Waaaaay back in 2008, Eiki Martinson wanted to do a fancy fireworks show for new years eve, but he also wanted to be able to sit back and watch it instead of scrambling to light all the fuses and run for cover. To pull it off, he was going to need a controller. Why go buy something that has been tested and designed by pros when you can cobble somthing together in your living room? Together with a few friends, he put together the board seen above.
On to the engineering, then: the microcontroller is an Atmel AVR, a 90S8515 running at 8 MHz to be exact (obsolete chip, sure, but I had one lying around—the next version uses an ATMega16 instead). This accepts RS-232 serial via the MAX-232 driver, interprets the byte it receives and fires the appropriate squib by pulling the gate of a NMOS high. The MOSFETs are STI P16NF06L’s in TO-220 packages, good for 16 amps of drain current each; this high-current capability is built in to accommodate some types of very low resistance squibs that need a lot of current to fire.