Subject: Request for Support: PLC Alarm Output for SCADA Communication Loss

Dear Einstein,

Greetings.

We are currently operating 8 water wells at various locations, each equipped with a Siemens S7-1200 PLC. These PLCs are connected to our SCADA system (WinCC V7.5 SP2) via WiFi antennas.

We have been facing a recurring issue where the PLCs intermittently lose communication with the SCADA system. To restore communication, we typically restart the WiFi antennas manually, which requires physically visiting each site — a time-consuming and inefficient process.

My question is:

Is it possible for the S7-1200 PLC to detect a loss of communication with the SCADA system and trigger a digital output as an alarm?

I intend to use this digital output to activate a relay that will restart the WiFi antennas automatically when a communication failure is detected.

Your assistance and guidance on how to implement such a feature (if feasible) would be greatly appreciated.

Taha Mohammed

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Split from S7-1200 leds ( maint, Stop, Run) are flashing continuously.

If the SCADA system has a built-in watchdog feature, use that to continuously toggle a bool tag controlled by the scada system.  Then when that bool tag is stuck in either ON or OFF for too long, you know the scada system is offline or inaccessible - both of which would seem to indicate action is needed.

There are other ways that come to mind, but that is the simplest.

If your scada system can toggle a bool tag every other data update (or less often if you find it suitable), you can then be assured the scada system is online.

Capability of the SCADA system to control rather than simply monitor would be a SADA system I suppose, because without Control, SCADA becomes SADA, which is SAD Always (to me).

Alruba

Subject: Request for Support: PLC Alarm Output for SCADA Communication Loss

Dear Einstein,

Greetings.

We are currently operating 8 water wells at various locations, each equipped with a Siemens S7-1200 PLC. These PLCs are connected to our SCADA system (WinCC V7.5 SP2) via WiFi antennas.

We have been facing a recurring issue where the PLCs intermittently lose communication with the SCADA system. To restore communication, we typically restart the WiFi antennas manually, which requires physically visiting each site — a time-consuming and inefficient process.

My question is:

Is it possible for the S7-1200 PLC to detect a loss of communication with the SCADA system and trigger a digital output as an alarm?

I intend to use this digital output to activate a relay that will restart the WiFi antennas automatically when a communication failure is detected.

Your assistance and guidance on how to implement such a feature (if feasible) would be greatly appreciated.

Taha Mohammed

Dear Einstein,

Thank you for your reply.

I wish to understand my issue.

I want to restart wifi antenna automatically via PLC according to communication loss.

I want to know if PLC has this feature to toggle digital output when communication lost.

Also how can I detect or enable watch dog feature?

Also please provide me with other ways

Dear Einstein,

Please provide me with a VB script code for wincc V7.5 SP2 .

This code send word value every 20 seconds to PLC, I will use this value to check communication from PLC side and trigger digital output if the PLC didn't receive this word value.

I appreciate your support and cooperation.

Taha Mohammed.

[snip]

Hello Alruba

it is a quite simple task in WinCC V7

-> use A global VBs or C Action with a cyclic trigger as you need:

(for example in VB Script)

How you can write a Tag with VB Script you can read in the help system:

https://support.industry.siemens.com/cs/ww/en/view/109792622/118089674379

And you have to activate the Global Script Runtime in the startup list of your WinCC Project of course.

With this information you should be able to get your handshake work on WinCC side

Bye Murof