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this is the first time I use a PLC from Unitronics.

I have a little experience with Siemens PLCs.


I have the following problem :

I have a machine which is now operated with a start/stop button. We want to add a timer function on this machine.

This machine is operated in a explosionsafe environment.


My idea was to have a SM43-J-T20 PLC in a explosionsafe box with a window, operated with a box with explosion safe buttons.

I have 4 buttons : "+", "-", "E" and "R".


With the "+" and "-" buttons I would like to set a timer on the display of the PLC, for example from 0 -> 99 minutes.

When we press the "E" button we would acknowledge the timer and when we press the start button of the machine, the timer would count down.

When the timer reaches 0, the machine would receive a stop command.

With the "R" button we can reset the timer to 0.

If we acknowledge the timer on 0 minutes, then the machine should work continuesly untill we press the stop button.


Who can help me a little bit on my way?


thanks in advance


with klind greetings



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  • MVP 2023

This was simple enough that I just threw together some code rather than try to explain what to do. Feel free to ask if you have any questions.


It may not be exactly what you're looking for, and I generally buffer inputs and other niceties that I didn't do here, but you should be able to figure out what to do from looking at this.


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