Main Parts of a PLCPower SupplyCPU (Central Processing Unit)I/O (Input/Output)Indicator lightsPLC Fors!ac"MiniShoe#o$MicroSoftwareChapter % PLC &iringInput 'ypesPro$iity SwitchesSwitchesPotentioeterL()'s(oltages*+%+, (dc*--%*+- (ac*-%.- (dc*+%+, (ac/dc/ (dc (''L)+--%+,- (ac,0 (dc+, (acInput Card1$aple+ , ( 2 CP o w e rS u p p l yn o ra l l y o p e n p u s h % # u t t o nn o ra l l y o p e nt ep e r a t u r e s w i t c hP L C I n p u t C a r d+ , ( 2 Ci t i s i n r a c " 3 # o # 3s l o t 4- -- *- +- 4- ,- /- .- 5P u s h # u t t o n ( # o # 6 4 6 I 7 ) a t a 7 * )' ep s e n s o r ( # o # 6 4 6 I 7 ) a t a 7 4 )C O M8 o t e 6 i n p u t s a r e n o ra l l y h i g h ip e d a n c e 7 ' h i se a n s t h a t t h e y w i l lu s e 9 e r y l i t t l e c u r r e n t 7: o t8 e u t 7Output 'ypesSolenoid (al9esLightsMotor StartersSer9o MotorsOutput (oltages*+- (ac+, (dc*+%,0 (ac*+%,0 (dc/(dc (''L)+4- (acOutput Card1$aple('ransistors)+ , ( ) CO u t p u t C a r dr a c " 3 s u e 3s l o t +C O M- -- *- +- 4- ,- /- .- 5+ , ( L ap! e l a y; + , ( ) CP o w e r* + - ( 2 CP o w e rM o t o rS u p p l yS u p p l yM o t o r ( s u e 6 + 7 O 7 ) a t a 7 4 )L ap ( s u e 6 + 7 O 7 ) a t a 7 4 )8 e u t 7C O MOutput Card1$aple('ransistors)+ , ( ) CO u t p u t C a r d( ;- -- *- +- 4- ,- /- .- 5+ , ( l ap! e l a y; + , ( ) CP o w e r* + - ( 2 CP o w e rM o t o rS u p p l yS u p p l y8 e u t 7C O MOutput Card1$aple(!elays)* + - ( 2 C / ) CO u t p u t C a r di n r a c " - *I / O g r o u p +- -- *- +- 4- ,- /- .- 5 + , ( l ap! e l a y+ , ( ) CP o w e r* + - ( 2 CP o w e rM o t o rS u p p l yS u p p l ySoe )esign Issues< )C 9oltages are usually lower= and therefore safer (e7g7= +,()7< )C inputs are 9ery fast= 2C inputs re>uire a longer on%tie7< )C 9oltages can #e connected to ore electrical systes7< 2C signals are ore iune to noise than )C7< 2C power is easier and less e$pensi9e to supply to e>uipent7< 2C signals are 9ery coon7!elaysContactor % Special relays for switching large current loads7Motor Starter % ?asically a contactor in series with an o9erload relay to cut off when too uch current is drawn72rc Suppression % when any relay is opened or closed an arc will @up7 'his #ecoes a a@or pro#le with large relays7 On relays switching 2C this pro#le can #e o9ercoe #y opening the relay when the 9oltage goes to Aero (while crossing #etween negati9e and positi9e)7 &hen switching )C loads this pro#le can #e iniiAed #y #lowing pressuriAed gas across during opening to suppress the arc foration72C coils % If a noral relay coil is dri9en #y 2C power the contacts will 9i#rate open and close at the fre>uency of the 2C power7 'his pro#le is o9ercoe #y adding a shading pole to the relay7Pro#le6 Bou are planning a pro@ect that will #e controlled #y a PLC7 ?efore ordering parts you decide to plan the #asic wiring and select appropriate input and output cards7 'he de9ices that we will use for inputs are + contact switches= a push #utton and a theral switch7 'he output will #e for a +,(dc solenoid 9al9e= a **-(ac light #ul#= and a ++-(ac /-:P otor7 S"etch the #asic wiring #elow including PLC cards7&iring )iagraL * 8P L CL *8I 6 - / -I 6 - / *I 6 - / +I 6 - / 4a c c o O 6 - / -O 6 - / *O 6 - / +O 6 - / 4s t o p s t a r tC ! *C ! *C ! *C ! *M C !P ? *L S *P ? +C ! +C ! +L * 8) r i l l S t a t i o n- * -- + -- 4 -- , -- / -- . -- 5 -- 0 -- C -* - -* * -* + -* 4 -!DL *L +S *- 4 /- / -- . -- 5 -- C -* - -* * -* + -C - % ** - - % ** * - % ** + - % *C - % ** - - % ** * - % ** + - % *disconnect circuit interrupter#rea"er (4 phase 2C)norally openliit switchnorally closedliit switchnorally openpush%#uttonnorally closedpush%#uttondou#le polepush%#uttonushroo headpush%#utton(4 phase 2C) (4 phase 2C)EIC &iring Sy#ols