I have two dynamically tagged momentary button for each of this START and STOP bit. Some reason, most of the time, B10.0 get stuck and latched in PLC, this causes not able to shut the motor down. Its control value is assigned to its respective tag as bidirectional with 2.5 sec, but still it gets hung up.
Any one experienced this type of problem or I am doing some thing wrong. ?
Quick, someone summon @pturmel to explain why momentary buttons are terrible!
edit: this will have to suffice until he shows up
If you’re not doing press and hold to move type control, you want the HMI to set the command and the PLC to reset it; don’t rely on the HMI to reset it (for many reasons). If you were doing press and hold to move style control, it’s more complicated.
This thread, going back some years, is the most detailed discussion of the problem:
Another thread on this issue -- somewhat heated at points:
Just out of curiosity, which PLC is this being run in?
Westlam, it is on SLC 500…
Daryl, neither your solution here, nor your near-identical post over in this topic, actually make momentary buttons release reliably when the button is released. Your solution simply limits the damage from a failure to reset, and arbitrarily limits how long a user is allowed to jog their machine with such a button.
I made this to deal with the issue. I've found that when the buttons get stuck, attempting to force the PB tag low doesn't work since it's being held ON by the button still.
The correct answer is to not use momentary buttons in Perspective. In Vision, the correct answer is to use a fast repeating and incrementing write message to signal "still pressed" to the PLC.
Yeah I understand this is a band-aid to the problem. Thank you for the response.
