Engineering & building time: 8 hours
I wanted to make a realistic Lego train level crossing. So I took two Lego micro motors (too bad that they don’t make them anymore), very handy since they are very small. Next to that, they also turn very slowly: just the stuff you need to create a realistic moving barrier!
The system contains two sensors: one sensing the train coming and one to sense that the train has passed the crossing. When the first sensor is activated, the barriers are lowered. And when the train activates the second sensor, the barriers are opened again. Since I was using cheap ass Chinese sensors, I needed to install a white brick on the train that triggered the sensors: another colour absorbed too much light.
The disadvantage of this realistic looking system is that you need to place the sensor at least two meters away from the crossing in order to have enough time to close the barriers before the train arrives at the crossing. This is not very handy on a busy track with multiple trains running on it: the barriers aren’t fully opened yet or they have to be closed again. You understand that it could create some angry faces among the minifigs waiting to pass the level crossing! So for the well being of the minifigs, I decided not to use the system anymore.
I now only use the 7866 set parts to open/close barriers at a level crossing, which open and close the barriers much faster. Less realistic, but it prevents annoyed minifigs!