Oyama Staging Yard II - Wiring

At the end of the last post, I left you with this picture.

Now it's time for some Whats, Whys and Hows. For those of you whose eyes glaze over when people start talking about wiring, electronics, and programming, you may skip this section and get your friend like me to come and do this. 

Basics and conventions

A big project like this needs some advanced planning and that starts with color coding the wiring so you can keep track of what is where. Here is mine for the track wiring:

Track Color Coding
	North Rail	South Rail
Normal Track	Black	White
Reverse Section	Blue	Green
Turnout Frogs	Red

These were chose mostly on cost consideration. I'm stripping the track buss wires from 12 AWG house wiring, which is about the least expensive wire you can buy, and that's even counting that I'm not using the bare ground wire. For the reverse loops, I had some blue and green wire from the old wiring in the train house, again this is 12 AWG. For shorter jumpers, such as connecting the terminal strips between sections, I use 16 AWG stranded wire. The track feeders are 22 AWG solid wire. I am using current sensing track occupancy detectors, to drive ABS signals. The sensors and section breaks are in the south (white or green). "North" and "South" on the reverse sections refer to the state when the reverser is not energized. In this case, when it is lined for track 1.

Tortoise Color Coding
Power	Yellow
Switch Inputs	Blue	Black
Switch Outputs	Red

The color coding for the Tortoises only applies between the connector and the terminal strip. These are 18 AWG wires.

Other Wiring
Tortoise Feeds	2 Cond. Brown cover red/white wires
Track Det. Leads	CAT5 (Blue) 4 pair / cable
Simple Serial Buss	3 Cond. Grey cover black/red/green wires
LED (lighting) Leads	Clear/white speaker zip cord
Others as noted below

Control and Detection

For detection and turnout control, I'm using the circuit boards supplied by RR-Cirkits. These are LocoNet compliant devices (yes, I'm using the Digitrax LocoNet for this, and NCE for controlling the trains) that are connected together with the Simple Serial Buss (SSB), a three wire buss that uses the same communication protocols as the LocoNet. The boards on this section are two Watchman boards, one Towerman board, and two SMD-8 (Stall Motor Driver - 8 outputs) boards. There is also an SSB-Adapter, which connects to the LocoNet and provides power for the SSB. These are shown below.

For track detection, the Watchman cards use 100:1 current transformers (also available from RR-Cirkits). These are placed on the track power leads at the point of detection, and connected to the Watchman boards using CAT5 cable, with each transformer connected to a twisted pair in the cable. This greatly simplifies the wiring, since the track power leads do not have to be brought to the detector circuits. The twisted pairs are connected to the green screw terminals on the Watchman boards. There are 8 detector circuits on each Watchman.

For this section, there is a separate track circuit for each turnout (11). This board also has the detection for the reverse loop tracks. This is four sections, with the reverse loop split in two and a short detection section at each end off the reverse loop. The last section on this part of the layout is the lead that connects to the helix that goes down to the rest of the layout. This is a total of 16 detection sections, which fills the two Watchman boards.

Each Watchman board also includes eight general purpose input/output lines, which are contained in a 10 pin ribbon cable connector. This connector also includes a +5 volt pin and a ground pin.

Above is the picture of the staging yard ladder from the last post. The I/O pins on the Watchman cards are configured as inputs and are used for switch position confirmation, using one of the auxiliary switches on each Tortoise switch machine. The other switch is used to power the turnout frog. To simplify the logic required, these inputs are are connected through multiple Tortoises as shown below, so there are 12 inputs, one for each track. When the yard ladder is lined for, say, Track 5, then the input for Track 5 is connected through the Tortoises to ground, and all others are open.

To get to track 5, you need to take the normal route through turnout 606, the reverse route through 604, and the normal route through 605. The reverse route through 605 leads to track 6.

The TowerMan has two sets of eight general purpose input/output circuits, like the ones on the Watchman boards. In this case, they are configured as outputs and connected to the SMD-8 cards with ten conductor ribbon cable. The SMD-8s drive the Tortoise switch machines. The SMD-8 cards have their own power supply, independent of the SSB.

The TowerMan and WatchMan boards also include programmable logic blocks, similar to a very simple programmable logic controller. RR-Cirkits also makes a SignalMan board for controlling signals, and a MotorMan boards for controlling various types of motors. The programming of these cards will be the subject of the next blog. I consider this to be an advantage, because a computer is not required for these boards to operate. It does require a computer running JMRI to program the boards.

That just leaves the control of the reversing loop polarity. This is an automatic circuit, but decidedly old school, compared to the high tech applied to the rest of the control system. There is a 12V DPDT relay which is wired, as shown below, so it is energized when the yard ladder is lined for Track 12. When any other track is lined, it drops out. This uses the same 12 volt power supply as the SMD-8 cards.

The wires labeled "Black" and "White" are the main track buss wires. "Blue" and "Green" are the reverse section buss wires.