We have a fairly large system that's been built up over the years for running a fireworks show from a computer (see here for the first generation software and hardware) using a pretty simple XBee-based wireless system. I'm in the process of working on a replacement system and I'm trying to tackle one of the annoying things in the current system…which is current.
Ideally I'd like to be able to run both the local microcontroller (I'm using a version of the XBee that has an on-board Freescale) and fire the electric matches with a single power supply. The problem, of course, is that firing the matches takes all current away from the uc, causing it to reset. I've tried thinking about how to isolate the matches, which are essentially shorts in the circuit from the uc, but I'm afraid I'm woefully out of my depth in this area. I'm assuming some capacitors would be involved but I don't know exactly what it would look like. The firing current of an electric match is around 1A and extremely rapid. Ideally we'd have up to 16 matches per system. Bonus points if the solution could also be used to power an on-demand flash :).
Best Answer
You not only need to store enough energy to run the MCU, you also need to prevent it from being used up by the match as well.
simulate this circuit – Schematic created using CircuitLab
This circuit will allow the supply to charge up the capacitor, but not allow it to feed back into the supply when the match is triggered. Note that the voltage to the MCU will be reduced by the forward voltage of the diode.