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I joined the forum a little over a year ago and got a lot of useful information from TractionFan and others concerning DCC and two rail. Since then I constructed a ceiling suspension that runs two 3 rail MTH trains. I figured rather than sell them run them from the ceiling. I had an O gauge layout that I demolished and moved to a bigger house with a 21 x 14 foot room for my HO layout. That is my background.

I’m in the process of building my L girder bench work. I’m just about ready to buy HO track and other equipment. I plan to go with peco code 83 track and Digitrax equipment. Like Thelic I’ve been reading a lot and really excited about software control. My gut feel at this point is to go with TrainController rather than JMRI. I’ve been reading/reviewing the TC user’s manual.

I’ve come up with following conclusions and/or questions at this point. Any comments would be appreciated.

  1. When creating Blocks is there an advantage to insulating both rails or only one rail?
  2. Thelic do you plan to test as you build? I would think adding complication a little at a time and test TC on each sub set of blocks would be the way to go. I would think feedback from TC operation on simpler “Schedules” is extremely valuable as you expand the layout.
  3. Block and sensor configuration is very critical. Is it reasonable to expect 100% collision free TC operation?
 

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Hi Ron,

I've done quite a bit of studying and learning since my last post here. I ended up buying a number of books including Digitrax Big Book of DCC as well as a number of the MR books. I'm waiting on the Signals and Interlockings book, but I think I have a good grasp on it. I'm also testing as I build. I considered TC over JMRI, but really the construction of the layout is the same. TC lets you get away with a few things since it can infer some information, but I wouldn't say its best practice. Once I have the layout up and running on JMRI I will consider TC, though I think I really would need silver or gold to accomplish what I want so there's obviously a large price gap over bronze.

To answer your questions:
  1. I'm using BXP88s, they require that each BXP88 be its own power district (Insulated at both ends), but each block can be a sub-district (insulated on one rail). It important to keep the rails the same. So break the B rails at the end of each block, and both A and B at the ends of the district. I suppose you could break both everywhere, but it would just result in more wires and having a single rail be continuous helps keep flex track aligned. The nice thing about the BXP88 is that it can be directly connected to the booster so there's no need for a power manager since they have their own breakers. Just keep adding BXP88s to the main bus from the booster. BXPA1s get isolated at both ends since they are auto-reversing units. Again, hook straight up to the main bus.
  2. I'm not testing JMRI or TC as I go, but I can see the occupancy sensors working with the test lead that comes with the BXP88.
  3. From what I understand yes this is very possible. I do recommend having detection on ALL rolling stock, and also detecting the track at turnouts. This keeps the software from throwing switches under trains that may be spanning interlockings.

Additional thoughts...
  • I switched from using the SE8Cs for turnout control to DS74s. This is additional cost since the SE8Cs actually can do the turnout control and I won't be using that feature. However the DS74s support routes that can be entered from the new Digitrax throttle. Furthermore, it lets me break the layout into more discrete systems: Power/Train control (BXP88/BXPA1), Turnout Control (DS74) and finally Signaling (SE8C).
  • I also combined the interlockings along the west end of the yard.
  • After much reading you should certainly plan on detecting your interlockings. At the very least they will need a power source on some sort of power management device, why not make it a BXP88 section and be done with it. If each discrete route through an interlocking is a block on a BXP88 they get individual breakers so derailing and shorting one switch will not shut down other routes. This means that crossovers are actually 2 blocks.
  • The same argument goes for your sidings, they need power management, might as well make them detectable too.

Just to further my argument lets look at cost per block (all prices in CAD, I was able to find these online, and in stock).

BXP88 = $180/8 blocks = $22.50 per block
BDL168 + Breakout board + PM42 + breakout board = $170 + $36 + $90 + $36 = $332/16 block = $20.75 per block

Keep in mind that the wiring for the BDL route is going to be way messier, the board is going to be further from the blocks since its 16 blocks all in one place, you only get 4 breakers, and no transponding. Also remember that the device cost is only a portion of the block cost, there's all sorts of forgotten hardware costs such as terminal strips, wire connectors and the wire itself.
Hi Ron,

I've done quite a bit of studying and learning since my last post here. I ended up buying a number of books including Digitrax Big Book of DCC as well as a number of the MR books. I'm waiting on the Signals and Interlockings book, but I think I have a good grasp on it. I'm also testing as I build. I considered TC over JMRI, but really the construction of the layout is the same. TC lets you get away with a few things since it can infer some information, but I wouldn't say its best practice. Once I have the layout up and running on JMRI I will consider TC, though I think I really would need silver or gold to accomplish what I want so there's obviously a large price gap over bronze.

