Seimens S7-200 history log after power loss

Alac

Member
Join Date
Mar 2016
Location
Gatineau
Posts
6
Hi all,

I am having a major fault on a S7-200. The fault always happens on weekends when no one is there to assest the situation and the plc is in a federal goverment building where it is not accesible on weekends. Every monday morning, an operator cycles power to the plc as they need the booster pumps to run for the week. If I look at the S7-200 manual, it says there is a history log of major CPU events but a colegue of mine tells me that the plc clears the history log when power is cycled. I am looking for a second oppinion as my colegue's info was from a shady source and not from experience.

From the manual:

"The S7-200 maintains a log that contains
a time-stamped history of major CPU
events, such as when power is applied,
when the CPU enters RUN mode, and
when fatal errors occur. Your time-of-day
clock must be configured in order to get
valid time and date stamps on the log
entries."

It says nothing about the power having to stay on to keep the logs. I know they say 'maintains' but it can be interpreted many ways. I thought that having a working baterry would keep the history log buffer alive, even on a power outage(in this case a 5 sec power outage) so that the logs are still available after a power loss.

Any insight here is apreciated.

Also, any insight as to why the plc is getting faults only on weekends would also be apreciated.(there are timers in the program but maximum timer time is 25 mins and nothing to my knowledge is different(inside and outside variables) from weekdays to weekends) It might also be a weird coincidence but it has happened 3 weekends in a row.

Thanks!
 
The picture to the right of the text you found might help, it shows Power Up and Transition to Run. It couldn't have those if it didn't store the data through a power cycle. I happen to have an S7-226 on the bench and checked that it matches the manual. It may be different in earlier firmwares.

As for why things are different at the weekends??
You are normally looking at things like where the janitor plugs in his oversize vacuum cleaner.
People 'fiddling' with the system because of boredom, 'what happens if I take this wire out?'.
Or power supply variations, the voltage will probably be a lot higher over the weekend, not so many lights or computers switched on.

Event History.jpg
 
Hi, thanks for the input, I went to see the machine today as I had some updates to do on the program. When I went to check the history log, the button was gray shaded (not available). No faults were in the memory neither. Maybe it is only available after a certain firmware version. It is currently running firmware version 1.23 which is not up to date. I tried many different things to have the button become available but nothing worked. I will check the manual to see if it is possible to update the firmware and maybe the log will become available afterwards.

Does anyone know what program is needed to update the firmware if at all possible. We have the basic software package that came with step7 micro/win.

I forgot to mention that an operator panel (op3) was connected to that plc but not used. The op pannel had an old program in it that was out of date. It wasn't programmed in with the plc. I disconnected it and I will wait until after the weekend to see if it changes anything.

Thanks!
 
There is a very little chance that someone is actually fidling with the machine as it is locked in a cab, locked in the sprinkler room, locked behind another door in the mechanical room. I would rather put my money on the power supply or op3 panel being the problem.
 
The PLC I have on the bench is firmware 2.01, I don't know when they added the History section. You can't upgrade the firmware for the S7-200 range, apart from by replacing the PLC.
 

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