It all depends on the detector type. Something like the Digitrax BDL-168 concentrates 16 detection sections in one board and requires you to run 16 heavy wires out from some central point to each detected block. Even if you mount it out under the layout somewhere, it's not likely you have 16 detection sections all within a couple feet of each other. I dislike this sort of thing for two reasons - all the heavy bus wire required, and the fact that the diode drop detection causes a voltage drop.
I intend to use a pulse transformer system like the RR CirKits BOD-8 (in fact I might just use the BOD-8 - I've had poor luck trying to design my own, and even some DIY ones when modeled in PSPICE don't seem to give the desired results). What I plan to do is run a heavy main bus wire for the length of a give power district. Along that bus, I will tap off to a sub-bus. Each sub-bus will feed one detection section, so the sense coil goes over the jumper connecting the sub bus to the main bus. The only long runs of wire will be the UTP pairs fromt he coil back to the BOD-8 main board, and there are only 8 of them, not 16, which makes it easier to fill up a board without a huge spiderweb of wires everywhere.
--Randy
Modeling the Reading Railroad in the 1950's
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giving some thought to adding pulse type block detectors
i wired my layout by running a bus under the trackwork, with feeders from the bus to one or more tracks running in parallel (e.g. siding, spurs, ...)
1) i had assumed the wiring with block detectors would run from some common panel where the block detectors would be located. Compared to the way I wired my layout, this approach would require extra wire.
2) it now occurs to me that the wiring could be minimized, or least the heavier bus wire, by having a bus and sub-buses with one or more feeders to a block with a block detector. In this case, the block detector would be located on the sub-bus near the block and a smaller gauge block detector output wire run back to some central panel (presumably there is a power/ground bus for the block detectors)
which is the more commonly used approach?
greg - Philadelphia & Reading / Reading