PLC - PLC Programming & Automation

The 5 PLC Programming Languages and When to Use Each

Ladder rung with Start_PB XIC, seal-in branch on Conv_Run, Stop_PB XIO and Guard_OK XIC driving the Conv_Run OTE coil

Ladder, FBD, Structured Text, SFC and IL compared on real hardware: what Studio 5000 v33 and TIA Portal V18 support, and which one to pick per job.

Common PLC Programming Mistakes: Six That Cost Hours

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Common Mistakes to Avoid in PLC Programming

A TON with a .PRE of 5000 that sits in a subroutine only called in Auto, with its rung left true, is already done on the first scan back after twenty minutes in Manual. Publication 1756-RM018A-EN-P prints the arithmetic that explains it, ACC = ACC + (current_time – last_time_scanned), so the timer bills the whole … Read more

PLC Networking: Switches, VLANs, DLR Rings and Ports

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Timing chart of a DLR ring during a cable break: link A drops, the beacon times out, the ring fault flag sets, and the I/O connection stays up throughout

PLC networking done properly: switch features that matter, an address plan, VLANs, DLR rings with 1783-ETAP, PROFINET RT and IRT, NAT and port numbers.

PLC Communication Protocols for SCADA: What to Pick

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Timing chart comparing polled Modbus TCP requests and responses at 25 ms against cyclic EtherNet/IP I/O packets at a 10 ms RPI

Modbus TCP, EtherNet/IP, PROFINET, OPC UA and MQTT compared by how they move data, with ports, poll rates and the mistakes that cost SCADA update time.

PLC I/O Modules: Sinking, Sourcing, Keying, Scaling

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Timing chart of a 24V DC input: the field sensor edge, the module input filter delay, and the controller tag updating at the next RPI

How to pick discrete and analog I/O, get sinking and sourcing right, set RPI and electronic keying, wire a 4-20 mA loop and scale the raw counts.

PLC Robot Integration: Handshakes, Safety and Cycles

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Timing chart of a pick cycle handshake between PLC and robot: cell ready stays high, part present rises, the PLC raises start cycle, the robot answers with busy and leaves home, then sets cycle done while the PLC drops start cycle

Map FANUC, ABB and KUKA signals into a PLC, build a pick cycle handshake that cannot drop, select the program by number, and set a sane RPI.

Counting Runtime Hours and Trending Vibration in the PLC

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Timing chart of condition monitoring sampling: the machine starts, a warm-up delay blocks sampling, one-second sample pulses run only while warmed up, and the level 1 alert sets after the average crosses the limit

Build PLC predictive maintenance on hardware you own: vibration and motor current inputs, runtime hours, moving averages, baselines and alarm levels.

RFID PLC Integration: Read and Write Tags from Ladder

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Timing chart of an RFID read cycle: the trigger bit, the reader busy bit, the done bit, and the UID landing in the UDT before the trigger is cleared

Pick HF or UHF, connect the reader over EtherNet/IP or Modbus, map the data into a UDT, and run a trigger, busy, done handshake that does not drop reads.

PLC Safety Interlock: Dual-Channel E-Stop on GuardLogix

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Timing chart of a dual channel E-stop: channel A opens, channel B follows shortly after inside the discrepancy time, the safety output drops at once, the E-stop is released, and the output only returns after the reset button is pressed and released

When a standard interlock is not enough, how to wire and configure a dual-channel E-stop on GuardLogix safety I/O, and the reset rule nobody may break.

OEE and Downtime Reason Codes from the PLC

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Ladder rung with four contacts, Auto examined on, Fault, Starved and Blocked examined off, driving the Running output coil that feeds the availability run timer

How a PLC state model feeds OEE, downtime reason codes and SPC triggers on a rotary filler: the ST block, the tag structure and the classic mistakes.

PLC Simulation and Virtual Commissioning: A Working Setup

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Timing chart of a simulated conveyor: the run command, the simulated photoeye going true three seconds later, and the drive feedback reaching the speed reference

Build a Logix Emulate chassis, run PLCSIM Advanced, test the HMI offline, and learn which parts of a machine you can trust a simulation to prove.

BPCS, SIS and the Cause and Effect Matrix on a Reactor

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Timing chart of a reactor high temperature trip: two of three jacket thermocouples vote high, the SIS trip relay trips, the feed valve closes and the quench valve opens

How the BPCS, the SIS and the package PLC split the work on a batch reactor, with a cause and effect matrix, cascade temperature control and IS barriers.