One of the issues I have been wrestling with recently is determining the most effective method of track occupancy detection. I have four stub-ended staging yards that will be hidden from the operators. Operators will need to know what tracks have trains and those that do not.
There are a number of options that are available for consideration:
Track occupancy determined by current draw – this type of detection on a DCC layout uses the additional current draw from a DCC locomotive to indicate if a section is occupied or not. The NCE BD20 is an example of a device that registers this current draw and indicates occupancy with a coloured LED on a control panel.
Track occupancy by infrared light detection – this type of detection is where an infrared beam, or pulse, of light is broken by a stationary or passing train. The beam of light can either come from between the rails or from the side. Examples include irdots from Heathcote Electronics, the reflective proximity sensor from Iowa Scaled Engineering, and infrared model train detection units from Azatrax.
Track occupancy is made visible via a camera and screen – this is where a small camera is set up to view the yard throat or yard of a set of hidden staging tracks. Vision is displayed to the operator on a screen attached to a control panel or on the fascia of the layout. I have read of layouts using this method with very satisfactory results. That said, I am experimenting with one such set-up using a car reversing camera and screen I bought cheap off eBay. More sophisticated (and expensive) options are available using home security cameras and screens.
Track occupancy determined by human eye. You might wonder how this is going to work if all the staging tracks are hidden! Well, two of the stub-ended staging areas are easily visible by the dispatcher who sits inside the turnback loop (peninsula) of the layout. As for the other staging track areas, I am considering a viewing slit between the top of the 3mm MDF scenic backdrop and the bottom of the upper deck so that operators can see all the tracks by eye (the hidden staging tracks would be illuminated by strip LEDs). This method is possibly the cheapest and the most assuring to operators, but it is less visually appealing in terms of the scenic backdrop.
I understand one can also do something with reed switches and magnets but this is not part of my considerations.
In the recent NMRA Magazine (October 2016) there is a very favourable review (pp:40-41) of Azatrax track occupancy detection. The review covered two methods – current draw and infrared detection. Since I am using dead sections at the end of each staging track to kill power to the locomotives, and therefore stop them running over the edge, I don’t see how track detection by current draw will work for me in that situation. The infrared method is the more effective solution, albeit I would need to ensure that the detector was at a suitable midway point along the stub-ended staging track to incorporate trains coming in and going out of staging. I wonder how often the gap between rollingstock plays havoc with the accuracy of the infrared detection!
As an operator, I must say that I prefer being able to physically see the staging tracks as I don’t trust technology to be 100% accurate all the time! This option can be accommodated by the camera/screen method, or via the gap between the top of the backscene board on the lower deck and the bottom of the upper deck. The latter method may not be too bad for me. My scenic areas on the lower deck are not directly under the top deck – they are stepped out so that the top of the scenic backboard reaches the front of the upper deck.
While I wrestle with the options and permutations, I can just continue with the current “method” which is the easiest of all – have no backscenes on the lower deck at all. Hidden staging is now well and truly visible!
DME Down Under 