Allen-Bradley 1771-QB Closed-Loop Control Linear Positioning Module

The Allen-Bradley 1771-QB Linear Positioning Module for PLC‑5 delivers two independent closed‑loop axes of hydraulic servo control, using magnetostrictive linear displacement transducers for precise position feedback. Designed for PLC‑5 backplanes, this dual‑loop module updates each axis every 2 ms and provides a single‑slot solution for compact linear positioning tasks. Each loop offers dual control inputs (two general‑purpose inputs per axis) with 8 mA max at 12 V or 16 mA max at 24 V, where Logic 0 is 0–4 V and Logic 1 is 10–30 V. The servo valve drive is supplied as an analog output source capable of 0–10 V DC or current outputs up to 100 mA, enabling direct control of hydraulic actuators. Backplane current draw is specified as 1.6 A max (typical about 1.1 A), underscoring its role as a power‑hungry but precise motion module within a PLC‑5 rack. The 1771‑QB integrates with common 1771 accessories, such as the wiring arm 1771‑WN, and is intended for applications requiring accurate linear positioning of tools or workpieces along one or two axes, where feedback from magnetostrictive transducers closes the loop for stable, repeatable motion. This module is typically used in hydraulic servo systems and other closed‑loop positioning setups that demand reliable axis control within legacy PLC‑5 architectures.