Lesson 5 - Simple Locking and Flank protection (Click on thumbnails to expand)
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Lesson 5 took us to an almost complete panel, certainly one that would work, this final lesson in the "easy colour lights" panel will complete the panel and introduce simple interlocking with flank protection.
There are two major faults outstanding with the panel, the one I won't deal with for now is that you can simply click on most of the signals and the aspects will change, with no change in other aspects or even a check to ensure the route is set.
The one I will deal with is flank protection and locking, this is an important concept and will be used a lot in the next, more complex, colour light panel, and as will be seen, for true semaphore operation it is required from the word "Go!"
If you take your previous panel and set a route from either s2 to s3 or from s9 to s8 and then click on the points which are not part of the route, you will see they are still free to move - this potentially means a shunt move could side swipe a train passing on the main, there is an additional problem, points can often be given the same DCC number, so they operate together, and if this was the case in this example the point will actually move under the train, even though a route is set over it - so how do we stop this ? Simple ! - our friend the flagman again.
We add a flagman that is used to grant permission for the points to be changed "a lock and a release (it can do both)" in railway parlance, once again I will deal with one line only, taking the down points, points 5, we want them to be locked when the route from s2 to s3 is set, so we add a trigger to the flagman which is the setting of the route (Fig 1) - it can be seen that although this example is easy, a complex junction can be locked by simply adding all the necessary triggers to the flagman.
Fig 1
We now add a condition on points 5, such that they need the flagman (fmLockPoint5) to be not triggered to allow them to change (Fig 2)
When we test the panel, all seems well, the route is set and the flagman indicates the points are locked (Fig 3)
Fig 3
If we initally set the point, 5, to the crossover position, it remains where it is (Fig 4)
Fig 4
To solve this problem we add the point into the operations tab on the route, rs2Tos3 - DO NOT USE THE LOCK here as, to me, there is a serious failing of RR, if you use lock to lock the point, you cannot then set a route over that point, even if it uses the point the way it is locked - so in our example you couldn't use rs9Tos8 - and ensure the point is changed to the way we require (Fig 5)
Fig 5
This completes our simple example (Fig 6)
Fig 6
Once again you can add the other locking if you wish or you can download the completed panel below, I have added rudimentary aspect control on s1 and s10 as an example of how to stop direct clicking, sometimes its easy, sometimes a bit more work is required (which will be covered in the next colour light lesson)
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Last updated : December 10, 2007 22:42