Product Type and Core Positioning

• Product Type Name: SLC 500 Digital Output Module.

• Output Type: Relay Output.

• System: Allen-Bradley SLC 500? I/O System.

• Primary Use: Serves as a "switching interface" between the PLC controller and field devices, converting digital control signals from the processor into physical switching actions to start/stop motors, control solenoid valves, illuminate indicator lights, etc.

Key Technical Specifications

• Number of Output Channels: 16 independent output points, providing high-density output capability and saving rack space.

• Output Form: Single Pole Double Throw (SPDT) relay. Each output point includes a common terminal (C), a normally open terminal (NO), and a normally closed terminal (NC), allowing flexible configuration as either normally open or normally closed contacts.

• Load Capacity:

• AC Load: Up to 2A @ 120/240V AC (resistive load).

• DC Load: Up to 2A @ 24/30V DC (resistive load).

• Can directly drive common industrial loads such as small motors, contactor coils, solenoid valves, and indicator lights.

• Isolation Method: Backplane bus isolation. Electrical isolation between the output circuit and the PLC backplane is achieved through internal relays, effectively preventing field interference from affecting the controller.

• Response Time: Relay actuation time is approximately 10ms ON / 5ms OFF, suitable for most medium to low-speed switching control applications.

• Surge Protection: Built-in RC snubber circuit or diode (for DC loads) to suppress back EMF generated when inductive loads (such as coils and motors) are disconnected, protecting relay contacts.

Physical Characteristics and Installation

• Dimensions: Dual-slot module occupying 2 slots, approximately 90mm wide.

• Mounting Method: Supports DIN rail mounting or panel mounting.

• Rack Compatibility: Installs in any slot of the 1746 series I/O racks (e.g., 1746-A4, A7, A10, A13), except for the CPU-dedicated slot at position 0.

• Wiring Method: Uses removable screw terminal blocks (typically 1746-TBNH or dedicated terminal blocks) for easy field wiring and maintenance.

• Power Supply: Obtains operating power (+5VDC and +24VDC) through the rack backplane, eliminating the need for additional power wiring.

Functional Features and Advantages

• High Channel Density: 16 output channels are particularly notable among similar relay modules, making it especially suitable for applications requiring a large number of discrete outputs.

• Strong Load Compatibility: Capable of driving both AC loads (e.g., AC solenoid valves) and DC loads (e.g., DC relays, LED lights), offering a wide range of applications.

• Electrical Isolation: Physical isolation provided by the relays enhances system noise immunity and safety.

• Ease of Use: Seamlessly integrates with the SLC 500 system and is configured and monitored via RSLogix 500 software.

• Status Indication: LED indicators on the module panel correspond to each output point, displaying their on/off status in real time for easy debugging and troubleshooting.

Typical Application Scenarios

The 1746-OB16 is widely used in various industrial fields requiring multi-point switching control, such as:

• Control of cylinders and solenoid valves in packaging machinery

• Spindle start/stop and cooling pump control in machine tools

• Control of fans and damper actuators in HVAC systems

• Indicator lights and alarms in process control panels