The basic concept for this project is a matrix of individually switchable terminals that will be connected to electrical firework igniters. The igniters don't need a ton of current, but given all the noise that must inevitably result from firing, I chose to switch the matrix using opto-isolated relay boards.
The first revision uses a pegboard substrate for the matrix. This is incredibly cheap, but a lot of work to solder. Since I had a lot of time to think while soldering, I was able to come up with a design that can be constructed out of reasonably-sized PCBs.
Another interesting improvement involves the use of CAT5 and RJ45's to connect the matrix to the igniters. This will need some testing as I'm unsure if the RJ45 connectors will withstand the currents involved.
Video of V1 firing: https://flic.kr/p/viXGJE