Product Overview
Part of the 1791 Block I/O series, the Allen-Bradley 1791-16BC is a compact, self-contained discrete I/O block designed for Remote I/O architectures. It integrates a power supply, PLC interface, I/O connections, and signal processing circuitry into a single unit that functions as a remote I/O adapter, eliminating the need for a separate chassis. With 16 inputs and 16 outputs operating at 10-30VDC, this module simplifies wiring and reduces cabinet space, making it an excellent choice for distributed control applications.
Key Technical Specifications
The Allen-Bradley 1791-16BC offers a robust set of specifications that ensure reliable performance in demanding industrial environments. Below are the core parameters:
| Parameter |
Value |
| Manufacturer |
Allen-Bradley |
| Product Type |
Block I/O |
| Part Number |
1791-16BC |
| UPC |
612598124756 |
| Weight |
2.25 lbs (1.02 kg) |
| Number of Inputs |
16 (2 groups of 8) |
| Input On-state Voltage Range |
10-30V DC |
| Input On-state Current |
11mA @ 30V max. |
| Input Off-state Voltage |
5V DC max. |
| Input Off-state Current |
1.5mA min. |
| Number of Outputs |
16 (24VDC outputs) |
| Output Voltage Range |
10-30VDC |
| External Power Voltage |
19.2-30VDC |
| External Power Current |
300 mA |
| Power Dissipation (max) |
17.8 Watts |
| Thermal Dissipation (max) |
60.6 BTU/Hr |
| Mounting |
Vertical / Horizontal |
Applications and Integration
The Allen-Bradley 1791-16BC is purpose-built for Remote I/O applications, enabling distributed control across a plant floor. It is compatible with Allen-Bradley controller platforms including PLC-2, PLC-3, PLC-5, and SLC 5000 families. Depending on the controller, the Remote I/O baud rate can be set from 57.6K to 230.4K baud. At 57.6K baud, the module supports up to 10,000 cable-feet; at 115.2K, up to 5,000 feet; and at 230.4K, up to 2,500 feet. This flexibility allows the 1791-16BC to be placed near the machinery it controls, reducing long wire runs and simplifying troubleshooting. Typical applications include material handling systems, packaging lines, and process control skids where distributed I/O improves system response and reduces installation costs.
Installation and Mounting
Mount the Allen-Bradley 1791-16BC in a suitable enclosure to protect it from dust, dirt, grease, oil, water, and chemicals. The module can be mounted vertically or horizontally; however, the output current rating depends on orientation and ambient temperature. At 60°C, vertical mounting allows 500 mA per output, while horizontal mounting allows 250 mA. At 30°C, these ratings increase to 1 A (vertical) and 500 mA (horizontal). Keep at least 2 inches of clearance on all sides for proper airflow. The module connects in a daisy-chain topology and operates as a Remote I/O adapter, requiring a scanner module to exchange data with the controller. The module is internally fused, so no external power fusing is needed, but note that outputs are not fused—ensure external protection if required by your application.
Maintenance and Reliability
Routine inspection of the Allen-Bradley 1791-16BC focuses on verifying the enclosure seal, checking for loose connections, and monitoring ambient temperature. The module’s maximum power dissipation of 17.8 Watts and thermal dissipation of 60.6 BTU/Hr indicate that adequate ventilation is essential for long-term reliability. Periodic cleaning of the enclosure and checking for corrosion on terminals will help prevent intermittent faults. Because the outputs are not fused, consider adding external fuses or circuit breakers to protect downstream wiring. The module’s robust design and low component count contribute to a long service life, reducing downtime and total cost of ownership.
Selection Guide
When selecting the Allen-Bradley 1791-16BC, verify that your controller supports Remote I/O communication and that the baud rate and cable length meet your system requirements. Confirm the input/output voltage range matches your field devices (10-30VDC). Also, ensure your enclosure provides the required clearance and environmental protection. For reliable sourcing, choose PLC Source PRO, a trusted supplier of industrial automation spares, to guarantee genuine Allen-Bradley components.