Product Overview
The Allen-Bradley 1785-L26B is a PLC-5/26 standard processor designed for robust control in demanding industrial environments. This industrial automation module delivers dependable performance with 16K of battery-backed SRAM, ensuring your program remains secure during power interruptions. With support for up to 512 analog I/O or 512 discrete I/O in any mix, the 1785-L26B offers flexible configuration to match your application needs.
Built for seamless integration, the 1785-L26B works with most 1771, 1794, 1746, and 1791 I/O modules, and its multiple communication ports—including RS-232/422/423, DH+, and Remote I/O—provide versatile connectivity options. Whether you are upgrading an existing PLC-5 system or building a new control solution, this processor delivers the reliability and performance you expect from Allen-Bradley.
Technical Specifications
| Specification |
Value |
| Manufacturer |
Rockwell Automation |
| Brand |
Allen-Bradley |
| Part Number |
1785-L26B |
| Module Type |
Standard Processor |
| Processor |
PLC-5/26 |
| Max User Memory Words |
16 Kilowords |
| Battery-Backed Static RAM |
Yes |
| EEPROM Program Backup Option |
Yes (using 1785-ME16, -ME32, -ME64, -M100) |
| Protected Memory |
Yes |
| Max Total I/O |
512 (any mix) or 512 in + 512 out (complementary) |
| Max Analog I/O |
512 |
| 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 |
| Max I/O Chassis Total |
13 |
| Max I/O Chassis Extended Local |
0 |
| Max I/O Chassis Universal Remote |
12 |
| RS-232-C/422-A/423-A Ports |
1 |
| Control Coprocessor Expansion Port |
Yes |
Key Features & Benefits
-
Battery-backed SRAM: Retains your program and data even during power loss, minimizing downtime.
-
Flexible I/O capacity: Supports up to 512 I/O points, allowing you to scale your system as needed.
-
Multiple communication ports: RS-232/422/423, DH+, and Remote I/O ports enable easy integration into existing networks.
-
Protected memory: Safeguards critical data from unauthorized access or accidental modification.
-
Wide environmental tolerance: Operates in temperatures from 0 to 60°C and humidity up to 95% without condensation.
Industry Applications
The 1785-L26B is ideal for applications requiring reliable control and monitoring, such as:
- Manufacturing assembly lines
- Material handling systems
- Process control in chemical or food processing plants
In a typical manufacturing line, the processor manages multiple I/O points, coordinating machine actions and ensuring smooth operation. Its robust design and flexible I/O configuration make it a dependable choice for critical processes.
Installation & Setup Guidance
Install the Allen-Bradley 1785-L26B in the left-most slot of a 1771 I/O chassis. Ensure the backplane provides 5 VDC with at least 2.6 amps available. Connect the serial port (25-pin D-shell) to your programming terminal using a standard RS-232 cable. For network connectivity, attach the DH+ port to the Data Highway Plus network and the Remote I/O port (Channel 1B) to remote racks.
When configuring the processor, select the appropriate I/O addressing mode (2-slot, 1-slot, or half-slot) based on your module types and density. Refer to the user manual for detailed configuration steps.
Maintenance & Reliability
Regular maintenance ensures long-term reliability. Periodically check the battery voltage to guarantee SRAM retention. Inspect the chassis and connections for dust or corrosion. The processor withstands operational shock of 30G and vibration of 1G at 10-500 Hz, making it suitable for harsh environments.
For extended reliability, consider using an EEPROM backup module (1785-ME16, -ME32, -ME64, or -M100) to store your program externally. This provides an extra layer of security against memory loss.
Compatibility & Integration
The 1785-L26B integrates seamlessly with a wide range of Allen-Bradley I/O modules, including 1771, 1794, 1746, and 1791 series. It supports up to 13 I/O chassis (12 universal remote and 0 extended local). The processor communicates via standard serial interfaces (RS-232, RS-422, RS-423) and DH+ networks, ensuring compatibility with existing Rockwell Automation systems.
Selection Guide & Purchasing Advice
Before purchasing, verify that your application requires a PLC-5/26 processor and that the I/O capacity fits your needs. Confirm the backplane power supply can deliver 2.6 A at 5 VDC. Also, check the communication ports required—if you need DH+ or Remote I/O, this model supports both.
At PLC Source PRO, we supply genuine, tested automation parts. Our inventory includes the Allen-Bradley 1785-L26B and compatible accessories. Contact our team for availability and pricing.