In the sketch below, you’ll find the current track layout that we are building for Lego World 2014:
In total we have 4 NXT bricks and 4 EV3 bricks. Two of the EV3 bricks are not used yet. They will be needed for the component which will load the wagons with candy.
The visitor shoots with one of the PUIstols ‘”one” or “two” a color (red, yellow, green or blue). The chosen color is read by EV3 #2. The computer directs the train (number one or two, controlled by NXT #1 or NXT #2) to the marshalling yard to pick up the corresponding wagon. The switch controls NXT #3 and NXT #4 have to set the switches to the right track. Next, the train delivers the candy (or something sweet) to the visitor. Finally, the train goes back to the marshalling yard to bring back the wagon. When the train hits the buffer (which is detected by EV3 #1), the train decouples the wagon.