Sunday, February 10, 2008
Wiring a crossing for DCC
There can be few layouts which get by without including a diamond crossing at some point, mine included. And for those of us using electrofrog trackwork and DCC that raises the question of how to wire it.
My first assumption was that it would require some complex wiring and a DPDT switch, but I chose to search the internet first for a definitive answer. I found rumours about using a revering loop module but nothing in detail. I couldn’t see how a reversing loop module would work, but then I don’t understand how they work as reversing loop modules, but I figured it was worth some experimenting.
Below is the technicolour diagram of what I ended up with.
The blue and green wires show the normal ‘two wires’ from the command station/controller. These are wired to either side of the crossing as they would be normally with blue to one rail and green to the other.
The short red lines show where an insulating joint is needed either side of the crossings frogs.
The inputs of the reversing module (I’ve shown a Lenz LK100 here, but another make would work equally well) are connected to the ‘two wires’ from the command station. It doesn’t matter which wire connects to which terminal, the module will switch them as necessary.
The outputs from the LK100 are in turn connected to the crossings frogs. Again it doesn’t matter which output goes to which frog, just as long as the frogs are insulated from neighbouring rails.
With my crossing wired as above when I run a train over the crossing there is a ‘click’ from the relay as the LK100 switches polarity and the train runs across the track completely unhindered.
PS. The diagram assumes that both the crossing tracks have the same orientation, ie neither is part of a reversing loop or figure of eight style layout. If so you’ll need to make some modifications, I suspect putting another reversing loop module over the other rails of the crossing (and inulating them) or on one or more approach roads.