With the blocks cut, it's time to hook up the wires. The wiring plan is actually pretty simple. For two-rail blocks as shown here, you'll need to run at least one pair of wires from each track block to the center poles on a Double Pole Double Throw (DPDT) toggle switch (or rotary switch if using more than two cabs.)
Bus wires connecting all of the upper and lower poles of the DPDT switches will distribute power from the two cabs. To control the power by cab A, turn the toggle switch up. For cab B, turn the switch down. If you use a DPDT-center off switch, the block can also be turned off completely so neither cab has control - a very useful feature.
As stated, you'll need at least one pair of wires (one for each rail) per block. For shorter blocks, a single pair may do. For longer blocks, multiple feeders attached to a common bus will provide better current. You may also want to use this combination of smaller gauge feeders and heavier bus wires on the short blocks too if you have a long run between the track and the toggle switch. It is much easier to attach the smaller gauge wire to the rails themselves, but the light wire may not be able to deliver adequate voltage over a run longer than a foot or two.
For more detailed instruction on wiring feeders and busses, read this article or watch my how-to video. Wires can be attached to the track using mechanical clips (common in larger scales) or by soldering directly to the rail. Tips are also available here if you need to brush up on your soldering skills.
Toggle (or rotary) switches can be located on a central panel, or along the fascia of the layout. The latter will allow you to walk along with your train if you have a walk-around throttle control. This option will also shorten the wiring runs from the track to the cab busses. On smaller layouts, a centralized panel is often an easier option. Panels can also be used on larger layouts where a dedicated operator, or dispatcher aligns the power for the different engineers.
Either way, the wiring on the back of the switches is the same. Choose switches that are rated for the voltage and amperage of the trains you are using. Some switches use screw terminals, others have tabs for soldering wire connections or using crimp-connectors. Any will work.
Attach the two block wires from the track to the center poles on the back of the switch. Remember to keep the wires consistant throughout all of the blocks. Do not cross wires. Color coding wiring helps a lot in this regard.
Next run a pair of wires from the first power supply (Cab A) to the lower pair of poles on the switch. Run a second pair from another power supply (Cab B) to the upper pair of poles. Remember that the physical position of the toggle switch will be opposite of the "live" wire connection. So lifting the switch up will connect the track wires to the lower bus (Cab A).
As with the block wires, use a heavy enough wire gauge for these cab busses. No. 14 or No. 12 should work for most applications. Color coding the different busses is also a good idea. Write down the color codes for all of your wiring in a convenient location.
Lastly, don't forget to label the toggle switches with the block name/number and the cab assignments. It is helpful to do this on the panel for operators and on the back at the switch for maintenance.
The basic wiring diagram above will work for most installations. Here are a few links to some additional track wiring applications you may encounter:
- Reverse Loops: track sections that turn a locomotive or train, be it a loop, wye or turntable, require special wiring to avoid a short. This is easy to do for both DC and DCC.
- Signals: this basic directional signal adds a little operational flavor to a basic DC block system.
- Block Detection: for more elaborate signalling systems, or to track trains in hidden areas, block detection can be added to your block wiring.