Help with adding an LED indicator to my fireworks ignightor

Absolutely. I'm a newbie and have been spending a lot of time at PyroUniverse.com where they have some great designs for e-firing systems. I just don't have the time or resources to put together one of those systems this fourth so I hoped to just "soup up" my very basic system a bit.

FWIW, this is one helpful and cool group - haven't had this sort of good response on usenet since way back when!

A reverse junction is very easy to damage. I doubt the series resistor would save the LED from damage.

I spent quite a bit of bench (aka prober) time investigating metal fuses on chips. [Trust me, this will become relevant.] A particular product had odd behavior after trim. It turns out the inductive kick from the wire leading from the popping circuit was damaging parasitic diode junctions on the chip. [They would be leaky, which caused problems at hot test.] The solution was to change the polarity of the zapper, so that once the fuse was popped, it would forward bias the on- chip diode, absorbing the remaining energy from the zapping capacitor. That is, the energy not used to zap the fuse. Diodes are reasonably rugged under forward bias condition, but reverse bias is another story. [Incidentally, the fuse popped in under a uS. I don't recall the rise time.]

Take a BJT and break down the EB junction on your curve tracer. If the current is kept low, say under 100uA, there isn't much damage. If you whack the junction, the transistor will be permanently altered in normal operation, should it still be lucky to work.

When you have a large reverse bias, there is a tendency for the weak link to pop. That is, the junction in question is not a point source but distributed. You get a high field, and some piece of the junction pops. Maybe a crystal defect was present where it zapped.