28 Dec 2013
A chance to make some progress
After a stupidly busy couple of months, the Christmas break has allowed a few days of fairly continuous work on the approach board (that I see from this blog I started in June).
I now have all of the points mounted on the northerly station approach board...
The flange screws you can see between the rails holding the trackwork in place are to allow for minor adjustments, the track will eventually be glued into place when the track is ballasted (at least a year away) and at that point the flange screws will be removed.
I want to check that the track runs perfectly before gluing it down.
I just can't work kneeling down for more than a minute or two so I have tried to make the construction of the layout as modular as possible - such that I can either work at my workbench or at least standing up. To that end the boards are all to some degree removable and the electronics are as modular as possible...
This board is the most complex, it requires 14 point motors and the track-work is split into 15 separate occupancy detection sections. This is because the complex station throat point work has so many possibilities that the required continuous track detection is tricky.
Continuous track detection means the computer never has to guess where a train is. It requires two things - (1) all track be occupancy detected (2) no single occupancy sensors are going to have two separate trains on simultaneously under normal operation.
The electronics for this board (like all of the electronics) hangs on hooks from a supporting L-girder in this case it contains 2 CML DAC-20 Digital point controllers and one Digitrax BDL-168 occupancy detector board.
The feeds to the track and points are mounted along the top on pluggable connector blocks, the feeds into the electronics are two cables attached on the right hand side by locakble circular connectors - one carrying the track feed and one the various power supplies required for the electronics.
There are 6 separate track feeds that come from two central Digitrax PM42 boards - these mean that any short circuit is more easily identifiable as it only affects one area of the track. One track feed goes to each of these hanging electronics boards. The whole board is assembled on the workbench and then can be plugged in when in position with no further wiring required, thus saving my knees.
