Creating an event log in Quantum Function Block Logic


Thread Starter

Chris Iannello

At Kennedy Space Center, we are working to create a first in first out event log consisting of a date and time and a integer code representing an event in the Modicon Quantum PLC (Function Block). We speculated that we might be able to use some defined data types in Concept to create a custom type with several bytes ( Array [year month day hour min sec event_code] ). We had discussed creating a pointer system to push items onto this stack and keep a rolling list of the last, say, 20 events. Here, we figured others have already done this and NASA was hoping to see how others have implemented this idea. Any comments/ideas would be greatly appreciated. Chris Iannello Power Systems NASA Kennedy Spce Center, Florida 321-861-3276

Anthony Kerstens

Some years ago I did see a 685E with rudimentary fault logging logic that employed several parallel fifo's to log multiple registers of data associated with a particular fault (fault ID, date/time, pressures, etc.). However, because of the nature of the system, the fifo's quickly got filled and the PLC needed to fire the data out to a dedicated printer in order to capture all the faults. I suppose they could have used longer fifo's, but I was onsite for other work. These days, there are more sophisticated technologies available for data logging. Anthony Kerstens P.Eng.
In Concept 2.2 (I can't verify for earlier versions) there is a built-in FFB called FIFO. The online help indicates that the stack can store upto 2000 bytes of data, so you could store 20 events of 50 integers (2 bytes each). It appears that using an integer array should work fine, but I'm not sure if you could create your own data structure or not. Check the help in Concept 2.2 for more info. Don Zunti, P. Eng. Delco Automation Canada