Using Circuit Breakers to Protect Individual Tracks:
Track Protection: I have wired my layout into multiple blocks. I use my MTH DCS system (with AIUs) to control the power to the blocks. The AIU selects the block and therefore controls the output from my transformer to the various blocks. I also use separate high current relays and individual circuit breakers for each block. The AIU selects each relay using a 12 volt signal. The relay is then used to connect power to the track.
I also use individual 3 ampere circuit breakers on all wiring to the track. I prefer to have complete protection of all circuits. This means that short circuits or overloads on an individual block circuit will not affect the power available for all other tracks.
Note: Since I use a Passive wiring scheme the individual TIU output to each block only requires an isolating resistor.
Turnout Protection: All my turnouts are powered by external power circuits. These circuits have both current limiting and fuses for protection. As a result a short circuit or overload caused by an individual turnout solenoid failure will immediately be cleared" without affecting any other circuit.
Control Modules:
I have built several control system modules for this purpose. See the attachments.
The first module is a convenience terminal board (AIU Patch Board) which connects directly to my AIUs:
The second module is a relay board which isolates the AIU relays from the higher current AC circuits.
I have built a relay interface board (Relay Board) for controlling my layout via the MTH 50-1001 DCS control system. This board contains 20 high current relays which are used for controlling turnouts (switches) and block feeders. As a standalone interface this relay board could also be used with "manually" operated toggle switches if desired. However it exactly matches the color coded terminal blocks shown on the AIU Patch Panel.
