Photo-Eye - PLC Programming & Automation

One Photo-Eye, Two Signals: Light-Operate, Dark-Operate and the Setting That Inverted Your Zone Logic

One retroreflective 42EF with its reflector, beam made on an empty zone and beam broken by a carton, and below it the output and LED state of a light-operate J model and a dark-operate K model in each case

Why a replacement photo-eye inverted your zone logic: light operate dark operate on a 42EF, which one to fit, and the rung that normalises it.

Catching an Intermittent Bit on an S7-1500 with a Trace: Trigger Condition, Sample Rate and Recording Length

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plc programming s7 1500 trace intermittent bit trigger sample rate recording length 1 plc

Catch a once-a-shift bit with an S7-1500 trace: pick the recording OB, keep Record every at 1, trigger on the latch, and let the pre-trigger show why.

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 Programming Exercises for Beginners: Six Worth Doing

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Beginner PLC programming exercises covering blinking LEDs, motor control, conveyor belts, and traffic lights, plus tips for practicing with a simulator.