For now I’ve been doing block detection on the Randall layout using NCE BD20 current detectors. I have part of the Mountain Panel wired, and I’d like to have more there. I’d like to also have block detection of part of the Valley, and that’s where I have been hitting a wall for the last two years. I just can’t figure out a clean way to do it.

Block detection using BD20-style current detectors can be done at various points. Let’s review the possibilities:

• At the panel, on the red wires out of the panel.
• Pros: it’s easy to identify which wire is for which block.
• Cons: Although that’s OK for the Mountain Panel, it’s a PITA for the Valley Panel which is such a mess that I’d rather not touch anything in there.
• Current version looks like this for the Mountain Panel:
  
• Here’s the Valley Panel and why I don’t want to touch it with a ten-foot pole:
  

• At the “spiked” connector grid that concentrates blocks for panel 1 + 2.
• Cons: This thing looks very delicate to solder. I basically don’t want to touch it.
• This is what this looks like for Mountain (top) and Valley (bottom):
  
  

• Next to the track, on the red wire side of each block, running long wires with twisted pairs to NCE AIU cards mountain around the layout. That was my initial plan back in 2016 before I decided it was a terrible idea.

• On the black wires “concentrator” under Stockton, which merges all the common-rails negatives from all the power districts together.
• The interconnection bar looks like:
  

• On the black wire bundle by the workbench, as allegedly used by the old DC detector.
• The bundled wires looping at the workbench in the back look like:
  
  

To be clear, the main issue is figuring out which wire corresponds to which block, since they are mostly unmarked. A few of them are labeled, and I’m not even sure I trust these labels. The black wires bundles by the workbench have their own markings that do not match with the block numbers. I believe these come from the mountain district only.

The second issue is that the through-hole CT sensors require the wire to be either disconnected or cut so that they can be threaded through the core transformer. I’d rather not have to do that if I can avoid it. Thus I’d rather do this where the wire has some kind of connection that I can easily desolder then resolder.

Last but not least, the third issue is that parts of this layout are better left untouched. The “train room exhibit” has to be functional 5 days a week, and some of the operators have very low tolerance to anything not working for even a short period of time. Thus any work I do cannot be disruptive, yet some is bound to be, for sure. That’s part of why I don’t want to start messing around with finicky complicated panels. Any work I do has to be able to be incremental and split into small enough tasks that I can handle each one in a day, once in a while when time permits.

For the common ground “concentrator” under Stockton, I posit that some blocks are likely merged due to the common rail design: in common rail, the “negative / ground” is a continuous rail along a subdivision, with only the “positive” rail being switched on/off by the block toggles.

OTOH the Randall layout was supposed to have DC block detectors, and that’s supposedly what this massive bundle of wires going to the back workbench is all about. So assuming these are still connected, they would be a logical place to put block detectors if I do not want to put them at the panel. I’ve tried following these wires and I quickly got lost.

One thing I don’t understand is how the DC block detectors could work detecting separate blocks on the black side if these were wired together via common rail. Something doesn’t add up here. I really wished someone had left some documentation on that behind.