Product Overview

The Allen-Bradley 1756-IB16I​ is a sixteen-channel, 24V DC isolated digital input module for the Rockwell Automation ControlLogix 1756 platform. It differs from an ordinary 1756-IB16 in one architecturally important respect: each pair of inputs shares an isolated common, so the module provides eight electrically independent commons across its sixteen points. This means eight different DC supply sources—at different potentials, from different panels, or from different pieces of equipment—can be read by one module without a single shared reference, and without the cross-talk, ground-loop, and common-mode problems that make a conventional grouped-common input card unusable in mixed-voltage panels.Each of the sixteen inputs is a sinking input with a nominal 24V DC operating voltage and a broad 10–31.2V range. The input current is 4.0 mA at 24V DC, and the fixed 5.0 mA threshold with 2.2 mA hysteresis gives the Allen-Bradley 1756-IB16I​ predictable switching behavior even when the field supply is poorly regulated or the cable run is long. The response time is 9.6 ms for both turn-on and turn-off, deliberately slow enough to ignore contact bounce and conducted transients from contactors and VFDs, yet fast enough for ordinary discrete sensing. A DC input filter is built into the module, and the input logic is isolated from the backplane by 1500V AC.A further capability that distinguishes the Allen-Bradley 1756-IB16I​ is the onboard 24V DC field-side supply. The module can deliver 250 mA at 24V DC to field devices, with an inrush capability of 2.6 A, allowing it to power a small bank of sensors, switches, or interposing relays without a separate DIN-rail supply. The field supply is independently isolated from the logic-side backplane, preserving the galvanic separation that is the module’s principal value. Sixteen input status LEDs give immediate visual confirmation of each channel, and the Allen-Bradley 1756-IB16I​ draws 1.4 A at 5.1V and 3 mA at 24V from the backplane while dissipating a maximum of 1.9 W—modest figures that simplify power and thermal budgeting in a densely populated 1756-A7 or 1756-A10 chassis.

Technical Specifications