Thursday, March 4, 2010

History of Programmable Logic Controllers





The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed.

PLC was first introduced in the 1960s. The PLC is made to reduce the burden of maintenance and replacement of engine control systems that use relays. Bedford Associates proposed MODICON (Modular Digital Controller) for companies in America. MODICON PLC 084 is first used in commercial production.

Increasing number of needs in the production process causes the system should be modified. If the system used a mechanical relay, of course it will be a big problem. Beside that its use limited period, the system also requires a careful treatment. If there is damage it will be very difficult to find. That is why control is needed that allows both the maintenance and application.

In the 70s, the dominant PLC technology is the machine and sequencer-based CPU bit-slice. AMD 2901 and 2903 are popular and used in PLC MODICON AB. communication skills in PLC emerged in early 1973. The first system is Modbus from MODICON.

In the 1980s an attempt was made to standardize communications with General Motor's protocol (MAP). In the 1990s carried out a new protocol reduction and modernization of the physical layer protocols are popular in the 1980s. The final standard was IEC 1131-3, trying to combine the PLC programming languages under a single standard.



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