Quote Originally Posted by mackrackit View Post
How would a 7805 be a problem? I would think it would actually clean the signal with a cap or two.
The cap is even worse. It can hold the input signal in a given state and cause false sensor readings. When it comes to PLCs, do it right and use optos for input and either optos or solid state relays for the outputs. The last thing you want is to go through the programming over and over trying to figure out why your timings are wrong.