Advantages of PLCs Cost effective for controlling complex systems. Flexible and can be reapplied to control other systems quickly and easily. Computational abilities allow more sophisticated control. Trouble shooting aids make programming easier and reduce downtime. Reliable components make these likely to operate for years before failure.CHAPTER - INTRODUCTION TO PLCSPLC Origin- eveloped to replace relays in the late !"#$s- Costs dropped and became popular by !"%$s- &ow used in many industrial designsRelays and Sce!aticSy!"olsn o r m a l l yo p e nn o r m a l l yc l o s e di n p u t c o i l' R' RLogical Control#it Relays!!()*Cwall plugrelay logicinput *+normally closed,input -+normally open,output C+normally open,ladder logic* - CRelay LogicIn a PLCladderpowersupply./0)com.inputsoutputspush buttonslogic12C*C power!!()acneut.* - ClightReading Ladder Logic3'T &45TR*26&15T7 '5T15T7* - 8C 4 F93:&ote; 1ower needs to flow through some combination of the inputs +*