[sdiy] comparators vs. clamping diodes as gate inputs to microprocessor?

[Seb Francis]

Chris Muir wrote:
>
> On Nov 5, 2009, at 10:24 AM, Danjel van Tijn wrote:
>
>> Anyone have thoughts on this? Most of the solutions I have seen
>> involve using comparators but Seb's clamp diode inputs (on his
>> website) look like a  nice and simple solution (and cheap).
>
> A comparator can be pretty bulletproof. As I mentioned last time this 
> came up, the LM339 works really well for this because it's open 
> collector. You can pull it up to whatever your logic level is. It also 
> doesn't care how sharp your input is, it becomes really snappy on the 
> output.
>

I'm not sure this is relevant for microproc. inputs which tend to have 
hysteresis.  You're still going to get a single point at which the input 
registers high rather than low.

Seb