I'm looking for a simple way to make it impossible to switch (activate and deactivate) a output (Q1) with a TD Function key while one other process is active/running.

This process is the clearing/purging of the buffer tank (a valve is opened and a vacuüm-pump is switched on), when this output (Q3) is activated the output (Q1); the power supply for the mass/flow-controllers is switched off. This is working, no problem here.

But this power supply is also a external readout-controller, and the PLC is programmed that this device which is powered via Q1 is on by default but may be switched off and back on with TD Function key F1. The problem is that the user is able to switch it back on when it should stay off and then when the clearing/purging for the buffer tank is done the program should switch the power supply (back on) again but then it will switch off again, which is not what we want.

To summarize: switching with F1 should be suppressed when Q3 (clearing/purging process) is already active. What would be the most simple way to set this requirement for F1?

Thanks, I've tried it and it's working almost like it should.

So now it's working like this.

Any other ideas or pointers for a possible solution to get all 5 points covered?

ixo65

I hope, this is want you wish...

  Works like a charm, just perfect. 

What would this forum be without you and your input, really? Amazing, thank you very much.