PLC Then and Now

History of PLCs

When the first electronic machine controls were designed, they used relays to control the machine logic (i.e. press "Start" to start the machine and press "Stop" to stop the machine).

A basic machine might need a wall covered in relays to control all of its functions.

There are a few limitations to this type of control.

Relays fail. The delay when the relay turns on/off. There is an entire wall of relays to

design/wire/troubleshoot.

A PLC overcomes these limitations, it is a machine controlled operation.

Recent developments

PLCs are becoming more and more intelligent.

In recent years PLCs have been integrated into electrical networks i.e. all the PLCs in an industrial environment have been plugged into a network which is usually hierarchically organized.

The PLCs are then supervised by a control center. There exist many proprietary types of networks.

One type which is widely known is SCADA (Supervisory Control and Data Acquisition).

Learn more in

PLC Programming with PLC Drive Industrial Automation Online Certificate Course

[Refer: http://goo.gl/g20Qf3 ; courses@wiziq.com]