Siemens 6ES7221-3BF50-0XB0 SIMATIC S7-1200 SB 1221 8DI 24VDC 100kHz Digital Input Signal Board

The Siemens 6ES7221-3BF50-0XB0 SIMATIC S7-1200 SB 1221 signal board adds 8 sink/source digital inputs at 24 V DC to a compact CPU, with a 100 kHz high-speed counting input option. It draws 108 mA from the backplane bus, dissipates 2.4 W, and mounts directly onto the CPU front without extra rack space.

Technical Specifications

Certifications & Standards

• CE
• UL
• cULus
• RCM
• KC

Selection Notes

This SB 1221 variant delivers 8 sink/source inputs at up to 100 kHz; a shorter-channel-count sibling in the same signal board family instead runs 4 inputs at 200 kHz. Pick this 8-channel version when the application needs more input points than count channels, and the 4-channel version when raw edge-detection speed on fewer points matters more. Signal boards mount directly onto the S7-1200 CPU front, adding I/O without consuming a rack slot, unlike SM-series expansion modules. The 707 V DC isolation test between channels and backplane bus is a standard type test rating, not a safety-isolation barrier.

Applications

Adds digital sensing capacity to a single S7-1200 CPU without a rack slot: proximity sensor banks, limit switches, and pulse counting from encoders or flow meters up to 100 kHz per channel.