Product Summary
The Allen-Bradley 1785-L26B is a PLC-5/26 standard processor that delivers 16 kilowords of battery-backed static RAM. It manages up to 512 total I/O in any mix or 512 inputs plus 512 outputs in complementary mode. This controller supports 512 analog I/O and works with multiple chassis types. It offers protected memory and an EEPROM backup option. Engineers rely on this module for robust field device control in demanding environments.
Product Procurement & Buyer Guide
Why Choose the 1785-L26B for Your System?
Procurement teams need a processor that balances memory capacity with I/O flexibility. The 1785-L26B provides 16 kilowords of user memory and battery-backed SRAM. This ensures program retention during power loss. The module handles any I/O mix or complementary configuration. You can scale from 512 in/out to 1024 total points. This reduces the need for multiple controllers and simplifies your BOM.
Critical Technical Specifications for Selection
The processor draws 2.6 amps at 5V DC from the 1771 chassis backplane. It supports up to 13 I/O chassis with up to 12 universal remote chassis. The I/O scan time per rack is 10 ms at 57.6 kbps, 7 ms at 115.2 kbps, and 3 ms at 230.4 kbps. Matching these scan rates with your application cycle time prevents bottlenecks. The unit also includes one RS-232/422/423 serial port and a Control Coprocessor expansion port.
Compatibility with I/O Modules and Networks
The 1785-L26B works with 1771, 1794, 1746, and 1791 I/O modules. It supports 2-slot, 1-slot, and half-slot addressing modes. This flexibility lets you mix 8, 16, and 32-point modules in a single rack. For communication, it offers a DH+ port and a Remote I/O port. These interfaces connect to Data Highway Plus networks and remote field devices. This makes the controller ideal for distributed control architectures.
Environmental and Certifications Assurance
This processor operates from 0 to 60°C and 5-95% humidity without condensation. It withstands 30G shock and 1G vibration at 10-500 Hz. The unit weighs 1.42 kg and comes in an open-style enclosure. It holds UL, CE, CSA, and C-TICK certifications. Procurement managers can trust these ratings for global deployment.
Expert Technical Evaluation & Performance Review
Memory and Logic Processing Capabilities
The 16K word battery-backed SRAM stores complex logic and data tables. Protected memory prevents accidental overwrites of critical sections. The EEPROM backup via 1785-ME16/32/64 or M100 allows quick program restoration. This design supports high-speed scanning for control loops and sequential tasks.
I/O Performance and Scan Time Analysis
The 1785-L26B scans a rack in 3 ms at 230.4 kbps. This enables fast response to discrete and analog inputs. The maximum 512 analog I/O capacity suits process control applications. The complementary I/O mode doubles the digital point count without extra hardware. This efficiency reduces overall system cost and wiring complexity.
Communication Ports and Isolation Integrity
Voltage isolation between communication ports withstands 500V for one minute. The isolation between the port and relay cartridge handles 1000V for one minute. This robust isolation protects the controller from ground loops and transient surges. The 25-pin D-shell serial port supports RS-232 and RS-423 interfaces. The DH+ and RIO ports enable reliable networking with legacy and modern devices.
Addressing Modes and System Scalability
The controller supports up to four I/O racks and thirteen chassis. It uses 2-slot mode for 8-point modules or pairs of 16-point modules. Half-slot mode handles any mix of 8, 16, and 32-point modules. This addressing flexibility lets you optimize rack utilization. You can build a system that matches your exact field device count.
Logistics & Standard Packaging Details
Express shipping is available via FedEx, UPS, and DHL. All items are securely packed in anti-static foam within a corrugated box. No certificate or warranty documents are included with standard packaging.
