Allen-Bradley 1771-OB DC Output Driver Module

Allen-Bradley 1771-OB is an 8-point digital DC output driver module for PLC-5 backplanes that switches DC loads from a 10–27 V DC range (commonly powered by 12–24 V systems). Each of the eight outputs can carry up to 1.5 A, with a total module current limit of 8 A to protect the backplane. Key specifications include an on-state voltage drop up to 2 V DC, off-state leakage current of about 1 mA per output, and a surge capability of 4 A for 1 ms per output. Turn-on and turn-off delays are specified at roughly 10 ms, supporting reliable control of field devices. The module is fused per output with 2 A, 8 AG fuses, and it draws approximately 165 mA from the I/O backplane at 5 V. Field wiring connections are made via the 1771-WA wiring arm, which interfaces with the PLC-5 rack. In practical use, the 1771-OB provides robust, discrete DC switching under PLC-5 control, making it suitable for driving DC actuators and signaling devices in industrial automation applications.