Allen-Bradley 1756-L55 ControlLogix Logix5555 Processor Module
Introduction:
The Allen-Bradley 1756-L55 is a legacy ControlLogix Logix5555 processor module. It ships without user memory but includes a 1756-BA1 battery. This module offers an RS-232 port for basic programming and monitoring tasks.
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Technical Overview of the 1756-L55 Processor
The Allen-Bradley 1756-L55 belongs to the early ControlLogix 5550 series (Series A). This processor module operates without any user memory installed. You must add a separate memory module for your control logic. The 1756-L55 works well for basic or legacy system replacements.
Key Electrical Specifications
The Allen-Bradley 1756-L55 draws power directly from the ControlLogix backplane. The backplane current at 5.1 Volts DC is 1.23 to 1.25 Amps . The backplane current at 24 Volts DC is only 0.014 Amps. Total power dissipation ranges from 5.6 to 5.7 Watts. Thermal dissipation is 19.1 to 19.4 BTU per hour.
The 1756-L55 provides continuous isolation voltage of 30 Volts. It has a basic insulation type through its RS-232 communication port. This module passes a dielectric test of 707 Volts DC for 60 seconds. This ensures reliable isolation between circuits.
Communication and Memory
The 1756-L55 includes one built-in RS-232 communication port. You need a serial cable to connect to this processor. Compatible cables are the 1756-CP3 or 1747-CP3. The 1756-L55 ships without any user memory installed. An optional memory module (purchased separately) is required for operation. The included 1756-BA1 battery retains program data when power is off.
Environmental and Physical Data
The Allen-Bradley 1756-L55 operates in standard industrial environments. Operating temperature range is 0 to 60 degrees Celsius (32 to 140 degrees Fahrenheit). Storage temperature range is -40 to 85 degrees Celsius (-40 to 185 degrees Fahrenheit). The enclosure type is open-style with no external housing.
This processor meets IEC 60068 standards for temperature, humidity, vibration, and shock. The 1756-L55 has a T4 IEC temperature code for hazardous locations. The module weighs approximately 0.35 kilograms (12.5 ounces). It occupies one slot in any ControlLogix chassis.
Installation Guidelines
The Allen-Bradley 1756-L55 installs into any available slot of a ControlLogix chassis. Compatible chassis include the 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17. Always power off the chassis before inserting or removing the 1756-L55 module.
Connect the 1756-BA1 battery to the designated battery port. This battery maintains memory contents during power loss. Use the 1756-CP3 serial cable to connect your programming computer. Set the correct communication parameters before going online with the 1756-L55.
Package Contents
When you order the Allen-Bradley 1756-L55, you will receive the following items:
One Allen-Bradley 1756-L55 ControlLogix Logix5555 processor module.
One 1756-BA1 battery (included and pre-installed).
One product information sheet with basic handling instructions.
No memory module is included (must be purchased separately for operation).
No serial cable is included (use 1756-CP3 or 1747-CP3).
Frequently Asked Questions (FAQ)
1. Can the 1756-L55 run control logic without an extra memory module?
No, the Allen-Bradley 1756-L55 ships with zero user memory. You must purchase and install a separate memory module. Examples include the 1756-M1, 1756-M2, 1756-M3, or 1756-M4 modules.
2. What type of battery does the 1756-L55 use?
The 1756-L55 uses the 1756-BA1 battery. This battery is included with the module when new. It retains your program and tag data when the system power is off.
3. Is the 1756-L55 compatible with modern ControlLogix chassis?
Yes, the Allen-Bradley 1756-L55 fits into all standard ControlLogix chassis. These include the 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17. The module always occupies one slot.
4. What serial cable works with the 1756-L55 processor?
The 1756-L55 requires a standard RS-232 serial cable. Use either the 1756-CP3 or 1747-CP3 cable. Do not use a straight-through DB9 cable as it may not communicate correctly.
5. Is the 1756-L55 still supported by Rockwell Automation?
The Allen-Bradley 1756-L55 is a legacy Series A processor. Rockwell Automation has discontinued this model. It is available now only as used or refurbished stock. For new projects, use a modern 1756-L7x or 1756-L8x processor instead.