The Siemens 3RK2402-2CE00-2AA2 is a Slimline Compact I/O module for control-cabinet use, designated as an AS-i SC22.5 4DI/4RQ A/B slave. It packs 4 digital inputs (PNP Type 2) and 4 relay NO outputs into a 22.5 mm wide housing that mounts via screw or snap-on onto DIN rail. It operates as an A/B slave per AS-Interface Specification 3.0, with a fixed slave profile of S-7.A.7 and an unchangeable ID1 code of 7. Address assignment is done through the front addressing socket.
Power supply and sensor feed — the key decision
The module draws 200 mA when powered solely via the AS-Interface cable, or 500 mA when an auxiliary supply (Uaux) is connected. That difference matters for bus loading: if you run the sensor supply from the AS-i bus, no extra power wiring is needed, but the module's own consumption plus the sensor load must stay within the AS-i power unit's budget. If you feed sensors from Uaux (20 to 30 V DC), the module can supply up to 4 A for external sensors, but you run a separate 24 V feed. The AS-Interface supply path delivers 2 A at 8.5 V to the module's internal logic; the external auxiliary path provides 1 V at 4 A for the sensor bus. For the relay outputs, the thermal current rating is 5 A, with specific switching capacities of 1 A at 24 V, 0.2 A at 110 V, and 0.1 A at 230 V. At 30 V DC maximum, the relay contacts handle 300 mA. When using AS-i Power24V, the 24 V output is limited to 300 mA.
I/O and wiring
The four digital inputs are PNP Type 2, suitable for 2- and 3-wire sensors. The four outputs are relay changeover contacts (normally open). There are no analog inputs or outputs, and no safety-related digital inputs — this is a standard digital slice for the AS-i bus. Terminals accept solid conductors: 1x (0.5 to 2.5 mm²) or 2x (0.5 to 1.5 mm²). For AWG, solid wire is 1x (24 to 14) or 2x (24 to 16). Stranded AWG is not permitted. Status of each input and output is indicated by yellow LEDs on the front.
Rated IP20, so it belongs inside a control cabinet, not on the machine frame. Shock resistance is 15g / 11 ms for the module alone, or 10g / 11 ms with a device connector attached. Dimensions are 22.5 mm wide, 100 mm high, 120 mm deep — a standard slimline footprint that leaves room for adjacent slices.