alarm - PLC Programming & Automation

Wellhead ESD Logic and RTU Polling on a Remote Pad

Ladder rung for a wellhead ESD permissive: reset push button sealed in, high pressure and high level switches healthy, emergency stop normally closed, driving the SDV permissive coil

Wellpad controller choice, an ESD permissive rung that will not auto restart, Modbus poll budgets over radio, flow computers and tank farm level control.

Assembly Line Station Logic: State Machine, Takt, Downtime

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Ladder rung releasing a body from an assembly station: body present, torque batch complete and vision result OK in series, with a normally closed contact for the downstream station blocked, driving the release output

Station and line PLC split, a PackML state machine in Structured Text, torque tool error proofing, andon stops and downtime that blames the right station.

PLC vs DCS Programming: Where the Two Part Ways

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Timing chart of an analog HI alarm: the process value crosses the limit, a three second on-delay expires, the alarm goes active and stays unacknowledged until the operator acknowledges it, then clears when the value returns below the limit

PLC vs DCS programming compared by an engineer who works on both: tags and rungs against loops and blocks, redundancy, alarms, batch and real cost.

HVAC Point Names, BACnet Objects and Overrides That Expire

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Ladder rung for stage 2 cooling: cooling demand in series with stage 1 running, the interstage delay timer done bit, and a normally closed contact on the minimum off timer, driving the stage 2 command

PLC building automation that a stranger can maintain: naming, sequences of operation in the code, staging, BACnet mapping, trends, alarms and overrides.

SunSpec Inverter Curtailment and Wind Pitch Rate Limits

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Timing chart of a battery state of charge window: grid charge command stops when state of charge passes 90 percent, charge inhibit latches, and discharge inhibit latches below 15 percent

SunSpec Modbus inverter limits, tracker stow, wind turbine pitch and yaw, a battery SoC window with BMS handshake, and curtailment setpoints over DNP3.

Generator Start Permissives, Sync Handover and Load Shed

by PLC

Ladder rung for a generator start permissive: start push button sealed in, lube oil pressure healthy, generator breaker open, lockout relay reset, driving the start sequence coil

Where the PLC stops and the relay starts, a generator start permissive rung, the synchronising handshake, load shed stages and switchgear interlocks.

Sequential Function Chart PLC Programming, Step by Step

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Timing chart of SFC step activity in a batch sequence, showing Step_Fill, Step_Mix, Step_Drain and the mixer output over sixty seconds

Build a working SFC in Studio 5000: steps, transitions, action qualifiers, the SFC Execution settings that decide what happens on a restart, and S7-GRAPH.

Machine Learning PLC Integration: Where the Model Runs and What the Controller Owns

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Ladder rung with ML_Valid examined on, ML_Stale examined off and Score_Hi examined on in series, driving the ML_Advisory output coil

The PLC does not run the model. What to publish, how the score returns as an advisory tag with a watchdog, and a pump anomaly detector on CompactLogix.

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.

Studio 5000 Logix Designer Add-On Instructions Create

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How to Create Add-On Instructions in Logix Designer One of the most powerful newer features of the RSLogix 5000 program is the ability to create Add-On Instructions, It is one of the features that makes the algorithm easy and enjoyable for plc programmers. How to create and use the Add-On instruction Now we will go … Read more

RSLogix Studio 5000, How do I open the Tag Editor?

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How do I open the Tag Editor? Tags are stored in the tag database associated with a Logix Designer project. Use the Tag Editor to create and manage tags. Access the Tag Editor from the Edit Tags tab in these windows: Controller Tags Parameters and Local Tags (when working with Program tags, Equipment Phase tags, Equipment Sequence tags, or Add-On Instruction tags) … Read more