The title says it all: Behind The Scenes of Radio-Frequency IDentification, Power Functions, BlueTooth and much more. Rolf explained in his article about the software side of our project. In this article I will explain how the hardware (Lego, Mindstorms, Power Functions, etc) is used.
As you can see in the picture, we use a ‘standard’ Lego train 3677. The train is powered by a battery box, and receives it commands by a Lego PF receiver (article 8884). The first wagon behind the train carries the NXT with two sensors connected:
The Hi-Technic IR link is used to send commands to the PF receiver (speed, forward/backward, stop, etc). The Lego NXT is connected by Bluetooth to the computer, running the .NET application. We have written a special library to connect directly to the NXT and send commands. So, due to the Hi-Technic sensor we are able to control the train directly by the computer.
We use RFID transponders (the credit cards, they provide a good signal) below the track to let the train know where it is on the layout.
If the train runs over a transponder, the signal is picked up by the Codatex sensor and the unique ID is send to the .NET application. Since we configured all used ID’s to specific track locations, our application ‘knows’ where each train is on the track when it passes such an RFID transponder. Depending on the location, the application can decide if the train should accelerate, decelerate or stop. We use about 10 transponders for the complete layout.
We are also in the phase of building a Windows 8 application that shows the track layout, the position of the train(s) and the position of the switches.