ABB CL-LMR.CX18DC2+CL-LER.18DC2 PLC Expansion Module – AC500

ABB CL-LMR.CX18DC2 + CL-LER.18DC2: Dual-Module Relay Output Assembly for AC500 Distributed Control Architecture

Within a modular PLC control loop, the base CPU module and its directly coupled I/O expansion define the deterministic boundary of the control system. The ABB CL-LMR.CX18DC2 functions as the local CPU and digital input base, while the CL-LER.18DC2 extends the relay output capacity via the AC500 S500 backplane bus. Together, this assembly delivers 18 × 24V DC digital inputs on the base unit, supplemented by 18 additional relay-switched outputs on the expansion side — forming a self-contained, high-density mixed I/O node suitable for machine control, process interlocking, and panel-level switching applications.

The S500 bus interconnect between the two modules operates at the backplane level, eliminating field-wiring overhead between CPU and expansion I/O. Cycle time determinism is preserved because bus arbitration is handled internally, independent of external network load. This architecture is particularly relevant in applications where scan-cycle jitter must remain below 1 ms — such as press control, conveyor sequencing, and safety-adjacent interlock logic.

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Technical Parameters

Hardware Logical Analysis

The CL-LMR.CX18DC2 base module integrates the CPU processing core with a local 18-point DC input front-end. Input signal conditioning is performed through RC filter networks with software-configurable time constants (0.1 ms to 32 ms), allowing engineers to suppress contact bounce on mechanical inputs without sacrificing response speed on solid-state sensors. Each input group is galvanically isolated from the logic supply at 500V AC test voltage — a design choice that protects the CPU backplane from ground-loop currents common in multi-panel installations.

The relay output architecture on the CL-LER.18DC2 uses electromechanical relay contacts rather than solid-state switching. This is a deliberate engineering decision: relay contacts provide true galvanic isolation between the control circuit and the field load, with no leakage current in the open state — a critical requirement when switching low-power pilot devices or intrinsically safe circuits. Each contact group is independently isolated, rated at 250V AC / 30V DC with a maximum switching current of 2A. The mechanical relay design also ensures compatibility with AC and DC loads without polarity constraints, simplifying field wiring in mixed-voltage panels.

The S500 backplane bus connecting the two modules uses a proprietary ABB parallel bus architecture with deterministic arbitration. Unlike fieldbus-based I/O expansion (e.g., PROFIBUS DP or EtherNet/IP remote I/O), the S500 bus operates at the backplane level with fixed latency — typically sub-millisecond — ensuring that relay output commands issued by the CPU are executed within the same scan cycle without network-induced jitter. This is the fundamental architectural advantage of local expansion over distributed I/O for time-critical switching applications.

EMC hardening on both modules follows EN 61000-4 series requirements: ESD immunity to 8 kV contact / 15 kV air discharge (IEC 61000-4-2), radiated immunity to 10 V/m (IEC 61000-4-3), and EFT/burst immunity to 2 kV on power lines (IEC 61000-4-4). The PCB layout employs ground plane segmentation to isolate high-frequency switching noise from analog and digital signal traces — a standard practice in ABB’s AC500 hardware design methodology.

System Integration Benefits

• Deterministic Scan-Cycle Performance: S500 backplane bus arbitration is fixed-latency, ensuring relay output commands are executed within the same PLC scan cycle — no network scheduling overhead.
• True Galvanic Isolation on Relay Outputs: Electromechanical contacts provide zero leakage current in the open state, compatible with intrinsically safe and low-power pilot circuits.
• Mixed-Voltage Field Compatibility: Relay contacts switch both AC and DC loads (up to 250V AC / 30V DC) without polarity constraints, reducing panel design complexity.
• Configurable Input Filtering: Software-adjustable RC filter time constants (0.1–32 ms) allow per-application tuning of input debounce without hardware modification.
• Scalable I/O Expansion: The AC500 S500 bus supports additional expansion modules beyond the CL-LER.18DC2, allowing incremental I/O growth without CPU replacement or rewiring.
• Integrated Diagnostics: Both modules report status via the AC500 CPU diagnostic buffer — input short-circuit detection, output overload flags, and bus communication errors are accessible in real time through ABB Automation Builder.
• Wide Ambient Temperature Tolerance: −25°C to +60°C operating range supports outdoor enclosures, unheated plant areas, and high-ambient machine cabinets without derating.
• IEC 61131-3 Multi-Language Programming: Full support for Ladder Diagram, Function Block Diagram, Structured Text, Instruction List, and Sequential Function Chart — engineers can select the language best suited to the application logic without platform constraints.
• DIN Rail Standardization: EN 60715 35 mm DIN rail mounting ensures compatibility with all major panel enclosure manufacturers and simplifies replacement in existing installations.
• Reduced Wiring Infrastructure: Backplane-level bus connection between CPU and expansion eliminates inter-module field wiring, reducing installation time and potential wiring fault points.

Quality Assurance & Global Logistics

Both the CL-LMR.CX18DC2 and CL-LER.18DC2 are manufactured by ABB in Germany under ISO 9001-certified production processes. Each unit carries CE marking, UL/cUL listing, and full compliance with the EU Low Voltage Directive and EMC Directive. ABB’s AC500 platform is designed for a 10-year product lifecycle with guaranteed spare parts availability — a critical factor for long-term plant maintenance planning.

Units supplied by siemensplc.com are sourced from verified distribution channels with full traceability. Pre-shipment inspection includes visual examination of housing integrity, label and serial number verification, and terminal block continuity check. Modules are packed in anti-static ESD bags with foam cushioning inside double-wall corrugated cartons — appropriate for international air freight handling.

Logistics are managed from our warehouse in Xiamen, China, with daily dispatch via DHL Express, FedEx International Priority, and UPS Worldwide Expedited. Typical transit times: 3–5 business days to Europe and North America; 2–4 business days to Southeast Asia. Full export documentation is provided with every shipment: commercial invoice, packing list, certificate of origin, and HS code declaration (HS 8537.10). For orders requiring CITES, REACH, or RoHS compliance documentation, contact our technical team in advance.

All units are covered by a 12-month warranty from the date of shipment, covering manufacturing defects and confirmed DOA (Dead on Arrival) units. DOA replacements are dispatched within 7 business days upon receipt of the defective unit and inspection confirmation.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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