Articles - PLC Programming & Automation

PLC Motor Control VFD Setup: DOL, PowerFlex 525, G120

September 13, 2026February 11, 2024 by PLC

Ladder rung: Start in parallel with the Run_Cmd seal-in contact, in series with a normally closed Stop and a Drive_Ready contact, driving the Run_Cmd output

Choose DOL or a drive, wire the stop so it works without the PLC, set the drive parameters and tags, then read the fault codes when it trips.

PLC HVAC Control: An Air Handler Sequence That Holds

September 13, 2026February 9, 2024 by PLC

Timing chart of an air handler start: occupied signal, outside air damper to minimum, supply fan running, and the cooling loop enabled after the delay

Write an AHU sequence on a CompactLogix: damper minimum position, supply fan VFD, chilled water PID, economizer changeover, compressor staging and BACnet.

PLC Program Documentation That Survives a Night Call

September 12, 2026February 8, 2024 by PLC

Ladder rung showing a filler conveyor motor start/stop with seal-in and descriptive tag names L3_FIL_Start_PB, L3_FIL_Stop_PB, L3_FIL_Mtr_OL and L3_FIL_Mtr_Run

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.

PLC Textile Machinery Control: Tension, Speed Sync and Yarn Break Stops

September 13, 2026February 7, 2024 by PLC

Ladder rung for the yarn break latch: Break_Sensor examined on with a parallel Break_Latched seal-in branch, in series with Reset_PB examined off, driving the Break_Latched output coil

What a warper, a sizing line and a stenter need from a PLC: draw ratios, dancer and load cell loops, yarn break stops and recipes on S7-1500 or Logix.

PLC Plastic Injection Molding and Extrusion: The Cycle, the Heaters and the Gates

September 13, 2026February 5, 2024 by PLC

Timing chart of one 22.5 s molding cycle: clamp locked from 1.5 s to 18.2 s, injection from 2 s to 3.2 s, hold pressure from 3.2 s to 6.2 s, cooling timer from 6.2 s to 18.2 s with screw rotation from 6.2 s to 12.7 s, mold open position reached at 20.2 s, ejector forward from 20.4 s to 21.4 s, mold closing again at 22.5 s and locked at 24 s

Injection molding from the controls side: the cycle as a state machine, barrel zone PID and thermocouple checks, EUROMAP 67 and 77, guards, and rubber.

The 5 PLC Programming Languages and When to Use Each

September 12, 2026February 3, 2024 by PLC

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.

PLC Networking: Switches, VLANs, DLR Rings and Ports

September 13, 2026February 1, 2024 by PLC

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

September 12, 2026February 1, 2024 by PLC

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

September 13, 2026January 30, 2024 by PLC

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

September 13, 2026January 30, 2024 by PLC

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.

PLC Predictive Maintenance: Vibration, Current, Hours

September 13, 2026January 30, 2024 by PLC

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

September 13, 2026January 30, 2024 by PLC

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.