To answer your questions:
  1. I'm using BXP88s, they require that each BXP88 be its own power district (Insulated at both ends), but each block can be a sub-district (insulated on one rail). It important to keep the rails the same. So break the B rails at the end of each block, and both A and B at the ends of the district. I suppose you could break both everywhere, but it would just result in more wires and having a single rail be continuous helps keep flex track aligned. The nice thing about the BXP88 is that it can be directly connected to the booster so there's no need for a power manager since they have their own breakers. Just keep adding BXP88s to the main bus from the booster. BXPA1s get isolated at both ends since they are auto-reversing units. Again, hook straight up to the main bus.
  2. I'm not testing JMRI or TC as I go, but I can see the occupancy sensors working with the test lead that comes with the BXP88.
  3. From what I understand yes this is very possible. I do recommend having detection on ALL rolling stock, and also detecting the track at turnouts. This keeps the software from throwing switches under trains that may be spanning interlockings.

Additional thoughts...
  • I switched from using the SE8Cs for turnout control to DS74s. This is additional cost since the SE8Cs actually can do the turnout control and I won't be using that feature. However the DS74s support routes that can be entered from the new Digitrax throttle. Furthermore, it lets me break the layout into more discrete systems: Power/Train control (BXP88/BXPA1), Turnout Control (DS74) and finally Signaling (SE8C).
  • I also combined the interlockings along the west end of the yard.
  • After much reading you should certainly plan on detecting your interlockings. At the very least they will need a power source on some sort of power management device, why not make it a BXP88 section and be done with it. If each discrete route through an interlocking is a block on a BXP88 they get individual breakers so derailing and shorting one switch will not shut down other routes. This means that crossovers are actually 2 blocks.
  • The same argument goes for your sidings, they need power management, might as well make them detectable too.

Just to further my argument lets look at cost per block (all prices in CAD, I was able to find these online, and in stock).

BXP88 = $180/8 blocks = $22.50 per block
BDL168 + Breakout board + PM42 + breakout board = $170 + $36 + $90 + $36 = $332/16 block = $20.75 per block

Keep in mind that the wiring for the BDL route is going to be way messier, the board is going to be further from the blocks since its 16 blocks all in one place, you only get 4 breakers, and no transponding. Also remember that the device cost is only a portion of the block cost, there's all sorts of forgotten hardware costs such as terminal strips, wire connectors and the wire itself.
Thelic,

Thanks for the feedback.

I think your point about only insulating one rail between blocks was good. The point being that a metal connection would help keep the joint from buckling on a curve when using flex track. Also I don’t see a need for all the extra wiring. I read that someone preferred insulating both rails and just make a electrical connection between one of the rails with a soldered wire. But I don’t remember why. That is why I wanted to pass it by you. I don’t see a need for insulating both rails except for reverse loops. You also mentioned insulating both rails to separate power districts. I still need to look into power districts.

I also like your reasoning for including the points end of a turnout in a block, even though the TC users manual does not show this in their blocking examples.

You suggested being able to detect all of my rolling stock through a block. Do you do this by using a low resistant axel on the trucks? I would guess 2 axels per car, the leading axel and last axel.

My gut feeling was to go directly to TC and ignore JMRI. But I think you may have changed my mind on this. I started to browse the JMRI operations user’s manual. What I’m seeing is an excel spread sheet interface (Input/Output) as opposed to the all “Bells and Whistles” TC interface. I would think most important is the robustness of the internal algorithms of TC versus JMRI. My initial reasoning from switching from MTH DCS O gauge to HO was that 3rd rail started to bother me. I wanted a more realistic look. I had A Lionel layout every Christmas as a kid and my imagination didn’t mind that 3rd rail, but age has changed that. Now, I’m getting caught up in this software interface thing! At this moment I think I’m going to start out with JMRI and go from there. I installed JMRI about a year ago but haven’t really played with the demo. I was busy building my MTH O gauge ceiling structure. The HO benchwork will be completed soon, then it is on to laying some track.

Your sharing of the McKinley RR link was very informative. Made me think I would need 3 sensors per block. One occupancy sensor and two position sensors.
 

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Power districts are necessary for how the BXP88 wants to be set up. It wants the A rail to be broken into 8 pieces, and the B rail to span all 8. The adjacent BXP88 wants the same thing, they shouldnt share the B rail between BXP88s or you potentially get a lot of current flowing down the common ground. Just don't do it.

The beauty of the BXP88 is that they ARE their own power district. No other devices are required.

The only reason I could think for breaking the B rail within a BXP88's district is if you want to add expansion gaps, or potentially have polarity issues like a crossover and want to use the same BXP88 for both tracks.


