The 1756-PLS ControlLogix Programmable Limit Switch (PLS) Module from Rockwell Automation is a specialized high-speed motion and positioning control module used to generate output signals based on rotary position feedback from a resolver.
Unlike standard I/O modules, the 1756-PLS is designed for precise machine timing applications, where outputs must be triggered at exact angular positions. It is commonly used in packaging machines, printing equipment, bottling systems, stamping presses, and rotating machinery automation.
The module continuously reads a resolver signal and activates or deactivates outputs based on programmed position “windows,” functioning like an electronic cam switch system.
Technical Specifications (Including Size & Weight)
| Parameter | Specification |
|---|---|
| Model | 1756-PLS |
| Series | ControlLogix Special Function Modules |
| Module Type | Programmable Limit Switch Module |
| Slot Requirement | 3 contiguous slots in ControlLogix chassis |
| Input Type | Resolver + 24V DC digital inputs |
| Output Type | 24V DC sourcing outputs |
| Number of Inputs | 16 digital inputs (typical configuration) |
| Number of Outputs | 16 DC outputs (4 groups) |
| Resolver Interface | 2Vrms excitation, sine/cosine feedback |
| Backplane Current (5V DC) | ~1.0 A |
| Backplane Current (24V DC) | ~125 mA |
| Power Dissipation | ~21–25 W |
| Output Voltage Range | 10–31.2V DC |
| Operating Temperature | 0°C to 60°C |
| Humidity | 5–95% non-condensing |
| Weight | ~0.9 kg |
| RTB Requirement | 3 removable terminal blocks (1756-TBSH / TBNH) |
Physical Dimensions
- Size (H × W × D): 145 × 35 × 140 mm (approx.)
(Actual footprint depends on 3-slot chassis installation requirement.)
Recommended Related Models
The 1756-PLS is often used alongside:
- 1756-L7 series ControlLogix CPUs (L71 / L73 / L75)
- 1756-EN2T EtherNet/IP communication modules
- 1756-IB16 / 1756-OB16 standard I/O modules
- 1756-MODULES for motion control systems
- Resolver feedback devices (846 series resolvers)
Popular ControlLogix Special Function Modules
Within ControlLogix systems, related motion/special modules include:
- 1756-PLS programmable limit switch module
- 1756-M02AE / M08SE motion modules
- 1756-HSC high-speed counter modules
- 1756-I/O standard digital and analog modules
These are used when standard PLC scan logic is too slow for precise timing or motion control.
