Subject:
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Re: reverse loops & block control
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Newsgroups:
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lugnet.trains
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Date:
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Sat, 7 Dec 2002 21:16:20 GMT
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Viewed:
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651 times
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Hello John, hello everybody,
> I have found that glass encapsulated reed switches laid between the
> conductor rails are activated by the coupling magnets and although I have
> not tried this I assume it could be used to automatically reverse the
> voltage while the train is on the rectified section.
And for sure it can be used for block control.
The whole idea of block control is that you can have more than one train
running on a single track without having them ever crash. As the name block
control suggests, the whole track is divided into blocks, each one longer
than the longest train you will ever run. (For practical reasons, they
should even be a lot longer than the trains.) If you make sure that one
empty block is always enforced between trains, they can never crash. For a
circle of track with five blocks, that lets you run two trains for example.
Four blocks won't suffice for that, because with one block in between
trains, you enter a deadlock situation, where none of the trains can move,
without violating the "one block free between trains" rule. Ideal would be
six or more blocks, but this results in quite large a layout, given some
reasonable train length that should be supported.
Key to an implementation of block control are signals at the beginning of
each block which prevent a train from entering as long as the block is still
occupied by another train. The 12V system is an ideal base for implementing
this, especially if you own a number of 7860 signals. If manual operation is
all you need, take five or more of them, set them up and operate them
according to the rules above, and you are all set with a pure LEGO solution.
Of course, in most cases you will want automatic operation. What it takes to
do that is automatic detection of trains entering and exiting a block. This
is where the reed switches mentioned by John enter the arena. Place one in
each block, such that the engine of a train entering the block will trigger
it. This will switch the signal at the beginning of the block to red, and
the signal for two blocks behind to green. It will not influence the signal
of the block just being left (which should already be red). You will need
one non-LEGO part per block to do these things: a bistable relay, i. e. one
that holds each of its two states without current flowing through it, or
some electronic equivalent to that. For 12V, these should be readily
available in model railroad shops. However, you will need at least a
double-pole double-throw switch (to reverse the polarity sent to the signal
post) and a simple on-off switch (to power the track section right before
the signal off and on), all coupled together in one relay. Each of those
bistable relays controls one block. It gets switched to red/off by the reed
switch in its own block, and to green/on by the reed switch in the block
after the next.
Like with the manually operated LEGO signals, this setup will not work
ideally with trains that are being pushed by a loco at their end, because
the train will go far beyond the red signal before its loco stops in front
of the signal. Still, if we make sure that each block is as long as the
longest trains we are running, they will never crash into each other. The
safety distance between trains might however be reduced to less than one
block in these cases.
The solution proposed here also does not address separate speed control for
the two trains. Ideally, the relays would also route one speed regulator
output per train to the block the train is currently in. This way, trains
could be regulated separately, but setting up the initial relay settings
would be a pain, I guess.
Without speed regulation, it is as easy as this: Set all relays to red/off
at the beginning. For every train waiting with more than its minimum allowed
distance to the next, set its block to green/on. Have fun ...
Disclaimer: I haven't tried all this personally yet, except 25 years back
with H0 trains. The most sophisticated LEGO setup I ever had used manually
switched signals in the train station to let only one train onto the track
circle at a time. I need to finish building my LEGO room in the basement
before I can try out larger and more sophisticated layouts ...
Greetings
Horst
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Message is in Reply To:
 | | Re: reverse loops & block control
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| Hi Esger. I am sure some folks would recommend DCC for a newly laid out complex network but as far as I can see this is almost impossible with the 12v system due to the problem of opening the motors and fitting the decoder inside. I have played (...) (22 years ago, 7-Dec-02, to lugnet.trains)
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