Allen Bradley Instructions (PLC)

From the very start of the use of machinery in industry, the demand of machine controls and automation is increasing day by day and demanding more complex systems. Earlier machines were controlled by mechanical means using cams, gears, leavers and other basic mechanical devices. These mechanical control systems were having lots of wear and tear and require large power for operation. Large and complex control systems were not possible to be designed using mechanical systems. Mechanical control systems occupy lot of space and it was very difficult and costly to modify the control process if required. Slowly these mechanical control designs were replaced by electrical drives, which were controlled by electromechanical relays. This system contained wired relay and switch control elements which were wired as required to provide the control logic necessary for the particular type of machine operation. But as manufacturing techniques improved and plant change over to new products.In late 1960 and early 1970, the first programmable logic controller was developed and found place in automotive plants where manufacturing techniques changes very rapidly due to change in model every year.