Product Overview
The Allen-Bradley 1785-L86B is a high-speed PLC-5/86 standard processor engineered for demanding industrial control applications. This industrial automation module occupies a single 1771 I/O chassis slot and delivers robust processing power for field device control and data handling. With a maximum user memory of 100 Kilowords and support for up to 3072 analog I/O points, the 1785-L86B is built to manage complex processes efficiently.
This processor includes protected memory and battery-backed static RAM, ensuring program integrity during power fluctuations. Its flexible I/O configuration—3072 total I/O (any mix) or 3072 inputs plus 3072 outputs in complementary mode—makes it suitable for a wide range of automation tasks. The 1785-L86B is designed for reliability, with an operational temperature range of 0 to 60 °C and compliance with CSA, UL, C-TICK, and CE standards.
Technical Specifications
| Specification |
Detail |
| Manufacturer |
Rockwell Automation |
| Brand |
Allen-Bradley |
| Part Number |
1785-L86B |
| Module Type |
Standard Processor |
| Processor |
PLC-5/86 |
| Max User Memory Words |
100 Kilowords |
| Battery-Backed Static RAM |
Yes |
| EEPROM Program Backup Option |
Yes (using 1785-ME16, -ME32, -ME64, -M100) |
| Protected Memory |
Yes |
| Max Total I/O |
3072 (any mix) or 3072 in + 3072 out (complementary) |
| Max Analog I/O |
3072 |
| 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 |
93 |
| Max I/O Chassis Extended Local |
0 |
| Max I/O Chassis Universal Remote |
32 Max. Per I/O Link |
| RS-232-C/422-A/423-A Ports |
1 |
| Control Coprocessor Expansion Port |
Yes |
Industry Applications
The 1785-L86B excels in manufacturing lines where high-speed processing and extensive I/O are critical. For example, in automotive assembly plants, this processor coordinates hundreds of sensors and actuators across multiple remote chassis, maintaining precise timing and synchronization. Its 3 ms scan time at 230.4 kbits/s ensures rapid response to production changes.
In material handling systems, the 1785-L86B manages conveyor networks and sorting equipment. The ability to handle 3072 analog I/O points allows for precise control of variable speed drives and analog sensors, improving throughput and reducing downtime. Additionally, its protected memory safeguards critical process parameters, which is essential in continuous processing industries like food and beverage.
Installation & Setup Guidance
When installing the 1785-L86B, ensure the backplane provides 3.3A at 5V DC. Mount the module in a single 1771 I/O chassis slot, and verify that the chassis is properly grounded to meet safety standards. Set the hardware address using the 2-slot, 1-slot, or ½-slot addressing modes to match your I/O configuration.
Connect the communication ports according to your network topology. The module offers one RS-232-C/422-A/423-A port and four Data Highway Plus/Remote I/O ports for flexible integration. For memory backup, use the EEPROM option with compatible modules (1785-ME16, -ME32, -ME64, or -M100). Always follow the manufacturer's guidelines for wiring and termination to avoid signal integrity issues.
Maintenance & Reliability
Regular maintenance of the 1785-L86B ensures long-term reliability. Check the battery-backed static RAM periodically to prevent memory loss during power outages—replace the battery every two years or as recommended. Keep the module's environment within the operational temperature range (0 to 60 °C) and humidity levels (5-95% non-condensing) to avoid thermal stress.
Inspect the backplane connections and communication cables for wear or corrosion. The module is designed to withstand operational shock up to 30G and vibration of 2G at 10-500Hz, but excessive mechanical stress can still cause issues. By following a preventive maintenance schedule, you minimize unplanned downtime and extend the service life of your control system.
Compatibility & Integration
The 1785-L86B integrates seamlessly with the 1771 I/O family, supporting 8-point, 16-point, 32-point, and intelligent I/O modules. It communicates over Data Highway Plus and Remote I/O networks, enabling connection to other PLC-5 processors and operator interfaces. The control coprocessor expansion port allows for additional processing capabilities when needed.
Programming is supported in Ladder Logic, Sequential, and Structured Text languages, giving engineers flexibility in developing control logic. The module is compatible with 1771 memory modules for expanded storage. This integration capability makes the 1785-L86B a versatile choice for both new installations and upgrades of existing Allen-Bradley systems.
Selection Guide & Purchasing Advice
Before purchasing the 1785-L86B, verify that your existing system can supply the required backplane current (3.3A at 5V DC) and that the chassis supports the module's dimensions. Confirm the number of I/O points you need and whether you require the complementary I/O configuration. Also, check if your application demands the EEPROM backup option; if so, order the appropriate memory module separately.
When sourcing this industrial automation module, choose a reputable supplier like PLC Source PRO to ensure genuine parts and reliable support. Confirm the part number and specifications before ordering to avoid compatibility issues. With proper selection, the 1785-L86B delivers dependable performance for years.