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Layout Bus Wiring

Posted by on Jun 6, 2016 in Tony's Tips |

We recommend you look at Parts Express part number SKRL-14-100. This is 100 feet of 14 gauge speaker wire for under $30. Change the -100 to -500 and you get a 500 foot reel. The spool has a molded ridge to identify polarity, but the website seems to show a color variation. While this is stranded rope lay (which does help inductance), the key feature is that the two conductors are molded closely together in parallel forming a transmission line. Hence, for equal currents in the wires, the magnetic fields are equal and opposite so they cancel leaving very little inductance for the DCC signal.

Here is a reply we gave to a customer looking at how to break out track feeds from the speaker wire bus. Of course, once you get the concept you can modify number of terminals, etc. He is using 12 gauge, but other than the crimp connection for the 12 gauge wire, all else applies:

Go to Digikey.com and look at the following parts. WM18321 – This is a crimp connector that crimps to 12 gauge wire and provides a connection for a #6 stud (6-32 screw).

Crimp Connector

WM5765 is an 8 position terminal block with 6-32 screws while WM9718 is a four position jumper wire that connects four terminal block positions together.

0387700108 Molex, LLC | WM5765-ND DigiKey Electronics

8 position Connector

0380021286 Molex, LLC | WM9718-ND DigiKey Electronics

Jumper

You cut your bus wire and crimp a WM18321 onto each of the four wire ends. Hold the terminal strip vertically. Connect the two silver wires in (left) and out (right) at position 1 of WM5765 and the two copper wires in (left) and out (right) at position 8 on WM5765. This basically connects the bus in and out of the terminal block. Now connect a WM9718 to positions 1 (with the silver bus), 2, 3, and 4. Connect a second WM9718 to positions 5, 6, 7, and 8 (with the copper bus). This gives you at least 6 open connections for each bus wire, and it is possible to connect more than one track feed to a terminal block connection screw. An alternative is to use positions 1 and 5 for the bus wires which gives 2, 3, 4 for silver bus connections and 6, 7, 8 for copper bus connections. This method is nice because the 12 gauge bus just flows through the termination area leaving multiple connection points for your drop connections. You can also use crimp connectors on the drop wires to really spiff things up.