Question

Describe the key differences of PLC (Programmable Logic Controller) construction styles and their typical applications , kindly answer with detailed explaination and good hand writing.

Answer 1

first we should know about what are the characteristics which come under construction of plc.Plc should be compact ,small in size ,easily available,simple in use,reliable and easily programmable.basically there are three types of plc's which are being used because of their construction.everyone has its unique feature and construction which make it suitable for its application

these are 1.unitary 2.modular 3.rack mounted

1.unitary plc : it has following equipment in construction;

1. power supply 2.main module (CPU) 3.input module 4. output module

advantages :small ,compact,easy access,cheapest and portable

disadvantages: these are not expandable,whole unit is replaced if there is any damage to any feature,

applications: it is used for applications which don't require more input or outputs for example car parking barrier

2.modular plc: it has same construction as unitary but we can increase input and output modules so that to increase the capacity and hardware changes

advantages: input,output sources can be expanded and on failure whole system is not changed

disadvantages: expensive than unitary

applications:the application which have multiple input and outputs such as in cotton industries,paper industries bottle industries

3.rack mounted plc: the system is similar as modular but these are made on standard cards which then combined together into racks inside control unit.the communication of modules is done through racks

advantages: ease of modification and expandable,more number of input and outputs,only failure part has to be changed

disadvantage:expensive then previous one's,

applications: used in steel manufacturing plants, electrical plants where wires and switches are manufactured,