Storing Elapsed Time of IEC TON Timer

Simplest solution I can think of:

1. Insert a new network above the current TON network.
2. Create TON enable request logic.  Maybe call it <myTimer>_Enable_REQ.  Anything currently to the left of the TON, put that on that newly created network in step 1 above.
3. In front of the TON, insert a NO contact with <myTimer>_Enable_REQ as the only thing.
4. Search for all occurrences of "<myTimer>_DB".Q.  Insert the following logic right after every reference to the TON's instance DB Q:

• NO contact with <myTimer>_Enable_REQ and then a MOVE "<myTimer>_DB".ET to <myTimer>_Last_ET

Use a N-TRIG or -|n|- or negative edge detector to detect when <myTimer>_Enable_REQ goes off.  When it does, divide "myTimer"_Last_ET by 1000 and store to "myTimer"_ET_for_HMI.

In this way, you can be sure not to miss capturing the latest elapsed time (since the PLC updates the timer DB every time it encounters the Q in logic).

FYI, this should work for s7-1200/1500 just fine since they use IEC TON timers.  I do not know how the s7-300/400's use IEC TON timers, so you may need to refer to F1-help if it does not work.

Deuce79

I have an S7-300 PLC with a program written in TIA Portal V15.

The program has a IEC Timer that I use to track a heating time.  I would like to move the elapsed time right before the timer resets to another memory location so I can display it on the HMI.

The timer itself works as is.  The ET is moved a DInt memory value. then it is divided by 1000 to convert it into seconds.

I've tried Negative Edge inputs and N_Trig to move the elapsed time but it doesn't store properly or makes the timer display incorrectly.  I did get it to where the timer times properly but the moved value is 16777216 or 2^24 and shows as "####".

Thank you.

Very close.

On network 17, rung 1, take the "timer enable" and the move block and shove them down to a new rung with a "timer".Q NO contact in front.

I am superstitious about forcing the NO .Q output from a TON at least once.  Supposedly all the current PLC firmware and TIA Portal versions state you do not need to do this.  However, there is no guarantee someone with older firmware and portal version would want to do the same thing and suddenly it would not work.

By having the NO ton.Q right after the TON (and having nothing to the right of the TON), it supposedly works on all platforms / portal / firmware versions.

Deuce79

Is this what you meant?  I originally had %M2.7 starting the timer %DB16.

I won't be able to download this to the PLC until tomorrow.

Thanks again for your help.

Simple solution is to delete the tags from the PLC tag table, then right click on them in logic, select Define tag, and let Portal assign the first available continuous memory to them.

Better way is to create a DB and create the tags in there.  It is impossible to overlap tags using a DB to collect them.

Deuce79

What should they be instead to avoid memory overlap?  I had heard that these memory bits take 2 spots in memory, but am not sure how to avoid the overlaps.

Thank you.