The NNE Scenic Railroad uses Digitcal Command Control (DCC) to control the trains. The digital control signals are supplied by a 5 Amp NCE Power Pro system using a Wifi equipped NCE PowerCab throttle. The system also uses the NCE RS232 connection to an old laptop running the open source Java Model Railroad Interface (JMRI) software in order to enable trains to also be controlled via a smart phone app. I currently have EngineDriver installed on my android phone for use when I wish to control the trains from my phone. However, I generally prefer the larger form factor and physical buttons of the PowerCab throttle. Ability to use a smart phone is to enable multiple trains to be controlled by separate operators prior to investing in additional dedicated throttles.
To house the control system and laptop under the layout while making them accessible, I built two racks with sliding trays to hold the components.
Each rack is open in the back and above for ventilation and ease of routing cables and wires. The trays use a ridged metal that provides some space for air flow below the components as well as acting as a heat sink. One rack is used for the control system components and the other for the laptop.
Because of the planned size of the layout, a single 5 amp system will only power a portion of the layout. I am planning for at least three 5 amp NCE boosters as well for a minimum of 4 separate power districts. Each power district has its tracks electrically isolated with insulated rail joiners from adjacent districts. The main system is used to power the track for Portsmouth and all of the lower level NH towns. The first booster, which is already in place, powers the yard in Salem, MA with its extension towards Boston as well as serving as the power that will be used for the entire helix from Salem up to Haverhill MA and further on up to the top level. I will also have a booster for Haverhill and all of the NH towns on the middle level and one more for the second helix and all of the towns on the upper level including the paper mill at Gilman, VT. The yard at Haverhill on the middle level and the paper mill at Gilman will have their track electrically isolated from the rest of the layout with insulated rail joiners in case I need to alter the distribution of the boosters or add a fourth booster.
Experience teaches not to rely on rail joiners to get the signal to the rails. While the metal rail joiners can work for a time, they may develop issues later that can be difficult to diagnose and require retrofitting of additional jumper wires later disturbing the finished scenery.
It is my practice that every length of rail receives its own jumper soldered to the bottom of the rail. I will cover the mechanics of how I position, fit, and place the rail sections with jumpers attached under Trackwork. With a jumper to each rail of each piece of track, including to the frog on turnouts with powered frogs, the task turns to getting the power from the main control station or the appropriate booster to the jumpers.
I use 14 gauge stranded wire for the two bus wires from the appropriate power source to a series of terminal strips. 20 gauge solid wire is used for the jumpers.
In areas of high track density, I use a separate terminal strip for each bus wire connecting the bus to the terminal strip, connecting all track jumpers of the same side of the track to the strip, and attach another length of bus wire to another position of the terminal strip to run to the next terminal strip for that side of the bus. For areas of lower track density, I use 5 position jumper plates that are isolated to each half of the terminal strip so I can use half of the positions for one side of the circuit and the other half of the same terminal strip for the other side of the circuit. This allows me to purchase the exact same 10 position terminal strips at a higher quantity and lower cost per strip for the entire railroad.
I use three types of turnouts on the railroad, as is discussed further under Trackwork. Some of my older turnouts are Peco Insulfrog turnouts. With an Insulfrog, no power is applied to the frog, with the expectation that even while one set of wheels of the locomotive is passing over the unpowered frog, the other set will still be on powered rail so the locomotive will not lose power. This works fairly well with Peco turnouts using most locomotives. But this approach can result in loss of power if one or more wheels or areas of track approaching or leaving the turnout are dirty. As a result, I have come to prefer powered frogs for all newer turnouts I purchase. Some are older Peco Electrofrog turnouts, but all more recent purchases being the newer and easier to prepare and install Peco Unifrog turnouts that can be powered or unpowered.
To power the Electrofrog and Unifrog turnouts, I use Tam Valley Frog Juicers. In areas with more than a few frogs to be powered, I use the Hex frog juicers that support providing power to up to 6 turnout frogs from the same board. For areas with only one or two frogs to be powered, I use smaller mono or dual frog juicers.
Here is an example of a hex frog juicer mounted and connected under the layout.
The two wires on the right come from the terminal strips to supply track power to the board. The 5 wires at the bottom left go back to 5 separate turnouts to power the frogs. The way frog juicers work is simple. At any point in time, power from one of the two bus wires is being supplied to the frog. As the train traverses the turnout, it will reach a point when the wheels on one side of the train will be in contact both with the frog and with the corresponding rail of the adjacent track. If the polarity of the frog is the same as the adjacent track, nothing happens. The train is properly powered and rolls on. If the power to the frog is the opposite polarity, a circuit on the board detects the short circuit in a fraction of a millisecond and immediately swaps the polarity of the power flowing to the frog. The spec for the timing for this polarity switch is faster than the timing to trigger the circuit breaker in the power supply, and is so fast that the human eye does not detect any change in the speed of the locomotive as the train continues on having been switched to the proper polarities to power the train.
I find that these boards work flawlessly with all of my locomotives, ensuring constant power to all wheels through the turnouts.
On a historical note, V1 and V2 of the layout used Tortoise switch machines to electrically control throwing the turnout direction with power routed from the Tortoise to the frog that would always match the direction the turnout was thrown. Electrically that is a slightly simpler arrangement. But as I will discuss under Trackwork, I chose with V3 to eliminate the use of Tortoise switch machines in favor of manualy thrown turnouts, so a different electrical approach was needed.