1.5:Differences between convolutional control panel and plc

In the beginning of the industrial revolution, especially in 1960&1970, automated machines were controlled by electromechanical relays these relays were all hardwired together inside the control panel, in some cases the control panel was so huge that it could cover the entire wall; every connection in the relay logic must be connected. wiring is not always perfect , it takes time to troubleshoot the system , this is a very time consuming affair , on top of that , the relays have limited contacts if modification is required , the machine has to be stopped space may not available and wiring has to be traced to accommodate changes . the control panel can only be used for the particular process . it cannot be changed immediately to a new system it has to be red one in terms of maintenance an electrician must be well trained and skillful in troubleshooting the control system conventional relay control panel are very inflexible. With the arrival of programmable controllers(PLC) , the control design and concept improve, so there are many advantages:

The advantage:

· The wiring of the system usually reduces by 80% compared to convolution control system.

· The power consumption is greatly reduced ass plc consume much less power.

· The plc is diagnostic function enable easy and fast troubleshooting of the system.

· Modification of control sequence or application can easily be done by programming through the computer software without changing the I/O wiring, if no additional input or output devices are required.

· In plc system spare parts for relay and hardware timers are greatly reduced as compared to convolution control panel.

· The cost much less compared to convolution system in situation when the number of I/O's is very large and control functions are complex.

· The reliability of the plc is higher than the mechanical relays and timers.

☺The summary of the advantage can be summarized in this list .the many features and benefits obtained with a programmable controller.

Inherent Features	Benefits
Solid-state components	• High reliability
Programmable memory	• Simplifies changes • Flexible control
Small size	• Minimal space requirements
Microprocessor-based	• Communication capability • Higher level of performance • Higher quality products • Multifunctional capability
Software timers/counters	• Eliminate hardware • Easily changed presets
Software control relays	• Reduce hardware/wiring cost • Reduce space requirements
Modular architecture	• Installation flexibility • Easily installed • Reduces hardware cost • Expandability
Variety of I/O interfaces	• Controls a variety of devices • Eliminates customized control
Remote I/O stations	• Eliminate long wire/conduit runs
Diagnostic indicators	• Reduce troubleshooting time • Signal proper operation
Modular I/O interface	• Neat appearance of control panel • Easily maintained • Easily wired
Quick I/O disconnects	• Service without disturbing wiring
System variables stored in memory data	• Useful management/maintenance • Can be output in report form