Buying feedback/occupancy detector modules for a model railroad can cost a lot of money, so I wanted to use a DIY solution for this as well. There are a lot of examples that can be found on internet and I tried the three modules below.
Note that I did not test the the units on a large scale model railroad or by introducing interference signals. But I did not have any problems with interference on any of them while using or testing.
This is a feedback module, based on S88N with 16 inputs.
You can order the PCB’s via the web page, no issues with ordering and the design works fine! However, the price of the PCB makes it still somewhat expensive
This is a feedback module, based on LocoNet with 15 or 16 inputs. This is basically a shield that is installed on an Arduino with some software and settings. Since I use current detection, I need two Okkie cards as well. This limits the the output to 15 pins since the first pin is only capable of pulse detection. The PCB and components can be ordered via the webpage. The Arduino have to be ordered separately.
This solution is nice and cheap. Compliments to the author (Nico Teering) for creating a cheap, flexible solution while hiding the deep technical stuff from the end user.
However, I encountered some problems with my Arduino and the installment (nothing to do with the software!) that I could solve myself, but would be a NO GO for others. At that time, I realized that changing an inoperative feedback module would not be a real plug and play thing… Also it would be a bulky module.
S88N Decoder, 8 Channel
This is an 8 channel S88 occupancy detector, based on S88N.
The schematic is nice and simple without the usual latches. The Gerber files of the PCB are provided, so the PCB can be cheap.
My demo track uses a 16 input feedback module and I still needed a lot of wiring to go from one end to the module. Two 8 input modules would have made things a lot easier and cleaner. Since this solution is the cheapest, cleanest and simplest, I decided to continue with this design.