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 requirements underwent change, the same case applied to the control system. Such frequent change turned out to be quite expensive. Since relays are mechanical devices, they have a limited shelf life that requires a strict maintenance program to be followed. Trouble shooting was also proving to be tedious due to the large number of relays involved.
Consider a machine control panel that has hundreds or probably thousands of relays. A size of that magnitude can be overwhelming due to the complex working of numerous individual devices. Such relays would have to be connected individually together using wires in a way that facilitates the achievement of a certain desired outcomes. During that particular time, so many problems had to be solved.
These modern controllers also had to be programmed easily by plant and maintenance engineers. The programming changes had to be easily performed and the lifetime prolonged. In addition, they had to survive the seemingly harsh industrial environmental conditions. The answers to these problems lay in using a programmed technique that most people were already familiar with as well as the replacement of mechanical parts with ones 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.
Abilities of communications began to appear in about 1973. The first of similar system was Modicons Modbus. It enables PLC to communicate with other PLCs as well as being used to machines at a distance from them. Whats more, varying voltages could be sent and received using them to introduce them to the digital world. It is unfortunate that lack of standardization and rapidly changing technology has reduced PLC communications to merely incompatible protocols and physical networks.
The 1980s witnessed General Motors developing manufacturing automation protocol (MAP) in an attempt to standardize communications. The time was ideal for decreasing the size of PLC and making them software compatible via symbolic programming to personal computers and not portable programmers or programming terminals.
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 requirements underwent change, the same case applied to the control system. Such frequent change turned out to be quite expensive. Since relays are mechanical devices, they have a limited shelf life that requires a strict maintenance program to be followed. Trouble shooting was also proving to be tedious due to the large number of relays involved.
Consider a machine control panel that has hundreds or probably thousands of relays. A size of that magnitude can be overwhelming due to the complex working of numerous individual devices. Such relays would have to be connected individually together using wires in a way that facilitates the achievement of a certain desired outcomes. During that particular time, so many problems had to be solved.
These modern controllers also had to be programmed easily by plant and maintenance engineers. The programming changes had to be easily performed and the lifetime prolonged. In addition, they had to survive the seemingly harsh industrial environmental conditions. The answers to these problems lay in using a programmed technique that most people were already familiar with as well as the replacement of mechanical parts with ones 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.
Abilities of communications began to appear in about 1973. The first of similar system was Modicons Modbus. It enables PLC to communicate with other PLCs as well as being used to machines at a distance from them. Whats more, varying voltages could be sent and received using them to introduce them to the digital world. It is unfortunate that lack of standardization and rapidly changing technology has reduced PLC communications to merely incompatible protocols and physical networks.
The 1980s witnessed General Motors developing manufacturing automation protocol (MAP) in an attempt to standardize communications. The time was ideal for decreasing the size of PLC and making them software compatible via symbolic programming to personal computers and not portable programmers or programming terminals.
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.