Allen-Bradley 1771-IVN/C Digital Input Module – PLC-5 1771 Series

Allen-Bradley 1771-IVN/C: 32-Point TTL-Compatible DC Digital Input Module for PLC-5 Control Architectures

The Allen-Bradley 1771-IVN/C is a 32-point, low-voltage DC digital input module designed for integration within the 1771 I/O chassis ecosystem. Operating across a 10–30 V DC input range with TTL-level compatibility, this module serves as the primary discrete signal acquisition layer between field devices—proximity sensors, limit switches, encoder outputs, and pushbutton arrays—and the PLC-5 processor’s data table. Its single-slot form factor delivers a point density of 32 inputs per chassis slot, a critical parameter in high-density discrete manufacturing environments where chassis real estate directly constrains system scalability.

Within a closed-loop control architecture, the 1771-IVN/C occupies the input side of the scan cycle. The PLC-5 processor reads the module’s 32-bit input image word during each I/O scan, updating the input data table before executing ladder logic. The module’s backplane interface draws 800 mA at 5 V DC from the 1771 chassis power supply, a load figure that must be factored into chassis power budgeting when populating high-density configurations. Series C represents the final and most stable hardware revision of this module, incorporating minor PCB-level refinements over earlier Series A and B variants without altering the electrical interface or firmware compatibility.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

The 1771-IVN/C employs optical isolation between the field-side input circuitry and the backplane logic bus. Each input channel passes through an opto-coupler stage that electrically decouples the 10–30 V DC field wiring from the 5 V DC backplane domain. This isolation barrier, rated to withstand transient voltages common in industrial field wiring environments, prevents ground loops and common-mode noise from propagating into the processor’s data table. In environments with variable-frequency drives, solenoid coils, or inductive loads switching in proximity to input wiring, this isolation mechanism is the primary defense against spurious input state changes.

The module’s input filter network introduces a hardware debounce delay—typically in the range of 1–3 ms per point—that suppresses contact bounce from mechanical switches and relay contacts. This filtering is implemented at the hardware level, independent of the PLC-5 scan cycle, meaning the processor receives a stable, settled logic state rather than a raw, bouncing signal. For applications where faster response is required, the PLC-5 processor’s high-speed counter or interrupt input features should be used in conjunction with dedicated high-speed input modules rather than the 1771-IVN/C.

The 32 input points are organized into two 16-point groups, each sharing a common return (DC common) terminal. This grouping allows the module to interface with two separate field voltage sources if required, provided both sources remain within the 10–30 V DC specification. The backplane connector is a 42-pin edge connector that mates with the 1771 chassis backplane, carrying both the 5 V DC logic supply and the bidirectional data bus. The module does not require an external field-side power supply connection to the backplane; field power is wired directly to the module’s terminal block via the 1771-WN wiring arm.

EMC performance is supported by the module’s PCB layout, which routes high-frequency backplane signals away from the field-side input traces. The chassis itself provides a Faraday cage effect when properly grounded per Rockwell Automation’s installation guidelines (Publication 1770-4.1). Series C hardware incorporates improved ground plane continuity on the PCB compared to earlier revisions, reducing susceptibility to radiated emissions from adjacent chassis slots.

System Integration Benefits

• High-density I/O consolidation: 32 discrete inputs per single chassis slot reduces the number of slots consumed by digital input functions, freeing slots for analog, specialty, or communication modules in space-constrained chassis configurations.
• Deterministic scan-cycle integration: The module’s input image word is updated synchronously with the PLC-5 I/O scan, ensuring that all 32 input states are captured at a consistent point in each scan cycle, supporting deterministic ladder logic execution.
• Optical isolation for noise immunity: Per-channel opto-isolation eliminates ground loop paths between field devices and the processor, a measurable benefit in plants with shared grounding infrastructure across multiple machine cells.
• Hardware-level input filtering: Built-in debounce filtering reduces the software overhead required to handle contact bounce, simplifying ladder logic and reducing the risk of false input transitions reaching the data table.
• Per-point LED diagnostics: Each of the 32 input points has a dedicated LED indicator on the module face, allowing field technicians to verify input state without connecting a programming terminal—reducing mean time to diagnose (MTTD) during fault conditions.
• Direct drop-in compatibility: Series C maintains full backward compatibility with Series A and B wiring arms (1771-WN) and chassis, eliminating the need for wiring modifications when replacing earlier revisions in the field.
• Broad processor compatibility: The module operates with the full range of PLC-5 processors from the PLC-5/10 through the PLC-5/80, as well as PLC-5/250 and PLC-5/VME variants, providing a single part number that spans the entire PLC-5 processor family.
• Dual common grouping for multi-source field wiring: The two 16-point groups with independent DC commons allow integration of field devices powered from two separate 24 V DC supplies, supporting machine designs where safety-rated and standard I/O circuits must remain electrically separated at the field level.
• Low backplane power consumption relative to point count: At 800 mA / 5 V DC for 32 points, the per-point backplane power draw is 125 mA per point—a figure that supports full chassis population without exceeding the capacity of standard 1771 power supplies in most configurations.
• Documented fault diagnostics via RSLogix 5: Module status and I/O fault data are accessible through the RSLogix 5 programming environment, enabling structured fault logging and remote diagnostics without physical access to the chassis.

Quality Assurance & Global Logistics

Every 1771-IVN/C unit supplied by siemensplc.com is sourced from traceable industrial supply channels and inspected against Rockwell Automation’s published specifications (Publication 1771-2.100). Physical inspection covers housing integrity, label authenticity, connector pin condition, and PCB visual examination. Functional verification confirms backplane communication and input point continuity prior to packaging. Units are shipped in anti-static packaging with full documentation including a packing list and, upon request, a functional test report.

Logistics operations are based in Xiamen, China, with established carrier partnerships for time-definite international delivery:

• Domestic China: SF Express / JD Logistics — 1–2 business days
• Asia-Pacific: DHL / FedEx — 3–5 business days
• North America & Europe: DHL Express / UPS — 5–8 business days
• Middle East, Africa & South America: FedEx International Priority — 7–12 business days

Full export documentation is provided for all international shipments: commercial invoice, packing list, and certificate of origin. HS Code 8537.10 applies. Customs pre-clearance support is available for high-value or time-sensitive consignments. All units carry a 12-month warranty from the date of shipment, covering verified manufacturing defects. DOA (Dead on Arrival) units are replaced within 5 business days of confirmed return receipt.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
© 2026 siemensplc.com. All rights reserved.