Hello,

If you want a two comparator circuit, have a look at this setup:


This cricuit is used in a voice modulator from the Dalek forum as sound to light circuit.

Bertus

 

The delay between the signal crossing and the interrupt launch is just some nanoseconds. But the problem was if the signal starts rising or falling. The solution is work with 2 comparators, for upper and lower limit.

Indeed. But now I recall a system that I inherited from a previous engineer that ran the analog signal directly into a digital device, a CD4538 one-shot. That solution was to have 2 stages, each with a gain of 1000, in front. Any signal produced a burst of distortion that was an adequate trigger. Crude but quite effective.