Allen Bradley CompactLogix PLC range
By Subhash Kandpal
The Allen Bradley CompactLogix controllers use the same programming and program organisation as the ControlLogix systems but utilise Allen Bradley 1769 MicroLogix 1500 system I/O and communications options. Their memory space is smaller than the ControlLogix systems but it is more than adequate for medium sized PLC applications.
The Rockwell CompactLogix controllers provide a solution for smaller, machine-level control applications, requiring a low-cost, modular solution. The CompactLogix system is also configured and programmed with RSLogix 5000.
Allen Bradley CompactLogix PLC systems use the same Logix control engine as the rest of the Logix series controllers. This means CompactLogix supports the Logix instruction set, task configuration and data tags.
The multi-tasking operating system supports 4, 6, or 8 configurable tasks (depending on the processor) that can be prioritized for executing the program code according to the application. Tasks can contain up to 32 programs, each containing separate routines.
Symbolic addressing using tags is used to identify data by its use in the application, independent of the hardware. You can create libraries of standard routines that can be re-used on multiple machines or applications.
The Allen Bradley CompactLogix PLC system also provides you with peer-to-peer communications to other devices via the following communication interface devices, DH-485, DeviceNet, Controlnetm and Ethernet
All CompactLogix controllers provide you with the following features and functionality:
• 3-position key switch.
• Battery backed memory.
• Channel 0 default RS232 communication.
• Built-in RS-232 port.
• Diagnostic LED's.
• Integrated Compact/1769 Bus.
All of the processors in the range have these functions other processors have an extra serial port, Ethernet port or ControlNet port.
All the Allen Bradley CompactLogix PLC processors have RUN-REM-PROG Key switch has the following functionality.RUN - PLC in RUN mode no edits possible. REM - PLC in remote mode control of the processor and remote programming available using RSLogix 5000. PROG - PLC in STOP or Program mode, program changes can be downloaded.
Allen Bradley CompactLogix Local I/O allows one additional bank of I/O modules can be added to a CompactLogix system. The first bank includes the CompactLogix controller in the far left position. Each bank requires its own power supply and the controller must be within four slot positions of the power supply. A maximum of one controller may be used in a CompactLogix system.
The system above has a main bank consisting of a processor, 2 I/O cards, a power supply and 2 more I/O cards. The second bank also has 2 I/O cards, a power supply and 2 more I/O cards.
Allen Bradley CompactLogix Remote I/O is achieved in the same way as the ControlLogix system it can be connected to a CompactLogix system only using an Ethernet port on the Processor, or a ControlNet port on the processor. A DeviceNet scanner module is also available for any of the CompactLogix controllers.
About the Author
Author is and Automation training company http://ww.da.t.co.uk/ who offer a wide range of Automation course for PLC's (Programmable Logic Controllers), SCADA and HMI systems and variable speed drives.
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