32-channel 24 V DC output module — the spares reality
The Siemens 6ES7322-1BL00-0AA0 is a SIMATIC S7-300 SM 322 digital output module packing 32 transistor outputs, each rated 0.5 A at 24 V DC. It requires the 40-pin front connector (sold separately) and fits a 40 mm wide slot in the S7-300 rack. This is a high-density module — 32 points in a single-wide footprint — so it's common in larger I/O cabinets where panel space is tight.
Output ratings and signal integrity
Each channel sources 0.5 A rated current, with a maximum of 2 A per channel at 40 °C and 3 A at 60 °C — note the derating direction: the module can actually deliver more current at higher ambient, which is unusual and suggests the thermal limit is set by the internal silicon junction, not the PCB copper. The response threshold for short-circuit protection is 1 A typ, and the protection is electronic (no fuse to replace). Switching times are 100 µs from 0 to 1 and 500 µs from 1 to 0. That's fast enough for most discrete control signals but not for high-speed pulse trains — the maximum resistive load switching frequency is 100 Hz, and with inductive loads it drops to 0.5 Hz. On lamp loads (high inrush), the limit is 10 Hz. The module has no diagnostics — no diagnostic alarm, no wire-break detection, no short-circuit indicator per channel. The only status feedback is the signal-level voltage at the output: for a logic 1, the output is L+ minus 0.8 V minimum. Channel-to-channel isolation is provided, and isolation is tested at 500 V DC.