We all know what the PLC is and what it is used for. But do we know its history from the beginning?
At the end of the 1960s, the well-known American car manufacturer, General Motors, had a new need related to the control systems to be used in its systems for the production of cars.
This is because with the introduction of the automation in production chain, it was difficult to manage and unify the control techniques of all the machines, considering that they often are produced by different companies.
Next step: from wired logic to a programmable one. The first step was to eliminate the high costs of replacing complicated relay-based control systems. In fact, the PLC replaced the wired control panels.
Do you know which was the first large-scale marketed PLC? The MODICON 084! It used technology based on particular components called bit-slices. Someone say that it was not a real success at the time, bacause initially it was slow, a little “cumbersome” and lacked some useful features. For this reason, in 1973 a new version called MODICON 184 was introduced, recognized as the first true mass PLC with great success!
But has Rockwell Automation done its part in this story? The meriti s of its brand: Allen Bradley!
In the 70s the first microprocessor-based machines were born, dedicated only to small systems. The most successful microprocessors were the 8080 types, which are still on the market today. The reference brand was Allen Bradley! The introduction of microprocessors has thus allowed the spread and construction of ever larger PLCs.
In the early 1970s, it was introduced into PLCs the ability to communicate through dedicated fieldbus networks and send / receive analog signals. A great advantage, considering that for the first time the machine can be controlled from distance. At the end of the 70s the Modbus serial communication protocol was introduced. Why is it considered a real turning point in the history of the PLC? Because thanks to this protocol it is possible to connect devices from different manufacturers and thus solve a major technical problem.
Here we are at 1980s. Studies continue quickly. The symbolic programming of PLCs is born through PC and no longer just using dedicated terminals! Micro and mini PLCs are introduced on the market for companies that use small machines, in order to lower costs and manage up to 8-10 I/O.
The 90s are the years of standardization. They try to introduce a standard international programming language based on a set of programming languages. The experts try to replace the PLCs with the PCs in the industrial automation, but it is not easy as the PCs were born for the industrial environment and often their cycle times are longer than those required in automation.
Today the PLCs are used in all stages of production to guarantee constant machine control. They are even more smarter with very short reaction times to ensure high performance!
A big thank you to all the engineers who have allowed a constant evolution over time that has made the PLC an essential tool!
