PLC Indicator Light Control: Ladder Logic and 2026 IO-Link Stack Lights
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PLC Indicator Light Control: Ladder Logic and 2026 IO-Link Stack Lights
Indicator light control is still the most common entry point for new PLC programmers, but the stack lights themselves have changed. In 2026, IO-Link tower lights (Banner K70 Pro, Schneider XVU, Patlite LR6) replace hardwired 24 Vdc tri-stack lamps, and ladder logic is migrating to structured text with tag-based addressing. This How-to rebuilds the classic indicator-light example with a 2026 hardw
Detail
24 Vdc tri-stack lamps are giving way to IO-Link tower lights (Banner K70 Pro, Schneider XVU, Patlite LR6) on PROFINET / EtherNet/IP.
The ladder rung pattern, run input + fault latch + one-shot, still works in Studio 5000 v36 and TIA Portal V19.
One M12 cordset replaces five discrete wires; the AOI maps Run / Fault / Ready / Warn / Override to a single process-data byte.
Banner K70 Pro IO-Link for AB racks, Schneider XVU for Modicon M580, Patlite LR6 for Mitsubishi MELSEC iQ-R.
Indicator-light control still teaches PLC scan, latch, and one-shot fundamentals, but 2026 hardware moves from hardwired tri-stack lamps to IO-Link tower lights on PROFINET or EtherNet/IP, one cable, one process-data byte, five colors.
The "three lights on a panel" exercise has been a PLC training staple since the Modicon 084 era, and for good reason, a tower lamp maps neatly onto the three output patterns every maintenance tech needs:
. If you can control three lights reliably, you understand scan order, output latch, and the difference between a level and an edge.
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