The Allen-Bradley 1756-PLS is a high-speed Programmable Limit Switch (PLS) module designed for the ControlLogix 1756 chassis platform. This module provides ultra-low-latency monitoring and control by executing position-based logic directly at the hardware layer, bypassing standard controller backplane scan times. It is specifically engineered for high-velocity applications that require precise position tracking and rapid output actuation, such as rotary indexing, stamping presses, and high-speed packaging lines.
Features
Hardware-level processing for real-time position monitoring and limit comparison.
Occupies three contiguous slots in a ControlLogix chassis.
Includes 16 digital inputs and 16 solid-state digital outputs.
Isolated I/O groups to reduce signal crosstalk and enhance noise immunity.
Supports direct interface with high-resolution resolver sensors.
Compatible with 1756-TBNH (cage clamp) and 1756-TBSH (spring clamp) removable terminal blocks.
Applications
This module is ideal for industrial environments where precise timing and position-dependent control are critical, including:
Automotive stamping and press machinery.
High-speed rotary indexing tables.
Automated bottling and packaging systems.
Material handling and high-speed motion synchronization.
Technical Specifications
Model
1756-PLS
Input Count
16 Single-Ended
Output Count
16 Solid-State
Input Voltage Range
10 to 31.2 VDC
Output Current
1.0 A per point
Backplane Current (5.1V)
1000 mA
Backplane Current (24V)
125 mA
Power Dissipation
25.7 W (at 30 deg C)
Operating Temperature
0 to 60 deg C
Weight
0.91 kg
Installation Guidelines
Ensure the ControlLogix chassis power is disconnected before inserting or removing the module to prevent electrical arcing and memory corruption.
The module requires three contiguous slots; verify chassis space availability prior to installation.
Use shielded cabling for resolver inputs to minimize EMI interference in high-noise industrial environments.
Ensure proper grounding of the chassis backplane to maintain signal integrity.
Verify that the selected Removable Terminal Blocks (RTB) are securely seated and locked into the module housing.
Maintain adequate ventilation around the chassis to manage the 25.7W maximum power dissipation.
FAQ
Does the 1756-PLS require a specific terminal block? Yes, the module requires three 1756-TBNH (cage clamp) or 1756-TBSH (spring clamp) removable terminal blocks for field wiring.
Can this module operate independently of the controller scan time? Yes, the 1756-PLS executes positional logic at the hardware level, allowing it to trigger outputs faster than standard backplane-dependent I/O modules.
