Answer / midhun pius 09946626427

Basically relay is a electromagnetic device,we can't do any
changes in its mode of operation it is works only normally
open/normally closed conditions as per its default
manufacturing set up.
But a PLC is a Programmable Logic Controller. It has a
number of inputs and out puts, we can define its conditions
by using a computer program known as Ladder Logic program.
Any time we can easily change that conditions by the ladder
program1

Answer / roy.bijoy067

a relay use in conventional system and it working/operation
is fixed put plc is used in automation system and it
operation can be change according to our need.

Answer / rajesh

a relay is just a small part and is usually a part of plc
plc is a system which has number of i/o controls


plc is much large compared to a relay

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