Allen-Bradley 1764-24BWA MicroLogix 1500 24 I/O Base Unit

Description

Product Introduction

The Allen-Bradley 1764-24BWA is a 24-point base unit for the MicroLogix 1500 PLC platform. Unlike traditional fixed-brick controllers, this split-architecture design houses the system power supply, embedded I/O wiring terminals, and backplane interface while accepting a slide-in 1764 processor module (such as the 1764-LSP or 1764-LRP).

Operating on 120/240V AC power, the 1764-24BWA delivers 12 DC inputs and 12 individually isolated relay outputs. Its split architecture allows maintenance teams to upgrade processor memory or replace damaged field wiring bases independently, cutting panel downtime during emergency repairs.

Key Technical Specifications

Application Scenarios & The “Trench” Experience

The Trench Story

It is midnight on a Friday when a plant operator over-tightens a terminal block on a stamping press control cabinet, cracking the internal trace on a MicroLogix 1500 base unit. The processor unit (1764-LRP) and all stored recipe data are completely intact, but the base cannot route power to the output relays. Instead of spending hours re-uploading programs, re-keying parameters, or wiring an entirely new PLC platform, you unclip the existing processor, slide it directly into a replacement 1764-24BWA base, transfer the removable terminal blocks, and power the press back up in under 10 minutes.

Specific Applications

• Automated Stamping Presses: High-speed 20kHz inputs capture position pulses from rotary encoders while clean relay contacts trigger hydraulic solenoid valves.
• Commercial HVAC Control: Drives large contactor coils and damper actuators via isolated relay outputs while monitoring pressure switch digital inputs.
• Batch Chemical Mixing: Utilizes 1769 Compact I/O expansion modules alongside the base I/O to handle multi-stage valve sequences and pump motor starters.
• Bulk Material Conveyors: Serves as a rugged localized controller running stop/start logic, optical sensor tracking, and safety interlocks.

1764-24BWA

1764-24BWA

1764-24BWA

Transparency SOP: Quality Assurance & Testing

We subject every 1764-24BWA base unit to rigorous testing on live 1764 hardware rigs before shipping:

1. Inbound & Mechanical Inspection: We check for damaged plastic latches, inspect the processor edge-connector socket for bent pins, and verify terminal block retention screws.
2. Processor Docking Test: We install a reference 1764-LSP processor to verify physical lock-in mechanism and smooth backplane bus handshakes.
3. Live I/O Channel Validation: All 12 digital inputs are fired individually with a 24VDC source, and input status LEDs are verified.
4. Relay Continuity & Load Testing: Each of the 12 relay channels is toggled under real electrical load to confirm zero contact resistance or contact welding.
5. Auxiliary Power Rail Audit: The onboard 24VDC auxiliary sensor power terminals are load-tested to verify regulated DC voltage output under full current draw.

The Veteran’s Tech Trap Guide

• ⚠️ Do Not Forget: This Unit Requires a Processor Module: The 1764-24BWA is a base unit only. It will NOT function or communicate without a 1764-LSP or 1764-LRP processor module seated into the top slot.
• ❗ Never Force the Processor Module: When sliding the 1764 processor into the 1764-24BWA base, line up the guide rails carefully. Forcing the processor down can bend or snap the gold-plated edge contacts on the base connector board.
• ⚠️ Expansion Bus Power Limits: While the 1764-24BWA supports 1769 Compact I/O modules, paying attention to power supply distance ratings is critical. Always calculate the total 5VDC and 24VDC bus current drawn by attached 1769 expansion modules to avoid backplane voltage drop.
• ❗ 120VAC Relay Circuit Isolation: The relay contacts on the 24BWA are isolated into distinct groups. Mixing 120VAC control power and 24VDC signals across adjacent terminals on the same block without verifying terminal separation can cause line-voltage shorts if a wire strays.

Frequently Asked Questions

Q: Is the 1764-24BWA a complete PLC by itself?

No. The 1764-24BWA is the base unit (power supply, input/output hardware, and expansion bus). You must install a 1764-LSP or 1764-LRP processor module into the top bay for logic execution and communication.

Q: What expansion modules work with the 1764-24BWA base?

The MicroLogix 1500 system uses 1769 Compact I/O modules (the same I/O used in CompactLogix systems) via a right-side bank expansion cable or direct bus connection.

Q: Do I need to re-download the program if I replace only the base unit?

No. Your program, retentive memory, and comm settings live on the 1764 processor module (or its memory card). As long as you transfer your original processor module into the new 1764-24BWA base, the system retains all logic and parameters.

Q: What is the difference between the 1764-24BWA and the 1764-24AWA?

The power supply for both is 120/240VAC with relay outputs. However, the 24BWA features 24VDC sink/source inputs, whereas the 24AWA uses 120VAC inputs. Make sure your field sensors match the input voltage requirement before installing.

Q: How does your 12-month warranty work on surplus 1764 hardware?

If the base unit experiences any hardware fault within 365 days of purchase, contact us for an immediate unit replacement from our ready surplus stock or a full return/refund if stock is unavailable.

Q: Is it better to replace this base unit or upgrade to a CompactLogix system?

If your goal is minimizing immediate downtime and panel re-engineering costs, replacing the 1764-24BWA takes minutes and requires zero wiring redrafts. If you are planning a full facility modernization, a CompactLogix migration can be scheduled for a planned shutdown later.