Hi again BBM,
Although I recommended the LM358 dual opamp in place of a 741 in post #4 above, in view of the application, I would probably recommend the LM2309 (UPDATE should read, LM2903) (part of the LM339 family) dual comparator to do a proper job.
In case you aren't familiar with competitors, this is what they are all about:
(1) In general, comparators have two inputs, + and - , and an output, just like an opamp.
(2) If the + input is more positive than the - input, the comparator's output will be a high voltage
(3) If the + input is more negative than the - input the comparator's output will be a low voltage.
And, to a first order, that is all there is to comparators.
You may ask, why bother with comparators, when an opamp will perform the same function. That is true, but comparators simply do the job much better in all respects. And if you need high speeds (2nS say) only a comparator will hack it; an opamp won't even come close. In general, because a comparator is designed just for one job it does, err... comparisons very well.
Just as there is a couple of ubiquitous, flexible, and user friendly op amps, there are the LM393 (dual) and LM339 (quad) comparators. These are also components that an electronics person should have in their spare parts boxes.
The only problem is that they are hellish expensive: you could pay as much as 30 pence UK for each package.
Unlike opamps, which inevitably have push pull outputs, many comparators, including the LM393/LM339, have open collector outputs. While this gives more flexibility in circuit design, it means that you need a pull-up resistor in order to get an output voltage.
DATA SHEETS
LM393 (dual):
https://www.ti.com/lit/ds/symlink/lm2903-n.pdf
LM339 (quad):
https://www.ti.com/lit/ds/symlink/lm2901.pdf
(all comparators in the two packages above are identical)