jeffaward

I am brand new to PLCs and Visilogic. I am looking to upgrade a punch press system to use a PLC and eventually add other aspects into the PLC control like low lube and part detection. This is my first attempt at using/programming a PLC so I want to start with the basics. I wanted to share my thought process and see if perhaps anyone might be able to give me encouragement or see an error in my thinking I attended 2 days of a Unitronic seminar so I have a general understanding from the exercises but no real world experience with programming. So here is my situation.... I have a Vision 350. Once my system is started, the V350 is to signal my servo feed. The feed will take this signal, close a switch and it will cycle. It will send a 24 vdc signal as it is in motion which I want to send to the V350. Once the feed has stopped, the signal will drop to 0 and the V350 will then move to the next rung and signal the press. I do not have the particulars on what the press will send but I am assuming it is similar to the feed for now. Once the press has cycled, the signal will drop to 0 and the controller will start the process again. Since each of my units have "brains" to determine their feed length and single stroke properties, I believe all I need is to set a direct contact on the ladder to send a momentary signal to start each unit. What I am unsure of is what element needs to be used when looking for the signal to drop to 0? Is this a negative transition or perhaps something that is directly related to the physical reading of the input...a comparison function? Any thoughts are greatly appreciated. Jeff