Allen-Bradley 1746-IN16 SLC 500 Digital Input Module

The 1746-IN16 is a 16-channel discrete digital input module manufactured by Allen-Bradley for the SLC 500 programmable logic controller system. Operating with a nominal rating of 24 VAC/VDC (sinking configuration), it converts field control signals into logic levels across the SLC 500 backplane. The module mounts into a single slot of any standard 1746 chassis and features channel-level LED status indicators for real-time visual signal verification.

Input Channel Configuration and Voltage Characteristics

The module accepts 16 discrete input channels operating over an expanded voltage range of 10-30 VAC/VDC. Designed as a sinking module, it receives current from sourcing field devices. Each channel draws a nominal input current of 8 mA at 24 V, with an off-state leakage current limit of 1 mA, rendering it compatible with proximity switches, pushbuttons, and industrial relay contacts.

Response Timing and Thermal Ratings

Signal filtering produces distinct propagation delays based on the field signal type. For DC control signals, signal delay for both ON-to-OFF and OFF-to-ON transitions is 15 ms, whereas AC control signals exhibit a 25 ms delay. The module consumes 0.085 A from the 5 VDC backplane bus, with a minimum power dissipation of 0.425 W and a maximum total module power dissipation of 6 W (0.35 W per point).

Chassis Integration and Wiring Accessories

The 1746-IN16 plugs directly into any available slot of an SLC 500 local or expansion rack (1746-A4, A7, A10, or A13). Field connections are routed through compatible terminal blocks, including the 1746-HT or pre-wired 1746-HCA wiring assemblies, allowing module removal without disconnecting individual field conductors.

Frequently Asked Questions

Q: Can the 1746-IN16 accept both AC and DC input signals on the same system? A: Yes, the module supports an operating voltage range of 10-30 VAC/VDC across its sinking input channels, though input propagation delay differs between AC (25 ms) and DC (15 ms) signals.

Q: How much current does the 1746-IN16 draw from the SLC 500 backplane? A: The module draws 0.085 A (85 mA) from the 5 VDC backplane bus.

Q: Does replacing a 1746-IN16 require disconnecting individual field wiring leads? A: No, when paired with removable terminal blocks such as the 1746-HT or pre-wired cable connectors like the 1746-HCA, the terminal block can be detached to replace the module while preserving field wiring.