Configured for high-density digital signal acquisition in PLC-5 control systems, the Allen-Bradley 1771-IBD (1771-IBD Digital Input Module) provides direct electrical interface for 16 discrete input channels. The module facilitates the conversion of field-level 10-30 VDC signals into logic-level data for backplane processing.

Technical Specifications

Backplane Bus Communication and I/O Scaling

The 1771-IBD utilizes the standard 1771 I/O backplane protocol to communicate with the PLC-5 processor. The module hardware supports 1/2, 1, or 2-slot addressing modes, allowing for flexible I/O density scaling within the chassis. Optoelectrical isolation is integrated into the circuitry to maintain signal integrity and provide transient protection between the field-side signaling devices and the PLC backplane bus. Firmware compatibility is dictated by the revision of the 1771 backplane interface, ensuring deterministic data exchange during scan cycles.

Package Contents

• 1 1771-IBD Digital Input Module

• 1 1771-WH Field Wiring Arm

Installation and Integration Procedures

• Chassis Preparation: De-energize the 1771 I/O chassis power supply before module installation or removal.

• Keying: Install plastic keying bands on the chassis backplane connector to match the module keying slots located between pins 10-12 and 16-18.

• Module Insertion: Align the module with the chassis card guides and apply uniform pressure to seat the module firmly into the backplane connector.

• Wiring Arm Attachment: Mount the 1771-WH wiring arm to the chassis pivot bar to allow for signal termination and modular module removal.

• Locking: Secure the module using the built-in chassis latching mechanism to ensure proper seating and electrical contact.

Technical FAQs

• What is the primary function of the 1771-WH wiring arm?The 1771-WH facilitates modular wiring, allowing users to remove the module for maintenance or replacement without disconnecting the individual field wires from the terminal block.

• Does the 1771-IBD support hot-swapping?No. The 1771 I/O system requires the chassis power to be cycled off before removing or inserting modules to prevent potential damage to the backplane circuitry.

• What is the purpose of the keying bands?Keying bands prevent the insertion of incompatible modules into a specific slot, which protects the module and backplane from electrical damage due to voltage or signal mismatches.

• How is the input signal isolated?The module incorporates optoelectrical isolation, which acts as a barrier to prevent high-voltage transients or electrical noise from the field devices from entering the PLC processor backplane.

• What is the maximum signal delay for this module?The 1771-IBD exhibits a typical signal delay of 1.3 ms (plus or minus 0.1 ms) for both the on-state and off-state transitions.

• Can this module be used in a 1771-A2 chassis?No. The 1771-IBD is specifically documented as incompatible with the 1771-A1, 1771-A2, and 1771-A4 chassis models.

• How should field wires be torqued?Wiring arm screws should be tightened to a specification of 7-9 inch-pounds to ensure a secure connection and prevent contact resistance.

• What indicates the status of the input channels?The front panel features 16 red LEDs to display the state of each input channel and 1 green LED for general module status indication.