Product Overview
Downtime on an SLC 500 line often traces back to a single failed I/O card. The Allen-Bradley 1746-IV8 is an 8-channel, 24 Volt DC sourcing discrete input module built for the SLC 500 platform. It lets your processor read change-of-state signals from field devices without an external power supply, because it draws 0.050 Amperes at 5 Volts DC directly from the backplane.
This single-slot module installs in any vacant slot of an SLC 500 chassis. Each of its eight inputs sits in one group, so wiring stays simple and troubleshooting stays fast. If you maintain legacy SLC 500 systems, this module is a practical replacement and upgrade path that keeps existing panels running.
Technical Specifications That Matter
Three parameters drive real-world performance on this module.
Wide 10-30 VDC Input Range
Every channel accepts 10-30 Volts DC source signals. That headroom tolerates the voltage sag and ripple common on 24 Volt DC industrial supplies, so nuisance input dropouts become far less likely.
Fast 8 ms Signal Delay
Both the Off-to-On and On-to-Off transitions carry an 8 ms signal delay. For limit switches, auxiliary contacts, and proximity sensors, this response keeps scan-cycle timing predictable.
Low Off-State Leakage
In the off state, the module holds a maximum of 5.0 Volts DC and 1 milliampere. Nominal input current is 8 milliamperes at 24 Volts DC. These figures matter when nearby sensors leak small currents that can falsely trigger lesser input cards.
Where the 1746-IV8 Fits
Material Handling and Conveyors
Photo-eyes and limit switches on sortation lines feed 24 Volt DC signals straight into the 1746-IV8. The 10-30 VDC window absorbs supply variation across long cable runs, and the 8 ms delay keeps tracking accurate at line speed.
Packaging and Assembly Cells
Auxiliary contacts from contactors and safety relays report machine state to the SLC 500 processor. With one group of eight channels, technicians trace faults quickly during shift handover.
Replacement and Upgrade Projects
When an existing input card fails, the 1746-IV8 drops into any vacant SLC 500 slot. No external supply, no rewiring of the backplane, and no new panel footprint. That is the core ROI argument: replace one card instead of rebuilding the rack.
Installation and Setup
The module installs directly into any SLC 500 chassis slot and occupies only one slot. Signal termination uses 14 AWG (2 millimeter) cable. Front-panel LED indicators show channel status at a glance.
Always remove power from the rack power supply before inserting or removing the module. The backplane supplies module power, and hot-swapping can cause an electrical arc. Arcing can injure personnel and wear the contacts on both the module and its mating connector. Worn contacts raise electrical resistance and reduce reliability.
The 1746-IV8 ships as open-type equipment for industrial environments. Operate it between 0 and +60 degrees Celsius (+32 to +140 degrees Fahrenheit) with relative humidity of 5 to 95 percent, without condensation. Storage range is -40 to +85 degrees Celsius (-40 to +185 degrees Fahrenheit).
Maintenance and Reliability
Plan periodic inspections of terminal connections and channel LEDs. Loose terminations and worn mating contacts are the most common causes of intermittent input faults. Keep the panel within the rated humidity range and free of condensation to protect the module long term.
Because the module needs no external supply, there is one less power source to fail. That simplicity lowers spare-parts cost and shortens mean time to repair. Keep one spare card on the shelf, and a failed input channel becomes a minutes-long swap instead of a production stoppage.
Compatibility and Integration
The 1746-IV8 belongs to the SLC 500 series and works with SLC 500 processors and chassis. It interfaces directly with auxiliary contacts, limit switches, sensors, and similar signaling devices. The number of modules you can add depends on the host processor’s I/O capability, available slots, and chassis count.
Selection Guide
Before ordering, confirm your field devices supply 24 Volt DC sourcing signals within the 10-30 VDC range. Verify your chassis has a vacant single slot and that your processor supports the additional input count. Check that off-state leakage from connected sensors stays below 1 milliampere.
SpareTechPLC supplies the 1746-IV8 and other SLC 500 modules for maintenance and upgrade projects. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Frequently Asked Questions
Does the 1746-IV8 need an external power supply?
No. It draws 0.050 Amperes at 5 Volts DC from the SLC 500 backplane, so no external supply is required.
What input voltage range do the channels accept?
Each of the eight channels accepts 10-30 Volts DC sourcing signals.
How fast does the module respond to input changes?
Both the Off-to-On and On-to-Off transitions have an 8 millisecond signal delay.
Can I install it in any SLC 500 chassis?
Yes. It is a single-slot module that installs directly into any vacant SLC 500 chassis slot.
What cable size should I use for signal termination?
Use 14 AWG (2 millimeter) cable for signal termination.
