Simulation Commands - what are those for?


[B]What are those “Simulation Commands” for, anyway?[/B]

Hopefully if you have any [B]remote I/O[/B] at all, you’re using at least a couple of these commands as part of your I/O re-enable logic. As described in the doc that comes with this free download (click here):

“The logic in the IO Enabler sample strategy is designed to automatically recover communications to any I/O unit that temporarily goes offline (that is, has communications disabled) for any reason. An I/O unit typically goes offline if there is a power interruption to the unit, which might be caused by lightning or an electrical fault in the plant. When an I/O unit goes offline, IO Enabler logic ensures the best overall strategy performance as well as automatically recovering I/O unit communication.”

[B]When else might I want to use these commands? [/B]
Would I ever want to purposely take my I/O Unit off-line? Sure. Here’s a situation that came up recently:

A professor at a university has some of our hardware in a lab (SNAP PAC Learning Centers) where students interact with the knob and switches hands-on. However, if a student can’t come to lab but would like to continue working on their assignment, the professor wants to use IP cameras and a [URL=“”][I]groov [/I]Box (since that makes it super easy to connect a camera, throw on some buttons AND let students have access via a smart phone or whatever browser they have handy).

But how would he switch from using actual the switches and knob to “virtual” gadgets (via the [I]groov [/I]interface)? As usual, we have several choices for how this could be done – including “simulating” the hardware which the students won’t actually be touching remotely.

Screenshot from [I]groov [/I]View:

Here’s what I came up with, I’d be happy to hear if you have other suggestions. The basic idea:

Besides the usual “Convenience Store” strategy variables, we add one Integer 32 flag to determine if we’re in remote mode or not; one float variable to replace the knob; & three more Integer 32 variables – one for each of the switches used: Emergency [B]alarm[/B], Freezer [B]Door[/B], and [B]Photo [/B]Sensor.

Notice in this case the OptoScript equivalent is much more compact since we can replace 9 blocks (3 condition and 6 action)…

…with just 3 lines of OptoScript code:

In case you want to copy/paste the OptoScript:

while (1) // loop forever

  // Block 1 - "Go remote?" condition
  if (IsVariableTrue( Remote_Option_On )) then 

    // Block 6 - disable communication to real inputs
    DisableCommunicationToPoint( Fuel_Level );

    DisableCommunicationToPoint( Emergency );
    DisableCommunicationToPoint( Freezer_Door );
    DisableCommunicationToPoint( Photo_Sensor );

    // Block 8 - set Fuel Level IVAL from groov input

    //  Because the Fuel_Level input point is disabled, using the command:
    // IvalSetAnalogPoint(groov_Fuel_Level_input, Fuel_Level);
    // (the command used in the Command Block equivalent)
    // would have the same result as this:
    Fuel_Level = groov_Fuel_Level_input;
    // Now update the 3 discrete values - using OptoScript we can 
    // assign the values directly (rather than needing those 3 condition blocks)
    Emergency = groov_Emergency; 
    Freezer_Door = groov_Freezer_Door;
    Photo_Sensor = groov_Photo_Sensor;
    // Block 5
  // Delay
  DelayMsec( 100 );


OptoScript + Simulation commands + [I]groov [/I]= whoo-hoo!

Happy coding,

Simulate digital input

Is there a way to simulate PID loops using PAC Sim or Simulation commands? In PAC Sim, the PID loops are automatically disabled because there is no physical brain attached. I can write simulation to, for example, decrease a liquid level from a level transmitter in a tank if the outlet valve is slightly open, and I can decrease it faster if the valve is open wider. But I can’t get the PID loop on my fake brain to do the calculations to automatically change the output, like it would in the field.

I’d like to be able to write simulation code for my entire plant to use as an offline functional testing and operator training tool. If I could get the PID loop IVALs to update like a normal PID would, then I could do this (without reprogramming the PID loop algorithm myself).