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The track is wired in a way that is almost certainly over-engineered. It has been done this way for reliability, and for ease of maintenance. This is for the long haul: I don't want to be fixing it before it is finished.
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If you have a good back and neck, great. If not - these are invaluable for all that work upside down underneath the railway! My creeper - despite being one of the lower cost models - has an adjustable backrest. This means I can sit reclined under the railway, as well as lie down. This has been invaluable during wiring and point motor installation work. |
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My CAD design shows the rail polarity, and location of power feeds to blocks. The rail polarity is marked by the rail being "red" or blue". The "red" rails are gapped between sections; the blue rail is continuous through the entire power zone. (The railway is also power zoned, and this makes wiring slightly more complex; the "blue" rail is also gapped between zones. See the power management page for more details).
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This "device" is simply a small piece of wood marked with the two track polarities - "red" and "black". It is to reduce errors when testing: this way, there is no danger of forgetting which is which - particularly when an assistant is working too! |
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Each piece of track has a pair of dropper wires: I am not relying on electrical connection via the fishplates. This is almost certainly overspecified. The dropper wires are 100-150mm lengths of 22SWG tinned copper wire, soldered to the rail bottoms before mounting. I have used 60%:40% leaded solder: lead-free solder melts at a much higher temperature and did NOT flow well at all. It may be possible to improve the "flow" that with different fluxes, but the temperature means more heat into the track and more opportunity to distort the plastic.
Once through the board, the dropper wires are fitted with coloured insulating sleeves, and terminated with a red butt splice crimp connector. These are readily available from many suppliers (buy in hundreds to keep the cost down) and terminate the "solid" wire locally. I used red and black sleeving, simply because I could get black at much lower cost than blue... I don't know why that is! don't mess around with the crude crimp tools that act like a pair of pliers - it will take all day and be less reliable. Buy a ratchet action crimp tool and don't ever have to worry about joint reliability.
At this point, each piece of track is connected via colour coded, insulated droppers to a pair of insulated terminals. Use a multimeter to make absolutely sure that the connections are right before proceeding. There should be no shorts between rails, and good connection to each dropper. As an observation, if this stage is completed as track is laid, it can be tested with trains running without fear of the droppers shorting below the baseboard.
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This shows two pairs of dropper wires under the baseboard. They are insulated, colour coded and connectorised: this makes subsequent operations easy and foolproof. The connections are simple bullet type crimp connectors; the power feed wires have the mating bullet connector crimped to them and the power to each track section can then be isolated. |
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The droppers from the track sections are joined to the power feeds using crimp connectors. "Scotchlock" type connectors make the tap-off joins onto the main bus runs; I couldn't find these that were specified to work with smaller than 0.75mm2 cable. This has forced all track bus wiring to use 24/0.2mm (0.75mm2) cable. This is, again, overspecified but unlikely to make a material difference to the cost of the railway.
Because the railway is power zoned, there are several track buses - not just one. Each zone has its own common return wire for the "blue" rail; the "red" rail is fed from the relevant block detector output. This means a lot more wiring than for non-block detection DCC wiring, even with the block detectors fairly well distributed around the railway. This is essential for computer controlled operation; ultimately the wiring has taken a little longer, but it isn't difficult and it is still easy to follow. However, an accurate record of "what is connected to where" is essential. When planning the block detection, I developed several spreadsheets that show what track section is in which power zone and which block detector provides the power.
Point frogs get power from the switch built into the SEEP point motors.
Testing
To ensure the wiring is correct, I've used several stages of testing.
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Visual inspection: make sure that each track section has a power connection, and comes from the correct wire.
- Isolation checks: remove the power connection from the return
"blue" rails, and check they are electrically isolated from
each other. (This picks up any rail sections that have been connected
to the "wrong" return wire).
- Short circuit check: use a coin to short each separate rail
segment. Check that the power manager boards detect and isolate the
short in one section only, and that the booster does not
"beep" indicating a short that the power manager didn't handle.
- Block detection check: use an LED to check that each section has power, and that the block detector reports this section (and only this section) as occupied to LocoNet.
If those tests pass, then the track has been wired correctly!
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