This pyromusical system, like most, is a collection of firing modules. I have given these modules the name "SmartRail" because the way I built them they look like rails/slats with a built-in microprocessor board.
See a SmartRail during construction and another after completion. Hillbilly engineering at its best -- microprocessors and duct tape.
Each SmartRail
The microprocessor board on the SmartRail is controlled remotely by the laptop computer. It receives commands from the laptop and sends data back to the laptop as requested. With this design we can use the laptop to remotely control the firing circuits, the continuity circuits, and can even measure the voltage on the 9 Volt battery and the 5 Volt capacitor to make sure they are at acceptable levels. This microprocessor board also has a non-volatile memory that defines when each cue should fire.
When the show starts, the laptop will send a command to the SmartRail to start its internal firing clock. This clock is synchronized with the laptop's own internal clock. As the clock reaches the appropriate time to fire each cue, the microprocessor will check for a heartbeat and then fire the cue.