Some additional ball guides are needed for the the ball to roll all the way back into the launcher on its own. This is necessary for repeted automatic fireing but should not be complicated to add.
The original goal of the game was that visitors would trigger the launcher from outside a big window in the facade. We have not yet reached that goal, but we have a few ideas. My favorite is to use a commercial light-switching motion sensor. This one seems suitable since it is powered by 3*1,5 volt batteries and we should be able to drive it with 5V if we use a resistor. I think ultrasound sensors are unlikely to work well through the glass window and anything requiring hardware to stay functioning on the outside of the building will be challanging to make robust enough to withstand vandalism.
The stepper motors makes an unpleasant noise which probably is amplified by the wooden frame everything is attached to. It is so loud that it would be unpleasant to sit and work in the same room as the machine. Possible fixes could be experimenting with stepper settings (smaller steps) or anti vibration padding inside the motor mounts.
To get the launcher to fire reliably we had to reduce the maximum spring tension, this made the ball not fly as far as we wished. This could probably be mititaged by reducing the friction in the release mechanism by making its components (shown below) out of a material with lower friction than plywood, like plastic.
