Well, not quite don’t break a leg but it’s close!
An integral part of the project was detecting where the ball was and whether it had passed a certain point or not. In order to do this I used some phototransitors coupled with some IR emitters as an improvised beam trip. When the ball passes between the phototransistors and IR emitter the arduino is able to detect the slight drop in the readings which indicates the ball has travelled past. This meant that we could flip booleans in the logic to indicate where the ball was in the system.
We had a slight issue with the bouncing of the sensors because occasionally the light levels would fluctuate and due to the fact the phototransistors detect a much wider range of light than an IR detector, it would occasionally simulate tripping the beam. To ensure this really was a ball passing through I wrote a small segment of code to ensure that the beam break time was synonymous with a real break.
Once I had created a working prototype on the breadboard I then created several smaller beam break modules using small squares of stripboard. These were mounted onto the small clips that held the track together and then the Emitter and phototransistor were aligned for best results.