The Allen-Bradley 1746-IO4 is a compact, entry-level combination I/O module designed for the SLC 500 series programmable controller family. This module provides a space-saving solution for small-scale automation tasks, featuring two 120V AC inputs and two relay contact outputs (Form A, Normally Open). It is an ideal choice for simple control loops or for expanding a chassis with minimal I/O requirements without occupying excessive slot space.
Features
Compact Design: Smallest combination I/O unit in the SLC 500 series.
Versatile Relay Outputs: Dry contacts support a wide range of switching voltages, including 5 to 265V AC or 5 to 125V DC.
Low Power Consumption: Minimal backplane current draw (30 mA at 5V DC) preserves the system power budget.
Flexible Input: Two integrated 120V AC inputs for standard industrial sensing.
Applications
The 1746-IO4 is commonly utilized in small machine control, auxiliary I/O expansion for SLC 500 chassis, and simple interlock or monitoring applications where only a few points of I/O are required.
Technical Specifications
Brand
Allen-Bradley
Product Line
SLC 500
Module Type
Digital I/O Combination Module
Inputs
2 x 120V AC
Outputs
2 x Relay (Form A, Normally Open)
Input Voltage Range
85–132V AC (47–63 Hz)
Output Voltage Range
5–265V AC / 5–125V DC
Max. Continuous Current (Relay)
1.5A at 120V AC / 1.2A at 24V DC
Backplane Current (5V DC)
30 mA
Backplane Current (24V DC)
25 mA
Signal Delay
35 ms (ON) / 45 ms (OFF)
Operating Temperature
-25 to 60 degC (-13 to 140 degF)
Installation Guidelines
Power Down: Always remove power from the SLC 500 chassis before inserting or removing any I/O module to prevent electrical damage or unexpected system behavior.
ESD Protection: Handle the module by its edges and avoid touching the backplane connector pins to prevent electrostatic discharge damage.
Mounting: Ensure the module is fully seated in the chassis slot and the top/bottom retaining screws are tightened to secure the module and ensure proper grounding.
Wiring: Use shielded cables for I/O signals to minimize EMI interference. Keep high-voltage AC wiring separate from low-voltage signal wiring.
Environment: Ensure the installation location provides adequate ventilation to maintain the operating temperature within the specified range.
FAQ
What is the primary function of the 1746-IO4?
The 1746-IO4 acts as a combination I/O module for the SLC 500 system, providing two AC inputs for sensors and two relay outputs for switching external devices.
Can the relay outputs switch DC loads?
Yes, the relay contacts are "dry" and can switch both AC and DC voltages within the specified ranges (5–265V AC or 5–125V DC).
