Types of Allen Bradley PLC

Types of Allen Bradley PLC

The company makes programmable logic controllers (PLCs), human-machine interfaces, sensors, safety components and systems, software, motors and drive systems, contactors, motor control centres, and systems of such goods, with revenues of around US $6.4 billion in 2013. Asset management services, such as repair and consultancy, are also provided by Rockwell Automation. Milwaukee, Wisconsin is the headquarters of Rockwell Automation.

Stanton Allen and Lynde Bradley started the company as the Compression Rheostat Company in 1903 with a $1,000 investment. The company was renamed Allen-Bradley Company in 1910, and it supplied the majority of discrete resistors used in electronics and other goods for the next century. [requires citation] It established a subsidiary in Galt, Ontario, Canada, in 1952, which employs In 1985, the fiscal year finished with $1 billion in sales, setting a new business record. Rockwell International paid $1.651 billion for Allen-Bradley in February 1985, making it the largest acquisition in Wisconsin history. Allen-Bradley effectively assumed control of Rockwell’s industrial automation sector.

PLCs can range in size from small modular devices with a few tens of inputs and outputs (I/O) in a housing built into the processor to huge rack-mounted modular devices with thousands of I/O that are frequently networked with other PLC and SCADA systems. They can be configured for a variety of digital and analogue I/O configurations, as well as expanded temperature ranges, electrical noise immunity, and vibration and impact resistance.

Programs for controlling machine function are often stored in non-volatile or battery-backed memory. PLCs were first created in the automotive sector to replace hard-wired relay logic systems with flexible, durable, and easily programmable controllers. They’ve been frequently used as high-reliability automation controllers in severe situations since then. Because output results must be delivered in response to input conditions within a certain amount of time, a PLC is an example of a hard real-time system. Otherwise, unexpected operation will occur. PLCs were created to replace relay logic systems in the automotive industry in the United States in the late 1960s.

Previously, factory control logic consisted mostly of relays, cam timers, drum sequencers, and dedicated closed-loop controllers. Design engineers found it impossible to change the automation process since it was hard-wired. Changes would necessitate rewiring and meticulous documentation updates. The entire system would become dysfunctional if merely one wire was out of place or one relay failed. Often, technicians would spend hours analyzing schematics and comparing them to existing wiring to troubleshoot problems. When general-purpose computers were accessible, they were quickly used to industrial control logic.

These early computers were unreliable, necessitating the use of specialized programmers as well as strict monitoring of working parameters including temperature, cleanliness, and power quality. Compared to older automation systems, the PLC offered significant advantages. It was more dependable, smaller, and required less maintenance than relay systems, and it tolerated the industrial environment better than computers. It could be simply expanded with more I/O modules, whereas relay systems necessitated complex hardware changes in the event of reconfiguration. This made it easier to iterate over the manufacturing process.

It was more user-friendly than computers that utilized general-purpose programming languages because it employed a simple programming language centred on logic and switching operations. It also allowed for the monitoring of its operation. Early PLCs used ladder logic, which looked a lot like a schematic picture of relay logic.

In this article, I’ll go through the several varieties of Allen Bradley PLCs that are used, ranging from tiny to large applications.

It’s crucial to know what type of PLC you’ll need when creating a control system.

The larger the project, the more advanced PLC is required to meet requirements.

Types of Allen Bradley PLC

There are three different types of PLCs that you can employ.

  1. Micro Logix
  2. CompactLogix
  3. ControlLogix

These three different types of PLCs are capable of handling the procedure. Their software, expansion module limitations, memory space, and communication protocol are all significant differences.

Micro Logix

PLCs of this type are employed in small control systems.

We can use it in situations where fewer I/O s are necessary.

For small-scale applications, this is a cost-effective alternative.

For programming, use the rslogix500 software.

Fixed I/O s (onboard I/O) are included.

There is no need for a real rack.

A ribbon cable is used to link the input and output cards.

RS-232/485, an Ethernet interface, is the supported communication port.

There are 32 discrete I/O points and 6 analogue I/O s on the controller.

It features an LCD display.


The medium control system uses this sort of PLC.

Machine control and packing systems both employ this form of PLC.

It has an integrated I/O system (onboard I/O).

We can utilize an expansion module to add more I/Os, however expansion modules have limitations.

The programming requires the Rslogix 5000 software.


Because it uses independent I/O modules, it’s also known as a modular PLC.

These are the sorts of PLCs that are used in processing, batching, and motion control.

For programming, you’ll need the Rslogix 5000 software.

Rack-based I/O modules are used.

EtherNet/IP, ControlNet, DeviceNet, and DH+ are all supported communication protocols.

CompactLogix Versus ControlLogix

Apart from the aforementioned points, compact and Control Logix share other similarities.

Both types of PLCs employ a symbolic name and can construct user-defined data types.

To communicate data, both use Ethernet/IP, DeviceNet, ControlNet, and DH communication protocols.

Both of these tasks necessitate the use of the rslogix5000 programme.

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