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Discussion Starter #1
Having some trouble figuring out the wiring for block detection. Here’s the background:

A. HO scale layout, 17’ x 13’.

B. Two loops / ovals, one on the outside (the main) and one on the inside (the branch line) which does not always parallel the main.

C. I have one Digitrax booster, which I will route to a PM42. The four outputs from the PM42 will be:
(1) the main;

(2) the branch line;

(3) the engine servicing area (roundhouse, turntable, etc.); and

(4) the yard (which is 10 feet long and like a peninsula outside of the 17 x 13 footprint).

D. I want to include block detection on the main and the branch line through two BDL168 boards from Digitrax.

E. It occurred to me that there would have to be an incredible amount of wiring if I put the BDL168s in one central location because, as I see it, I would have to run heavy gauge wire from the vicinity of the BDL168 all the way to each block (each a “home run” if you will). I want to avoid or minimize this if possible.

F. My thought was to put one BDL168 at one end of the ovals (call it the left side) and one at the other end of the ovals (the right side). I would then:

--Route the PM42’s power sub-district 1 (the main) to a tee / a split, with one side going to two zones of the left BDL168 (giving me eight detection blocks) and the other side going to two zones of the right BDL168 (giving me another eight detection blocks).

--I would do the same thing with the PM42’s power sub-district 2 (the branch line).
This would mean that the left BDL168 would handle eight detection blocks of the main on the “left” side of the layout and eight detection blocks of the branch line on the “left” side. The right BDL168 would do the same at the other end. At the end of the day, I would have:

--Sixteen detection blocks on the main (eight handled through the left BDL168 and eight handled through the right BDL168); and

--Sixteen detection blocks on the branch line (eight handled through the left BDL168 and eight handled through the right BDL168).

G. The runs from the left and right BDL168s would be shorter, overall and on average, saving a considerable amount of wire (and cost).

QUESTIONS:

1. Does anyone see a problem with this? Are there any particular consequences to having each BDL168 handle part of the main and part of the branch line?

2. When I eventually get train control software, will I still be able to “hook” together, logically, half of the main line blocks from one BDL168 and the other half of the main line blocks from the other BDL168?

3. Does everyone just bite the bullet and run rather long heavy gauge wire from their BDLs at a central location and out to detection block? And doesn’t take an fairly significant amount of wiring?

Any thoughts would be most appreciated. I’m new to this, and I did not see anyone asking this particular type of question before. Go easy on me. :)

Best,

Tim
 

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Hi Tim,

You are embarking on a feet of model railroading that few others dare to go.
Setting up your block detection with the BDL168 will turn out to be easier than you are making it out to be.
The main thing is to just keep track of what is where. Yeah, you can control groups of blocks with the BDL168 in a mix or match fashion. It's only relaying information about each block to your SE8C if that's what you will use for signal control. Just keep track of what you name each block and it will be easy to do your signal programming later on.
Use of those little test boards is very important as your work through your wiring plan.
Make sure you don't have any group loops in your plan. A ground loop would be where you have two wires (buss lines) coming from the BDL168 and following under the track for track feeders. It becomes a loop when you join the two wires at a distant point.
What Train Controller software are you planning to use?
 

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Discussion Starter #3
Thank you so much for your insight, Ken! Much appreciated. I like the way you said it: mix and match. That's exactly it.

The way my layout is coming together and space constraints, I wanted to do a majority of the wiring before putting my plywood sheets down on the grid. The framing is all built, the plywood sheets have been cut to size, the track plan settled on. So I just want to lay out most of the wiring before getting covering it all up.

I consider myself a fairly bright person, and I can understand what Digitrax says in their manuals, but . . . I'm having trouble putting it together in my head--the way that the various pieces work together.

Will be careful not to do a ground / group loop. But here's a question for you: I've read over and over again that I should put a feeder on each rail. If I have a block that spans more than one piece of track, I just take the wire that is the output of the BDL168 for that block and solder several feeders to it. Is that correct?

Not sure on the TC software yet . . . was exploring JMRI, but have heard folks talk at length about TrainControl (or TC)?

Best,

Tim
 

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Although it has been out of my mind for a while, I was planning on doing something similar for a project I have been working on that has been put to the side for time reasons at the moment. I was planning on doing the same thing, splitting the BDL168's between 2 locations to keep wiring down.

If you are thinking of using JMRI for example, it should not matter which blocks are where, because you line them all up virtually in JMRI as I recall, so that should be fine. Just try to keep them in small groups in logical order as best you can, for trouble shooting purposes, as it will make things easier in the end.

Good luck, let us know how things progress!
 

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Discussion Starter #5
Will do, John! And you hit the nail on the head with "line them all up virtually in JMRI." Ken's "mix and match" phrase and your "line them up virtually" was exactly what I was trying to get at.

Thanks so much!

Tim
 

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Putting feeders to each rail will ensure no dead rail issues later, i.e. years from now due to corrosion at the rail joiners. If you're using flex track, you can put one feeder to each rail then solder the rail joiners to the next flex track rails. That way, you only have to provide feeders to every other section of flex track.
On the construction of your benchwork, installing the wiring before scenery will save you much headaches as well as a kinked neck. I'm not clear on your sequence of construction, but I would recommend that you lay all your track first, then go back and apply the wiring. The open grid work will still be easy to reach into.
On the point of laying track, I used a flexible caulk on the cork roadbed then layed the track down and was able to make the minor adjustments so the track had perfectly straight tangents and gradual easements in the curves. If you use track spikes you tend to end up with minor deviations in the track.
 

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I notice that you have a reverse loop on your layout.
It will have a reverse loop controller. Does the manual
for the detection system describe how it is to
be wired?

Don
 

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You need to pay attention to the reverse loop section of your layout (C1 & C4) as DonR mentions. I think you should combine C1 and C4 into one single block so only 1 train can be in that section at a time. The PM42 can be used as an automatic reversing power controller, but you'll have to use 1 of the 4 power outputs for just that single purpose. If you also want to detect trains in that section (which you probably do), you'll also need to use 1 of the 4 sections of a single zone of the BDL168. The other 3 sections of that zone will have to be wasted.

Positioning the BDL168s on opposite sides of your layout should work just fine. I've done that on my layout and its been working for me. You don't have to do this, but to save the most wire, you'll also need to have the PM42 near the BDL168. You might want to consider actually getting 2 PM42s so that you can pair a PM42 and BDL168 right next to each other. That will also help mitigate that fact you need to use 1 PM42 output for just the reverse loop block as I mentioned above. That's what I've done on my layout. The thing to remember about the BDL168 is that it only handles 1 side of the red/black wire pair that will power each block. In my case, all the red wires for each block comes back to my BDL168s and the black wires come back to my PM42s. Its not quite as bad as it might sound since the black wires from the PM42 can be run in a bus fashion and not home-run fashion.

As was already mentioned, the blocks don't have to be consecutively numbered or wired for the automatic train control software to work right.

Hope that helps.

Mark
 
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