Question disable button after emergency stop

[mathieulev11]

Hello, I have plc Schneider TM241CE40T with the hmi HMIS5T.
Do you have idea how to disable a button after an emergency stop to vijeo designer ?
My problem is when the emergency stop is activated and the operator toggle button, if is reset safety, the action executes.

I would like what the button is deactivated after my security is loss.

 

[the_msp]

Welcome,

I don't work much with Schneider, but I don't think that is a safety PLC. Safety should either be hardwired or implemented with a safety controller.

If you are attempting to e-stop and reset with a standard PLC and HMI, don't walk away from the job, run.

 

[ASF]

I don't think that's the issue here. I think what's going on is that:
1. Operator presses emergency stop button (hardwired safety circuit)
2. While emergency stop button is pressed, operator presses button on HMI to start a sequence. Sequence does not start because hardwired emergency stop circuit is tripped
3. Operator resets hardwired safety circuit
4. Sequence automatically starts because button had already been pressed on the HMI

This is not good - in machine safety standards it explicitly calls out that equipment should not restart upon a safety system reset.

So, OP wants to hide a button on the HMI while the safety circuit is tripped, so that they can't press this button, so that the machine won't restart when the safety circuit is reset.

I don't have any experience with the equipment specified, but I'm sure there is a way to animate the visibility of a button, such that it is invisible when the safety circuit is tripped (provided that the PLC has an input signal to know when the safety circuit is tripped).

However, my very strong advice would be that this is not the correct approach, or at least, not a complete approach. A HMI takes a second or two to update - what happens if the e/stop is pressed and the operator presses the button at the same instant, after the safety circuit is tripped but before the HMI updates to remove the button? What happens if a SCADA system can also write to the button bit in the PLC?

The best approach is to modify the PLC logic to ignore the button if the safety circuit is not healthy, or to continuously force reset the machine sequence/action while the safety circuit is not healthy. Then, no matter what buttons are pressed or signals sent, the machine will not restart upon safety circuit reset.

Also, OP, welcome to the forum!

 

[mathieulev11]

Hi, thank for all your reply !

ASF, Yes that's is exactly my problem.

I looked in the configuration of the button, I did not find how to deactivate it from a bool. Maybe there is a scripted way.

However, I saw that there was a condition that allows to vanish the button with a bool or condition. I will try this.

 

[JesperMP]

Dont hide the button or any such trickery to achieve the safe and reliable start function.

In the PLC code, disable the start function when there is an emergency stop. The PLC should know when there is an emergency stop by for example an aux contact from the safety relay.

Also, activating the start function should be by a rising edge of the HMI button. If the operator is constantly pushing the button, or the bit from the HMI is hanging for some reason (i.e. the button is pressed and the HMI then crashes), it will have no negative effect such as activating the start function unexpectedly.

 

[mathieulev11]

Hi JesperMP, my safety relay is connected in dual channel to my PLC. Also, in my program, the PLC outputs cannot be activated when there is an emergency stop.

And yes, my buttons are almost all rising edges.

However, I have just understood that I will have to put all my buttons with a rising edge with bit sets, reset, in my program with the series emergency stop. Like that, impossible to start anything.

Thanks for the help !