I am sure this topic has been addresses before, but I was not able to find references by searching and there were no similar examples/tutorials.
Perhaps someone can point me to a prior discussion or an example.
I need to control a geared AC motor for up and down motion of a small lift to two end point switches (top & bottom).
If I use polarity reversing relays, I need to make sure that both up and down (HMI) buttons are not pressed at the same time.
Questions:
What's the best way to implement a tri state switch -- up, down and neutral or do a lockout of the unused button?
Should I do polarity reversal in the PLC or wire up two double pole relays (the old fashioned way)?
Thanks!