Save PLC Output Points: 7 Methods (2026)

Detail

Multiplexing and shift registers still dominate in 2026 for sequential loads (displays, indicator stacks, conveyor zones).

Latching (seal-in / OTL/OTU) is the cheapest win for on/off actuators; pair it with mechanical or solid-state interlock.

Diode ORing is still valid for mixed-voltage panels, but modern high-density modules (e.g.

Three forces push the count up every year: more sensors (per-machine safety and vision), more status indicators (lights, beacons, HMIs), and more valve manifolds (proportional and IO-Link islands). Even a "small" 2026 workcell now has a color stack light, a tower light with buzzer, four pneumatic valves, a vacuum generator, and two indicator relays , that is nine outputs before any motion.

The first rule is to count honestly. Walk the panel and write down every discrete load, then mark which ones are mutually exclusive. About 30% of "needed" outputs disappear the moment you ask the question. The remaining gap is what the techniques below close.

devices one at a time. A 4-by-4 matrix uses 8 outputs to drive 16 indicators, halving the point count. The trade-off is update latency: only one row is energised at any instant, so the scan period must be faster than the human eye (about 20 ms total, or 1.25 ms per row for 16 rows).

MicroLogix 1400 panels, and in Mitsubishi FX5U indicator stacks. The trick is to drive the matrix with sinking outputs (transistor, NPN) and a ULN2003 / ULN2803 row driver, never with a relay output , relay dry contact multiplexing is a known failure mode after a few million cycles.