A pyrotechnic cost is about off by passing a excessive voltage via a filament inside it, melting the filament and igniting the cost. We might consider quite a lot of circuits that might do that, however maybe we wouldn’t have provide you with [Michał Słomkowski]’s resolution. He’s used the ringer crank generator from an outdated navy area phone. It’s an outdated challenge he’s shared with us because of its latest republishing on his web site.
The essential precept is easy sufficient, winding the generator fees a capacitor financial institution via a bridge rectifier. Then a thyristor is used because the set off machine, dumping the contents of the capacitor into the filament. However the full circuit has a few refinements. There’s a cost indicator circuit utilizing a few Zener diodes and an LED, and a filament tester which passes a non-triggering present via the filament from a 9 volt battery. We like using an over-the-top high-current thyristor, little question what he had in his junk field.
Maybe it’s an emblem of how far know-how has moved, that right this moment it’s surprisingly uncommon to discover a bridge rectifier or a thyristor, and constructing this machine right this moment would contain a microcontroller and possibly an AliExpress inverter module as a matter in fact.
In the meantime, ought to area telephones curiosity you, we’ve been there earlier than.
