PLC History:
- In late 1960’s PLC’s were first introduced.The primary reason for designing PLC’s is to eliminate large cost involved in replacing complicated relay based machine.
The above picture is a complicated relay panel used in 1960’s
- In 1968, the hydramatic division of the general motors(An
The above picture is an typical PLC based control panel.
- In 1960’s industries used electro-mechanical relays,timers,counters were used.
- Control panel consists of electro-mechanical drives with lengthy wires.These Mechanical devices have a limited life time with high maintenance and involves more trouble shooting.
- In mid 90’s communication abilities began to appear,
- In 1980’s the size of the PLC’s are gradually reduced and software programmable through symbolic programming
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