On 4/18/2013 5:13 AM, Michael A. Terrell wrote:

wrote:

Speculation is that the bombs were set off by cell phone. I wonder if
a cell signal would penetrate the metal of a pressure cooker. Mine
barely works in my metal shop building; with the doors open. Any
experts want to weigh in?


Don't most have an alarm clock function?


From the photos, it was just a small timer and battery.
Printed circuit board even.

I did some research (way back then) for my (licensed)
pyromaniac boss for a laptop controlled fireworks sequencer
circuit.

We found that TTL logic levels would safely and reliably fire
electrical squibs.

I still put a ground bar relay in it - just because I'm fond
of all my fingers!

But it did work quite well.