block detectors. I’d originally planned one PM42/BDL168 per scene, meaning that wires would have to cross a table boundary in the Urban and Riverside Station scenes.
And that was a problem, for several reasons. First, running wires between tables violates my “keep all wires except bus wires local” design goal (it makes the layout harder to disassemble), second while the BDL168 can support 16 occupancy detectors, in some places I needed more than four on one track, which broke the association of the PM42 circuit breaker element to a single track, meaning a short would shut down a second line. And finally, I wanted to do Transponding, and the BDL168 only supports 8 transponding sensors (using a pair of RX4 sets), meaning some blocks would be able to report which train was in them, and some would only be able to report that some train was present, but not which. None of these were fatal flaws, but they were eating at me. And I finally realized that I only needed two more sets (seven instead of five) to fix these problems.
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A Matter of Time
Railroads have always been concerned with time. Early ones used timetables alone to keep trains on the same track from colliding. This didn’t work very well, particularly given the accuracy of mid-1800‘s pocket watches and the lack of synchronized time sources, and many lives were lost. Signaling systems and other protection methods were gradually developed. But timetables continued to be important for all trains in scheduling the use of tracks even with other systems used for protection, and timetables were required for passenger trains, as trains from different places needed to coordinate their arrival and departure at interconnection points, so passengers could move smoothly from one to the next as part of a longer journey. Railroads gradually developed standards for time-keeping (and they’re responsible for the adoption of the standard time zones used in the U.S.), and also influenced the development of clocks and watches to provide accurate and synchronized time sources.
Japanese passenger trains today are famed for their obsessive adherence to schedules, with deviations measured in seconds, not minutes. So it only seems reasonable that a model railroad of a Japanese passenger line should operate to timetable (well, eventually,I need a yard/staging tracks before that will be much fun).
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Japanese passenger trains today are famed for their obsessive adherence to schedules, with deviations measured in seconds, not minutes. So it only seems reasonable that a model railroad of a Japanese passenger line should operate to timetable (well, eventually,I need a yard/staging tracks before that will be much fun).
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Adding a DCC Meter, And Related Topics
Although I wrote about the power panel previously, there were a couple of things left undone. I was missing one of the ammeters for the lighting power (the store I get them from had run out), and I’d misplaced one of my LNRP LocoNet Repeater panels, so I’d substituted a UP5 panel I took off the old HO layout. Also, I’d realized that my portable RRampMeter DCC volt/amp meter was useful, but wiring it into the system when I wanted to check something was a real nuisance. Over the summer I bought or found the missing bits, and finally decided to order a new RRampMeter (the version without the nice case) to mount as a permanent part of the circuitry (I’m keeping my other meter--the one with the case--for workbench and other testing uses). So it’s a good time to summarize what the panel does, and talk about the new meter a bit.
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LocoNet: A DCC Control Bus
DCC is really about getting power and control information to the track. But there’s another side to it: how do the commands from the throttle (the controls) get to the DCC system, and how do different parts of the DCC system communicate with each other? The first part isn’t covered by the NMRA’s DCC standards, so each manufacturer does the throttle-to-command-station link in their own proprietary manner. The second part is partially standardized, as the NMRA has Recommended Practice RP-9.1.2 Power Station Interface to describe how a command station sends commands to booster stations, but they don’t say anything about how devices like stationary decoders or occupancy detectors report their status, although there’s a draft of a standard for an “NMRAnet” control bus being developed which will probably fill this gap, someday.
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Track Voltage, Motor Voltage, and DCC
As I’m finishing up the wiring for the two upper-level loops (one of which will be DCC-only, the other will be the switchable DC/DCC line), I’m also getting my DCC electronics set up and ready for use. There are several aspects to this, and I’ll cover others in future musings. But today I’m going to write about track and motor voltage. I could have just used the command station as it came, and it probably would have worked fine. But I like understanding exactly what’s going on under the hood, and so I ran a number of tests and spent some time researching what the track voltage should be, and why, and what that meant for the motor on a train. And if I ever add a booster, it will be important for it and the command station to be set to output the same voltage (this avoids problems when a train bridges between two power districts), so I may as well pick a voltage now.
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Grade Crossing Plans
I should be building the topography under the soon-to-be Riverside Station scene’s Commuter Station, instead I’m still obsessing over the scenery where that scene meets the River Crossing scene, and specifically the exact design of the grade crossing I’m going to build there, someday.
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Scotty I Need More Power!
25 July 2010 00:12 Filed in: Electrical,Electronics
DCC doesn’t need to be complicated. At the simplest, it’s a pair of bus wires from the command station running under the track, with feeders connecting the track to it at intervals. I can, however, make anything complicated. Probably more complicated than it needs to be. It’s a talent.
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Kato DE10
20 July 2010 00:04 Filed in: Model Trains
Kato’s DE10 freight locomotive isn’t new; they came out a year ago. But they promptly sold out, and I hadn’t been able to get one until just recently. There are two versions, a “warm region” model and a “cold region” model that adds circular windshield wipers and a small snowplow. Both versions operate in the Tōkyō region.
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More Electrical Work
Rather than turning my attention immediately to the Riverside Station scene, I decided to get the electrical systems ready for the eventual use of the two “ground level” loops, which will require DCC. And that meant I needed to finalize my plans. And although most of them had been worked out last year, and revised (in my head if nowhere else) over the winter, there was still a bit of planning needed before I was ready to start cutting wire. This had to encompass the DCC systems (both power and the LocoNet control bus) as well as the various power strips to supply them, and some additional power supplies for eventual LED lighting. I’d started thinking more intensely about this while I was working on the wiring recently, but needed to bring that to conclusion and write down the results.
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Kato Modular Buildings
21 May 2010 19:43 Filed in: Structures,Electronics
Today I’ll turn my attention to what goes atop the scenery: buildings. There’s going to be much more on this, and I’ve created a Structures section of the website with its own index page to contain such material, but so far it’s pretty vacant. Today’s post introduces the first page there, describing Kato’s modular multi-story buildings.
Kato makes several modern six-story buildings that are generic enough to use in any city, although they also include signs to decorate them for a Japanese one. But what really makes these buildings special is that they’re modular, and while Kato doesn’t sell the floor units separately, you can combine two or more buildings to make some reasonably tall structures. Read More...
Kato makes several modern six-story buildings that are generic enough to use in any city, although they also include signs to decorate them for a Japanese one. But what really makes these buildings special is that they’re modular, and while Kato doesn’t sell the floor units separately, you can combine two or more buildings to make some reasonably tall structures. Read More...
Inaugural Train
The first train ran tonight. As you can see, the table is still a bit unfinished. I added the legs and framing for the end that won’t have scenery, and put down the plywood for the subway level return loop. Read More...
