Allen-Bradley 1791-16A0 – 16-Point 120V AC Block I/O Input Module | 1791 Series
Engineering Background
The Allen-Bradley 1791 Block I/O series was developed by Rockwell Automation to deliver distributed I/O capability in compact, panel-mount form factors. Designed for integration with PLC-5 and SLC 500 platforms via Remote I/O (RIO) link, the 1791 series eliminates the need for a dedicated I/O chassis, reducing panel footprint and wiring complexity in distributed machine architectures.
Product Positioning
The 1791-16A0 is a 16-point discrete input module rated for 120V AC field devices. It is the preferred choice for retrofit and expansion projects where existing field wiring operates at 120V AC and engineers require a proven, rack-free I/O solution that communicates natively over the Allen-Bradley Remote I/O network. Konmask.com supplies this module from verified surplus and authorized channels, supporting MRO procurement teams with reliable lead times.
Complete Technical Specifications
| Catalog Number | 1791-16A0 |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Series | 1791 Block I/O |
| Module Type | Discrete Input |
| Number of Inputs | 16 points |
| Input Voltage | 120V AC |
| Input Voltage Range | 74–132V AC |
| Input Frequency | 47–63 Hz |
| ON-State Voltage (min) | 74V AC |
| OFF-State Voltage (max) | 20V AC |
| ON-State Current (min) | 5 mA |
| OFF-State Current (max) | 2.5 mA |
| Input Impedance | Approx. 12 kΩ at 60 Hz |
| Communication Interface | Allen-Bradley Remote I/O (RIO) 1771 protocol |
| Backplane Current (5V DC) | 500 mA max |
| Power Dissipation | 5W max |
| Operating Temperature | 0°C to +60°C (32°F to 140°F) |
| Storage Temperature | -40°C to +85°C |
| Relative Humidity | 5–95% non-condensing |
| Enclosure Rating | IP20 (open style) |
| Wiring Type | Screw terminal, removable terminal block |
| Dimensions (H × W × D) | Approx. 180 × 100 × 75 mm |
| Weight | Approx. 500 g |
| Agency Certifications | UL Listed, CE Marked, CSA Certified |
| Compatible Platforms | PLC-5, SLC 500 (via RIO adapter) |
Proven Application Environments
- Automotive Assembly Lines – Distributed I/O nodes monitoring 120V AC limit switches, proximity sensors, and safety interlocks across conveyor systems.
- Food & Beverage Processing – Washdown-adjacent panel installations reading AC-powered level switches, flow sensors, and door interlocks.
- Water & Wastewater Treatment – Remote pump station monitoring with RIO-linked PLC-5 controllers reading float switches and valve position feedback.
- Material Handling & Palletizing – High-cycle discrete input acquisition from photoelectric sensors and end-of-travel switches on sortation equipment.
- MRO Retrofit Projects – Drop-in replacement for failed 1791-16A0 modules in legacy PLC-5 and SLC 500 systems without requiring platform migration.
- OEM Machine Builders – Panel-mount I/O expansion where chassis-based 1771 I/O is cost-prohibitive for small node counts.
Engineering Advantages
- Rack-Free Architecture – Eliminates the 1771 I/O chassis; mounts directly to DIN rail or panel surface, reducing BOM cost and panel depth.
- Native RIO Protocol – Communicates directly on the Allen-Bradley 1771 Remote I/O link; no gateway or protocol converter required when used with PLC-5 or SLC 500 RIO scanner.
- 16-Point Density – High input density per module minimizes node count and RIO address consumption in large distributed systems.
- Removable Terminal Block – Field wiring remains in place during module swap, reducing MTTR during maintenance events.
- Wide Voltage Tolerance – 74–132V AC input range accommodates line voltage fluctuations common in industrial environments without nuisance faults.
- Proven Longevity – Rockwell Automation’s 1791 series has a multi-decade installed base; replacement modules are available through Konmask.com to extend system life.
System Architecture & Signal Flow
The 1791-16A0 connects to the Allen-Bradley Remote I/O network via a two-wire shielded twisted-pair cable (Belden 9463 or equivalent). The module occupies one full rack address (16 input bits) on the RIO scanner’s I/O map. Signal flow is as follows:
- Field Device (120V AC sensor/switch) → screw terminal input on 1791-16A0
- Input Conditioning Circuit → optical isolation → logic-level signal
- Local Microprocessor → assembles 16-bit input word
- RIO Transceiver → transmits input data to PLC-5 or SLC 500 scanner over RIO link
- PLC Processor → reads input image table; executes ladder logic
Optical isolation between field-side 120V AC and logic-side 5V DC provides noise immunity and protects the PLC backplane from field-side transients.
Sourcing & Quality Verification
All 1791-16A0 modules supplied by Konmask.com undergo the following verification process before shipment:
- Visual inspection for physical damage, corrosion, and counterfeit indicators
- Label and date-code verification against known Allen-Bradley manufacturing records
- Functional power-on test where test equipment is available
- Anti-static packaging with humidity indicator card
- Certificate of conformance available upon request for regulated industries
Konmask.com sources from authorized distributors, verified surplus dealers, and direct OEM decommissions. We do not knowingly supply counterfeit or non-original components.
Procurement Process
- Confirm Quantity & Lead Time – Contact us at support@konmask.com or +0086 19859288691 to verify current stock and lead time before placing a large order.
- Request a Quote (RFQ) – For orders of 3+ units or project-based procurement, request a formal quotation with volume pricing.
- Place Order – Add to cart and complete checkout, or submit a purchase order via email for net-terms customers.
- Shipping & Documentation – Standard shipment includes packing list, commercial invoice, and country of origin declaration. Expedited DHL/FedEx available.
- After-Sales Support – Our engineering team is available to assist with installation questions, compatibility verification, and warranty claims.
Technical FAQ
Q: Is the 1791-16A0 compatible with ControlLogix or CompactLogix?
A: Not natively. The 1791 series uses the legacy Allen-Bradley Remote I/O (RIO) protocol, which is not supported by Logix5000 controllers without a 1747-SN or 1771-ASB adapter and a third-party RIO scanner module. For Logix platforms, consider migrating to 1734 POINT I/O or 1769 Compact I/O.
Q: Can I mix 1791-16A0 input modules with 1791 output modules on the same RIO drop?
A: Yes. Multiple 1791 modules can share the same RIO drop address space, subject to the scanner’s rack address capacity and the total I/O word count per rack.
Q: What cable is required for the RIO link?
A: Allen-Bradley specifies Belden 9463 (blue hose) or equivalent shielded twisted-pair cable. Maximum RIO link distance is 3,048 m (10,000 ft) at 57.6 Kbaud.
Q: Is a 24V DC version available?
A: Yes. The 1791-16B0 is the 24V DC input equivalent. Contact Konmask.com for availability.
Q: What is the warranty on surplus modules?
A: Konmask.com offers a 90-day functional warranty on all surplus modules. Extended warranty options are available upon request.
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Contact: support@konmask.com | +0086 19859288691
