555 IC Project - 'Red Alert' Siren query.

[Yorkie]

Thanks for that useful additional info Mark.

Can't answer the other points - I didn't build it myself - I just designed and etched the PCB for a chum who then built it, having originally built it (unsuccessfully) on strip-board.

I'll pass on the info about the piezo sounder having its own driver.

Amazing the breadth of uses to which 555s can be put which go far beyond timers and sound generators - a mountain of stuff on the net about them, including on youtube (stepper motor/servo/DC motor controllers etc). Despite their oft mentioned vices and limitations, it's easy to see why it's still in use several decades after it made its first appearance.

I guess that these days, to many experimenters 555s yesterdays news, with PICs, Arduino etc coming more to the fore, but for simple souls like me...