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Block Detection and Signaling




Block Detection has been installed on all mainline trackage throughout the layout. Block detection is by RR Cirkits. The TC-64 is the brain of the system. The TC-64 is a 64 line input/output controller that reports to LocoNet. BOD-8 block detection modules can either plug directly into or be remotely wired to the controller. The BOD-8's are located throughout the layout. Toroidal Transformers are used to detect current in each block and report it back to the BOD-8's. The block detection system is sensitive enough to pick up a single 20Kohm resistor anywhere in the block.


Each car has two 20K ohm resistors (one on each truck) to allow the block detection system to recognize rolling stock.

Below is a general guide to the setup of the block detection system (linked from RR Cirkits site).


Below is the Physical setup on the current railroad.




Signals are driven but a Digitrax SE8c signal decoder. Thanks to previous documentation and careful planning, setup of the SE8c was relatively simple. The tedious part of the setup was equipping each signal head with a set of plugs to ease installation. I used Tomar H-856 Single head (3 vertical lights) and H-866 Double head (3 vertical lights) signals for the lower level. Searchlight signals will be used for the upper level. 


                                      
                                                    
                                Tomar H-856 Single Head                              Tomar H-856 Double  Head
                                  3 Light Vertical Signal                                       3 Light Vertical Signal


The main driver of the signalling system is the Digitrax SE8c signal decoder. There are two of these decoders on the layout. Each level has its own SE8c. These boards are capable of driving 32 individual signal heads. In general, each switch location that is protected by signals generally uses four (4) signal heads. That allows each SE8c to protect 8 switches. The SE8c is also capable of controlling eight (8) slow motion type switch machines (although I do no use this feature of the SE8c). There are limitations to this board, however. It does not have on board logic to drive the signals per prototype practice. Logic to run the signals is done on a computer via a interface (in this case a Locobuffer USB by RR Cirkits).

Digitrax  SE8c Signal Decoder

The hard part of the whole system is integrating the signalling and the block detection systems with turnout control into one whole system. This is done via a computer and code written to take the inputs of the block detection system and the turnout controls and outputting it to the actual signals.  The CFRR uses JMRI's Panel Pro to create the signalling logic necessary to run the railroad. A Schematic was created to represent the railroad in JMRI. Controls were then added to control turnouts.

Lower Level Dispatcher/Signal Logic Panel



Upper Level Dispatcher/Signal Logic Panel (Incomplete)

The first thing that must be done when adding controls, sensors and signals to the panel is to create some tables that identify each hardware detector, control and signal head. Panel Pro is setup quite well to add these tables. In the case of the RR Cirkits block detection, it is treated the same as if it were a Digitrax product. There are certain naming conventions that are need to create each object. For example, a sensor is labeled as "LS##", a turnout control is "LT##", and a signal head is "IH:SE8C:"###";"###" where # corresponds to the hardware number. Turnout and block detection sensors are fairly straight forward to add to the panel. The sensors simply relay what the hardware (block detectors) on the layout are reading. The turnout controls actuate the turnouts when they are thrown. The signal heads are a bit more complex as each requires the creation of some logic to run them. Each signal is added to the panel and logic was created for each signal head via the simple signal logic utility built into Panel Pro.

 Example Simple Signal Logic Setup

In some situations (Switch 5, 6 and 7 in the case of the lower level panel) require "virtual" signals to be created to have the logic operate correctly. These signals only exist in the program and not physically on the railroad. These virtual signals allow signals (such as switch 7) to show the correct aspects for the desired routes. The signals shown for switches 5 and 6 on the lower level panel are virtual and do not actually exist on the railroad.


Scratch built Signal       Scratchbuilt Triple Head Signal
Scratchbuilt Searchlight Signals

The Upper level has recently had signals installed. The upper level uses searchlight signals instead of the 3 light vertical signals used on the lower level. All but one signal on the upper level is scratchbuilt. The signals are made from brass and resin cast parts. The actually lights are bipolar (3-wire) LED's.  The mast, ladder, and landings are brass. The relay box and target heads are cast resin.


Picture Credits:

Signal Pictures are from Tomar's website.
Digitrax pictures are from their website.
RR cirkits pictures are from their website.
All other are created by the Owner of the CFRR.
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