Wiring
Overview
Abstract
Simplified cabling saves time and money. With RTB I try to reduce cables under the boards with focus on the requirements of modular layouts.
Power Management
Signal: YES, Power: NO
Power Domains (Powerboards) are connected via the FDX bus using CAT5 cables. The cable is only for the communication between the Powerboards and does not carry any power lines. The End-to-end distance of the FDX bus should not exceed 150m. This is not a hard limit but a guideline. With up to 16 Powerboards per RTB domain, the average distance between two Powerboards would be 10m, which to me is a reasonable spread of power domains.
Note: All signals on the FDX bus are RS-485 differential.
DCC Distribution
Signal: YES, Power: YES
The DCC signal is distributed via the HDX bus within a Power Domain. If the distances are short and the expected current draw is within ribbon cable specs, the 10-pin HDX cable alone is sufficient to distribute power and the DCC track signal. Otherwise the optional but separate Power + DCC cable path with higher cross-section should be used to lower the voltage drop. The end-to-end HDX bus length should be less than 10m. Optionally, the HDX bus can be terminated by a bus termination device. This device monitors and reports the signal quality at the end of the bus.
Note: The Data-x lines are RS-485 differential, while the DCC-x lines carry the full voltage swing from the booster.
Each HDX bus supports up to 56 real-time feedback tracks. With up to 16 HDX busses, the total number is 896 real-time feedback tracks per RTB domain. Please refer to the scale-out section to grow further.
Accessory Control
Signal: YES, Power: YES
Accessory modules are connected via the EDG bus. Instead of few big accessory modules, many small modules are to be used. This enables a flexible combination of functions and features by aggregating different types of modules. EDG modules are daisy-chained using a 6-pin EDG bus ribbon cable carrying the bus signal and power. Like HDX, the EDG bus also provides a separate but optional cable path for power distribution with higher cross section should the expected current draw exceed the ribbon cable specifications.
Note: The Data line on the EDG bus is 3.3V logic level.