This is a snip from the Big Book of DCC showing typical breakdown of the classic timesaver shelf layout. You can see how they combine the switches into control points (switches in the same block). They have used 4 unit detectors and have not shown double vs single gaps, but it gives you an idea of what switches to include in each control point. You can see the "I" block actually contains 3 separate switches.
View attachment 575127





Detecting rolling stock is as simple as adding a resistors to the outer wheels of the rolling stock. Either:
  • Glue a surface mount resistor to the wheels and use conductive paint to connect it to the metal wheels. (DON'T ATTEMPT TO SOLDER YOU WILL MELT THE WHEELS)
  • Use a set of wipers and a truck mounted resistor.
  • Use resistive paint to join the wheel halves together. This will require an ohm meter and patience to get the right resistance.
  • Buy premade resistive wheelsets.



Ron I'm going to point you to the build thread of Mark VerMurlen

Mark did an excellent job documenting his TC layout. The meat and potatoes are really on page 3 or so. Mark used a single block for each stopping section and his trains apparently stop within an inch or so once calibrated.

A warning. This layout WILL make you envious.

(1) Modified Peace River HO Layout | Model Train Forum


There's also some good discussion and pointers from Mark in my first layout design thread.

This layout was not built, but most of it was used for the design of my current one.
(1) L Shaped 8'x8' Layout | Model Train Forum
 

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Thelic,

Thanks for the information. I’m making notes on your hardware suggestions.

I looked at both your links. I see we have something in common. I’m a retired software engineer (mainly developing math algorithms), hence my excitement about diving into DCC software control. I’m experienced in software but not hardware. I like your layout design, yes it should keep you very busy, what fun, huh?

I plan to read through the TC users manual and use this thread to share observations and or comments I have. Since we are going down the same path, you are however a few months ahead of me, maybe we can share what we think and experience.

The plan I have is to manually control one train and have TC (computer) to control all other trains (reference McKinley RR link). My experience with digital control at this point is using MTH’s DCS system on my previous 3 rail O gauge layout. One problem I frequently ran into is poor communication between engine and the system because of, I don’t want to say dirty, but an unclean track section, especially at slow speed. Even one weeks accumulation of dust on the track could cause poor communication at slow speeds. At higher speeds the train momentum would carry the train over these unclean sections and there wasn’t a problem.

The TC manual indicates that block control can be accomplished using one occupancy sensor per block and a quality defined speed and/or braking profile. Since braking results in very slow speed before stopping I can see communication between engine and computer being interrupted and a possible collision occurring.

Given that, my plan at this point, would be to use one occupancy sensor and 2 position sensors on each block.
 

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As soon as I get my DS74's and 50' Loconet cable I'll start having some better JMRI testing information available. I'm hoping maybe by this time next week.

A hard wired LocoNet backbone boosts your house's resale value right?
Thelic,

You are way ahead of me. I’m still working on my bench. I haven’t purchased any HO or Digitrax equipment yet. Was the “Big Book of DCC” very helpful? Maybe I should purchase it. Have you looked at www.dccwiki.com? Is the information here similar that what is in “Big Book of DCC”?

The following is my understanding of the TC interface and algorithms. The description of the algorithms is just my speculation. It’s probably not necessary to understand the algorithms but it may help to understand how to define the sensor parameters like speed/ braking profiles along with block length. I don’t know, like I said my ignorance level is high right now.

I didn’t mean to imply that coasting over dirty track at higher speeds wouldn’t be a problem. It was not a problem for my O gauge layout because I, and not a computer, was controlling the trains. My O gauge track is Atlas-O nickel silver. It would be a problem if TC is controlling the train. TC, from what I understand, can only monitor block and point occupancy to determine train location. I’m guessing that the TC algorithms use speed/braking profile to command engine speed so that the engine stops within the block length. The speed/braking profiles and block length are determined from user inputs. The critical thing here is the electrical/binary signal connection from track rail to engine wheel. I feel if this connection is interrupted in any way (maybe dirty track) the calculation displacement might be larger than the user defined block length. The simple solution would be to use a position sensor to ensure the train stops within the block length. It would be interesting to make some test runs into a block that TC commands the train to stop in using only an occupancy sensor. Then measure the distance displaced by the train before it stops. Repeating the tests for differing rail conditions, maybe mask the rail to wheel connection slightly.

I had signaling set up on my previous 3 rail O-gauge layout. I used Atlas-O 3 rail signaling system. Working with 3 rail is so nice! Middle rail is hot and outer rails are common. A block is defined by insulating one of the common rails at each end. The signal hot wire is attached to voltage source. All engine and rolling stock axles transmit current. When the block is entered the circuit is closed (grounded) by the connection of the outer rails via the axle. How neat is that! I now have the signaling system set up on my new O gauge ceiling railway.

Lemonhawk,

In reference to a double rail gap, I see your point about flexibility. I’m keeping that in mind. Thanks.
 

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I like to always use a double gap, you can always make the "Common Rail" connection on a terminal barrier strip or other connection device. This just give you more flexibility.
Lemonhawk,

As I learn more I’m starting to see your point about double gaping for flexibility, I’ll kept that in mind. Thanks.

Ron
 
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