Step 7 Variable issues in the PLC program.

[larry]

Zuviel Werbung?
-> Hier kostenlos registrieren

According to these, I tried to remove the M200.1 variable from the AND operation in network1. Delete or not delete this variable, the function is the same. The variable M200.0 "emergency stop relay reset" results are all 1 ， What is the meaning of the author writing about this variable ？ I use s7 400 and wincc 7.5

 

[L4s3r73k]

Reading your question I do not understand, what your problem is.
But first things first, what I understand from picture....

1: There is some "E-Stop reset" button with a dynamic condition to permit or deny that this button gets pressed.

2: The button has a click event with script which contains a tag which gets set but not resetted by the script.

3: The "button_pressed" tag from (2) and the permission bit is declared in the HMI connection.

8: The permission for the button is only true if there is not the E-Stop resetting and from somewhere the M200.1 is coming.


I dont fully understand this but there seems to be a logical error. Maybe the M200.1 equals the feedback contact of an E-Stop Relay (which seems to be inverted E-Stop OK Signal.

 

[larry]

Zuviel Werbung?
-> Hier kostenlos registrieren

Reading your question I do not understand, what your problem is.
But first things first, what I understand from picture....

1: There is some "E-Stop reset" button with a dynamic condition to permit or deny that this button gets pressed.

2: The button has a click event with script which contains a tag which gets set but not resetted by the script.

3: The "button_pressed" tag from (2) and the permission bit is declared in the HMI connection.

8: The permission for the button is only true if there is not the E-Stop resetting and from somewhere the M200.1 is coming.


I dont fully understand this but there seems to be a logical error. Maybe the M200.1 equals the feedback contact of an E-Stop Relay (which seems to be inverted E-Stop OK Signal.

Whether I delete this variable or not, the task will be completed the same way. The value of m200.0 has always been 1. AI explains as follows:

• HMI (WinCC): Responsible for human-machine interaction. It controls the button's operability based on the PLC's "reset conditions met" status and sends the press signal to the PLC when the button is operated.
• PLC: Responsible for the core safety logic.
  • Determines if the "reset conditions" are truly met.
  • Receives the "button pressed" signal from the HMI.
  • Executes the critical logic: Reset Action = Reset Conditions Met AND Button Press Signal.
  • Performs the actual reset operation (e.g., resetting safety relays, clearing E-stop status bits, etc.).

Therefore, when writing the secondary E-stop reset logic in the PLC program, both are indispensable: you must include both the "reset conditions met" and the "button press signal" and connect them with an AND. Writing only the button signal creates a serious safety hazard. HMI disabling is good user experience and a first line of defense, but the AND logic in the PLC is the essential final safety barrier.

Is this explanation reasonable?

 

[L4s3r73k]

If the value M200.0 is always 1, there can be various reasons:

1. There is a bit(field) in the cpu defective.
2. The word or bit gets elswhere written in the cpu or external.

As you see in the logic posted, the M200.0 only can be set when there is an true signal of the HMI and the the E-Stop relay not energized which will cause the True signal in the feedback circle. I do not know If I do make me understandable.

Normally you have some E-Stop relay you energize when E-Stop is okay/released. And this relays have feedback contacts which have the inverted state of the relay itself. So I am very very sure that this logic we see, the M200.1 is this feedback. So the logic only accepts an E-Stop Reset, when the E-Stop has been caused. So if M200.0 is always true should that mean either one of the upper reasons or there is the Estop Reset Signal Signal always true from HMI while the mentioned feedback is also true. Last also can be a malfunction of the contact itself that it is stuck.

Please observe. But for helping more I'd need more information.

 

[DeaD_EyE]

To find the ghost in the machine, look for assignment list.

Ger: Select the CPU -> Menu: Werkzeuge -> Belegunsplan
Eng: Select the CPU -> Menu: Tools -> Assignment List


PS: By the way, you can switch the language in TIA Portal.

 

[JesperMP]

Zuviel Werbung?
-> Hier kostenlos registrieren

We cannot see where M200.1 is set.

To find the ghost in the machine, look for assignment list.

I think it is better to look in the cross reference. Just hit F11 when M200.1 is selected.

The tag symbol "Reset emergency stop" is also ambiguous.

I am guessing M200.1 is some logic to control that M200.3 "WinCC_allowed_to_press" is set, and that triggers the display of the reset button in the HMI. If you find where M200.1 is set via the cross reference, then it will probably be clear.