Using IEC timers in Siemens SCL source files

[p17061]

Hello,

I want to create a FC function that uses SCL code that checks deviation of a controllers actual measured value from its setpoint and then gives an alarm if the actual measured value is above or below the setpoint by a certain %. The alarm should be delayed by 15 seconds. I have some code that I am trying to use but I am not sure how to incorporate an SFB4 TON into the SCL source code. Can someone help me to understand how to use the SFB4 so I can trigger it within the function and give the alarm after 15 seconds?

VAR_INPUT
nFlowSetpointNs: INT; // Flow Nominal Setpoint
nFlowMe: DINT; // Flow Actual Measurement
nFlowDevUpPercentNs: DINT; // Flow Deviation Setpoint Upper Percentage
nFlowDevLowPercentNs: DINT; // Flow Deviation Setpoint Lower Percentage
tFlowDevTimeDly: TIME; // Flow Deviation Time Delay Nominal Setpoint
END_VAR

Var_OUTPUT
bFlowDeviationAlarmSt :BOOL; // Flow Deviation Alarm Status

END_VAR


BEGIN

IF nFlowMe < nFlowSetpointNs * nFlowDevUpPercentNs OR nFlowMe > nFlowSetpointNs / nFlowDevLowPercentNs
THEN bFlowDeviationAlarmSt := True;
ELSE bFlowDeviationAlarmSt := False;
END_IF;

Thanks
Peter

 

[L D[AR2P#0.0]]

Don't use an FC, use an FB and incorporate the SFB as a multiple instance.

Here's a previous example: http://www.plctalk.net/qanda/showthread.php?t=38840&highlight=scl

 

[p17061]

Is this the best way when I need to create alarms for about 30 different devices? I wanted to use an FC so I could call the FC in a function block and just insert the flow setpoints, actual flows, and alarm status' PLC tags into the FC IN and OUT variables and let the FC handle the comparing of setpoint vs. flow, count the 15 seconds and trigger the alarm.

 

[PeterW]

If you are calling the FC 30 times then you cannot use an FB/SFB inside as the IDB would be fixed.

You can call the FB 30 times from within a main FB and make the called FB a multiple instance.