This is my first experiment with RFID based train tracking. The goal is not just detecting if a train passes by, but also identify the locomotive, possibly even the carriages.
This first setup was just for verifying if the RFID reading is even possible in this scenario. Checking if multiple readers interfere with each other and also don't detect trains from the neighboring lanes. So I setup three readers with standard track spacing. All of them are power with 5V, but only one of the reader is actually connected to the USB serial adapter.
I was using RDM630 based readers with EM4100 RFID tags. The tags cost 2 euros each. If I want to put one in every carriage I may need to look for a cheaper version.
The test was successful. I got the best results if I put the tags on the very bottom of the trains. There is no interference, but the reader does miss tags when the train goes too fast. Next step will be to add an ATtiny microcontroller for each reader and use a single I2C bus to collect all the sensor information from the layout. The same microcontroller could also handle LED signals and possibly other sensors. I was think adding an optical reflection sensor for the cases when RFID is missed.