OPC UA PLC Integration: From PLC Tag to SCADA Client
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
PLC Water Treatment: Levels, Lead/Lag Pumps and Dosing
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
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
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
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
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
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
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
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
Allen-Bradley Function Block: What Decides Execution Order
A function block routine that verified fine last week now has a question mark on four blocks and will not download. Or worse, it downloads, runs, and one value on the HMI is always one scan behind the others. Nobody moved a block. Somebody added a wire. Execution order in FBD has nothing to do … Read more
PLC Sequencer Instructions: SQO, SQI and the Position 0 Trap
An eight-station rotary indexer on a 5069-L330ER. An SQO drives the station outputs, and on the first false-to-true transition the outputs light station one. Not station zero. Station zero never fires at all, and the operator wants to know why the first pot off the carousel is empty. That is not a bug in your … Read more
PLC Programming Exercises for Beginners: Six Worth Doing
The first program almost everybody writes is a motor start and stop with a seal-in. It works on the bench. Wired into a real panel, the same logic can leave a motor running with the stop button pressed and a broken wire nobody can see. That gap between working and correct is what these exercises … Read more
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