I'm looking for some advice on how to accomplish the following in ladder logic:
I have 3 inputs that are being used to command the PLC to move to 1 of 8 predefined positions. I'm trying to figure out a robust way to respond to those inputs. Ideally I want to make sure that whatever external system is controlling the inputs has plenty of time to make its changes before I start to move. For example if the inputs are currently "0,0,0" and the external system is in the process of changing to "0,1,1" I don't want to initiate a move while the inputs are in the intermediate state of "0,0,1".
Currently I just have a 1s timer that checks the state of the inputs but that still leaves the possibility that I check the state while the inputs are in the middle of changing.
The best way, in my opinion, would be for a timer to start when the system sees an input change and the PLC won't initiate the move until the timer expires. However there are a total of six events that could trigger the timer (3 inputs, either on or off). I have no idea how to design this using ladder logic.
