USB (Re: Next completely OT topic:)

But that is not part of the requirement. Adding unnecessary feautres is often a way to overcomplciate things and end up with a poor design. As you might have guessed I regard the microcontroller as by far the most complicated solution. There are far too many components involved (think of all the transistors inside that microcontroller), and for me the design time would be by far the longest. Of the other 2 solutions, it's not so celar which is the simpler one. The 2 transistor circuit certainly has the fewest active components. But it's harder to design than the 555 circuit, and the 555 is not hard to fully understand (I sometimeswonder if anyone actually reads the 555 data sheet rather than jsut using the ocmmon circuits, it's well worth doing that). Practically, which I used would probably depend on the components I could quickly find. -tony