Backing Up a ControlLogix Properly, and Restoring When It Matters
Store a ControlLogix project to a 1784-SD2 card, pick the Load Image setting you need, and what an upload or a card restore will not give back at 3am.
Rockwell Studio 5000
Logix Designer, RSLogix 500/5000, RSLinx, FactoryTalk and the faults you meet on a ControlLogix or CompactLogix line.
Alias Tags in Studio 5000: When They Help and When They Hide the Problem
What a Studio 5000 alias tag shares with its base, how it changes a force and a cross reference, and the tag scheme an alias cannot fix on a 1756-IB16.
Cross-Referencing a Tag in Studio 5000 to Find Every Rung That Writes It
Find every instruction that writes a tag in Studio 5000, tell a write from a read, and work out why an output with two writers flickers on a 1756-OB16D.
Forcing an Input on a ControlLogix, and Being Certain You Removed It
Install a force on a 1756-L83E, enable it, then prove it is gone: the three FORCE indicator states, the GSV that reads force status, Remove vs Disable.
Discrepancy Time on a Dual-Channel Safety Input: What It Protects and How to Pick It
Pick a discrepancy time for a 1791ES dual-channel input from the device that drives it, know which setting the DCS instruction sees, and clear the fault.
Reading a CompactLogix Tag from a Raspberry Pi with pycomm3
Four lines of Python on a Raspberry Pi 4 read a CompactLogix tag – a REAL out of a 5069-L306ER – and nothing at either end is licensed. pycomm3 1.2.16 speaks EtherNet/IP to TCP port 44818 itself, which takes the OPC server, the Windows box it used to live on and the licence out of … Read more
Singulation on a Zero-Pressure Accumulation Conveyor: The Release Rule That Stops Two Boxes Leaving Together
On a 1.5 m zone pitch at 0.28 m/s, a 600 mm carton is invisible to both photo-eyes for 3.2 seconds of its journey between them. An upstream zone whose release permissive is nothing more than “the next eye is clear” will use that window to send a second carton, and the two of them … Read more
A Conveyor Jam Timer That Does Not Nuisance-Trip: Setting the Time From Zone Length and Belt Speed
Time it with a stopwatch before you type anything into the preset: the longest carton you run, crossing the photo-eye, on the slowest zone. A 1219 mm carton at 0.28 m/s sits on that eye for 4.35 seconds, which is why the 2000 ms that came across with the copied project trips every time the … Read more
A MSG Instruction That Actually Works: Path, Type and the Error Codes
16#0204 appears twice in the same Rockwell reference manual with two different meanings, and which of the MSG instruction error codes tables you are reading decides where you spend the next hour. In the extended error codes for error 0001 it is Unconnected message timeout. In the module fault codes it is Connection Request Error: … Read more
Two PLCs, One Tag: Produced and Consumed Tags on ControlLogix
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
Sinking or Sourcing: Matching a PNP Sensor to the Input Card You Have
PNP sensor wiring is decided on the input card’s spec sheet, and almost nobody reads that row. Under Voltage category, a 1756-IB16 says 12/24V DC sink and a 1756-IV16 says 12/24V DC source — same form factor, same 16 points, same 5V off-state threshold, and only one of them will ever see a PNP sensor … Read more
Reading a 4-20 mA Transmitter into a 1756-IF8: Wiring, Range and the Raw Value
A 1756-IF8 analog input in integer mode lands on roughly -20,030 counts at 4 mA and 30,920 at 20 mA, which are not numbers anybody memorises. If the value in front of you is 3277, the card in the rack is a 1769-IF4 or 1769-IF8 running the Scaled-for-PID data format, and none of the 1756 … Read more
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