Signal / Block detection

[Bsklarski]

I am thinking ahead here, well planning ahead. What would be a good easy and least expensive way to add signals that work to a small layout? I like Dr Vollmers  method of sensors with timers to turn the signals back, but what if the train stops, speed is slow, ect? I would rather not have to cut rails and add blocks. Can you add sensors or photo cells to see when a train actually gets past the next signal before it starts to reset? Looking for ideas.

[jagged ben]

It's possible to do some stuff with optical sensors.  But without real block detection your signal system could only perform in a realistic manner under limited operations scenarios.  For example, if you basically always have one train running in the same direction on a single loop, it wouldn't be too hard to use optical sensors in lieu of real block detection.  You could place infrared sensors with beams running across the track.  Possibly it wouldn't be too hard to program that for running the train in both directions, but hey, you asked for 'easy'.  Now you're getting away from that.   

Now say you have a double track loop with the tracks right next to each other and the trains running in opposite directions, well, then it's probably going to be difficult to detect the tracks separately with inconspicuous sensors.   (Maybe it works if you have strategically placed tunnels you can put them inside, so you can place separate sensors above the tracks instead of across them.  Other ingenious methods may be possible.... but again, you asked for 'easy'.)   And if you have multiple trains entering and exiting frequently from different routes, it's going to be difficult to program the signals realistically with only optical sensors.   

As far as making this work, the only 'off the shelf' system I'm aware of that could take an optical sensor and make it part of a logical signal system is JMRI and RR-Cirkits Tower Controller series.  All other products that I'm aware of require cutting rails to separate blocks.    If you really want to do easy and cheap, there is a Kato signal product that uses a timer, but as you mentioned that would not account for if the trains stops or slows.

Is your layout DC or DCC, and if DCC are your turnouts DCC controlled? 

[eric220]

You could put optical sensors at the operating block borders, plus at least one in the middle of each block. Have the border sensors trip both adjoining blocks as occupied, and the intermediate sensors only their own block. Intermediate sensors would have to be placed to properly account for movement onto diverging routes, but that could be worked out as the design progresses. This will only work properly if the distance between sensors is less than the length of your shortest train.

Depending on how short your trains get, how many blocks you want, how many diverging routes you have, it's probably going to be easier to make the cuts and electrically isolate the blocks. Remember, you only have to isolate one rail. Even with optical sensors, you're going to have to cut through the roadbed to place the sensors so they can "see" through the tracks. Electrical isolation and current detection will by far produce the best results; after all, that's how the prototype did it.

[John]

Look at the costs .. even a small layout can become expensive to signal, especially if you want more than just lights ..  the easiest way to do it is to use an either a commercial board, from either digitrax or team digital .. or roll your own ..

Rob Paisley has a good website for the "roll your own" folks ..  http://home.cogeco.ca/~rpaisley4/CircuitIndex.html