PLC - PLC Programming & Automation

PLC Cybersecurity: Hardening a Logix Cell Step by Step

Timing chart of a controller restart: run mode drops while the download happens, then the first scan bit pulses, the restart timestamp is written and the unplanned download alarm latches on the SCADA

Zones and conduits, the controller key switch, FactoryTalk Security, firewall rules for 44818 and 502, and a backup you have actually restored.

PLC Conveyor Control: Zone Logic, Jams and PowerFlex

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Ladder rung for a conveyor zone: the line running bit, the zone photo-eye blocked, the downstream photo-eye clear and no jam latched, driving the zone run request

Zone accumulation, cascade start and stop, jam timers that do not nuisance trip, and driving a PowerFlex 525 over EtherNet/IP from a CompactLogix.

PLC PID Control: Set Up and Tune a Loop in Studio 5000

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Timing chart of a loop startup: setpoint step, control output saturated at 100 percent, deviation alarm active, then the process variable settling inside a 1 degC band

Scale the analog signals, pick PID or PIDE, put the loop in a periodic task, then tune from a bump test. Siemens PID_Compact covered as well.

OPC UA PLC Integration: From PLC Tag to SCADA Client

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Timing chart of an OPC UA subscription showing 250 ms sampling pulses, a PLC tag value change, and notifications leaving at the 1 second publishing interval

Connect a PLC to SCADA with OPC UA: KEPServerEX channels, the S7-1500 built-in server, certificate trust, subscription rates and why OPC DA kept breaking.

PLC Water Treatment: Levels, Lead/Lag Pumps and Dosing

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Timing chart of lead and lag pump alternation: the lead call starts pump 1, the lag call brings in pump 2 at high level, and on the next cycle pump 2 takes the lead

Wet well level control, pump alternation that shares the wear, chlorine dosing with long dead time, and remote sites over cellular Modbus that go quiet.

PLC vs DCS Integration: Getting a Skid onto the DCS

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Timing chart of a DCS to PLC heartbeat: the DCS counter steps every second, the PLC echoes it, and the Comms OK bit drops three seconds after the counter freezes

How a packaged skid PLC gets tied into DeltaV, Experion or PCS 7: link protocol, Modbus register map, heartbeat, engineering units and alarm ownership.

HMI PLC Setup: Build Your First PanelView Plus Screen

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Timing chart showing a finger press on the HMI, the tag write, the PLC Start_PB bit and the resulting Motor_Run coil, with about 60 ms of delay between each

From a blank FactoryTalk View ME application to a running PanelView Plus screen: shortcuts, tag syntax, a momentary push button and the MER transfer.

EtherNet/IP PLC Communication: Setup, RPI and Faults

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Timing chart of EtherNet/IP implicit I/O at 10 ms RPI showing producer and consumer packets against a 25 ms periodic task scan

Set up EtherNet/IP between a Logix controller, remote I/O and a drive: RPI, unicast vs multicast, MSG paths, and the fault codes you will really see.

PLC MES Integration: Tags, Handshakes and Work Orders

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Timing chart of an MES to PLC work order handshake showing Request from the MES, Ack from the PLC, Done when the order is latched, and both bits clearing after Request drops

What MES really needs from the controller: OEE counters, downtime reason codes, a work order UDT, a request and acknowledge handshake, an OPC UA bridge.

ControlLogix Ladder Troubleshooting, Rung by Rung

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Ladder rung with a bug: XIC Conv3 Start in series with XIO Conv3 EStop driving OTE Conv3 Run, with no seal-in branch around the start contact

A rung by rung ControlLogix ladder troubleshooting method: read the highlighting, use cross reference and search, find double coils, read the fault record.

EtherCAT PLC Systems: Cycle Time and Distributed Clocks

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Timing chart of a 1 ms EtherCAT cycle showing the task window, the frame on the wire, and the SYNC0 pulse that applies outputs on every slave at the same instant

Set up an EtherCAT bus in TwinCAT 3: ESI files, scanning the line, picking a cycle time, distributed clocks and the CRC counters that find a bad cable.

Allen-Bradley Faults and Solutions: Read the Type and Code

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The controller is in Program mode, the OK indicator is flashing red, and the Major Faults tab in Studio 5000 reads Type 4, Code 20. Two numbers, and they are the whole diagnosis. An instruction reached for an array element that does not exist. Nothing is wrong with the hardware. Type tells you which part … Read more