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The History of Programmable Controller Parts

The History of Programmable Controller Parts

Programmable logic controllers are the heart of any servo system. And if you’ve spent any time in the manufacturing world, you know that servo drives are at the heart of most large-scale industrial processes.

However, this wasn’t always the case. Early manufacturing equipment wasn’t designed to create products on such a wide scale. But as more and more demand was placed on factories, they needed equipment that could produce larger quantities of goods without breaking down. There was only one solution for it: automation. Our quest to achieve this automation is found in the history of programmable controller parts.

Challenges Before Programmable Logic Controllers

There was a form of automation before programmable controller parts. Up until the late 1960s, manufacturing facility machinery operated on a system of switches called relays. Each relay, controlled by an electromagnetic current, operated individual motors within a factory’s operating system.

While this system was functional, it ran into a number of practical problems in larger-scale operations.


The idea of a single switch operating a single motor may seem simple on the surface. However, it can quickly become complex, considering how many individual motors and other devices would have needed their own relay in a factory. A single system may have a hundred different relays, and just one of them going out could render a whole system useless.

On top of this, if a system went down, there was no simple way to tell which relay was faulty. Troubleshooting was a tedious process that involved going through every individual switch to identify a problem. Programming the system was equally tedious, and any little change to the system needed to be performed by a trained engineer.


Along with relay systems, there were some other earlier systems that used basic computer functions as well. However, the problem with these was that they were too delicate, especially for industrial settings. Too much exposure to grime, dust, and oil—the sorts of materials that were common in a factory—could render the computer useless. This made them incredibly impractical for manufacturing purposes.

The Birth of PLCs

With all these difficulties, it was clear that manufacturers needed to find a solution if they were going to continue to expand. So, the Hydra-matic division of General Motors commissioned several companies to create a device to solve the problem. The goal was for this device to perform the same tasks while being easier to reprogram and rugged enough to withstand harsh industrial settings.

Fortunately, several technological advances were present at the time that allowed the PLC to come to light. Among them were printed circuit boards, analog computers, video display terminals, and early numerical control technology.

Dick Morely and the Modicon

Of all these companies, one of the most successful was the team at Bedford Associates, led by head technician Dick Morely. Morely’s team focused on simplicity with their design, creating a system that mirrored the relays without the complexity. To that end, his Modicon 084—so named because it was Bedford Associates’ 84th project—utilized a ladder programming system.

From here, Bedford Associates created a separate company devoted to the manufacture and sale of PLC devices, called Modicon after the equipment. The first few years of production didn’t go especially well. But as the team continued to enhance its design, they eventually developed the Modicon 184. With more “bells and whistles,” as Morely put it, this design took off, earning Morely the nickname of “Father of PLC.”

Odo Josef Struger and the PLC

Although Bedford Associates arguably won the race in winning the contract from General Motors, it was technically not the first to create a machine with the name programmable motor controller. This name came from a different company that General Motors had approached about creating a new solution to the relay problem— Milwaukee-based Allen Bradley.

The Allen-Bradley team, led by Austrian-American engineer Odo Josef Struger, was well-versed in relay systems. As such, they were able to create two different systems for General Motors relatively quickly. However, both were deemed too complex or too slow to meet customer demand.

It wasn’t until after the advent of the Modicon that they created the Bulletin 1774 PLC, the first device to have the name “programmable logic controller.” Because of this, Struger is also often called “the Father of PLC.” Eventually, the Allen-Bradley company merged with a company called Rockwell Automation, but they continued to make key contributions to the PLC race.

The PLC’s Growing Pains

Even though the PLC was a functional system, it didn’t mean it was perfect. And many companies were still reluctant to take on this new system. After all, computers at this time were still sensitive pieces of hardware, prone to malfunction if the conditions of the room weren’t perfect. Other engineers and computer programmers, such as Scott Zifferer and Neil Taylor, worked to improve the physical setup and the programming performance of PLCs.

However, as computer technology became more sturdy and more sophisticated, the PLC became an industry standard and continued to grow in its functionality. Eventually, manufacturers were able to create systems that could work with other types of programming languages, such as functional block diagrams or sequential function charts.

Additionally, PLC technology began to merge with other types of manufacturing technology, such as distributed control systems. While PLCs were designed to automate a single piece of equipment, DCSs were designed to automate an entire factory or manufacturing system. With this kind of connectivity, PLC systems were able to revolutionize the processes of entire companies.

Programmable Logic Controllers Today

The history of the programmable logic controller has brought us to a modern world where one can find these systems in manufacturing plants across the world. Beyond that, technology using PLCs has also worked its way into other parts of our daily lives. For example, one can find these systems at work in:

  • Three-color traffic lights
  • Automatic doors
  • Elevators
  • Conveyor belts
  • Wind turbine systems
  • Water tank level systems
  • Roller coasters

Whatever application you’re using programmable logic controllers for, Industrial Automation has the PLC spare parts you need to keep your servo systems functional.

The History of Programmable Controller Parts

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