Happy New Year! I don't think I have ever felt so good about the start of a new year as I feel now.
In December I posted a two-part article that described the design and construction of my automated signalling system which used block detection to identify the presence of a train. The system continues to work flawlessly.
In earlier posts, I have mentioned my participation in Free-mo (see January 27, 2019 post which explains Free-mo model railroading and March 21, 2020 post which explains that the middle level of my home layout consists of Free-mo modules). I have seen working signalling systems on a Free-mo set up at the Big Valley Alberta event which is hosted by the Calgary Free-mo group and where I found that the added realism makes for a good experience.
I decided that it would be impractical to employ block detection to signalling for Free-mo for the following reasons:
- Free-mo modules are designed and constructed by various people. Modules can be short (say 2 metres) or long (say 30 metres, in multiple sections). In my experience, most are 2 to 4 metres in length. While the Free-mo standard must be followed for the main buss wiring, this does not mean that the wiring to a module has been designed in such a way that a detection circuit could be installed easily without redoing a lot of the wiring. If a person is reluctant to redo their wiring then the signalling system would be frustrated by one module being "dark".
- Even if a local group of Free-mo modellers agreed to make the necessary modifications to all of their modules to accommodate block detection, one of the benefits of Free-mo is for people with Free-mo modules from other locations to be able to join the group. Since their modules would not have been modified, their modules would be "dark" for signalling purposes.
- The design of my block detection signalling system placed signal masts at each end of a block. Say if one were to go to the trouble of rewiring all Free-mo modules for a local group there would need to be added a huge number of wires under each module (with an equal number of reliable connections between module sections) to mount signal masts at the end of each module. The wiring of Free-mo is extensive enough without adding many more wires to the mix. This point only refers to the wiring under each module - also, there would need to be wiring to allow the system to communicate the presence of trains to each adjacent module which adds even more wiring.
I decided that the more practical approach would be to make use of dedicated signal modules "signal-mos" on which the signal masts would be mounted. Each signal-mo would be one foot long and would conform with the "mini-mo" supplemental standard published by Free-mo.org. A mini-mo can be narrower than the normal Free-mo standard but I decided that a layout would look better if the signal-mo is the same width as the adjacent modules. Since the signal-mos would be used on mainline track this means a 26-inch signal-mo width and double track.
All wiring related to the signals would be mounted underneath the signal-mo. The only wiring leading from a signal-mo would be a 6-conductor flat "telephone-style" cable connecting the signal-mo with each adjacent signal-mo. Aside from the normal buss wiring for all Free-mo modules, there would be no other connections to adjacent modules.
The presence of trains would be detected with the use of an infrared detection device which looks like this one which I purchased from eBay:
In this photograph, the device is sitting atop the smallest-size Post-in-Note pad to show scale. One of these would be mounted underneath the centre of each track on each signal-mo. The trim-pot which has an X-shape is used to adjust the sensitivity of the infrared detection. One of the "LED" devices on the left is an infrared light emitter and the other is an infrared light detector. When a train passes over the sensor some of the infrared light bounces off the underside and is detected. The three electrical leads consist of positive and negative leads (5 volts DC) and VCC to which is attached a wire leading to an Arduino mounted underneath the track. One Arduino is required for each of the two tracks. The ground wire is also common with the Arduino.
How the Signals will Operate
The following depicts how the system works without showing any of the electronics or wiring:
Some key points:
- Two-track mainline; the trains are travelling in the same direction that seems to be conventional "normal" travel when there is a double-track mainline (perhaps those in the UK, Australia, Japan, etc. follow a different practice because they drive their cars on the other side of the road from those of us in North America, Europe, etc.).
- The rails coloured white for each signal-mo (each of these would be 1 foot long and 26 inches wide). The rails coloured grey depict all other Free-mo modules (anywhere from 1 foot to infinity in length and 26 inches wide at module ends).
- When the train on the lower track passed over the last signal-mo, the IR sensor mounted under the track triggered the backward-facing signal to show red, protecting the train travelling in the module to the right. This same signal-mo tells the adjacent signal-mo to the left of the occupancy so that signal turns yellow as a warning to approaching trains and the requirement to slow down.
- The engineer of the train on the lower track sees a green signal because both the next module to the right and the one after that are unoccupied.
- The same principles apply to the other track and also work the same way if the trains were to be operated in the opposite direction.
What a Signal-mo consists of:
Wiring
The following diagram depicts the wiring mounted underneath each signal-mo:
To wire this under each person's individual module along with all of the other wiring and hardware that is under there would quickly become a nightmare.
The following diagram shows the signal-mo with the 6-conductor flat telephone style wires that take signals to adjacent signal-mos:
Complete Picture
Finally, here is a diagram of the complete picture with only one of the signal-mos showing its wiring:
Coming up - my next post will explain the construction and assembly of the various "real-life" components.