TON_R Retentive Timer
Hi,
I am trying to use a TON_R (Retentive Timer) to turn on and off based on the status of a bit. However I cannot find the "Power On/Off" bit of this timer. That bit seems to be what enables the timer.
As you can see from the picture I attached, the IN input does not really enable the timer therefore I can't use that input to control the timer status.
How can I enable/disable the timer using any bit or input?
Thanks,
Diego Villanueva
Comments
Hi Diego,
If you ignore the "Power" part of the graph, the timer behaves identically to a standard On-Delay Timer (TON).
The "Power" status indicates when the PLC loses power, so there is no "Power On/Off" bit in the software.
The IN input controls the timer in the same way as for a standard TON timer - that is, the Q output goes high precisely "PT" (time) after the IN input goes high.
If you are looking to "suspend" the timer while it is running (i.e. while the IN input is high), then you can achieve this with a standard TON timer by not executing the timer function (e.g. jumping over the TON block) on the "suspend" condition. This is easiest to do in ST, but it is also possible in LD using the JMP instruction (and it will be easier in LD once PLCnext Engineer supports EN/ENO, in a future release).
If this is not the timer behaviour you are looking for, please let us know and perhaps we can suggest a more suitable type of timer.
~ Martin.
Actually I need to correct the accepted answer here.
I have just tried what I suggested, and I was wrong about the way that the standard TON timer behaves.
When a running timer is not executed, the elapsed time does not increase, but as soon as the timer is executed again the elapsed time jumps to the value that it would have been, had the timer never been suspended. So, the TON timer cannot be "suspended" in the way that I suggested (sorry).
I can't see any obvious alternative, but perhaps someone else has a solution.
~ Martin.