PLCs were initially introduced in the late 1960s. The main reason for the design of such a device was to eliminate the high cost involved in the replacement of the complicated machine control systems that were relay based. Bedford Associates proposed something known as Modicon, which stand for a Modular Digital Controller to a major United States car manufacturer. At the time, other companies proposed computer based schemes, and one of them was based on the PDP-8. The first PLC in the world was brought into commercial production by the Modicon 084.
When production needs changed so did the control system. It becomes expensive to cater for such changes if they occur on a frequent basis. Relays happen to be mechanical devices, as well as having a short lifespan that needs a set maintenance program to be adhered to. It was also proving tedious to perform troubleshooting owing to the huge number of relays to be catered for.
Now picture a panel for machine control that was inclusive of hundreds or even thousands of individual relays. Such huge size can boggle the mind, bearing in mind the complicated initial working of many individual devices. The relays would have to be wired individually together in a manner that a desired outcome is achieved. At that time there were numerous problems to be dealt with.
The then modern controllers had to undergo easy programming by engineers of maintenance and plant. Additionally, the programming alterations had to be done easily, as well as prolonging their lifespan. Solution to these issues lay in the use of a programmed technique that most technicians were familiar with and replacing the mechanical parts with parts that were in solid state.
The technologies for PLC that were dominant in the 1970s were bit-slice based CPUs and sequencer state machinery. When considering AB PLCs and Modicon ones, the most popular ones were AMD 2901 and the 2903 versions. Convectional microprocessors did not possess the power needed to rapidly solve PLC logic in all except the smallest PLCs. The microprocessors then went on to undergo evolution, with the manufacture of better PLC based on the microprocessors. In these times they are still being manufactured with reference to 2903. However, a faster PLC is yet to be made by Modicon to better the 984A/B/X.
In around 1973, communications abilities started to appear. Modicons Modbus was the earliest such system. The PLC could now communicate to others and they could be located a distance from the machine they were actually controlling. Additionally, they could now be used to receive and send varying voltages in order to enable them get into the analogue world. Unfortunately, continuously changing technology together with lack of standardization has made PLC communications nothing but physical networks and incompatible protocols.
During the 1980s, General Motors came up manufacturing automation protocol, abbreviated as MAP, when trying to standardize communications. Also, it was the best time to reduce PLC size and alter them to be software compatible. This was achieved by through symbolic communications rather than program terminals and handheld programs.
The 1990s have witnessed new protocol introduction and the popular protocols salvaged from the 1980s to be modernized. The company that originally commissioned the Modicon 084 went on to switch to control system that is PC based.
When production needs changed so did the control system. It becomes expensive to cater for such changes if they occur on a frequent basis. Relays happen to be mechanical devices, as well as having a short lifespan that needs a set maintenance program to be adhered to. It was also proving tedious to perform troubleshooting owing to the huge number of relays to be catered for.
Now picture a panel for machine control that was inclusive of hundreds or even thousands of individual relays. Such huge size can boggle the mind, bearing in mind the complicated initial working of many individual devices. The relays would have to be wired individually together in a manner that a desired outcome is achieved. At that time there were numerous problems to be dealt with.
The then modern controllers had to undergo easy programming by engineers of maintenance and plant. Additionally, the programming alterations had to be done easily, as well as prolonging their lifespan. Solution to these issues lay in the use of a programmed technique that most technicians were familiar with and replacing the mechanical parts with parts that were in solid state.
The technologies for PLC that were dominant in the 1970s were bit-slice based CPUs and sequencer state machinery. When considering AB PLCs and Modicon ones, the most popular ones were AMD 2901 and the 2903 versions. Convectional microprocessors did not possess the power needed to rapidly solve PLC logic in all except the smallest PLCs. The microprocessors then went on to undergo evolution, with the manufacture of better PLC based on the microprocessors. In these times they are still being manufactured with reference to 2903. However, a faster PLC is yet to be made by Modicon to better the 984A/B/X.
In around 1973, communications abilities started to appear. Modicons Modbus was the earliest such system. The PLC could now communicate to others and they could be located a distance from the machine they were actually controlling. Additionally, they could now be used to receive and send varying voltages in order to enable them get into the analogue world. Unfortunately, continuously changing technology together with lack of standardization has made PLC communications nothing but physical networks and incompatible protocols.
During the 1980s, General Motors came up manufacturing automation protocol, abbreviated as MAP, when trying to standardize communications. Also, it was the best time to reduce PLC size and alter them to be software compatible. This was achieved by through symbolic communications rather than program terminals and handheld programs.
The 1990s have witnessed new protocol introduction and the popular protocols salvaged from the 1980s to be modernized. The company that originally commissioned the Modicon 084 went on to switch to control system that is PC based.
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