Here are a couple of pictures of the breadboard setup:
The first picture is of the breadboard itself. The components are marked and the green dots are where the wires from the photointerrupter go.
Breadboard (click for larger, more legible version)
The second pictures includes the photo interrupter mounted to the barrel using duct tape (what else). Note that this was before the Max7219 and display was mounted:
Breadboard and business end of airsoft gun (click for larger version)
Jens Willy Johannsen
greetings , Im building something like this but the only thing Im missing is the phototransistor , can You tell me the name of the one You used please?Thank you very much greetings from Italy