OSR, me, and my photoeyes

[cwal61]

Addohm post #7:

Here is the logic I've already been using. It works great for the leading edge detection. [highlight]I need it to ignore the trailing edge detection.[/highlight]

He is only interested in the leading edge. He can add debounce timers if needed.

 

[Lancie1]

CWA, Those leading and trailing-edge comments confused me too. Usually that would refer to one or two photoeyses that are looking for the beginning or ending edge of a part. I don't think that is the situation here. Look at the pictures - the photoeyes are stacked one above the other. I think Addohm is talking about the fact that the PEs are not exactly in line, or may get knocked out of alignment due to flimsy supports. Then one of them randomly becomes the "lead" PE and the other lags in activation by some small time period. In this case leading and trailing seem not to be referring to a spot on the part, but instead to which PE is being activated first.

What I would like to know is why are there two PEs? Is it redundancy in case one fails (one detection out of two is good enough)? If so, then the logic again needs to be different - the two PEs in parallel (OR logic) as in Post #14 may be all that is needed to latch the Knock-Off relay. Maybe some parts are taller than others, and the top PE never activates, in which case the logic again has to be something else.

 

[cwal61]

Lancie, I know. A picture of Parts not moving would clear up some questions or a diagram of Situation. I took it that he is trying to detect bad form not height. That's why I think he is looking at Leading Edge.

 

[Lancie1]

That's why I think he is looking at Leading Edge.

I think that would mean in this case to "only look at whichever PE gets triggered first (whether it be Bottom or Top or fluctuates between the two, and ignore the other one)". If that is true, then the logic is fairly simple.