Programmable Logic Controllers PLCs

Programmable logic controllers have been around forever (in technology years).  Their proven reliability in harsh environments and design to handle many inputs and outputs has made them the foundation of many factory automated systems.  

Today there are a lot of alternatives to the traditional PLC.  In some applications we use a computer based control engine, otherwise know as a soft PLC.  In other applications it is reassuring to know that the PLC is one less thing you'll have to worry about.  

PLCs can be combined with most other technologies to provide a sophisticated control and monitoring system.   Most of our information regarding PLCs can be found in our PLC Tutorial.  

The most common architecture we prefer is a PLC to do the real-time control and monitoring with Visual Basic or C# as the operator interface.  

Frequently Asked Questions

What experience do you have with PLCs?  Keith has over 15 years experience programming PLCs and over 25 years of programming experience.  Some competitors hire electricians and technicians as PLC programmers when they have little actual programming experience.  Although it is admirable all the skills these electricians and technicians have, our programmers are engineers or have many years of full-time PLC programming experience.  PLC programming is not something that we do only a few times a year -- it is something we do all year.  

What industries have you done PLC work in?  Since most projects require a PLC we have therefore done PLC work in most industries.  For a complete list of industries we have worked in please go to the Industries page.  

What is the smallest PLC job you have done?  Probably a press that had one output (to drive the press) and a four inputs (start, end of limits, light curtain).  We have done PLC projects with no I/O!  They were used as communications gateways that translate from one industrial network to another.  

What is the largest PLC job you have done?  Most large jobs usually have several PLCs tied together.  However, the job using only one PLC would probably be the entire chemical plant we did with one A-B PLC-5/80 (someone else specified the use of only one PLC -- we would have had several PLCs and computers tied together).  There were thousands of I/O, about  50 drives / pumps / blowers on remote I/O, 20 remote I/O racks, 10 scales, 50 meters, hundreds of valves, and five SCADA nodes all networked together.  

Programmable Controller related links

• Major Automation Companies  -- All of these companies have PLCs.  
• Control Engines  -- Soft PLCs are an alternative to traditional programmable logic controllers
• Computer - PLC communications
• Industrial Networking and communications  -- an important part of  PLC systems
• Programmable Controller Books -- prescreened by HTS
• Search for other programmable controller books  
• PLC Tutorial  -- This tutorial contains several pages on what PLCs are good at, what they are not good at, what the major components are, and our views on how they should be used. 
• Hexadecimal conversions  -- learn how to convert from hex to decimal and back.  
• Visual Basic and C# -- see how easy it is to create an operator interface for your PLC   
• Signal Conditioning -- you got to condition it before you can use it
• Our PLC programming page

External PLC Links

• PLC Tutor Great message boards to ask PLC related questions.

• History of the PLC from the inventor of the PLC, Mr. Dick Morley

• Industrial Text and Video has good instructional books and videos on programmable logic controllers and other factory automation systems.   Several of their books written by L.A. Bryan are sold separately.  

• The PLCopen (IEC 1131-3) hopefully American PLC manufacturers will adopt this standard.  

• Northwest Tech PLC training kit

• Koldwater Software Electrical design and training software for ladder diagrams, motor controls, PLCs, and DeviceNet

• TII Technical Education Systems Explorer IV-A Principles of Programmable Logic Controllers

• Learning Pit PLC and Ladder Logic Simulators, Programmable Software Simulations, Course Materials, Curriculum and Support For Trades and Technology Training

• Hugh Jack on-line PLC book

• InGear -- OPC and ActiveX PLC communications
• Automated Solutions -- OPC and ActiveX PLC communications

• ConsoliTech   Visual Basic HMI Industrial Control Toolkit; PLC Communications ActiveX OCX's- Modbus, AB, PLCDirect, etc 

We try to offer a fair and balanced opinion on every page of our website.  We would appreciate more information from other users to express their opinions which we will then incorporate.  If you have questions or comments please post them on our message board (see button in left hand column) so that others can read and benefit.