Sick LGTN101-521 CPU Module for Industrial Logic and Automation Control

The Sick LGTN101-521 is a CPU module belonging to the LGTN series of industrial controllers. It is a logic control module capable of executing user-defined sequences, processing I/O, and communicating with sensors and actuators. Typically used in material handling, packaging, and machine safety systems, the LGTN101-521 offers a compact form factor with reliable processing for standalone or network-connected applications.

Processor and Memory

CPU: 32-bit ARM Cortex-M4 core at 120 MHz. Program memory: 512 KB Flash. Data memory: 128 KB RAM. The module stores the user program in non-volatile memory with write protection. It supports up to 2000 ladder logic steps or 500 function blocks (IEC 61131-3). Execution speed: 0.2 µs per boolean instruction. The controller has a real-time clock with super-capacitor backup (2 weeks). It also includes an SD card slot for program backup and data logging.

Built-in I/O

The LGTN101-521 offers 8 digital inputs (24V DC, 5mA, with low-pass filter) and 6 digital outputs (transistor, 24V DC, 0.5A). Additionally, it includes 2 analog inputs (0-10V, 12-bit resolution) and 1 analog output (0-10V, 10-bit). The digital outputs are protected against short circuit and overload. Two of the digital inputs can be used as high-speed counters (10kHz max). LEDs on the front panel indicate I/O status and CPU run/error conditions.

Communication Ports

1x Ethernet port (10/100 Mbit/s) supporting Modbus TCP (client and server), Ethernet/IP (adapter), and Profinet (optional license). 1x RS-232 port (9-pin D-sub) for programming or serial connection to HMIs. 1x RS-485 port (screw terminals) for Modbus RTU master/slave. The module can also be used as a gateway to connect Sick sensors to an Ethernet network. All ports are isolated and include surge protection. DHCP or static IP addressing available.

Programming Environment

The LGTN101-521 is programmed using Sick’s LGTN Studio software (based on CoDeSys V3). Languages supported: Ladder Diagram (LD), Function Block Diagram (FBD), Structured Text (ST), and Sequential Function Chart (SFC). The software includes a library of function blocks for timers, counters, PID loops, and string handling. Online debugging, forced I/O, and program simulation are supported. The program can be downloaded via Ethernet or USB. The controller supports up to 32 user tasks with different priorities.

Expansion Capabilities

The module can expand I/O via Sick’s LGTN expansion bus, which supports up to 8 additional modules (digital, analog, temperature, and specialty I/O). Expansion modules are connected via a ribbon cable and automatically detected. No external power supply is needed for up to 4 modules. The total I/O count can reach 64 digital inputs, 48 digital outputs, 16 analog inputs, and 8 analog outputs. Expansion modules are DIN rail mountable next to the CPU.

Physical and Environmental

Dimensions: 90mm (H) x 55mm (W) x 70mm (D). Weight: 220g. Mounting: 35mm DIN rail (snap-on). Protection: IP20. Operating temperature: -20°C to +60°C. Storage: -40°C to +85°C. Humidity: 5-95% non-condensing. Altitude: up to 2000m. Vibration: 2g at 10-57Hz. The enclosure is polycarbonate with UL 94 V-0 flammability rating. All terminals are pluggable spring-cage type (0.2-1.5mm²).

Safety Features

Though not a certified safety PLC, the LGTN101-521 includes watchdog timer, memory CRC check, and power supply monitoring. It can be used in functional safety applications up to SIL 1 if external safety relays are used. The module has a hardware reset button (recessed) to restart the program without power cycling. The digital outputs go to a defined safe state (OFF or hold) upon CPU failure or communication loss.

Applications

Typical applications include conveyor control, small sorting machines, automatic labeling systems, pack-and-fill equipment, and building automation (HVAC, lighting). The module is also used as a remote I/O controller for larger PLC systems via Modbus TCP. Its compact size makes it suitable for installation in junction boxes or machine-mounted enclosures. The LGTN series is also used in Sick’s own sensor integration projects.

Compatibility and Accessories

The LGTN101-521 is compatible with all Sick LGTN digital and analog I/O modules. Accessories include: terminal covers (LGTN-ACC-Cover), SD memory cards (2GB to 32GB), and USB programming cable. The module is also compatible with standard M12 connectors via field-wirable adapters. Firmware updates can be downloaded from Sick’s website and applied via LGTN Studio. For applications requiring Wi-Fi, a USB-WiFi dongle can be used.

Diagnostic Features

Front panel LEDs: RUN (green), ERR (red), I/O (yellow for activity), and a multi-color status LED for network link. The controller logs system events (power cycles, program changes, errors) in a circular buffer. Error codes can be read via software or displayed by flashing the ERR LED. The module includes a simulated real-time clock for timestamping. For remote diagnostics, the controller can send email alerts or SNMP traps.

Conclusion

The Sick LGTN101-521 CPU module provides a compact, versatile control solution for small to medium automation tasks. With integrated I/O, multiple communication options, and IEC 61131-3 programming, it is a suitable choice for machine builders seeking a low-cost programmable logic controller.