Control Systems
On a simple model layout, the only control system is the throttle, a supply of variable-voltage DC electricity, wired directly to the tracks. On any larger layout, things get much more complex.
Digital Command Control (DCC) is an important part of this. It provides the variable voltage to the train motors, using a command station and one or more booster stations (on simple systems the booster is integrated into the command station). DCC can also be used to run accessories, such as track switches (“turnouts”), signals, and other things. But DCC is essentially a one-way communications system: command station to train/accessory. It is also limited in capacity, and with a lot of devices it can slow down. Keeping this system dedicated to running trains, and moving other systems to a separate Control Bus, is a better design approach for large layouts.
There are many kinds of Control Bus, and a survey of the available types can be found on the Control Bus page in my Layout Control section. My goals for a control bus for this layout are related to handling train detection and signaling, primarily. I may also use it for throttles and turnout control, although that is still to-be-determined. One important consideration is that there should be some way to interface hobbyist electronics, such as an Arduino, to it, so that I can design my own controlled devices. At the same time, I’d prefer to have commercial products available for more common things.
Finally, there are human-facing controls and displays. These can be simple, such as switches and LED lights, or more complex. My intent here is to use JMRI. There are two roles for this. First, a large central system potentially running scripts to control devices based on the state of train detectors and other systems, but also managing throttles (including support for wireless smartphone throttles). And second, smaller systems running on touchpanel-equipped Raspberry Pi computers mounted to the layout fascia for local controls. I’m going to avoid LED indicators and actual physical switches for the most part. I’ve been experimenting with this for a while, but haven’t built a fully-functional test system yet, something I need to do before proceeding to layout construction.
So in sum, I need both DCC systems and some kind of as-yet-unselected control bus system, and I need a central JMRI system connected to both, along with subordinate JMRI systems (the latter may only connect to the control bus and local devices, I’m not sure yet just how I’m architecting this portion).
