[sdiy] gates and clock inputs to a microprocessor

[Danjel van Tijn]

> on the Arduino module i used MC34072 comparators with the threshold set to
> 1.2v or thereabouts, on digital inputs and outputs. works fine. the opamps
any reason for this particular opamp over say the lm741/747?

> are powered from a unipolar supply so there's no negative voltage
> possibility.
makes sense. What about protecting the input pins from negative voltage?


> someone correct me if i'm wrong here, but the pullups only come into play
> when there's nothing connected to the input. it's to prevent the pin from
I was wondering about that... I did see a lot of designs that used
100K pulldowns though..


> on the analogue inputs & outputs i used opamps with scaling and biasing to
> convert the Ard's 0-5v voltage range to +/-5v at the outside world. this is
> so that an Ard LFO sketch could have a bipolar output, and that bipolar
> input signals would behave "properly". just like an analogue module.
for me I am only outputtin unipolar gates but they should probably be
scaled to 0-12V ompamps should be fine for this app.

cheers,
    Danjel