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.
PLC & HMI
Every PLC and HMI tutorial on plctr.com: project setup, ladder and structured text, communication, troubleshooting and commissioning, written from the plant floor.
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.
A Safety Relay or a Safety PLC: Where the Crossover Actually Is
Count the safety functions before you pick the box. Where a 440R relay wins, where a 440C-CR30 takes over, and what a safety network adds to the job.
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
Going Online on an S7-1500: Monitoring a Block, a Watch Table, and Values That Will Not Update
Monitor a block on an S7-1500, build a watch table, and work out why a value sits there: modify against force, optimised blocks, and what STOP does.
The First Download to an S7-1200: PG/PC Interface, the Subnet, and Why No Accessible Devices Appear
Start search comes back empty on an S7-1200. Work through the PG/PC interface, the subnet, the flash-LED check and a CPU that loads but stays in STOP.
Adding an S7-1214C to a New TIA Portal Project: Order Number, Firmware and Device Name
Get a CPU 1214C into an empty TIA Portal project: read the order number off the front, pick the firmware the bench CPU can take, and set the device name.
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
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