1791-IOBW

The Allen-Bradley 1791-IOBW is a Block I/O module with Thirty-Two (32) 24VDC sink input channels and Thirty-Two (32) 24VDC source output channels. This module is a modular automation device that is built with a Remote I/O adapter, power supply, communication interface, signal conditioning circuitry as well as the I/O interfaces.

The 1791-IOBW is a legacy device. It works as a Remote I/O module for controller platforms such as PLC2, PLC3 and PLC5 automation platforms as well as SLC500 controllers with RIO scanner 1747-SN installed however, the 1791-IOBW is not compatible with 1747-DSN.

This module supports Block I/O instructions such as Block Transfer Read (BTR) and Block Transfer Write (BTR) instructions. Using this instructions, data from the Block I/O module may be sent to the controller via Block Transfer Read (BTR) instruction while commands from the processor may be sent to the module using Block Transfer Write (BTR) instruction. These instructions are sent over a physical RIO cable medium, specifically, Belden 9463 cable or equivalent. With Remote I/O protocol, this Block I/O module may be connected to the controller following Daisy-chain topology. It supports transmission speeds of 57.6K for 10,000 cable-feet; 115.2K for 5,000 cable-feet and 230.4K 2,500 cable-feet.

The 1791-IOBW’s external power supply ranges is 18 to 26.4V dc with current of 100mA @ 24V dc. It can withstand an inrush current of 2.0A for 10ms, initial surge. This module has power dissipation of 15.1 Watts (maximum) with7.6 Watts (typical) and Thermal Dissipation of 51.8 BTU/hr (maximum)with 25.9 BTU/hr (typical).

The device has a rack address switch, various configuration switches, and a termination register switch. LED indicators are also provided for Power, Active, Fuse, and Communication switches. A separate LED array is also provided to monitor the Input/ Output status. 37-pin, removable terminal blocks are provided in two separate blocks to connect the remote I/O. Module configuration such as last state, last rack, I/O group, baud rate, and processor restart lockout is set using the embedded configuration switches. To connect external power and remote I/O links, a separate terminal block is also provided. External power to the device must be in the range of 18 to 26.4 Volts DC. The 1791-IOBW has a maximum power dissipation of 15.1 Watts and a maximum thermal dissipation of 51.8 BTU/hour. The dimensions of the device are 156.21 X 178 X 44.7 millimeters. To connect the device, use gauge 14 stranded wires at maximum, but no larger. The device is to be operated between 0 and 60 degrees Celsius and can be stored between -40 and 85 degrees Celsius. While installing, remember to connect the left side terminals to the input and the right side terminals to the output. Use a Belden9463 cable type while connecting the remote I/O link and while using a remote I/O link wiring, remember to always wire the blocks in series and never in a parallel manner. To terminate both ends of a remote I/O link, always use a terminator register, even if it is the last block on a PLC system remote I/O link It is important to note that the 1791-IOBW is not compatible with the 1747-DSN I/O distributed scanner module.