Vehicle Identification

Radio Frequency Identification (RFID) is becoming a widespread method for identifying items - from key fobs to animals. A small unpowered device (called a tag) transmits a unique identification number whenever it gets close to a reader. With industry finding many uses for this technology prices have come down and availability has increased to the point where it is feasible to consider its use on a model layout.

You can purchase RFID units specially designed for model railway use from LDT, although these are somewhat expensive. An alternative it to create your own using the ID-12 RFID Reader Module from Mannings RFID Shop. The reader has an RS-232 output and so can be interfaced directly into a computer. Cards with multiple RS-232 ports are available (look on eBay for cheap ones) that would allow a number of readers to be linked to one computer.

With an RFID tag in each vehicle you could identify each vehicle that passes a given point where a reader is installed. This information could then be used to route the vehicle, control its speed or display information about it for the benefit of people watching the layout.

How The System Could Work - 1

An RFID reader is positioned just before the junction that gives access to the bus station from the main road. The junction is normally set to route vehicles along the main road.

When the RFID reader identifies a bus the computer sets the route into the bus station and to the correct stand for the service being operated. It also sends a command to the bus to reduce its speed.

On a computer screen the details of the arriving vehicle are displayed for people watching the layout.

Once the bus has passed over the junction the vehicle location magnet activates a reed switch which resets the junction for the main road.

How The System Could Work - 2

A roundabout or gyratory road has a number of exits. A RFID reader is located on the approach to the roundabout.

For general traffic the computer picks an exit at random (this could be weighted so that the major exits take the heaviest traffic).

If the RFID detector identifies a bus the computer overrides the random selection with the correct exit for that vehicle‘s route.

How The System Could Work - 3

An RFID reader is located at the entrance to a set of hidden holding loops.

When a bus passes over the RFID it is automatically assigned to an empty loop and its departure time is calculated (including any randomly generated delays for traffic congestion).

At the appropriate time it is released from the hidden loop back on to the layout.

A computer screen could display the details of which vehicles are in the hidden loops and their planned departure times. General traffic is routed straight through without stopping.

Why Use Vehicle Identification AND Location?

Cost. Whilst the RFID tags are relatively cheap and can be installed in all vehicles, the readers are relatively expensive.

By using RFID readers where they can add intelligence to the system and reed switches where we just need to know if a vehicle is present we can minimise the cost (and complexity) of the control system.

See also the related topic of vehicle location.