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Martijn Meerts

Automated computer control chapter 2 - Basics of blocks

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Martijn Meerts

Automated computer control chapter 2 - The basics of blocks.

 

 

A vital part of automated computer control, is for the computer to know which train is where. Optimally, the locomotives would continously send a signal to the control center with such information as decoder number, speed, direction and which block its in. However, bi-diretional digital isn't that far yet, and even if it could send back most of these variables, determining which block a locomotive is in is difficult.

 

Instead, we need a system that detects on which part of the layout the train is. There are a variety of ways to do this, including using reed switches and magnets or infrared signalling. However, in my opinion, the most reliable way is block control.

 

So what is a block? A block is nothing more then the stretch of track between 2 signals. Those signals don't have to be physical signals, they can be imaginary. Prototypical railways generally use a block system to track their trains as well.

 

01-blocks.jpg

 

The general idea is that a layout is divided into multiple blocks. Depending on the system used, the blocks are either isolated on 1 or 2 rails. In most cases for 2-rail systems, only 1 rail is isolated. The reason for the isolation has to do with detecting when a block is occupied or not. More on that later.

 

To put everything into context, let's use an oval as an example. An oval can be divided into 4 block. The 2 straight sections are 1 block each, and the 2 180 degree curves are 1 blocks each.

 

02-blocks_oval.jpg

 

Purely theoretically, 3 trains can run on an oval that's divided into 4 blocks without ever running into each other. The problem is that the moment a locomotive enters a new block, it will need to start decelarating because the next block is occupied. Its very similar to driving while in a traffic jam. You can only move when the car in front of you moves, and he can only move when the car in front of him moves. Imagine a traffic jam that runs in a circle, and you'll get a good idea of the problem.

 

Running 2 trains is much better, but if 1 train is faster than the other, you will still have the problem that the faster train will regularly need to slow down.

 

The most optimal solution would actually be running only 1 train. Generally, a train will want to have at least 2 free blocks in front of it. That way there's little chance it needs to slow down, unless you have a fast training running behind a slow train. For example, an express train would be faster than a freight train. (That situation can be avoided though, but adding either sidings so the express train can overtake the freight train, or make sure the express train has priority over the freight train at a train station or other stop.)

 

So, dividing in oval into blocks is really rather pointless, but an oval is something everyone will recognize, and the blocks are easy to set up ;)

 

Below is a flash movie that shows the 3 different setups. With 1 train, there's no problem. With 2 trains, there's no problem either because both trains run at the same speed. With 3 trains however, trains need to stop a lot, either because they sometimes run slower or faster, or because the length of some blocks is much shorter than others. Of course, the step with 3 trains is exaggerated, but it shows the problems you get when running too many trains at a time.

 

http://www.jr-chiisai.net/_div/computer_control/chapter02/03-blocks.swf

 

 

 

Now that we have a basic idea of what a block is, the next chapter will talk about some more advanced topics related to blocks, including brake and stop sections, occupancy and feedback, and deciding where to install blocks.

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CaptOblivious

So far, totally awesome! The next chapter is the one that I'm interested in: deciding how to break things up (esp stations!)

 

You might flesh this out with a little on intermediate aspects. The page you posted earlier suggested that some lines have as many as 6 (!!) aspects: stop, extreme caution, caution, proceed, proceed with speed limit x, proceed with no speed limit.

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Guest ___

So far, totally awesome! The next chapter is the one that I'm interested in: deciding how to break things up (esp stations!)

 

You might flesh this out with a little on intermediate aspects. The page you posted earlier suggested that some lines have as many as 6 (!!) aspects: stop, extreme caution, caution, proceed, proceed with speed limit x, proceed with no speed limit.

 

My old model railroad club has a twin track 85 foot long layout with blocks. We only had 3 aspects. It would be really interesting to see how to wire in and operate with all those intermediate aspects.

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Martijn Meerts

The signals are real basic for several reasons.

 

1. The examples show regular block sections as opposed to station area's. Usually only a 2-aspect signal is used in this case.

2. It's easier to explain things when keeping it simple at first.

3. Animating multiple aspects in Flash is a lot of work ;)

 

 

Signalling really deserves it's own chapter (or more than 1 chapter really), but the thing is, in computer controlled DCC signals are mainly just visual. They don't actually have any function. The computer takes care of all that. I don't have any experience with signalling yet, since due to the high cost of them, we didn't install any on my father's layout.

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CaptOblivious

Fair enough. The masts qualify as layout animation or the like in this case, but understanding the signaling system of the prototype (I would think) goes a long way to helping plan and program an automated layout. But I am happy to wait, as you are right: basics first.

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Martijn Meerts

The main problem is, I don't know of any program that would allow for a Japanese signalling system. While there are a few out that have customizable signals, most are designed around the German system.

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Guest ___

However as you stated it's very similar to that of the German signaling so I would not expect that minor changes should not be the difficult.

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Martijn Meerts

However as you stated it's very similar to that of the German signaling so I would not expect that minor changes should not be the difficult.

 

 

True, but it would have to be the programmer(s) that add the Japanese signalling system to the program, and I don't see that happen anytime soon ;)

 

Of course, since the physical signs are really just to make things look better, you could use the German signal system within the program, but use the Japanese signals on the layout. Wiring up the various aspects to the computer program should be quite doable.

 

Also, some aspects such as speed limitations for shunting for example are often just static signs, so not all aspects need to have a signal.

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Martijn Meerts

Just finished the text and most images for chapter 3, but I was wondering.. Does anyone have any layout designs he would like to see turned into blocks? It might give a better idea compared to me drawing a few situations and adding blocks to those ;)

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CaptOblivious

Yes! How about a basic oval with a siding on one side representing a station with two tracks? How about an oval with two such sidings, one on each side?

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Martijn Meerts

You don't want anything more advanced than that? ;)

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Martijn Meerts

Slight update...

 

Been real busy recently with various things, so I haven't managed to draw any trackplans/block plans, but I'll have some up this weekend at the latest.

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CaptOblivious

Slight update...

 

Been real busy recently with various things, so I haven't managed to draw any trackplans/block plans, but I'll have some up this weekend at the latest.

 

Take your time! I know all about being busy ;) Your comments on this topic are such a great contribution, I think we can stand to wait a few more days.

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