PRODUCT INFORMATION
Product Overview
The Allen-Bradley 1785-LT2 is a PLC-5 processor module designed for centralized industrial control applications. This controller includes 13 KWords of internal SRAM memory. Memory capacity expands up to 17 KWords or 21 KWords using memory expansion options. The unit executes ladder logic and Sequential Function Chart programming languages. It controls up to 1024 total I/O points across standard configurations.
This processor supports connection to 1771 series power supplies and remote I/O chassis networks. It includes dedicated communication ports for Data Highway Plus and Remote I/O links. The module requires complete system power disconnection before removal or replacement. Convection cooling maintains safe operating limits up to 60 degrees Celsius inside industrial control enclosures.
TECHNICAL DATA
Technical Specifications
| Parameter | Specification |
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| Category | PLCs |
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| Product Line | PLC 5 |
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| GTIN | 10612598008893 |
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| Weight | 3.00 lbs (1.36 kg) |
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| Max I/O Chassis Universal Remote | 16 Max |
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| Max I/O Chassis Total | 17 |
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| I/O Scan Time Per Rack | 10 ms at 57.6 kbits/s, 7 ms at 115.2 kbits/s, 3 ms at 230.4 mbits/s |
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| Module Type | Processor |
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| Communication Ports | DH+; Remote I/O |
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| Controller Memory | 13 Kilowords SRAM |
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| Controller Memory expansion | up to 17 or 21 Kilowords |
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| Controller Redundancy | Supported |
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| Max Total I/O | 3072 (any mix) or 3072 in + 3072 out (complementary) |
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| Analog I/O | 1024 |
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| DH+ Channel | Yes |
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| Remote I/O Channel | Yes |
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| Number of Words | 13 Kilowords SRAM (expands to 17 or 21 Kilowords) |
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| Max Analog I/O | 3072 |
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| Max I/O Chassis Extended Local | 0 |
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| RS-232-C/422-A/423- A Ports | 1 |
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| Control Coprocessor Expansion Port | Yes |
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| UPC | 10612598008893 |
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TECHNICAL INFORMATION
Features
- Standard internal memory of 13 KWords SRAM expandable to 17 KWords or 21 KWords.
- Integrated Data Highway Plus and Remote I/O communication ports.
- Serial communication interface supporting RS-232-C, RS-422-A, and RS-423-A protocols.
- Execution of ladder logic and Sequential Function Chart control programs.
- Controller redundancy support via the 1785-BCM backup communication module.
- Compatibility with optional 1785-MJ and 1785-MK backup EEPROM memory cartridges.
TECHNICAL INFORMATION
Applications
- Centralized machinery and plant floor automation using 1771 I/O hardware.
- Remote I/O distributed monitoring across remote chassis networks.
- Peer-to-peer data interchange over industrial Data Highway Plus communication trunks.
- High-availability process control utilizing dual-controller redundancy schemes.
TECHNICAL INFORMATION
Connections / Interfaces
- One dedicated Data Highway Plus (DH+) network connection port.
- One dedicated Remote I/O (RIO) network communication link.
- One configurable RS-232-C / RS-422-A / RS-423-A serial programming interface.
- Dedicated control coprocessor expansion interface.
TECHNICAL INFORMATION
Installation Guidelines
- Never insert or remove this processor while chassis backplane power is active.
- De-energize all chassis supply power and confirm the area is non-hazardous before handling.
- Maintain clear enclosure clearance to ensure adequate vertical convection airflow.
- Provide filtered fan air or an air exchanger if ambient air beneath the chassis exceeds 60 °C.
TECHNICAL INFORMATION
Configuration Guidelines
- Configure serial ports and network station addresses prior to final system commissioning.
- Select matching Remote I/O transmission rates across all network adapter chassis.
- Install optional 1785-MJ or 1785-MK EEPROM cartridges for non-volatile logic backup.
TECHNICAL INFORMATION
Compatibility
- Allen-Bradley 1771 series I/O chassis and universal remote I/O adapters.
- Allen-Bradley 1785-BCM backup communication module for redundant controller architectures.
- Power supply models 1771-P3, 1771-P4, 1771-P4S, 1771-P4S1, 1771-P4R, 1771-P5, 1771-P6S, 1771-P6S1, 1771-P6R, 1771-P7, and 1771-PS7.
TECHNICAL INFORMATION
Compliance and Certifications
- IEC 60664-1 Pollution Degree 2
- IEC 60664-1 Installation Category II
TECHNICAL RESOURCES
Documentation
COMPATIBILITY
Compatibility & Replacement
COMPATIBLE MODELSAllen-Bradley 1771 series I/O chassis and universal remote I/O adapters. Allen-Bradley 1785-BCM backup communication module for redundant controller architectures. Power supply models 1771-P3, 1771-P4, 1771-P4S, 1771-P4S1, 1771-P4R, 1771-P5, 1771-P6S, 1771-P6S1, 1771-P6R, 1771-P7, and 1771-PS7.
Verify compatibility against the exact Part Number, revision and manufacturer documentation before ordering.
PART VERIFICATION
Before You Order
Industrial automation parts can share similar model names, suffixes and revisions. Confirm the complete manufacturer Part Number before purchase.
01Check Part NumberMatch the complete ordering code on the existing unit.
02Confirm RevisionCheck suffix, hardware or firmware when applicable.
03Send a Label PhotoWe can review a clear label photo when identification is uncertain.
ORDERING PROCESS
From RFQ to Dispatch
1Submit Part Number2Verify Product Identity3Confirm Stock & Condition4Issue Quotation5Dispatch & Tracking
PRODUCT FAQ
Frequently Asked Questions
What is the standard memory capacity of the Allen-Bradley 1785-LT2?
The 1785-LT2 includes 13 KWords of SRAM. It can be expanded to 17 KWords or 21 KWords.
Can the 1785-LT2 processor be removed or inserted under power?
No. The 1785-LT2 does not support removal or insertion under power. Power must be off before servicing.
Which communication protocols are integrated into the 1785-LT2 module?
The module includes embedded Data Highway Plus, Remote I/O, and an RS-232-C/422-A/423-A serial communication interface.
What is the reference price for an Allen-Bradley 1785-LT2 controller?
Observed market reference pricing is approximately $126.00 USD for refurbished units. Pricing figures are indicative market reference pricing only and are not a final quotation.
