Control System Programing

Why use a Programmable Logical Controller (PLC)

For many of us who have been designing industrial control solutions this seems like an unenlightened question.  I am surprised and disappointed when I find engineers trying to implement control solutions on Windows and Linux using programming language frameworks made for data processing.

  1. The operating system of a PLC is real time and deterministic
    1. Windows and Linux are not (without a modified kernel)
  2. The languages included in the  IEC 61131-3 are mainstream
    1. The languages included are the basis of the controls industry and have an established presence as accepted tested platform.

For many the low memory capabilities and the seemingly proprietary nature of the development environments seem to be ungraceful adding complexity to their design that is unwelcome.  It is important to remember that we are addressing memory and processing a very low level in order to keep processing time very short.  I often find myself explaining that a PLC is like a loop that is constantly running, to programmers that work in business application development.  The speed that this loop runs is called a scan rate that scan rate can be controlled to guarantee timely response.

Here are a few of the leading manufacturers of PLCs control solutions we integrate

Rockwell Automation / Allen Bradly (Control Logix, Compact Logix, Micrologix, and Legacy Products)

Siemens (S7-300, S7-1200, S7-1500, and Legacy Products)

Automation Direct (Direct Logic Series, Productivity 3000, Click, and other legacy products)