PLC stands for programmable logic controller. A PLC simply is an electronic component that does nothing until it has been given a program to follow. Once programmed complex procedures and automation procedures can be accomplished by wiring the device into the control circuits. Chris has had many years’ experience writing programs for Zelio smart relays both for himself and for other electricians around the Waikato. PLCs come in a variety of shapes, brands and sizes. The cost vary according to requirements but having tried several kinds I have found that there’s not much you cannot do with a zelio Smart relay.