I have been experimenting with RFID to allow me to determine which engine and carriages are passing a certain location.
I have uploaded a video to YouTube if you are interested.

I have found the tag is read most reliably when it is attached to the carriages. The train can go fast and it still detected. The Large Glass Ampoule is the best, but the 18mm button works well enough to be used.

I have found a different RFID reader which is under $20 and small enough to fit under the track. I want to try this one next.

Hi: The LISSY system the Uhlenbrock has seems similar in function to RFID. However, with the cheap tags, an updated LISSY-like system would be a very good idea using RFID off the shelf. This could them be incorporated into other controllers or to a computer in the standard ways.--MM

RFID

Nice video

Very interesting.

When I was looking at different train identification methods some years ago, my conclusion was that RFID would be the theoretically best method. It has some advantages that are difficult to meet alltogether with other methods:

- Identification, not just detection
- No need for line of sight
- No mechanical contact
- No need for modification of loks
- No need for power supply to the tag, allows detection of unpowered units too

However, at that time all RFID readers I could find were bulky and expensive, and I considered it too big a project to design something better myself. So I developed an IR based system instead.

Still RFID technology is much more expensive than IR technology. The IR system I built costs only 2-3 Euro per detection point, which is very hard to beat with off-the-shelf RFID readers. Some big manufacturer should really make a development effort and create a cost-effective RFID system optimized for model railroads. But it is a big development investment if you want to make it really good.

Another factor that may stop it is that there are patents on this, and the "inventors" want to have their (I assume not so small) share of the possible profit. I write "inventors" with quotation marks because I think there is not so much invention in the idea itself.

When it comes to technology, I think it would be better to use the 13.56 MHz frequency rather than the 125 kHz frequency. According to what I found out it would be easier to build small tags and small readers with that frequency. You would also get a shorter reader range, which would minimize the risk for erroneous readings from e.g. parallel tracks or tracks on different levels. But as a hobbyist you are limited to the equipment you can buy for reasonable money, and there I think the 125 kHz systems still dominate.