Arrays, UDTs and Structures Over OPC UA: What the Client Actually Sees Insert one DINT called Jam_Count into the TR14_Belt user-defined type, put it after the State member where it belongs logically, and download to the 1756-L83E. Fault_Code moves from byte 4 to byte 8, and Starts, Run_Seconds, Speed_mps, Motor_Amps and Last_Fault_S each move four … Read more
COP and CPS Instructions on a ControlLogix: Which One Copies What A COP with a Length of 20 moved five bytes. The source was Packer_Raw, a SINT[5]; the destination was Packer_Scaled, a DINT[10]; the rung went true on every scan of a 1756-L71 and nothing faulted, nothing latched, nothing appeared in the Minor Faults tab. … Read more
A UDT holding a STRING, eight REALs, four DINTs and four BOOLs is 140 bytes, and the Data Type Editor in Studio 5000 prints that number under Data Type Size before you have written a rung. Fifty of them in a PLC recipe UDT array is 7000 bytes and one base tag, and that last … Read more
Siemens gives you a Retain checkbox and a published memory budget. Rockwell gives you neither. Here is what each one really keeps, and how to check it.
Produced and consumed tags stop at 500 bytes, and at 480 once the data crosses a network, because the transfer spends 20 of them on overhead. Try to produce an INT array and Logix Designer refuses: DINT, UDINT, LINT, ULINT, REAL and LREAL are the atomic types that go across on their own, and anything … Read more
The infeed conveyor’s GuardLogix 5580 consumes one safety tag from the case packer’s 5580, CP_Safe, and at 02:04 every night for a week CP_Safe.ConnStatus.ConnectionFaulted went to 1 for between two and nine seconds, the consumed data went to zero, the conveyor’s CROUT dropped its contactors, and the shift lead reset it and wrote “network” on … Read more
Add one Static to an FB and every setpoint in the instance DB goes to zero. How the memory reserve prevents it, how to size it, and how to recover.
Tag naming, rung comments, UDT and AOI descriptions, pass-through and L5X exports that keep a Studio 5000 or TIA Portal project readable years later.
Build PLC predictive maintenance on hardware you own: vibration and motor current inputs, runtime hours, moving averages, baselines and alarm levels.
Build PLC batch control the ISA-88 way: procedure and phase breakdown, the phase state model, recipe parameters in a UDT, hold and restart logic.
A working IIoT setup for a plant floor PLC: edge gateway choice, MQTT and Sparkplug B topics, a decoded payload, store and forward, deadbands and security.
If there are software or hardware errors in the PLC, you may not want to catch the error or stop your whole system due to the error. In these cases, you can use a fault routine to clear the fault and allow some part of your system to continue running. Failure routine runs the routines … Read more