Product Overview

The 6ES5440-8MA12​ is a SIMATIC S5-440 series digital output module from Siemens, configured as 4 channels of 24 V DC / 0.5 A, non-floating (non-isolated, common-L+ sourced), in the compact “Version M” mechanical form. It belongs to the S5 compact / distributed-I/O branch — the same narrow-rack family as the 6ES5431-8MC11​ DI we covered previously — seating into S5-90U, S5-95U, S5-100U central racks and into ET 100U / ET 200U distributed I/O heads hung off an IM 314/324 link from a S5-115U/135U host. This platform distinction is the first thing to lock: where the S5-115U central rack uses the 32-point 421 (non-floating DO) and 451 (relay DO) in compact-U or standard depth, the 6ES5440-8MA12​ is the 4-point 24 V DC DO for the narrower S5-100U backplane, which has a different edge-connector pitch and shallower depth than a S5-115U rack. Trying to force a 421-4UAxx into a S5-100U slot (or vice versa) is a physical non-starter; the 6ES5440-8MA12​ is the module that fits.Within the S5 DO选型树, the branching is parallel to the DI tree we’ve already built: 440 = non-floating 24 V DC DO (source type, L+ switched, load returns to L- / M depending on S5-100U PS topology); 441 = floating 24 V DC DO (galvanically isolated groups, for when the 24 V DC load supply floats relative to S5 M); 451 = relay DO (voltage-free contact, for AC loads or when isolation + higher voltage/current is needed). The 6ES5440-8MA12​ is the entry-level 440: 4 outputs, 0.5 A each, 2 A total across all four, L+ rated 20–30 V DC (ripple-inclusive), short-circuit protected with automatic re-enable when the fault clears, and a red FAULT LED that lights on short-circuit or loss of L+ load voltage. The “8MA12” suffix decodes as: 8 = compact S5-100U/ET100U mechanical family, MA = 24 V DC 0.5 A non-floating DO, 12 = component revision (8MA11 → 8MA12 succession; interchange within the same BOM without project change).From an obsolescence standpoint, the 6ES5440-8MA12​ rides the same S5 end-of-life curve as the rest of the compact family — S5-100U was officially retired years ago, and the 440-8MA12 was cancelled without direct S7 replacement (the migration path is S7-1200/1500 + ET 200SP, but that’s a full re-panel, not a drop-in). The installed base it serves is S5-100U skids: packaged water-treatment lift stations, small OEM machinery (Italian packaging, German labeller, Austrian feeder), grain/feed mill auxiliaries, building-services plant rooms, and Eastern European/Asian 1990s exports where a S5-115U was over-specced and a S5-100U was the cost winner. NOS and refurbished 6ES5440-8MA12​ units trade because a failed DO on a S5-100U skid is a stop-event — four 24 V DC points typically drive local indication lamps, small solenoid valves, interposing relays to 115 V AC MCC coils, or BERO proxy power — and the plant won’t migrate that skid for a DO failure. Supplying the 6ES5440-8MA12​ means supplying the exact 4×24 V DC / 0.5 A non-floating density in compact M, not a 421 (wrong rack) and not a 451 relay (overkill for 24 V DC/0.5 A and different channel count).

Technical Specifications