No, I believe he stated that the program starts with the NO contact ( I believe this is tied to the physical input) already True and in FB and in the bit in IDB and the result of this is that the timer doesn't see the transition and doesn't time out again meaning the output remains false.
TIA IEC timer: unwanted behaviour
- Thread starter DairyBoy
- Start date
No, I believe he stated that the program starts with the NO contact ( I believe this is tied to the physical input) already True and in FB and in the bit in IDB and the result of this is that the timer doesn't see the transition and doesn't time out again meaning the output remains false.
Tanks, L D[AR2,P#0.0], new info for me to learn there.
Kalabdel, you have read it correctly; in my case the FB instances are for scaling analogue inputs from process sensors and incorporate four adjustable (e.g. via HMI) switching thresholds. The scaled value is compared with the presets and in each case, debounced by a TON. The Q of each TON is the output for that threshold. So there will be many instances where the TON En conditions will be true when the processor starts running following a power cycle, e.g. tank levels.
The controlled plant in this case includes a section which gathers and pumps collected rainwater between silos. This area runs 24/7 and is expected to resume operation following a power interruption. However, as it's still at the commissioning (and wish-list developing) stage, there are times when I need to modify FBs that necessarily impact on their iDBs.That's when I first encountered the non-restarting timer problem.
Kalabdel, you have read it correctly; in my case the FB instances are for scaling analogue inputs from process sensors and incorporate four adjustable (e.g. via HMI) switching thresholds. The scaled value is compared with the presets and in each case, debounced by a TON. The Q of each TON is the output for that threshold. So there will be many instances where the TON En conditions will be true when the processor starts running following a power cycle, e.g. tank levels.
The controlled plant in this case includes a section which gathers and pumps collected rainwater between silos. This area runs 24/7 and is expected to resume operation following a power interruption. However, as it's still at the commissioning (and wish-list developing) stage, there are times when I need to modify FBs that necessarily impact on their iDBs.That's when I first encountered the non-restarting timer problem.
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Yeah, I see what he stated, bu I don't believe it. I've done hundrets of 1200's and a dozen 1500's and I think I'd have some problems by now if this was the case..
I do this on most of my programs (with s7-1200, but it has the same IEC-TON) and I never had a problem. Can you post your timer call, please?
moggie
Lifetime Supporting Member
Probably not related to your problem (?) but still worth a read
https://www.dmcinfo.com/latest-thin...eshooting-your-siemens-simatic-s7-1200-timers
https://www.dmcinfo.com/latest-thin...eshooting-your-siemens-simatic-s7-1200-timers
moggie, Thanks for that. Not strictly relevant but a perfect example of how platform quirks can leave you scratching a hole in your head before even getting to the application debug. This is only my third Siemens application, the last one being about three years ago, so it's a steep one each time.
S7-300 had at least IEC timer issue with t#0s. Timers don't time never with that time.
On 1200 it is at least different, and IEC TON with t#0s works.
You maybe need to check that it isn't case on 1500.
When you load DB block, what is timers setpoints. Can it be t#0s on one scan after download?
Also, what if you change to shared IDB with enought spares to TON timers, then you don't need make modifications to IDB of TON timers and you make modifiactions to FB and Ton timer IDB different time
On 1200 it is at least different, and IEC TON with t#0s works.
You maybe need to check that it isn't case on 1500.
When you load DB block, what is timers setpoints. Can it be t#0s on one scan after download?
Also, what if you change to shared IDB with enought spares to TON timers, then you don't need make modifications to IDB of TON timers and you make modifiactions to FB and Ton timer IDB different time
I agree. I've played with his code and tried everything possible to recreate the issue he described on transition from start-stop-start and could not. Interesting nonetheless.
I don't have 1500 CPU, but I understanded that problem was after downloading IDB and FB modifications to CPU, not normal boot.
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